**6. Medical potential of mannans as a drug nanocarrier systems**

Glucomannans have a variety of applications, including food industry used as an emulsifier and thickener and medicine as a preventative of chronic disease and weight control agent [21]. Likewise, galactomannans also found many applications in food industrial as a thickener and food additive due to their rheological properties [121]. Moreover, galactomannans are widely used as versatile materials in industries such as textiles, paper, pharmaceutics, cosmetics, petroleum, drilling and explosives [93,122].

Galactomannans have also significant potential in medical applications such as innate immune system stimulation. On the other hand, the mannooligosaccharides (MOS) derived from these polysaccharides have also prebiotic activity for selective growth of Bifidobacterium spp., and Lactobacillus spp. [123]. They have also been described to present anticoagulation and fibrinolytic activity [124] and the MOS may prevent adherence of toxic bacteria to the intestinal wall, mediated by lectins, thus presenting anti-infectious potential [123,125,126].

In the research of Apostolopoulos *et al.* oxidized mannan conjugated to MUC1 fusion protein (M-FP) was used as a target for tumour immunotherapy and M-FP appeared to confer the survival/disease-free interval advantage in patients with early stage breast cancer [8].

In another study, the factors important to gene delivery and DNA vaccination that could contribute to the improved immunogenicity of oxidized mannan poly-L-lysine (OMPLL)– DNA and reduced mannan poly-L-lysine (RMPLL)–DNA immunization were investigated [9]. It was shown that OMPLL and RMPLL were able to complex with DNA to form particles that were taken up by charge dependent binding and endocytic pathways. High possibility of delivery of DNA was observed since the particles formed were able to protect DNA from DNase I digestion. More significantly, direct effect of OMPLL and RMPLL was observed on the antigen presentation of dentritic cells (DCs).

In 2010, Guo et al. reported that marine bacterium *Edwardsiella tarda* produced two extracellular polysaccharides ETW1 and ETW2, mannans with different molecular mass, that exhibited strong antioxidant activities [55]. To investigate the antioxidant activities of the two polysac‐ charides, antioxidant properties based on hydroxyl, DPPH radical scavenging and lipid peroxidation inhibition assays were carried out. The scavenging abilities of ETW1 and ETW2 on DPPH radicals, hydroxyl radicals and lipid peroxidation inhibition were concentrationdependent.

In 2011, Ferreira et al. prepared nanogel made of mannan [11]. The properties of the resulting nanogel were characterized and cytocompatibility was tested by using two cell lines, namely, mouse embryo fibroblasts 3T3 and mouse macrophage-like J774. The results of study revealed that the mannose receptor binds ligands at the cell surface and these receptor-ligand complexes were internalized via the endocytic pathway. Internalization of the nanogel caused cytotoxicity since the non-phagocytic cell line was not affected and internalization was confirmed with J774. The high nanogel toxicity observed with the macrophage cell line indicated that the cell line J774 was not suitable for studies with mannan-C16 nanogel and primary cultures of macrophages that do not exhibit cytotoxicity should be used instead.

since an amphiphilic form of mannan can spontaneously incorporate proteins and other

Glucomannans have a variety of applications, including food industry used as an emulsifier and thickener and medicine as a preventative of chronic disease and weight control agent [21]. Likewise, galactomannans also found many applications in food industrial as a thickener and food additive due to their rheological properties [121]. Moreover, galactomannans are widely used as versatile materials in industries such as textiles, paper, pharmaceutics, cosmetics,

Galactomannans have also significant potential in medical applications such as innate immune system stimulation. On the other hand, the mannooligosaccharides (MOS) derived from these polysaccharides have also prebiotic activity for selective growth of Bifidobacterium spp., and Lactobacillus spp. [123]. They have also been described to present anticoagulation and fibrinolytic activity [124] and the MOS may prevent adherence of toxic bacteria to the intestinal

In the research of Apostolopoulos *et al.* oxidized mannan conjugated to MUC1 fusion protein (M-FP) was used as a target for tumour immunotherapy and M-FP appeared to confer the

In another study, the factors important to gene delivery and DNA vaccination that could contribute to the improved immunogenicity of oxidized mannan poly-L-lysine (OMPLL)– DNA and reduced mannan poly-L-lysine (RMPLL)–DNA immunization were investigated [9]. It was shown that OMPLL and RMPLL were able to complex with DNA to form particles that were taken up by charge dependent binding and endocytic pathways. High possibility of delivery of DNA was observed since the particles formed were able to protect DNA from DNase I digestion. More significantly, direct effect of OMPLL and RMPLL was observed on

In 2010, Guo et al. reported that marine bacterium *Edwardsiella tarda* produced two extracellular polysaccharides ETW1 and ETW2, mannans with different molecular mass, that exhibited strong antioxidant activities [55]. To investigate the antioxidant activities of the two polysac‐ charides, antioxidant properties based on hydroxyl, DPPH radical scavenging and lipid peroxidation inhibition assays were carried out. The scavenging abilities of ETW1 and ETW2 on DPPH radicals, hydroxyl radicals and lipid peroxidation inhibition were concentration-

In 2011, Ferreira et al. prepared nanogel made of mannan [11]. The properties of the resulting nanogel were characterized and cytocompatibility was tested by using two cell lines, namely, mouse embryo fibroblasts 3T3 and mouse macrophage-like J774. The results of study revealed that the mannose receptor binds ligands at the cell surface and these receptor-ligand complexes were internalized via the endocytic pathway. Internalization of the nanogel caused cytotoxicity

agents, potentially providing a new nanostructure drug delivery system.

petroleum, drilling and explosives [93,122].

