Synthesis Of Polyphosphazenes Containing Different Side Groups And Their Application In Drug Control Release

Polyphosphazenes (PPHOSs) are hybrid inorganic-organic class of polymers with wide range of properties from rubber like behavior to potential for biomedical applications such as tissue engineering and drug delivery applications. PPHOSs have inorganic backbone and organic side groups of various types and these side groups determine the properties of PPHOSs. The simplest example is polydichlorophosphazene (PDCP), which has nitrogen and phosphorous attached with alternative single and double bonds and has two reactive chlorines attached on each repeating unit. The macromolecular substitution of these chlorines with suitable organic nucleophiles determines the properties of final polymer. An infinite number of nucleophilic groups can be replaced over PDCP backbone and produce polymers of versatile range of properties.Recently, many kinds of PPHOSs with different side groups were synthesized, which have ability to self-assemble into nanoparticles or blend with other kind of polymers to prepare such material that can be used for drug delivery or tissue engineering applications.In this regard, PPHOSs with different kind of side groups were synthesized and characterized by 1H-NMR,31P-NMR and GPC. Depending upon the structure of synthesized polymers, their blending ability with other biocompatible polymers and ability to self-assemble into nanoparticles were studied. The miscibility of synthesized polymers with other biocompatible polymers was studied by FTIR and DSC. For drug release applications, drug loaded microspheres, nanoparticles and nanofibers were fabricated and in vitro drug release kinetics was studied at physiological conditions.Drug delivery system is referred as an approach to deliver the therapeutic agents to the target site safely in order to achieve the maximum therapeutic effects. In this perspective, synthesis of three PPHOSs poly[bis(butyl p-oxybenzoate diethylamino)phosphazene] (PPOBADEAP), poly[bis(methyl 4-(2-hydroxyethoxy) benzoate diethylamino) phosphazene] (PHEBDEAP) and poly[bis(ethyl salicylate butyl p-oxybenzoate)phosphazene] (PESPOBP) was described. The successful synthesis was confirmed by 1H-NMR,31P-NMR and GPC. In order to obtain unique properties, PPOBADEAP, PHEBDEAP and PESPOBP were blended with poly(methyl methacrylate) (PMMA). The miscibility of resultant blends was studied by DSC. It was found that synthesized PPHOSs were partially miscible with PMMA. Furthermore, these novel blends were used to fabricate microspheres and evaluated for sustained release of hydrophilic drug (aspirin as model drug). Empty and aspirin loaded microspheres were fabricated by oil-in-oil-in-water (o/o/w) emulsion solvent evaporation method. Fabricated microspheres were spherical in shape with porous surface. The size of microspheres was less than 240 μm. Microspheres of the two blends showed excellent encapsulation efficiency (about 93%), controlled burst release (2.3% to 7.93%) and exhibited sustain in vitro drug release (13.44% to 32.77%) upto 218 hours. The degradation study of these microspheres was carried out by GPC and Scanning Electron Microscopy (SEM). At physiological conditions, the surface degradation of microspheres and diffusion process controlled the drug release sustainability. Furthermore, it was found that the degree of porosity was increased with degradation and the resulting porous network was responsible for water retention inside the microspheres. The percentage water retention was found to be interrelated with degradation time and percentage drug release.The purpose of this study was to develop anticancer drug carrier, which involves the encapsulation of camptothecin (CPT). In this regard, the synthesis of novel and biodegradable amphiphilic poly[bis(polyethylene glycol 1-adamantanamino)phosphazene] (PPGAPs) composed of polyethylene oxide (PEG) and 1-(1-adamantyl)ethylamine (1ADA) as side groups was reported. In first step, PEG was grafted on PDCP backbone via replacement reaction between chlorine atoms of PDCP and hydroxyl group of PEG. Then remaining chlorine atoms were replaced with 1 ADA to synthesized PPGAPs. The successful synthesis of PPGAPs was confirmed by the 1H-NMR,31P-NMR and GPC. It was found that the mole ratios of 1ADA to polyethylene oxide are 1.78:0.22, and 1.9:0.095 in PPGAP-1 and PPGAP-2 respectively. The critical micellization concentration (CMC) was measured by fluorescence probe technique using nile red and was found to be less than 60 μg/mL. The CMC values for PPGAP-1 and PPGAP-2 were 54.73 μg/mL and 6.58 μg/mL. The micellization behavior of PPGAPs was evaluated by transmission electron microscopy (TEM) and micelle size was less than 80nm for PPGAPs, which was in accordance for drug delivery applications. The lipophilic character of 1ADA facilitates the PPGAPs to self-assemble at lower concentrations. CPT was loaded to the fabricated micelles by dialysis method. The CPT encapsulation efficiency was less than 25%. However, percentage encapsulation efficiency and loading contents for PPGAP-1 and PPGAP-2 were found 22.64%,2.8% and 15.2%,1.9% respectively. The results showed that the interaction between 1ADA