In vitro biocompatibility of magnetic thermo-responsive nanohydrogel particles of poly(N-isopropylacrylamide-co-acrylic acid) with Fe3O4 cores: Effect of particle size and chemical composition

Poly(acrylic acid-co-acrylamide)/Polyacrylamide pIPNs/Magnetite Composite Hydrogels: Synthesis and Characterization

Novel composite hydrogels based on poly(acrylic acid-co-acrylamide)/polyacrylamide pseudo-interpenetrating polymer networks (pIPNs) and magnetite were prepared via in situ precipitation of Fe3+/Fe2+ ions within the hydrogel structure. The magnetite formation was confirmed by X-ray diffraction, and the size of the magnetite crystallites was shown to depend on the hydrogel composition: the crystallinity of the magnetite particles increased in line with PAAM content within the composition of the pIPNs. The Fourier transform infrared spectroscopy revealed an interaction between the hydrogel matrix, via the carboxylic groups of polyacrylic acid, and Fe ions, which strongly influenced the formation of the magnetite articles. The composites' thermal properties, examined using differential scanning calorimetry (DSC), show an increase in the glass transition temperature of the obtained composites, which depends on the PAA/PAAM copolymer ratio in the pIPNs' composition. Moreover, the composite hydrogels exhibit pH and ionic strength responsiveness as well as superparamagnetic properties. The study revealed the potential of pIPNs as matrices for controlled inorganic particle deposition as a viable method for the production of polymer nanocomposites.

Hybrid magnetic scaffolds: The role of scaffolds charge on the cell proliferation and Ca2+ ions permeation

Magnetic scaffolds with different charge densities were prepared using magnetic nanoparticles (MNP) and xanthan gum (XG), a negatively charged polysaccharide, or hydroxypropyl methylcellulose (HPMC), an uncharged cellulose ether. XG chains were crosslinked with citric acid (cit), a triprotic acid, whereas HPMC chains were crosslinked either with cit or with oxalic acid (oxa), a diprotic acid. The scaffolds XG-cit, HPMC-cit and HPMC-oxa were characterized by scanning electron microscopy (SEM), inductively coupled plasma atomic emission spectroscopy (ICP-AES), superconducting quantum interference device (SQUID) magnetometry, contact angle and zeta-potential measurements. In addition, the flux of Ca²⁺ ions through the scaffolds was monitored by using a potentiometric microsensor. The adhesion and proliferation of murine fibroblasts (NIH/3T3) on XG-cit, XG-cit-MNP, HPMC-cit, HPMC-cit-MNP, HPMC-oxa and HPMC-oxa-MNP were evaluated by MTT assay. The magnetic scaffolds presented low coercivity (<25Oe). The surface energy values determined for all scaffolds were similar, ranging from 43mJm^-2 to 46mJm^-2. However, the polar component decreased after MNP incorporation and the dispersive component of surface energy increased in average 1mJm^-2 after MNP incorporation. The permeation of Ca²⁺ ions through XG-cit-MNP was significantly higher in comparison with that on XG-cit and HPMC-cit scaffolds, but through HPMC-cit-MNP, HPMC-oxa and HPMC-oxa-MNP scaffolds it was negligible within the timescale of the experiment. The adhesion and proliferation of fibroblasts on the scaffolds followed the trend: XG-cit-MNP>XG-cit>HPMC-cit, HPMC-cit-MNP, HPMC-oxa, HPMC-oxa-MNP. A model was proposed to explain the cell behavior stimulated by the scaffold charge, MNP and Ca²⁺ ions permeation.

In situ synthesis of magnetic poly(N-tert-butyl acrylamide-co-acrylic acid)/Fe3O4 nanogels for magnetic resonance imaging

P(TBA-co-AA)/Fe₃O₄ nanogels were prepared by in situ synthesis with a small size of 118.9 nm and high r₂ relaxivity of 512.01 mM⁻¹ s⁻¹.