320 Application of Nanotechnology in Drug Delivery

the antigen presentation of dentritic cells (DCs).

dependent.

**6. Medical potential of mannans as a drug nanocarrier systems**

wall, mediated by lectins, thus presenting anti-infectious potential [123,125,126].

survival/disease-free interval advantage in patients with early stage breast cancer [8].

In 2012, the mannan nanogel cytocompatibility was tested in mouse embryo fibroblast cell line 3T3 and mouse bone marrow-derived macrophages (BMDM). [12]. The essential focus of the study was to assess nanomaterial cytocompatibility and to analyze the internalization by macrophages. The results of this study indicated that the mannan nanogel was biocompatible to mouse embryo fibroblast 3T3 cells and mouse BMDM. Essentially, no cytotoxic effect was observed with mannan nanogel up to about 0.4 mg/mL in *in vitro* experiments. Cell survival rate only dropped significantly at higher tested concentration after 48 h of incubation. Comet assay, under tested conditions, revealed no DNA damage in mouse embryo fibroblast 3T3 cells but possible DNA damage in mouse BMDM. Upon internalization by mouse BMDM mannan nanogel was localized in vesicles, as judged by the non-even distribution over the cytoplasm, and concentration of the fluorescence in internalized structures. Exit of nanogel from the mouse BMDM was observed when cells were incubated in fresh medium. Confocal colocali‐ zation image analysis denoted that the entrance and exit of nanogel and FM 4-64 might occur by the same processes – endocytosis and exocytosis – in BMDM.

Sato et al. [127] examined the adhesion inhibitory effect of mannan coating on acrylic denture surfaces against *Candida albicans* and *Candida glabrata*. The outermost layer of the *Candida* cell wall is covered with hydrophilic polysaccharides, such as mannan or galactomannan [128]. These mannans on the fungal surface function as adhesins, which are involved not only in the adhesion to the host cell [129,130] but also in the adsorption to plastic plates. On the other hand, when the plastic surfaces of culture dishes were coated with mannan, the adherence of *C. albicans* to the dishes was significantly inhibited [131,132]. The results of this study indicated that mannan inhibited the adhesion of *Candida* in a concentration-dependent manner, but mannose was not able to inhibit *Candida* adhesion even at a high concentration. The application of 0.1 mg/mL of mannan coating overnight showed inhibitory effects on the adhesion of the hyphal form of *C. albicans.* In the case of *C. glabrata*, the inhibitory effect was also observed to occur in a concentration-dependent manner, and the 10 mg/mL of mannan led to significantly higher anti-adhesive effects. This indicated that mannan effectively prevented the adhesion of two major *Candida* species to the denture surface, indicating the possibility of applying such a coating for clinical dentistry.

Superparamagnetic iron oxide nanoparticles (SPIONs) have been used as a contrast agent in magnetic resonance imaging (MRI) or as a carrier platform in the applications of drug [133-135] and gene delivery [137,138]. It was previously reported that mannan-coated SPION (mannan-SPION) could be specifically targeted to macrophages by the interaction with mannose receptors on antigen-presenting cells (APCs) [139]. Vu-Quang et al., [10] investigated the physicochemical properties, the *in vitro* and *in vivo* uptakes of carboxylic mannan-coated SPION (CM-SPION) using MRI and assessment of systemic toxicity. Results of the study showed that CM-SPION achieve longer circulation than mannan-SPION without compromis‐ ing specificity. The intracellular accumulation of CM-SPION in macrophages was higher than those of either PVA-SPIONs or Dex-SPIONs. The intracellular localization of CM-SPIONs was pre-dominantly observed in the cytoplasm of APCs. In the light of these results, authors claimed that CM-SPION could be regarded as a safe and potential contrast agent in LNtargeted MR imaging.

gastrointestinal tract occurs and leads to diarrhea when KGM was used in the applications such as pharmaceutical excipients or drugs. On the other hand, when prepared as styptic sponge, which used to stop bleeding, the higher the water adsorption rate of it, the better the hemostasis effect may be. Modifications of KGM lead to alteration in the water adsorption of

Mannan as a Promising Bioactive Material for Drug Nanocarrier Systems

http://dx.doi.org/10.5772/58413

323

In the previous studies, it was reported that KGM can be specifically degraded by colon βmannanase [158], an enzyme generated by human colon bacteria [159]. On the other hand, based on the toxicity tests Ancui et al. reported KGM as a stable and safety material for

