Modification of the dynamic swelling behaviour of poly(2-hydroxyethyl methacrylate) hydrogels in water through interpenetrating polymer networks (IPNs)

Photopolymerized Starchstarch Nanoparticle (SNP) network hydrogels

Starch is an attractive biomaterial given its low cost and high protein repellency, but its use in forming functional hydrogels is limited by its high viscosity and crystallinity. Herein, we demonstrate the use of fully amorphous starch nanoparticles (SNPs) as functional hydrogel building blocks that overcome these challenges. Methacrylation of SNPs enables hydrogel formation via photopolymerization, with the low viscosity of SNPs enabling facile preparation of pre-gel suspensions of up to 35 wt% SNPs relative to <10 wt% with linear starch. Small angle neutron scattering indicates a significantly different microstructure in SNP-based hydrogels compared to linear starch-based hydrogels due to the balance between inter- and intra-particle crosslinks, consistent with SNPs forming denser and stiffer hydrogels. Functionalized SNPs are highly cytocompatible at degree of substitution values <0.25 and, once gelled, can effectively repel cell adhesion. The physicochemical versatility and biological functionality of SNP-based hydrogels offer potential in various applications.

Evaluation of the controlled release ability from the poly(2-hydroxyethyl methacrylate-co-3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]-undecane) polymer network synthesized in the presence of β-cyclodextrin

The study presents the possibility to use the 2-hydroxyethyl methacrylate--HEMA copolymer with a comonomer with spiroacetal moiety, 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]-undecane)-U, as polymer network for loading the indomethacin--INN as drug model, and also, the controlled release evaluation of the prepared bioactive system. The macromolecular compounds were prepared by radical dispersion polymerization in the presence of a pair of surfactants. The use of cyclodextrin as surfactant allowed the building of the host-guest complexes by inclusion of hydrophobic molecules. Also, the cyclodextrin supplemented the hydrogen bonds and the hydrophobic interactions responsible for the stability of the achieved complexes. The copolymers composition and the INN inclusion onto the polymeric matrix were confirmed by FTIR analysis. The porous structure of the lyophilized P(HEMA-U) samples was illustrated by SEM images. The swelling studies evidenced the interdependence between P(HEMA-U) network properties and the spiroacetal moiety amount. Thus, the copolymers presented the increase of the equilibrium swelling degree with pH and temperature. Also, the polymeric matrices manifested dual sensitivity with pH and temperature. The in vitro release of the INN drug from the polymeric network as well as the in vivo experimental studies evidenced the benefit consequence of the spiroacetal compound presence. The clinical observation of the experimental groups does not show any behavioral modifications to suggest a possible toxic effect of these polymeric formulations with and without INN.

Investigation on magnetically controlled delivery of doxorubicin from superparamagnetic nanocarriers of gelatin crosslinked with genipin

Gelatin (Type B) nanoparticles were prepared by a single W/O emulsion technique and characterized by infrared (IR) spectra, transmission electron micrographs (TEM), surface potential measurements and magnetization studies. Whereas the IR spectra clearly confirmed the presence of gelatin, genipin and doxorubicin in the loaded nanoparticles, the transmission electron micrographs (TEM) image depicts smooth surface, spherical shape and non-uniform size of nanoparticles (up to 100 nm). The prepared nanoparticles were loaded with doxorubicin, a well known anticancer drug, and in vitro release dynamics of entrapped drug was investigated as a function of various experimental factors such as percent loading of the drug, chemical architecture of the nanocarriers, and pH, temperature, ionic strength and nature of the release medium in presence and absence of magnetic field. The nanoparticles were also studied for their water sorption capacity. The drug release process was analyzed kinetically using Ficks power law and a correlation was established between the quantity of released drug and swelling of the nanoparticles.

Oral Controlled Release Dosage Forms. II. Glassy Polymers in Hydrophilic Matrices

Part I of this article reported general considerations of oral controlled release dosage forms and the applications of cellulose ether polymers in hydrophilic matrices. Part II of this study describes the advantages and disadvantages of limited swelling hydrophilic matrices, their preparation, mechanism, and parameters affecting drug release from these systems.

Fibrinogen adsorption onto macroporous polymeric surfaces: correlation with biocompatibility aspects

The present work focus on the adsorption of fibrinogen (Fgn) on to the semi-interpenetrating polymer networks (IPNs) of polyethylene glycol (PEG) and poly(2-hydroxyethyl methacrylate-co-acrylonitrile) and attempts to correlate the adsorption behaviour of proteins to the blood compatible aspects of the polymeric surfaces. The semi-IPNs were prepared by copolymerizing 2-hydroxyethyl methacrylate and acrylonitrile in the presence of PEG and a crosslinker ethyleneglycol dimethacrylate (EGDMA). The prepared spongy gels were characterized by FTIR and Environmental Scanning Electron Microscopy (ESEM) for structural and morphological analysis. The prepared semi IPNs were studied for their water sorption capacity and the data were utilized to evaluate network parameters such as average molecular weight between crosslinks (M(c)) and crosslink density (q). The adsorption of Fgn was carried out on to the prepared polymeric matrices and static and dynamic aspects of the adsorption process were investigated. The adsorption process was also studied as a function of pH and ionic strength of the protein solution and chemical architecture of the semi IPN. The antithrombogenic properties of the IPN's were also judged and correlated with water sorption and protein adsorption findings.

