Synthesis and characterization of functional polyesters tailored for biomedical applications

Adsorption mechanism and modelling of hydrocarbon contaminants onto rice straw activated carbons

The adsorption of Diphenolic acid (DPA), 2,4-Dichlorophenoxyacetic acid (2,4-D), and 2-methyl-4-chlorophenoxyacetic acid (MCPA) were examined in aqueous solution using activated carbon rice straw. The rice straw was activated by using two reagents, zinc chloride and phosphoric acid and named as RSZ, RSP, respectively. The results showed that both carbons have a relatively high adsorption capacity. Concerning the adsorption kinetic, the second-order model has better fit than the first model to experimental data. The adsorption yield of both carbons increased in the order: DPA < 2,4-D < MCPA. The pore volume diffusion model satisfactorily fitted the experiment on both carbons. Furthermore, solution pH has a high influence on the adsorption capacity for both carbons. The adsorption mechanism of selected pollutants onto carbon samples has been controlled by dispersion interaction π-π electrons and electrostatic interaction, moreover, the contribution of pore volume diffusion is the controlling mechanism of the overall rate of adsorption.

Preparation and characterization of biodegradable amphiphilic polymers and nanoparticles with high protein-loading capacity

Multiblock copolymers containing carboxyl groups in the side-chains and at the chain ends were prepared from ABA triblock copolymers of ε-caprolactone, or lactide (as A block), and ethylene glycol (as B block). ABAn multiblock copolymers were prepared after chain-end functionalization and chain extension with pyromellitic dianhydride. A series of polymers were synthesized by varying the poly(ethylene glycol) and polyester molecular weight and the chirality of the lactide. Nuclear magnetic resonance analysis was used to confirm free carboxyl groups in the polymer backbone and at the chain ends. Thermal analysis indicated that the presence of pyromellitic dianhydride residues interfered not only with the formation of crystalline phases but also with the thermal degradation of chain-extended polymers. The biocompatibility of these amphiphilic polymers as evaluated with mouse embryo fibroblasts was acceptable. Both the parent ABA triblock copolymers and the carboxylated polymers were processed into nanoparticles. Depending on the polymer structure and reaction conditions, a narrow size nanoparticle distribution from ~10 to 250 nm was obtained. The nanoparticles were loaded with 60%–90% albumin and released 80%–90% of the albumin absorbed. Overall, this system was found to be well suited for the preparation of high-capacity injectable protein drug delivery.

Nanoparticles made of multi-block copolymer of lactic acid and ethylene glycol containing periodic side-chain carboxyl groups for oral delivery of cyclosporine A

The purpose of this study was to evaluate the potential of new carboxylated multi-block copolymer of lactic acid and ethylene glycol (EL14) for nanoparticle (NP) formation and their ability to deliver high molecular weight hydrophobic drug--cyclosporine A (CsA). CsA-loaded EL14 NPs were compared with traditional poly(lactide-co-glycolide) (PLGA) NPs, both prepared by emulsion-diffusion-evaporation process. On the one hand, the increase in drug payload from 10 to 30 per cent for EL14 NPs showed no difference in particle size, however the entrapment efficiency tends to decrease from 50 to 43 per cent; on the other hand, the more hydrophobic PLGA showed an increasing trend in entrapment efficiency from 20 to 62 per cent with increasing particle size. Over 90 per cent of CsA was released in vitro from both the nanoparticulates; however, the release was much slower in the case of more hydrophobic PLGA. On in vivo evaluation in rats, the NPs made of EL14 showed a higher C(max), a faster T(max) and enhanced tissue levels to that of PLGA that are crucial for CsA's activity and toxicity; however, the overall bioavailability of the nanoparticulates was similar and higher than Neoral. Together these data demonstrate the feasibility of NPs made of low molecular weight, hydrophilic polymer EL14 for efficient delivery of CsA.