الفهرس 
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Abstract
In drug delivery applications, a biodegradable polymer acts as a transient mask which protects the therapeutic agent from physiological degradation until the desirable, organ is reached. Controlled drug release also improves patient compliance. The reduced need for repetitive dosing is a relief to many patients, including the elderly and those who are chronically ill. By placing the polymer implant adjacent to the surgical site, drug delivery is enhanced in the appropriate tissues, and the efficacy of the therapeutic agent is improved. Potentially toxic drugs, typically anticancer agents, can be delivered in high concentrations to the tumor site, increasing the efficiency and at the same time minimizing systemic exposure and subsequent side-effects.
In the current work, five diblock copolymers were synthesized to be used as drug delivery carriers. The diblock copolymers consisted of poly (e-caprolactone) (PCL) as a hydrophobic segment and methoxy poly (ethylene glycol) (mPEG) as a hydrophilic segment. The copolymerization was carried out by the ring opening polymerization of e-caprolactone monomer in presence of methoxy poly (ethylene glycol) as a macroinitiator using stannous octoate as a catalyst. The prepared methoxy poly (ethylene glycol)/ poly (caprolactone) (PECL) diblock copolymer was characterized by different tools including FT-IR, ‘H-NMR, DSC, and WXRD to confirm its structure.
The well defined PECL diblock copolymers were formed into nanoparticles using two techniques, nanoprecipitaion and emulsion-solvent evaporation. The prepared nanoparticles were characterized for morphology by SEM, particle size and zeta-potential. The results showed that the prepared nanoparticles had size ranging from 43.24 - 68.56 nm with monomodal size distribution. SEM showed that the nanoparticles were spherical with smooth surface. Aluminum phthalocyanine chloride (AlPc), a photosensitizer used in photodynamic therapy (PDT), was incorporated into PECL nanoparticles by a nanoprecipitaion method. The average size of drug-loaded nanoparticles ranged from 66.46 to 99.14 nm. The encapsulation efficiency of the drug-loaded nanoparticles was 78% approximately.
The in vitro release of aluminum phthalocyanine chloride (AlPc) from PECL nanoparticles were assessed for the drug loaded PECL-2 nanoparticles as well as drug loaded PECL-5 nanoparticles, which represent lowest and highest molecular weight, respectively. Data for in vitro release of AlPc from two selected nanoparticles formulations indicated a triphase release pattern. A fast release phase after the first day 3f AlPc located at or near the nanoparticle surface followed by a slow release phase after 7 days characteristic of diffusion of AlPc entrapped in the polymer matrix