Antioxidant Gallic Acid-Functionalized Biodegradable in Situ Gelling Copolymers for Cytoprotective Antiglaucoma Drug Delivery Systems

In clinical ophthalmology, oxidative stress has been proposed as the initiating cause of ocular hypertension, which is one of the risk factors for glaucomatous damage and disease progression. In an attempt to improve the therapeutic efficacy of intracamerally administered pilocarpine, herein, a cytoprotective antiglaucoma drug delivery system composed of antioxidant gallic acid (GA)-functionalized gelatin-g-poly(N-isopropylacrylamide) (GN) biodegradable in situ gelling copolymer was developed for the first time. Analyses by UV-vis and Fourier transform infrared spectroscopies showed the formation of biopolymer-antioxidant covalent linkages in GNGA structures through a radical reaction in the presence of water-soluble redox initiators. The synthesized GNGA polymers with strong free radical scavenging effectiveness exhibited appropriate phase transition temperature and degradation rate as injectable bioerodible depots for minimally invasive pilocarpine delivery to the ocular anterior chamber. During the 2-week in vitro study, the sustained releases of sufficient amounts of pilocarpine for a therapeutic action in alleviating ocular hypertension could be achieved under physiological conditions. Results of cell viability, intracellular reactive oxygen species level, and intracellular calcium concentration indicated that the incorporation of antioxidant GA into GN structure can enhance cytoprotective effects of carrier materials against hydrogen peroxide-induced oxidative stress in lens epithelial cultures. Effective pharmacological responses (i.e., reduction of intraocular pressure and preservation of corneal endothelial cell morphology and density) in rabbits receiving intracameral GNGA injections containing pilocarpine were evidenced by clinical observations. The findings of in vivo studies also support the hypothesis that the GNGA carriers are more advantageous over their GN counterparts for the improvement of total antioxidant status in glaucomatous eyes with chronic ocular hypertension. The synthesized multifunctional molecules may be further used as potential polymer therapeutics for intraocular delivery of bioactive agents.

Low toxicity and long circulation time of polyampholyte-coated magnetic nanoparticles for blood pool contrast agents

Polyampholyte-coated (poly(acrylic acid) (PAA)-co-3-(diethylamino)-propylamine (DEAPA)) magnetite nanoparticles (PAMNPs) have been prepared as contrasting agent used in magnetic resonance imaging (MRI). Excellent biocompatibility is required for contrasting agents used in high-resolution magnetic resonance angiography. To evaluate the biocompatibility of PAMNPs, some experiments have been conducted. The hemolysis, plasma recalcification, dynamic blood clotting, prothrombin time, inflammatory cytokine release and complement system activation assays were carried out to investigate the hemocompatibility. To evaluate the toxicity to vessel, MTT test and vascular irritation tests were conducted. Tissue toxicity test was also performed to investigate the biocompability in vivo. We also looked into the biodistribution. The results showed that PAMNPs at the working concentration (0.138 mM) present similar hemocompatibility with negative control, thus have no significant effect to vessels. PAMNPs were mainly distributed in the liver and the blood. The circulation time in blood was considerably long, with the half-time of 3.77 h in plasma. This property is advantageous for PAMNPs' use in angiography. PAMNPs could be metabolized rapidly in mice and were not observed to cause any toxic or adverse effect. In short, these results suggest that the PAMNPs have great potential to serve as safe contrast agents in magnetic resonance imaging (MRI).

Magnetic thermoresponsive ionic nanogels as novel draw agents in forward osmosis

Magnetic thermosensitive ionic nanogels were prepared based on strong ionic monomer AMPS and thermosensitive monomer NIPAM via precipitation polymerization in the presence of Fe₃O₄ nanoparticles and investigated as draw solutes in FO.