Invention of a novel hydrogel systems designed for colon-targeting drug delivery was reported in 2004 [158]. This hydrogel was composed of KGM, copolymerized with acrylic acid, and crosslinked by the aromatic azo agent bis(methacryloylamino)-azobenzene. Chen, Liu and Zhuo, copolymerized KGM and acrylic acid (AA) with N, N-methylene-bis-(acrylamide) (MBAAm) to form a novel hydrogel system [161]. Studies on swelling behaviors and degra‐ dation showed that the gel is pH-sensitive and could be degraded by Cellulase E0240 con‐ taining β-mannanase. Further researches demonstrated that the IPN hydrogel composed of KGM and poly(acrylic acid) (PAA) and cross-linked by N, N-methylene-bis-(acrylamide) (MBAAm) was still pH-sensitive and a potential carrier for colon-targeting drug delivery. Xu et al., prepared oxidized konjac glucomannan (OKG) for OCDDS which was pH-sensitive and could be used without the destruction of drugs in gastric acid [162]. Furthermore, Korkiati‐ thaweechai et al., prepared controlled release of diclofenac sodium (DFNa) film from CTS (chitosan)-OKG [163]. This study suggested that the proportion of OKG in the formulation may affect the release profile and the formulation may be used for further study as a long term intestine controlled release drug model (at least 3 days), including as colon targeting drug

Guar gum derived from the seeds of *Cyamopsis tetragonolobus* is a naturally occuring galactomannan polysaccharide that consists of 80% galactomannan, 12% water, 5% protein, 2% acid insoluble ash, 0.7% ash and 0.7% fat. Guar gum has been reported as an inexpen‐ sive and flexible carrier for oral extended release drug delivery [164]. Guar gum can be used for colon delivery since it can be degraded by specific enzymes in this region of the gastrointestinal tract. GG provides protection to the drug in the environment of the stomach and small intestine, and drug delivery to the colon where it is degraded by the enzymes excreted by specific microorganisms. Guar gum shows high potential as a carrier for oral controlled release matrix systems. Furthermore, excipients to GG can be used to modu‐

Locust bean gum also known as Carob bean gum consists mainly of a neutral galactomannan polymer made up of 1,4-linked D-mannopyranosyl units and every fourth or fifth chain unit is substituted on C6 with a D-galactopyranosyl unit. Locust bean gum is a neutral polymer and its viscosity and solubility are therefore little affected by pH changes within the range of 3-11 [166]. Locust bean gum was used to produce matrix tablets with and without the crosslinker, glutaraldehyde [101]. A commercially available tablet system (TIMERx®) developed

late drug release from these matrix systems [165].

it. Moreover, KGM have gel-forming and film-forming properties [157].

medicinal purposes [160].

carrier.

The effective conjugation of iron oxide nanoparticles with various biomolecules has been used for novel therapeutic-and drug delivery purposes [139-142]. Ultrasmall superparamagnetic iron oxide (USPIO) targets biomarkers of atherosclerotic plaques and improvements of USPIO make possible to obtain better plaque images at lower doses. Mannose units of mannan polysaccharides are recognized by mannose receptors on immune macrophages and they lack of significant toxicity. As a result, in the study of Tsuchiya [143], MRI-and histologic analyses were performed to compare the uptake by the rabbit atherosclerotic wall of four types of SPIO particles, i.e. SPIO, mannan-coated SPIO (M-SPIO), ultrasmall SPIO (USPIO), and mannancoated USPIO (M-USPIO). Resuts of study reveal that mannan-coated iron particles had a greater affinity for active atherosclerotic plaques than non mannan-coated iron particles. Intracellular iron uptake was also higher in cells treated with M-USPIO than USPIO.

Glucomannans have diverse applications in biomedical and pharmaceutical areas due to the advantages of the polysaccharide such as weigt loss in obesity, decreased carbohydrate absorption in diabetes type 2, antitumor activity against sarcoma in cancer, decreased LDL levels in cholesterol, recognition of mannose receptors in targeting, antiseptic coating and sustained release profiles, increase of stability, improvement of the interaction between polmers, enhancement protein association of pharmaceutical forms of glucomannan. Gluco‐ mannan has been investigated as a pharmaceutical excipient in tablets, films, beads and hydrogels, due to its gelling, solubility and biodegradable properties [143-146].

Electrostatic interaction between the negative carboxylic groups of carboxymethylated-GM and the positive amino groups of chitosan was used for the preparation of nanoparticles made of carboxymethylated-GM and chitosan [147]. These nanoparticles were within size range of 50–1200 nm and exhibited a positive charge. Additionally, these nanoparticles elicited an ability to entrap and release bovine serum albumin (BSA) [147,148] The objection of use of GM in these nanoparticles was to increase their stability and their controlled release properties. Sande et al. reported that the introduction of GM into the nanoparticles lead to a facilitated interaction with the intestinal epithelium both *in vitro* and *in vivo* [149, 150]. The results of studies revealed that GM–chitosan nanoparticles offer attractive features as carriers for transmucosal drug delivery applications.

