**1. Introduction**

Bone is the second most widely transplanted tissue after blood. More than 2.2 million bone graft operations are performed annually worldwide in order to repair bone defects in orthopedics and dentistry [1]. Bioactive glass ceramics (BGCs) are one of the most promising synthetic bone replacements come regeneration material which has the ability to chemically bond with living bone tissue and stimulate bone

growth without promoting inflammation or toxicity, developed by Larry Hench at the University of Florida in 1969 [1–4]. In early the heated glass powder, the microcomposite between apatite and β-wollastonite (CaO·SiO2) within a homogenous glassy phase showed not only a bioactivity but also high mechanical strength [4]. This BGCs was called A/W derived from the names of crystalline phase. The bioactivity of glass ceramics is believed to be due to the dissolution of calcium from wollastonite and/or the glassy phase. In case of treating bone defect, the bone regeneration rate depends on the material's composition [5]. Hydroxyapatite (HA) is the inorganic part of human bone [6]. The bonding with bone process is associated with the formation of HA layer on the implant's surface [7]. BGCs can either be synthesized by the melt quenching or sol–gel method. Early BGCs were prepared by the melt quenching method. Sol–gel processing was started practicing in early 1990s for bioactive glass synthesis. Sol–gel derived bioactive glasses are made of a colloidal silica solution synthesized by the hydrolysis of alkoxide precursor to form a sol. Tetraethyl orthosilicate (TEOS) is commonly used as silica precursor, Triethyl phosphate (TEP) is used to add phosphate, salt calcium nitrate used to introduce calcium and Na2O included to decrease the melting temperature [8, 9]. Sol–gel derived bioactive glasses can provide higher surface Si-OH groups, which promote active places for more functionalization. The greater specific surface area that enhance the rate of hydroxyapatite formation is considerably higher degree of bioactivity compare to the melt quenching process [10–12]. Mesoporous bioactive glass ceramics (MBGCs) are considered the third-generation bioactive glasses were developed in 2004 by the combination of sol–gel method. MBGCs can possess more optimal surface area, ordered mesoporous structure, variable pore size and volume, improved in *in vitro* apatite mineralization in simulated body fluid (SBF) comparing with non-mesoporous bioactive glasses (NBG) [13]. However, BGCs having higher specific surface area and pore volume accelerates the hydroxyapatite formation and increase prolong the bioactive behavior [9]. MBGCs also get focused because of having more potential applications, such as catalysis, adsorption/separation, nanomaterial synthesis and also in biomaterial science as bone scaffolds for drug delivery and bone regeneration [9].

Mesoporous bioactive glass ceramic (MBGC) has brought a significant revolution in material science in terms of drug delivery. MBGC has some important properties which make itself more potential for drug delivery, such as well-ordered pores, large pore volumes and high specific surface area. As a result, MBGCs can easily entrap the drug molecules with its highly ordered mesoporous channel with a pore range of 2 to 50 nm [12, 14–17]. These characteristics greatly enhance MBGC for bone forming bioactivity, higher drug loading efficiency and lower drug release kinetics comparing with conventional BGCs [18–21]. Moreover, the mesosized pore are too small to promote cell growth. To overcome this limitation, the macroporous networks was studied and it suitable for tissue scaffolds that mimic the structure of porous bone structure [1].

Sol–gel technology is a wonderful progression in science with various applications since 1800s [12]. It is the process of making ceramic and glass materials using relatively low temperature hydrolysis and condensation reaction followed aging, drying and thermal stabilization [1]. Use of different surfactants (eg: P123, F127) during MBGCs preparation amplify the pore volume and surface area, which enhance the drug loading efficiency [16]. 45S5 and S53P4 bioactive glasses with a system of SiO2-Na2O-CaO-P2O5 considered more attention for bone tissue regeneration and regeneration properties due to their excellent bioactivity, biocompatibility, osteogenic and angiogenic effects [4, 18, 22–24]. Perioglas® was the first commercial product of 45S5 glasses, later reestablished by NovaBone® and BoneAlive® commercialized with composition of S53P4 [4].

Conventional treatment of bone infections like osteomyelitis involves surgery to remove necrotic bone tissue and repeated irrigations combined with the use of *Three-Dimensionally Ordered Macroporous-Mesoporous Bioactive Glass Ceramics for Drug… DOI: http://dx.doi.org/10.5772/intechopen.95290*

systemic antibiotics administration, wound drainage and implant removal. Systemic therapy of antibiotics has various adverse effects and risk of developing bacterial resistance to drugs. Local drug delivery system solves the problems by providing more advantages including high drug delivery efficiency, continuous action, reduced toxicity and convenience to the patients. Administration of single dose of localized drug with desired therapeutic range can reduce the need for follow-up care, reduce the risk of side effects, toxicity and increase patient compliance [19, 20, 25].

In our study, the hierarchically macroporous structured and mesosized pores of 45S5 and S53P4 BGCs were synthesized by sol–gel method and evaluated their *in vitro* bioactivity. The bioactivity effects of both bioactive glasses were investigated in SBF solution. The *in vitro* drug release properties in PBS were evaluated. Gentamicin sulfate (GS) was chosen as a model drug to encapsulation in the MBGCs to obtain a drug delivery system. GS is a broad-spectrum bactericidal antibiotic belonging aminoglycoside class; antibacterial activity is due to its ability to irreversibly bind ribosomes and half bacterial protein synthesis. GS vastly used in orthopedic treatments [26–28].