In vitro toxicity evaluation of ultra-small MFe2O4 (M = Fe, Mn, Co) nanoparticles using A549 cells

As ferrite nanoparticles (MFe₂O₄) have been widely used in biomedical field, their safety evaluation has been paid great attention both in vitro and in vivo.

Interrelationship between cross-linking structure, molecular stability, and cytocompatibility of amniotic membranes cross-linked with glutaraldehyde of varying concentrations

Chemical cross-linker concentration has a marked influence on the interrelationship between cross-linking structure, molecular stability, and cytocompatibility of a glutaraldehyde-treated amniotic membrane for a limbal stem cell niche.

Biodegradable in situ gelling delivery systems containing pilocarpine as new antiglaucoma formulations: effect of a mercaptoacetic acid/N-isopropylacrylamide molar ratio

Ocular drug delivery is one of the most commonly used treatment modalities in the management of glaucoma. We have recently proposed the use of gelatin and poly(N-isopropylacrylamide) (PNIPAAm) graft copolymers as biodegradable in situ forming delivery systems for the intracameral administration of antiglaucoma medications. In this study, we further investigated the influence of carrier characteristics on drug delivery performance. The carboxyl-terminated PNIPAAm samples with different molecular weights were synthesized by varying the molar ratio of mercaptoacetic acid (MAA)/N-isopropylacrylamide (NIPAAm) from 0.05 to 1.25, and were determined by end-group titration. The preparation of gelatin-g-PNIPAAm (GN) copolymers from these thermoresponsive polymers was achieved using carbodiimide chemistry. Our results showed that the carboxylic end-capped PNIPAAm of high molecular weight may lead to the lower thermal phase transition temperature and slower degradation rate of GN vehicles than its low molecular weight counterparts. With a decreasing MAA/NIPAAm molar ratio, the drug encapsulation efficiency of copolymers was increased due to fast temperature-triggered capture of pilocarpine nitrate. The degradation of the gelatin network could greatly affect the drug release profiles. All of the GN copolymeric carriers demonstrated good corneal endothelial cell and tissue compatibility. It is concluded that different types of GN-based delivery systems exhibit noticeably distinct intraocular pressure-lowering effect and miosis action, thereby reflecting the potential value of a MAA/NIPAAm molar ratio in the development of new antiglaucoma formulations.

Effect of chemical composition on corneal cellular response to photopolymerized materials comprising 2-hydroxyethyl methacrylate and acrylic acid

Characterization of corneal cellular response to hydrogel materials is an important issue in ophthalmic applications. In this study, we aimed to investigate the relationship between the feed composition of 2-hydroxyethyl methacrylate (HEMA)/acrylic acid (AAc) and material compatibility towards corneal stromal and endothelial cells. The monomer solutions of HEMA and AAc were mixed at varying volume ratios of 92:0, 87:5, 82:10, 77:15, and 72:20, and were subjected to UV irradiation. Results of electrokinetic measurements showed that an increase in absolute zeta potential of photopolymerized membranes is observed with increasing the volume ratios of AAc/HEMA. Following 4 days of incubation with various hydrogels, the primary rabbit corneal stromal and endothelial cell cultures were examined for viability, proliferation, and pro-inflammatory gene expression. The samples prepared from the solution mixture containing 0-10 vol.% AAc displayed good cytocompatibility. However, with increasing volume ratio of AAc and HEMA from 15:77 to 20:72, the decreased viability, inhibited proliferation, and stimulated inflammation were noted in both cell types, probably due to the stronger charge-charge interactions. On the other hand, the ionic pump function of corneal endothelial cells exposed to photopolymerized membranes was examined by analyzing the Na(+),K(+)-ATPase alpha 1 subunit (ATP1A1) expression level. The presence of material samples having higher anionic charge density (i.e., zeta potential of -38 to -56 mV) may lead to abnormal transmembrane transport. It is concluded that the chemical composition of HEMA/AAc has an important influence on the corneal stromal and endothelial cell responses to polymeric biomaterials.