In the report of Zhang et al., use of konjac glucomannan (KGM) in oral colon targeting drug delivery system (OCDDS) was reviewed [151]. Based on the previous studies of KGM, it could be considered as a significant natural polysaccharide in OCDDS. It was known that KGM gel systems were able to maintain integrity and control the release of theophylline and diltiazem for 8 hours [152]. KGM hydrolysate was reported to have prebiotic potential for beneficial gut microbiota [153,154]. KGM is a water soluble polysaccharide because of hydrogen bonding in its structure [155,156]. The stronger the hydrogen bonding between their molecules, the harder for it to dissolve in water. Water solubility can be either advantageous or disadvangeous according to its application. Due to the high water adsorption rate, deficiency of free water in gastrointestinal tract occurs and leads to diarrhea when KGM was used in the applications such as pharmaceutical excipients or drugs. On the other hand, when prepared as styptic sponge, which used to stop bleeding, the higher the water adsorption rate of it, the better the hemostasis effect may be. Modifications of KGM lead to alteration in the water adsorption of it. Moreover, KGM have gel-forming and film-forming properties [157].

those of either PVA-SPIONs or Dex-SPIONs. The intracellular localization of CM-SPIONs was pre-dominantly observed in the cytoplasm of APCs. In the light of these results, authors claimed that CM-SPION could be regarded as a safe and potential contrast agent in LN-

The effective conjugation of iron oxide nanoparticles with various biomolecules has been used for novel therapeutic-and drug delivery purposes [139-142]. Ultrasmall superparamagnetic iron oxide (USPIO) targets biomarkers of atherosclerotic plaques and improvements of USPIO make possible to obtain better plaque images at lower doses. Mannose units of mannan polysaccharides are recognized by mannose receptors on immune macrophages and they lack of significant toxicity. As a result, in the study of Tsuchiya [143], MRI-and histologic analyses were performed to compare the uptake by the rabbit atherosclerotic wall of four types of SPIO particles, i.e. SPIO, mannan-coated SPIO (M-SPIO), ultrasmall SPIO (USPIO), and mannancoated USPIO (M-USPIO). Resuts of study reveal that mannan-coated iron particles had a greater affinity for active atherosclerotic plaques than non mannan-coated iron particles.

Intracellular iron uptake was also higher in cells treated with M-USPIO than USPIO.

hydrogels, due to its gelling, solubility and biodegradable properties [143-146].

transmucosal drug delivery applications.

Glucomannans have diverse applications in biomedical and pharmaceutical areas due to the advantages of the polysaccharide such as weigt loss in obesity, decreased carbohydrate absorption in diabetes type 2, antitumor activity against sarcoma in cancer, decreased LDL levels in cholesterol, recognition of mannose receptors in targeting, antiseptic coating and sustained release profiles, increase of stability, improvement of the interaction between polmers, enhancement protein association of pharmaceutical forms of glucomannan. Gluco‐ mannan has been investigated as a pharmaceutical excipient in tablets, films, beads and

Electrostatic interaction between the negative carboxylic groups of carboxymethylated-GM and the positive amino groups of chitosan was used for the preparation of nanoparticles made of carboxymethylated-GM and chitosan [147]. These nanoparticles were within size range of 50–1200 nm and exhibited a positive charge. Additionally, these nanoparticles elicited an ability to entrap and release bovine serum albumin (BSA) [147,148] The objection of use of GM in these nanoparticles was to increase their stability and their controlled release properties. Sande et al. reported that the introduction of GM into the nanoparticles lead to a facilitated interaction with the intestinal epithelium both *in vitro* and *in vivo* [149, 150]. The results of studies revealed that GM–chitosan nanoparticles offer attractive features as carriers for

In the report of Zhang et al., use of konjac glucomannan (KGM) in oral colon targeting drug delivery system (OCDDS) was reviewed [151]. Based on the previous studies of KGM, it could be considered as a significant natural polysaccharide in OCDDS. It was known that KGM gel systems were able to maintain integrity and control the release of theophylline and diltiazem for 8 hours [152]. KGM hydrolysate was reported to have prebiotic potential for beneficial gut microbiota [153,154]. KGM is a water soluble polysaccharide because of hydrogen bonding in its structure [155,156]. The stronger the hydrogen bonding between their molecules, the harder for it to dissolve in water. Water solubility can be either advantageous or disadvangeous according to its application. Due to the high water adsorption rate, deficiency of free water in

targeted MR imaging.

322 Application of Nanotechnology in Drug Delivery

In the previous studies, it was reported that KGM can be specifically degraded by colon βmannanase [158], an enzyme generated by human colon bacteria [159]. On the other hand, based on the toxicity tests Ancui et al. reported KGM as a stable and safety material for medicinal purposes [160].

