PEG Content In Copolymers Research Articles

Temperature-sensitive polyethylenglycol/N-isopropylacrylamide hydrogels: Impact of material parameters on swelling and drug release

In this study, we fabricated Temprature-sensitive polyethyleneglycol/N-isopropylacrylamide (PEG/NIPAAm) hydrogels by a free-radical polymerisation method with variation in the content of monomer, polymer and cross-linking agent. Swelling was performed in USP phosphate buffer solutions of pH 7.4 for selected samples. It was observed that swelling and drug release from hydrogels can be modified by changing composition and degree of cross-linking of the hydrogels under investigation. As expected LCST increased from 34 to 39C as PEG content in copolymers increased from 2 to 8% (w/w). The presence of polyethyleneglycol in the hydrogel formulation resulted the higher mechanical strength and swelling. Network structure was evaluated by different parameters and FTIR confirmed the formation of cross-linked hydrogels. The percent swelling, equilibrium swelling, diffusion constant values are evaluated for PEG/NIPAAm hydrogels at 1% of Insulin solution at room temperature. Drug release increased by increasing PEG contents in hydrogels while increasing the concentration of cross-linking agent had the opposite effect. Based on the release kinetic of the Insulin drug, the hydrogels displayed a non-Fickian diffusion mechanism. According the diffusion kinetic data in hydrogels became clear that diffusion kinetic data were best described by Higuchi model. Permeation from PEG/NIPAAm hydrogels followed a Super Case II transport mechanism, most likely driven by macro molecular chain relaxation and swelling of hydrophilic polymers.

In vitro macrophage uptake and in vivo biodistribution of PLA–PEG nanoparticles loaded with hemoglobin as blood substitutes: effect of PEG content

The aim of the present work is to investigate the effect of PEG content in copolymer on physicochemical properties, in vitro macrophage uptake, in vivo pharmacokinetics and biodistribution of poly(lactic acid) (PLA)-poly(ethylene glycol) (PEG) hemoglobin (Hb)-loaded nanoparticles (HbP) used as blood substitutes. The HbP were prepared from PLA and PLA-PEG copolymer of varying PEG contents (5, 10, and 20 wt%) by a modified w/o/w method and characterized with regard to their morphology, size, surface charge, drug loading, surface hydrophilicity, and PEG coating efficiency. The in vitro macrophage uptake, in vivo pharmacokinetics, and biodistribution following intravenous administration in mice of HbP labeled with 6-coumarin, were evaluated. The HbP prepared were all in the range of 100-200 nm with highest encapsulation efficiency 87.89%, surface charge -10 to -33 mV, static contact angle from 54.25 degrees to 68.27 degrees , and PEG coating efficiency higher than 80%. Compared with PLA HbP, PEGylation could notably avoid the macrophage uptake of HbP, in particular when the PEG content was 10 wt%, a minimum uptake (6.76%) was achieved after 1 h cultivation. In vivo, besides plasma, the major cumulative organ was the liver. All PLA-PEG HbP exhibited dramatically prolonged blood circulation and reduced liver accumulation, compared with the corresponding PLA HbP. The PEG content in copolymer affected significantly the survival time in blood. Optimum PEG coating (10 wt%) appeared to exist leading to the most prolonged blood circulation of PLA-PEG HbP, with a half-life of 34.3 h, much longer than that obtained by others (24.2 h). These results demonstrated that PEG 10 wt% modified PLA HbP with suitable size, surface charge, and surface hydrophilicity, has a promising potential as long-circulating oxygen carriers with desirable biocompatibility and biofunctionality.

Possibility of wound dressing using poly(l-leucine)/poly(ethylene glycol)/poly(l-leucine) triblock copolymer

ABA-type block copolymers (abbreviated as LEL) composed of poly(L-leucine) (PLL) as the A component and poly(ethylene glycol) (PEG) as the B component were synthesized by ring-opening polymerization of L-leucine N-carboxyanhydride initiated by primary amino group located at both ends of PEG chain. A silver sulfadiazine (AgSD)-impregnated wound dressing of sponge type was prepared by the lyophilization method. Morphological structure of this wound dressing by scanning electron microscopy was observed to be composed of a dense skin layer and a porous inner layer. Equilibrium water content of LEL wound dressing increased with an increase in PEG content in the block copolymer due to the hydrophilicity of PEG. AgSD release from AgSD-impregnated wound dressing in PBS buffer (pH = 7.4) was dependent on PEG content in the block copolymer. Release of AgSD was increased in proportion to the PEG content in the copolymer. Antibacterial capacity of AgSD-impregnated wound dressing was examined in agar plate against Pseudomonas aeruginosa and Staphylococcus aureus. It was found that the suppression of bacterial proliferation in the wound dressing was dependent upon the PEG content. In cytotoxicity test, cell damage did not occur by the release of AgSD from the LEL sponge matrix of AgSD-medicated wound dressing. In in vivo test, granulous tissue formation and wound contraction for the AgSD- and dehydroepiandrosterone-impregnated LEL-2 wound dressing were faster than for any other groups.

Studies on Properties and Drug Delivery Systems of PTMC-b-PEG-b-PTMC Block Copolymers

ABSTRACT ABA type block copolymers of poly(trimethylene carbonate) with poly(ethylene glycol) were synthesized and characterized. The dynamic contact angle of PTMC-b-PGG-b-PTMC(PTPEPT) block copolymer film was determined. It revealed that the acceding angle (θa), decreased with the increase of PEG content in copolymers, indicating that the PEG fractions lead to higher hydrophilicity of PTPEPT copolymers. The potential application of PTPEPT copolymers for drug delivery systems was investigated. The measurement of drug delivery using PTPEPT as matrices showed that the release rate of Levonorgestrel (LNG) increased with the increase of hydrophilicity of copolymer samples. No obvious burst effect of release of LNG could be observed in the LNG/PTPEPT systems especially when the PTMC block became longer. In a short period, about 25 days, the release rate of LNG remained almost constant.

Synthesis and characterization of ABA-type block copolymer of poly(trimethylene carbonate) with poly(ethylene glycol): Bioerodible copolymer

ABA-type block copolymers of poly( trimethylene carbonate) with poly( ethylene glycol) (M n 6820), PTMC-b-PEG-b-PTMC, were synthesized by the ring-opening polymerization of 1,3-dioxan-2-one (trimethylene carbonate) in the presence of poly(ethylene glycol) with stannous octoate catalyst, and the copolymers with various compositions were obtained. The PTMC-b-PEG-b-PTMC copolymers were characterized with Fourier transform infrared and nuclear magnetic resonance spectroscopies. The intrinsic viscosities of resulting copolymers increased with the increase of 1,3-dioxan-2-one content in feed while the molar ratio of monomer over catalyst kept constant. It has been observed that the glass transition temperature (T g ) of the PTMC segments in copolymers, recorded from differential scanning calorimetry, was dependent on the composition of copolymers. The melting temperature (T m ) of PEG blocks in copolymer was lower than that of PEG polymer, and then disappeared as the length of PTMC blocks increased. The results of dynamic contact angle measurement clearly revealed that the hydrophilicity of resulting copolymers increased greatly with the increase of PEG content in copolymers.