**6.3 Photodynamic antimicrobial chemotherapy (PACT)**

The use of most of the existing photosensitizers has been harshly hampered because of their significant self-quenching effect, poor water solubility, lack of selectivity against bacterial cells, and possible damage to the surrounding tissues. Therefore, to overcome the limitations, the PS encapsulated hydrogels were prepared recently. Recently, hydrophilic photosensitizer (PS) for instance 5, 10, 15, 20-tetrakis (1-methylpyridinium-4-yl)porphyrin tetraiodide (TMPyP) incorporated xylan-based *Xylan-Based Hydrogels: A Polymeric Carrier for Sustained and Targeted Delivery of Drugs DOI: http://dx.doi.org/10.5772/intechopen.109201*

hydrogels were synthesized which showed prolonged release of PS up to 24 hours with a cumulative release of 100%. TMPyP-loaded hydrogel were effective against *Pseudomonas aeruginosa*, *Escherichia coli*, *Staphylococcus aureus* strains, and *Bacillus cereus*, while ineffective in the dark. This PACT showed to be promising antimicrobial treatment to overcome the challenges of multidrug resistant bacteria [29].

#### **6.4 Skin care**

The bio-compatibility [11] and cyto-compatibility [6] of xylan based hydrogels were confirmed through experiments and thereby the fabricated hydrogels may be used as a potential material in skin. Fu and co-workers were prepared attractive hydrogels by using dialdehyde xylan (DAX) as a crosslinker for substrate gelatine (G). The properties of hydrogels were further improved in terms of texture, antibacterial, and cyto-compatibility by the introduction of glycerol (Gly) and nicotinamide (NCA) and the prepared DAX-G-Gly-NCA hydrogel showed highly fascinating materials in the application of skin care [6].

#### **6.5 Targeted drug carriers**

The delivery of drugs to the colorectal is the major problem in the treatment of colorectal cancer because of the instability of drugs in the gastric environment of upper GIT. This problem can be solved if the release time of drugs extended or drugs are binded strongly with the matrix material. Hore and Kohne [30] showed delayed drug release by enhancing the binding of a loaded drug to the hydrogel matrix. The multiresponsive (temperature, pH, and magnetic) xylan-based hydrogels encapsulate the magnetic nanoparticles which would facilitate drug release in specific region and realize drug controlled delivery remotely [11]. In a study, the drug loading to the hydrogel is done by immersing the dried hydrogel to the phosphate buffer saline (PBS) solution having pH 7.4. The drug loading and cumulative drug release properties of a hydrogel could be improved significantly using pore-forming agents. Suitable pore-forming agents gave rise to the enhancement of the drug release properties of the hydrogels due to the introduction of desirable pores within the network of the hydrogels. Study showed that the cumulative drug release has been substantially improved up to 71.05%, when hydrogel prepared with NaHCO3 pore-forming agent [31]. Gao and co-workers [11] prepared a pH susceptible xylan-based hydrogels with *N*-isopropylacrylamide (NIPAm) and acrylic acid (AA) using *N,N*′-methylene-bis-acrylamide (MBA) as a cross-linker and 2,2-dimethoxy-2-phenylacetophenone as a photoinitiator by using ultraviolet irradiation. The prepared hydrogels showed efficient encapsulation efficiency of acetylsalicylic acid (upto 97.6%) and cumulative release of 26.35 and 90.12% in the gastric and intestinal fluid, respectively. The porous xylan-β-cyclodextrin based hydrogels were synthesized by using glycol diglycidyl ether as a crosslinker in alkaline medium. The model drugs of curcumin and 5-fluorouracil (5-FU) were loaded 26 and 56%, respectively. Furthermore, the hydrogels were showed the highest cumulative release of 37% curcumin and 56% 5-FU and after 24 hours [32].

## **7. Conclusions**

The most of the drugs have been reported to be unstable in the gastric environment and are susceptible to absorption in the upper gastrointestinal tract (GIT)

therefore; delivery of a drug to the targeted site via GIT requires protection. The protection of drugs can be achieved by encapsulation within polymeric network of xylan based-hydrogels. The drug-loading and drug-release profile can further be enhanced by pore-forming agent. The non-cytotoxic and biocompatible nature of hydrogels endow to skin care application. The photosensitizers encapsulated hydrogels showed promising antimicrobial treatment to overcome the challenges of multidrug resistant bacteria. The acetylated xylan-based polymeric network of hydrogels encapsulates the magnetic nanoparticles which endow the excellent catalytic activity and provide a sensitive response to H2O2 detection even at low concentration.