Dynamics of controlled release of heparin from swellable crosslinked starch microspheres

The microspheres of crosslinked starch have been prepared and characterized by IR spectral analysis and SEM technique. The prepared microspheres were loaded with an anticoagulant drug 'heparin' and the kinetics of in-vitro release of heparin was investigated spectrophotometrically at physiological pH (7.4) and body temperature (37 degrees C). The influence of percent loading of heparin, chemical architecture of the microspheres and pH of the release medium were examined on the release profiles of the drug. The chemical stability of heparin was tested in phosphate buffer saline (pH 7.4) and the release was also studied in various simulated biological fluids.

Studies on alpha-amylase induced degradation of binary polymeric blends of crosslinked starch and pectin

A blend matrix of crosslinked starch and pectin was prepared and characterized by infra-red (IR) spectroscopy, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The prepared blends were investigated kinetically for water sorption studies and alpha-amylase induced degradation adopting a gravimetric procedure. Based on the experimental findings, a plausible mechanism including both diffusion and surface enhanced degradation was suggested and degradation profiles were interpreted. The influence of various factors such as chemical architecture of the blend, pH and temperature of alpha-amylase solution were examined for the swelling and degradation kinetics of crosslinked starch-pectin blends. The effect of concentration of enzyme solution was also studied on the degradation profile of the blends. A correlation was established between the extent of degradation and water imbibing capacity of the degrading blends.

Design of gelatin nanoparticles as swelling controlled delivery system for chloroquine phosphate

Gelatin nanoparticles were prepared by a single W/O emulsion technique and characterized by infrared (IR) spectra, scanning electron microscopy (SEM) and particle size analysis. The prepared nanoparticles were loaded with chloroquine phosphate (CP), a well known antimalarial drug, and the release dynamics of entrapped drug was investigated as a function of various experimental factors such as percent loading of the drug, chemical architecture of the nanocarriers, and pH, temperature, ionic strength and nature of the release medium. The nanoparticles were also studied for their water sorption capacity by optical microscopic method taking advantage of the aggregation of nanoparticles. The drug release processes was analyzed kinetically using Ficks power law and a correlation was established between the quantity of released drug and swelling of the nanoparticles.

Effect of the crosslinking degree and the nickel salt load on the thermal decomposition of poly(2-hydroxyethyl methacrylate) hydrogels and on the metal release from them

Polymeric matrices of poly(2-hydroxyethyl methacrylate) (PHEMA) crosslinked with different percentages of ethylene glycol dimethacrylate (EGDMA) as well as different loads of nickel salt were synthesized. Nickel release from the polymeric systems, and their thermal stability were analyzed. A high percentage of the nickel loaded was released, although strong interactions between the polymeric matrices and the nickel ion must be established since a total nickel release did not take place. The values of the diffusion coefficients showed that nickel release depended on the amount of nickel salt loaded in the polymeric matrix and also on the crosslinking degree of the gels. On the other hand, the presence of nickel salt induced an evident thermal instability in the polymeric matrices, although all the polymeric systems can be considered thermally stable.

Water sorption dynamics of a binary copolymeric hydrogel of 2-hydroxyethyl methacrylate (HEMA)

The water imbibing property of poly(2-hydroxyethyl methacrylate) (poly HEMA) has been improved by copolymerizing HEMA with acrylamide in the presence of a hydrophilic polymer such as polyethylene glycol (PEG). The hydrogel was characterized by IR spectral analysis and several network parameters such as average molecular weight between crosslinks (Mc), crosslink density (q) and number of elastically effective chains were evaluated. The swelling ratio of the hydrogel was found to be influenced by varying the chemical architecture of the hydrogel, i.e. by changing the proportions of PEG, HEMA, acrylamide and crosslinking agent in the feed mixture of the hydrogel. The degree of water sorption was studied as a function of the experimental conditions such as the pH and temperature of the swelling medium and presence of salt ions in the outer solution. The dynamics of the swelling process was studied quantitatively and kinetic constants such as the swelling exponent (n) and diffusion constant (D) were also evaluated. The hydrogels prepared of varying composition were judged for antithrombogenic nature of their surfaces by blood-clot formation test.