Invention of a novel hydrogel systems designed for colon-targeting drug delivery was reported in 2004 [158]. This hydrogel was composed of KGM, copolymerized with acrylic acid, and crosslinked by the aromatic azo agent bis(methacryloylamino)-azobenzene. Chen, Liu and Zhuo, copolymerized KGM and acrylic acid (AA) with N, N-methylene-bis-(acrylamide) (MBAAm) to form a novel hydrogel system [161]. Studies on swelling behaviors and degra‐ dation showed that the gel is pH-sensitive and could be degraded by Cellulase E0240 con‐ taining β-mannanase. Further researches demonstrated that the IPN hydrogel composed of KGM and poly(acrylic acid) (PAA) and cross-linked by N, N-methylene-bis-(acrylamide) (MBAAm) was still pH-sensitive and a potential carrier for colon-targeting drug delivery. Xu et al., prepared oxidized konjac glucomannan (OKG) for OCDDS which was pH-sensitive and could be used without the destruction of drugs in gastric acid [162]. Furthermore, Korkiati‐ thaweechai et al., prepared controlled release of diclofenac sodium (DFNa) film from CTS (chitosan)-OKG [163]. This study suggested that the proportion of OKG in the formulation may affect the release profile and the formulation may be used for further study as a long term intestine controlled release drug model (at least 3 days), including as colon targeting drug carrier.

Guar gum derived from the seeds of *Cyamopsis tetragonolobus* is a naturally occuring galactomannan polysaccharide that consists of 80% galactomannan, 12% water, 5% protein, 2% acid insoluble ash, 0.7% ash and 0.7% fat. Guar gum has been reported as an inexpen‐ sive and flexible carrier for oral extended release drug delivery [164]. Guar gum can be used for colon delivery since it can be degraded by specific enzymes in this region of the gastrointestinal tract. GG provides protection to the drug in the environment of the stomach and small intestine, and drug delivery to the colon where it is degraded by the enzymes excreted by specific microorganisms. Guar gum shows high potential as a carrier for oral controlled release matrix systems. Furthermore, excipients to GG can be used to modu‐ late drug release from these matrix systems [165].

Locust bean gum also known as Carob bean gum consists mainly of a neutral galactomannan polymer made up of 1,4-linked D-mannopyranosyl units and every fourth or fifth chain unit is substituted on C6 with a D-galactopyranosyl unit. Locust bean gum is a neutral polymer and its viscosity and solubility are therefore little affected by pH changes within the range of 3-11 [166]. Locust bean gum was used to produce matrix tablets with and without the crosslinker, glutaraldehyde [101]. A commercially available tablet system (TIMERx®) developed by Penwest Pharmaceuticals Company consisting of locust bean gum and xanthan gum showed both *in vitro* and *in vivo* controlled release potential [167].

Alginate is a non-toxic polysaccharide that have properties such as pH sensitivity. This pH sensitivity is favorable forintestinal delivery of protein drugs. However, drug leaching during hydrogel preparation and rapid dissolution of alginate at higher pH are major limitations since when it enters the intestine, these limitations cause to very low entrapment efficiency and burst release of entrapped protein drug. To overcome these limitations, George and Abraham used another natural polysaccharide, guar gum which is included in the alginate matrix along with a cross linking agent to ensure maximum encapsulation efficiency and

Mannan as a Promising Bioactive Material for Drug Nanocarrier Systems

http://dx.doi.org/10.5772/58413

325

In the study of Coviello et al. [101], two galactomannans, guar gum and Locust bean gum, have been investigated for their possible use as matrices for modified drug delivery. They were crosslinked with glutaraldehyde (Ga) and then used for the preparation of tablets. This preparations increased the rate of release of small guest molecules due to the fact that the chemical reaction with Ga introduced meshes with a size larger than those present in the

In the study of Voepel et al. [183], hydrogels based on acetylated galactoglucomannan (AcGGM) were synthesized and examined for their properties in drug-release systems using two model substances of different molecular weight, size, and polarity (caffeine and vitasyn blue). AcGGM was synthetically modified to yield a polysaccharide with either neutral or ionic pendant groups. These precursors were formulated to produce either a neutral, covalent hydrogel or a physically cross linked hydrogel. Neutral and ionic hydrogels based on HEMA-Im– modified AcGGM (M-AcGGM) and maleic anhydride modified M-AcGGM (CM-AcGGM) were studied in view of their chemical, physical and drug release properties. In the case of the neutral hydrogels, half of the total drug release (50 wt % release) was reported to occur between 13 and 35 min and 50 to 90 min for caffeine and vitasyn blue, respectively. The majority of the caffeine (80 wt %) was released between 40 and 120 min, on the other hand, the majority of vitasyn blue was released between 125 and 250 min. When maleic anhydride was added to the M-AcGGM, ionic poly(CM-AcGGMco-HEMA) hydrogels could be achieved. Slower release of caffeine was found in these hydrogels, especially at acidic conditions because

of the pH responsitivity obtained through the introduced carboxylic functionalities.