and CPT molecules was poor. The release behavior of CPT from micelles was conducted at physiological conditions (pH 7.4 and 37℃ temperature). The percentage CPT release contents were determined by fluorescence spectroscopy. The CPT loaded micelles retained the loaded cargo molecules inside upto 31 hours.80-85 loaded CPT was released from micelles within 31 hours. Finally, the hydrolytic degradation study for PPGAPs was conducted by 31P NMR. Throughout 5 weeks of degradation study, appearance of phosphate peaks at ～0 ppm confirmed the degradation.Reductive responsive nano-vehicles have ability to deliver the anticancer drugs to the intracellular compartments. The purpose of this study was to develop reductive sensitive nano-carriers based on polyphosphazenes. Amphiphilic polyphosphazenes with hydrophilic reductive sensitive side group were synthesized and characterized. The reductive sensitive PEG (PEG-SS-NH2) was synthesized via two steps. In first step, PEG was allowed to react with 4-nitrophenyl chloroformate (4NPC) to produce reactive intermediate. Then in second step, reactive intermediate was allowed to react with cystamine to prepare PEG-SS-NH2. The peaks at 7.36 ppm for -NH2,4.41 ppm for-NH and 3.50 ppm for PEG repeating confirmed the synthesis of PEG-SS-NH2. Then for the synthesis of poly[bis(D-phenylalanine methylate PEG-SS-amino) phosphazenes] (PDPPs) first PEG-SS-NH2 was grafted on PDCP backbone via macromolecular replacement reaction. Then D-phenylanine ester (DMPE) was allowed to react partially substituted PDCP. Finally, the successful synthesis of PDPPs was confirmed with 1H-NMR,31P-NMR and GPC. The synthesized copolymers showed solvent dependent self-aggregation and form spherical micelles by using THF as co-organic solvent in dialysis method. Nile red is a fluorescent dye and at proper spectral conditions, it can be used to detect lipophilic micro-environments by using fluorescent spectroscopy. CMC values for PDPPs was found ranging from 5.73 μg/mL to 11.24 μg/mL. CMC value depends on the combination of hydrophilic and hydrophobic mole ratios. The CMC value can be changed by altering the mole ratio of the hydrophilic and hydrophobic side groups. Micelles can encapsulate the hydrophobic drug such as CPT and IND. The obtained micelles were spherical in shape with size ranging from -37 nm to -114 nm. In this study, CPT was selected as model anticancer drug to evaluate the carrying and release ability of bioreducable PDPPs. In in vitro release experiments, CPT loaded micelles release the 70% to 80% of the loaded CPT in the presence of reducing agent (DTT) within 15 hours. The results indicated that these reductive sensitive amphiphilic polyphosphazenes may find an application as anticancer drug carriers for safe drug delivery.Controlled drug delivery using nanofiber drug reservoirs is a widely explored area to maximize the therapeutic efficiency, stability and bioavalaibility of the drugs. The aim of present study was to develop drug loaded electrospun nanofibers for sustain release applications. Two types of polyphosphazenes (PPHOSs) were synthesized. One type was hydrophobic containing butylparaben/diethylamine as side groups and another type was hydrophilic containing PEG/1 ADA as side groups. The complete replacement of side groups on PDCP backbone confirmed by 1H-NMR and 31P-NMR. The synthesized PPHOSs were homogeneously blended with PLGA. The resultant mixture of polymers (blend) shows properties both of the parent polymers. Normally, FTIR and DSC measurements were applied to study the miscibility of the polymer blends. The DSC curve for PPOBADEAP/PLGA shows a single Tg at 23.03℃, which is higher than theoretical value. Though appearance of single Tg was the evidence of miscibility of PPOBADEAP with PLGA. On the other hand, the miscibility study of PPGAP/PLGA was not clear from DSC study. Indomethacin (IND) and camptothecin (CPT) loaded nanofibers based on PPHOSs/PLGA blends were fabricated. First IND as a model hydrophobic drug was loaded into PPHOSs/PLGA nanofibers with 2% and 5% by weight with respect to polymer weight and then CPT was loaded to the PPHOS/PLGA nanofibers. The homogeneous entrapment of drugs was characterized by FTIR, DSC, SEM, TEM and fluorescence microscope. The interaction of polymer blends with IND was investigated by FTIR and DSC curves. For carbonyl region, The red shift of peaks was the evidence that IND was uniformly dispersed or physically crosslinked in polymeric network. The increase in Tg with the increase in IND concentration was the evidence that IND molecules might have physical interaction with polymeric chains via hydrogen bonding and such interaction was also confirmed from FTIR results. Furthermore, the uniform distribution of CPT without crystallization inside fibers was further confirmed in similar way. Finally, in vitro performance of CPT loaded nanofibers was studied. The initial burst release of drug was higher in case of PPGAP/PLGA than PPOBADEAP/PLGA. Nanofibers released the cargo CPT in a sustain pattern. Within 4.5 hours,17%-44% CPT was released from drug loaded nanofibers. In addition, it was found that hydrophilic PPHOS/PLGA nanofibers released CPT faster than hydrophobic PPHOS/PLGA nanofibers.