Controlled release of tetracycline hydrochloride from silica based polycaprolactone nanohybrides

Abstract

Biomaterials can be synthetic or natural materials which is designed for interact with the biological systems. There are various type of biomaterials such as metals, seramics and polymers. Biodegradable biomaterials that naturally degrade or completely dissolve in their physiological environments have gained attention for both invasive and noninvasive health monitoring due to providing an unique opportunity for therapeutic field. Biodegradable polymers are classified into two main categories as natural and synthetic polymers. Polymers offer high adjustability in terms of their chemical structure and morphology and they contain hydrolysable bonds and these bonds makes them prone to chemical degradation via hydrolysis or enzymecatalyzed hydrolysis. Biodegradable polymers are using in controlled drug delivery, anticancer drug delivery, protein and peptide delivery, gene delivery, and enzyme immobilization at industry and researches. Biodegradable polymers can degrade in two main ways; partially or fully degrade to monomeric units. Polymers' degradation rate is heavily affected by various factors. Examples of these factors are the following such as the morphology, molecular weight, its distribution, crystallinity temperature and environmental conditions. Polylactic acid (PLA), polyglycolic acid (PGA), poly(lactic-co-glycolic acid (PLGA) and poly(ε-caprolactone) (PCL) are some of the most used synthetic biodegradable polymers. These are polyester polymers that have chemical structure with ester bond linkages and these polymers most used in industry are aliphatic polyesters. Polycaprolactone (PCL) is a linear aliphatic polyester hydrophobic semi-crystalline. PCL can synthesis with two different methods. These are the condensation of epsilon-hydroxycaproic acid and the ringopening polymerisation (ROP) of e-CL. In the condensation of epsilon-hydroxycaproic acid which is a polycondensation, 6-hydroxycaproic acid is polymerising by using lipase from Candida antarctica. ROP is the most preferred route and it gives a polymer with a higher molecular weight and a lower polydispersity. PCL is mainly synthesized by ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) monomer. There are three different ROP catalytic system and metal-based catalysts are the most used catalysts for ROP of ε-CL. The metal based compounds takes part in the ROP of lactones can be describe as catalysts, initiators, initiating systems or catalytic systems. PCL have wide applicability and advantage such as biocompatibility, controlled degradability, miscibility with other polymers, and if its properties can be controlled and it can be made inexpensively, it can be a very useful polymer. Drug delivery systems (DDSs) are developed to prevent problems such as reducing therapeutic efficacy and causing unwanted side effects for improving drug safety and helping to improve patient compliance and convenience. DDS have many important applications in every field of medicine such as cancer, pain, diabetes and ischemia, myocardial treatment. Release pattern of DDS mainly effect by the delivery vehicle , the drug properties, and the environmental conditions. Drug delivery systems varies based on their route, mechanism and materials used in and there are several approaches of DDS. One of these approaches is polymers that used in a variety of fields in pharmaceutical applications. Polymers have advantages in DDSs as providing controlled release of therapeutic agents in constant doses over long periods and their cyclic dosage, and tunable release of both hydrophilic and hydrophobic drugs. In the first part of this study performed RHA preparation and activation of RHA, immobilization followed by polymerization to obtain nanohybrid polymers. Rice husk ash (RHA) is obtained by burning husks of rice. prepared and then silanized with 3-Glycidoxypropyltrimethoxysilane (3-GPTMS). RHA silanized by using 3-GPTMS as support material to immobilize free enzyme Candida antarctica lipase B. Enzymatic ring-opening polymerization (eROP) of ɛ-caprolactone was provided by immobilized lipase enzyme Candida antarctica lipase B (CALB). eROP reaction started along with ε-caprolactone and immobilized enzyme, then G-PCL/RHA nanohybrid obtained after terminating the reaction with chloroform followed by the precipitation. In the second part of the study microspheres prepared by trying different conditions to find best efficiency ones and followed by Drug release experiment to the highest effiency microspheres. Drug loaded microspheres were prepared by W/O/W double-emulsion-evaporation method which is water-in-oil method. Since the drug used in study is a water-soluble drug active substance, have to find the right ratio for both PVA and drug amount. Because of this, tried to find best PVA percentage by using different PVA percentages. Here found the best ratio is %1 PVA. Then looked at the drug amounts by preparing microspheres in %1 and different drug amounts. G-PCL/RHA drug-loaded microspheres with best drug loading efficiency we can get were obtained. Drug release experiments were carried out at pH 7.4 condition The release profiles of the drug-loaded G-PCL/RHA microspheres were determined and afterwards the drug release percentages are calculated. According to drug release results, the highest cumulative drug release percentage was %56 at pH 7.4 in %0.5 PVA, 10mg drug amount conditions microspheres with 72 hours burst level and %29 drug loading. Meanwhile the highest drug loading, efficiency, was in %1 PVA and 10mg drug amount conditions with %54 drug loading. In the last part of study, experiments has been finalized with charactization of microspheres to analyse microspheres by using Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). FTIR spectra of G-PCL/RHA nanohybrid and drug-loaded G-PCL/RHA microspheres were compared along with literature tetracycline hydrochloride FT-IR spectra and the presence of tetracycline hydrochloride in the micropheres demonstrated. FT-IR results showed both G-PCL/RHA nanohybride and tetracycline FT-IR spectra on G-PCL/RHA microspheres FT-IR results. This proved the tetracycline hydrochloride presence on G-PCL/RHA nanohybrid microspheres. TGA results showed the decomposition temperatures and organic weight losses of drug-loaded G-PCL/RHA microspheres and tetracycline hydrochloride. According to DSC analysis, showed the melting and crystallization points of PCL polymer. Microsphere structures were observed by SEM analysis. Particles of the G-PCL/RHA microspheres were seen to be spherical and sphere-like structures with various size but they were more disadvantage cause of not being as highly porous compare to the literature microspheres. For better understanding drug-polymer interactions and higher how to get higher drug efficiency of microspheres on drug release mechanism, analysis methods can be developed in further studies. Beside drug release of hydrophylic drugs loaded microspheres can be carried out in vivo. Such studies exist in the literature.