Roos et al. synthesized hydrogels from *O*-acetyl-galactoglucomannan (AcGGM) with encap‐ sulated bovine serum albumin (BSA), to investigate the influence of substitutions and the feasibility of BSA-release mediated by the addition of *β*-mannanase to hydrolyze the hydrogel [184]. Hydrogels were prepared from AcGGM substituted with various amounts of 2 hydroxyethylmethacrylate groups and loaded with BSA. The degree of substitution of HEMA and the presence of *β*-mannanase *An*Man5A were two parameters that influenced the release of BSA from the hydrogels in water. Increasing HEMA substitutions on the glucomannan backbone from 0.1 to 0.36 caused lesser spontaneous release of BSA. However, the addition of *β*-mannanase *An*Man5A increased the BSA release due to enzymatic hydrolysis of AcGGM. The hydrogel with DSHEMA (degree of sustitution) 0.36 released almost all remaining BSA from the hydrogel within 8 h after addition. The results of the study provided significant insights into further developments of AcGGM-based hydrogels for the application of drug delivery

controlled drug release [182].

simply entangled systems.

Guar gum hydrates and swells in cold water [168]. This gelling cause to retardation of the drug release from the tablets [169,170]. Guar gum is being used to deliver drug to the colon due to its drug release retarding property and susceptibility to microbial degradation in the large intestine [171,172]. Guar gum based matrix tablets of dexamethasone and other antinflamma‐ tory agents were prepared and used in colon targeting [173]. Whereas negligible drug release was observed in simulated gastric and intestinal fluids, significant increase in drug release was reported in simulated colonic fluid.

Colonic drug delivery system based on pectin (polygalactronic acid) and galactomannan coating was reported by Lee et al. [174] and Pai et al. [175]. These two polysaccharides, pectin and galactomannan, were used as coating material of a conventional tablet or capsule. The coating of pectin/galactomannan mixture was shown to be strong, elastic and insoluble in simulated gastric and intestinal fluids such that it would protect drug from being released in the upper GI tract. Researches revealed that in the colon, bacterial degradability was preserved. Moreover, extended film resistance to hydration, subsequent solubilization, film degradation rate by enzymes and drug release rate were found to depend on the varying ratio of pectin to galactomannan. Higher galactomannan percentage caused to decreased bacterial degradation in the colon and prolonged duration of negligible drug release in the upper GI tract. Compared with the combination of pectin and ethyl cellulose [176] or amylose and ethyl cellulose [177], combination of pectin and galactomannan was advantageous due to faster *in vivo* degradation of both pectin and galactomannan by microflora in the colon.

Matrix tablet of indomethacin with guar gum was prepared and the suitability of guar gum as a carrier in colonic drug delivery was investigated in another study [178]. The results indicated the specificity of these matrices for enzymes triggered the drug release in the colon. In another *in vivo* study, matrix tablets containing around 77% guar gum were loaded with technetium-99m-DTPA as tracer and scintigraphs were taken at regular intervals in six healthy human male volunteers [179]. These tablets were found to remain intact releasing only small amount of tracer in the stomach and the small intestine. However, bulk of the tracer was released in the ascending colon thereby suggesting that the enzyme triggered degradation by colonic bacteria.

Rubinstein and Gliko-Kabir investigated a biodegradable property of guar gum cross-linked with borax [180]. The time required for degradation of these crosslinked guar gum and borax showed that release of drug would be in proximal colon. The same group analysed phosphated cross-linked guar gum hydrogels for their potential as colon drug carriers *in vitro* and *in vivo* in 2000 [181]. *In vitro* studies revealed that these hydrogels loaded with hydrocortisone were able to resist the release of 80% of the drug for 6 h in phosphate buffer. *In vivo* studies in rat showed that degradation of modified guar gum by enzymes was concentration dependent. Thus, the phosphated crosslinked guar gum could be considered suitable for colon drug delivery.

Alginate is a non-toxic polysaccharide that have properties such as pH sensitivity. This pH sensitivity is favorable forintestinal delivery of protein drugs. However, drug leaching during hydrogel preparation and rapid dissolution of alginate at higher pH are major limitations since when it enters the intestine, these limitations cause to very low entrapment efficiency and burst release of entrapped protein drug. To overcome these limitations, George and Abraham used another natural polysaccharide, guar gum which is included in the alginate matrix along with a cross linking agent to ensure maximum encapsulation efficiency and controlled drug release [182].

by Penwest Pharmaceuticals Company consisting of locust bean gum and xanthan gum

Guar gum hydrates and swells in cold water [168]. This gelling cause to retardation of the drug release from the tablets [169,170]. Guar gum is being used to deliver drug to the colon due to its drug release retarding property and susceptibility to microbial degradation in the large intestine [171,172]. Guar gum based matrix tablets of dexamethasone and other antinflamma‐ tory agents were prepared and used in colon targeting [173]. Whereas negligible drug release was observed in simulated gastric and intestinal fluids, significant increase in drug release was

