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Background: Development of pH-responsive nanoparticles capable of rapid degradation in the acidic environments in the endosomes and lysosomes of tumor tissues but relatively more stable in the physiological pH (pH 7.4) is desirable., Objective: To show that the number of methoxy groups on the benzene ring of benzaldehyde bisacrylate acetal crosslinkers should affect the rate of hydrolysis of the crosslinkers and in vitro availability of the drug loaded into the nanoparticles., Method: Three pH-sensitive acetal crosslinkers were synthesized and characterized by 1H NMR, 13C NMR, FT-IR and high resolution mass spectroscopy (HR-MS). The nanoparticles were fabricated by free-radical dispersion polymerization method. Hydrolysis studies were carried out on the crosslinkers and nanoparticles; drug release studies were done on docetaxel-loaded nanoparticles at pH 5.0 and pH 7.4. The statisitical experimental design was randomized complete block design followed by analyses of variance with F-test of significance. Pairwise comparison test was used to locate specific differences among parameters of the crosslinkers and the nanopaticles., Results: Scanning electron micrographs showed the formation of spherical particles. Particle size analysis showed that the nanoparticles are within nanosize range with negative zeta potential. Data showed that the rate of hydrolysis and drug release were faster at pH 5.0 compared to pH 7.4. Hydrolysis and drug release studies were dependent on the structure of the acetals: Di(2-methacryloyloxyethoxy)- [2,4,6-trimethoxyphenyl] methane crosslinker showed the fastest rate of hydrolysis, followed by di(2- methacryloyloxyethoxy)-[2,4-dimethoxyphe-nyl] methane and di(2-methacryloyloxyethoxy)-[4-methoxyphenyl] methane., Conclusion: The pH-responsive nanoparticles are suitable for the delivery of bioactive agents, especially anticancer drugs., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.)

Quality by design (QbD) in the pharmaceutical industry involves designing and developing drug formulations and manufacturing processes which ensure predefined drug product specifications. QbD helps to understand how process and formulation variables affect product characteristics and subsequent optimization of these variables vis-à-vis final specifications. Statistical design of experiments (DoE) identifies important parameters in a pharmaceutical dosage form design followed by optimizing the parameters with respect to certain specifications. DoE establishes in mathematical form the relationships between critical process parameters together with critical material attributes and critical quality attributes. We focused on the fabrication of biodegradable nanoparticles by dispersion polymerization. Aided by a statistical software, d-optimal mixture design was used to vary the components (crosslinker, initiator, stabilizer, and macromonomers) to obtain twenty nanoparticle formulations (PLLA-based nanoparticles) and thirty formulations (poly-ɛ-caprolactone-based nanoparticles). Scheffe polynomial models were generated to predict particle size (nm), zeta potential, and yield (%) as functions of the composition of the formulations. Simultaneous optimizations were carried out on the response variables. Solutions were returned from simultaneous optimization of the response variables for component combinations to (1) minimize nanoparticle size; (2) maximize the surface negative zeta potential; and (3) maximize percent yield to make the nanoparticle fabrication an economic proposition.

Purpose: Nanoparticle size is important in drug delivery. Clearance of nanoparticles by cells of the reticuloendothelial system has been reported to increase with increase in particle size. Further, nanoparticles should be small enough to avoid lung or spleen filtering effects. Endocytosis and accumulation in tumor tissue by the enhanced permeability and retention effect are also processes that are influenced by particle size. We present the results of studies designed to optimize cross-linked biodegradable stealth polymeric nanoparticles fabricated by dispersion polymerization., Methods: Nanoparticles were fabricated using different amounts of macromonomer, initiators, crosslinking agent and stabilizer in a dioxane/DMSO/water solvent system. Confirmation of nanoparticle formation was by scanning electron microscopy (SEM). Particle size was measured by dynamic light scattering (DLS). D-optimal mixture statistical experimental design was used for the experimental runs, followed by model generation (Scheffe polynomial) and optimization with the aid of a computer software. Model verification was done by comparing particle size data of some suggested solutions to the predicted particle sizes., Results and Conclusion: Data showed that average particle sizes follow the same trend as predicted by the model. Negative terms in the model corresponding to the cross-linking agent and stabilizer indicate the important factors for minimizing particle size.

The macromonomer method was used to prepare cross-linked, paclitaxel-loaded polylactide (PLA)-polyethylene glycol (stealth) nanoparticles using free-radical dispersion polymerization. The method can facilitate the attachment of other molecules to the nanoparticle surface to make it multifunctional. Proton nuclear magnetic resonance and Fourier transform infrared spectra confirm the synthesis of PLA macromonomer and cross-linking agent. The formation of stealth nanoparticles was confirmed by scanning and transmission electron microscopy. The drug release isotherm of paclitaxel-loaded nanoparticles shows that the encapsulated drug is released over 7 days. In vitro cytotoxicity assay in selected breast and ovarian cancer cell lines reveal that the blank nanoparticle is biocompatible compared with medium-only treated controls. In addition, the paclitaxel-loaded nanoparticles exhibit similar cytotoxicity compared with paclitaxel in solution. Confocal microscopy reveals that the nanoparticles are internalized by MCF-7 breast cancer cells within 1 h. Preliminary biodistribution studies also show nanoparticle accumulation in tumor xenograft model. The nanoparticles are suitable for the controlled delivery of bioactive agents., (© 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.)

A hydrolyzable crosslinker (N,O-dimethacryloylhydroxylamine (MANHOMA)) was synthesized by a modified method and was characterized using 1H-NMR, FTIR, and melting point determination. Naltrexone-loaded nanoparticles were prepared by copolymerization of poly(ethylene glycol)1000 monomethyl ether mono methacrylate (PEO-MA), methyl methacrylate (MMA) and N,O-dimethacryloylhydroxylamine (MANHOMA) in 0.4% poly(vinyl alcohol) aqueous solution. The nanoparticles were characterized by FTIR, particle size determination and transmission electron microscope (TEM). The TEM photomicrographs of the nanoparticles show a crosslinked core surrounded by a ring formed by the polyethylene glycol tail of PEO-MA. The loading efficiency of the nanoparticles and in vitro drug availability from the nanoparticles were investigated. The naltrexone-loaded hydrolyzable crosslinked nanoparticles were able to sustain the release of naltrexone for different periods of time, depending on the monomer feed composition. [Copyright &y& Elsevier]