Colonic drug delivery system based on pectin (polygalactronic acid) and galactomannan coating was reported by Lee et al. [174] and Pai et al. [175]. These two polysaccharides, pectin and galactomannan, were used as coating material of a conventional tablet or capsule. The coating of pectin/galactomannan mixture was shown to be strong, elastic and insoluble in simulated gastric and intestinal fluids such that it would protect drug from being released in the upper GI tract. Researches revealed that in the colon, bacterial degradability was preserved. Moreover, extended film resistance to hydration, subsequent solubilization, film degradation rate by enzymes and drug release rate were found to depend on the varying ratio of pectin to galactomannan. Higher galactomannan percentage caused to decreased bacterial degradation in the colon and prolonged duration of negligible drug release in the upper GI tract. Compared with the combination of pectin and ethyl cellulose [176] or amylose and ethyl cellulose [177], combination of pectin and galactomannan was advantageous due to faster *in vivo* degradation

Matrix tablet of indomethacin with guar gum was prepared and the suitability of guar gum as a carrier in colonic drug delivery was investigated in another study [178]. The results indicated the specificity of these matrices for enzymes triggered the drug release in the colon. In another *in vivo* study, matrix tablets containing around 77% guar gum were loaded with technetium-99m-DTPA as tracer and scintigraphs were taken at regular intervals in six healthy human male volunteers [179]. These tablets were found to remain intact releasing only small amount of tracer in the stomach and the small intestine. However, bulk of the tracer was released in the ascending colon thereby suggesting that the enzyme triggered degradation by

Rubinstein and Gliko-Kabir investigated a biodegradable property of guar gum cross-linked with borax [180]. The time required for degradation of these crosslinked guar gum and borax showed that release of drug would be in proximal colon. The same group analysed phosphated cross-linked guar gum hydrogels for their potential as colon drug carriers *in vitro* and *in vivo* in 2000 [181]. *In vitro* studies revealed that these hydrogels loaded with hydrocortisone were able to resist the release of 80% of the drug for 6 h in phosphate buffer. *In vivo* studies in rat showed that degradation of modified guar gum by enzymes was concentration dependent. Thus, the phosphated crosslinked guar gum could be considered suitable for colon drug

showed both *in vitro* and *in vivo* controlled release potential [167].

of both pectin and galactomannan by microflora in the colon.

reported in simulated colonic fluid.

324 Application of Nanotechnology in Drug Delivery

colonic bacteria.

delivery.

In the study of Coviello et al. [101], two galactomannans, guar gum and Locust bean gum, have been investigated for their possible use as matrices for modified drug delivery. They were crosslinked with glutaraldehyde (Ga) and then used for the preparation of tablets. This preparations increased the rate of release of small guest molecules due to the fact that the chemical reaction with Ga introduced meshes with a size larger than those present in the simply entangled systems.

In the study of Voepel et al. [183], hydrogels based on acetylated galactoglucomannan (AcGGM) were synthesized and examined for their properties in drug-release systems using two model substances of different molecular weight, size, and polarity (caffeine and vitasyn blue). AcGGM was synthetically modified to yield a polysaccharide with either neutral or ionic pendant groups. These precursors were formulated to produce either a neutral, covalent hydrogel or a physically cross linked hydrogel. Neutral and ionic hydrogels based on HEMA-Im– modified AcGGM (M-AcGGM) and maleic anhydride modified M-AcGGM (CM-AcGGM) were studied in view of their chemical, physical and drug release properties. In the case of the neutral hydrogels, half of the total drug release (50 wt % release) was reported to occur between 13 and 35 min and 50 to 90 min for caffeine and vitasyn blue, respectively. The majority of the caffeine (80 wt %) was released between 40 and 120 min, on the other hand, the majority of vitasyn blue was released between 125 and 250 min. When maleic anhydride was added to the M-AcGGM, ionic poly(CM-AcGGMco-HEMA) hydrogels could be achieved. Slower release of caffeine was found in these hydrogels, especially at acidic conditions because of the pH responsitivity obtained through the introduced carboxylic functionalities.

Roos et al. synthesized hydrogels from *O*-acetyl-galactoglucomannan (AcGGM) with encap‐ sulated bovine serum albumin (BSA), to investigate the influence of substitutions and the feasibility of BSA-release mediated by the addition of *β*-mannanase to hydrolyze the hydrogel [184]. Hydrogels were prepared from AcGGM substituted with various amounts of 2 hydroxyethylmethacrylate groups and loaded with BSA. The degree of substitution of HEMA and the presence of *β*-mannanase *An*Man5A were two parameters that influenced the release of BSA from the hydrogels in water. Increasing HEMA substitutions on the glucomannan backbone from 0.1 to 0.36 caused lesser spontaneous release of BSA. However, the addition of *β*-mannanase *An*Man5A increased the BSA release due to enzymatic hydrolysis of AcGGM. The hydrogel with DSHEMA (degree of sustitution) 0.36 released almost all remaining BSA from the hydrogel within 8 h after addition. The results of the study provided significant insights into further developments of AcGGM-based hydrogels for the application of drug delivery

Bioadhesive poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles were reported as promising drug delivery systems [185], and surface modification of nanocarriers was provided by application of mannan-based PE-grafted ligands (MAN-PEs) [186]. Kong et al. investigated MAN-PE-modified bioadhesive PLGA nanoparticles as active targeting gene delivery system using plasmid enhanced green fluorescent protein (*pEGFP*) as the model gene [187]. In the reported study, in order to achieve active targeting to the liver, surface of of PLGA nanopar‐ ticles was modified by the application of MAN-PEs. *In vitro* and *in vivo* behavior of mannanmodified DNA-loaded PLGA nanoparticles were compared with nonmodified DNA-loaded PLGA nanoparticles. Spherical shapes were observed for nonmodified DNA-NPs while the mannan-modified MAN-DNA-NPs had a dark coat on the white balls, that indicated the successful coating of mannan-PE. The mean particle size of NPs was around 100–200 nm, which was ideal for the nanoparticulate system. MAN-PEs-modified *pEGFP*-loaded bioadhesive PLGA-NPs could be targeted to the liver and successfully transfected the Kupffer cells (KCs).

composition of polysaccharides is highly influenced by the environmental conditions and strictly depends on the availability of the activated sugar monomers. Currently, main sources for mannan are plants, algae and fungi where production may take months and greatly depends on geographical or seasonal conditions. On the other hand, microbial sources could be a feasible alternative for the sustainable and economical production of mannan at industrial scale. Microbial fermentation would not only enable the use of low-cost resources for the economical production, but also provide control over the chemical structure, monomer composition and physicochemical and rheological properties of the final product. There are only few reports on microbial mannan production and from these, thermophiles stand out with their high production rates due to their high metabolic activity. Moreover, such simple systems enable the effective application of systems-based approaches to obtain tailor-made

Mannan as a Promising Bioactive Material for Drug Nanocarrier Systems

http://dx.doi.org/10.5772/58413

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Finally, mannan is a very promising bioactive material for drug nanocarrier systems since its amphiphilic structure can incorporate diverse biomolecules, potentially providing novel nanostructure drug delivery systems. Hence, development of high mannan producer cell factories would overcome the problems associated with the sustainable production of this

Industrial Biotechnology and Systems Biology Research Group, Department of Bioengineer‐

[1] Ramberg JE., Nelson ED., Sinnott RA. Immunomodulatory dietary polysaccharides: a

[2] Harris PJ., Stone BA. Chemistry and molecular organization of plant cell walls. In: Himmel ME. (ed.) Biomass recalcitrance. Blackwell: Oxford; 2008. pp 60–93.

[3] Chauhan PS., Puri N., Sharma P., Gupta N. Mannanases: microbial sources, produc‐ tion, properties and potential biotechnological applications. Applied Microbiology

[4] Mikkonen KS., Tenkanen M. Sustainable food-packaging materials based on future biorefinery products: xylans and mannans. Trends in Food Science & Technology

systematic review of the literature. Nutrition Journal 2010; 9(54).

polymers.

important biomaterial.

Songul Yasar Yildiz and Ebru Toksoy Oner\*

ing, Marmara University, Istanbul, Turkey

\*Address all correspondence to: ebru.toksoy@marmara.edu.tr

and Biotechnology 2012;93(2) 1817–1830.

2012;28(2) 90-102.

**Author details**

**References**

In the study of Wu et al., mannan-PEG-PE (MN-PEG-PE) modified bioadhesive PLGA nanoparticles were obtained as a targeted gene delivery system [188]. Mannan was the target part that bind to the mannose receptor (MR) in the macrophage, and PEG-PE was the spacer linked into the surface of NPs. The results of this study confirmed that mannose-mediated targeting could successfully deliver genes into MR expressing cells. Improved transfection efficiency was observed in the case of mannose containing targeting ligands, such as in DNA loaded PLGA NPs. The results supported the active targeting ability of mannan containing PEG-PE modified bioadhesive PLGA nanoparticles, and the resulting vectors would be very useful in gene delivery both *in vitro* and *in vivo.*

In the study of Kaur, sustained and targeted release nanoparticles of didanosine were formu‐ lated using gelatin as polymer and mannan-coating to further enhance its macrophage uptake and its distribution in organs that act as major reservoirs of HIV [189]. Coating of nanoparticles with mannan further retarded the drug release (42.5 ± 1.7% over 24 h) and increased the cellular uptake of nanoparticles (N-C3-M) as was evident by higher staining intensity and complete lysis within 2 h of incubation. The better cellular uptake of mannan-coated nanoparticles might be due to the presence of mannosyl receptor predominantly on the macrophage cell surface, which was used by the cells for endocytosis and phagocytosis [190,191]. The results showed higher accumulation of didanosine in brain when administered through mannan-coated nanoparticles. Didanosine is a hydrophilic drug and its ability to cross the blood brain barrier was very low; however, mannan-coated nanoparticles provided enhanced delivery of dida‐ nosine to brain. Hence, mannan-coated gelatin nanoparticles resulted in a significantly higher concentration of didanosine in spleen, lymph nodes and brain.
