Radiation synthesis of a thermo-pH responsive binary graft copolymer (PP-g-DMAEMA)-g-NIPAAm by a two step method

Thermo-pH-Salt Environmental Terpolymers Influenced by 2-((Dimethylamino)methyl)-4-methylphenyl Acrylate: A Comparative Study for Tuning Phase Separation Temperature

This study offers a comparison between three different types of thermoresponsive (TR) and thermo-pH-salt (TPR) multiresponsive polymers including homopoly(N-isopropylacrylamide) (PNIPAAm), copolymers with three different monomers, 2-hydroxyethyl methacrylate (HEMA), N,N-dimethylacrylamide (DMAAm), and styrene (S) at three different concentrations (5, 10, and 20 mol %), and a PNIPAAm terpolymer with 5, 10, and 20 mol % 2-((dimethylamino)methyl)-4-methylphenyl acrylate (DMAMCA) and 10 mol % HEMA, DMAAm, and S monomers. All polymers were chemically analyzed with 1H NMR and Fourier transform infrared spectroscopy (FT-IR) as well as gel permeation chromatography (GPC) for the molecular weights and dispersity and differential scanning calorimeter (DSC) for the glass transition temperatures. The cloud point, also known as the phase separation temperature (Cp), was determined for all polymers by a turbidity test using a UV-vis spectrophotometer; a micro-differential scanning calorimeter was used for measuring the cloud point in deionized water. The influence of a tertiary amine cationic group of DMAMCA changed the behavior of TR copolymers into TPR by shifting the cloud point of the TPR to higher values in acidic solutions (lower pH) and to lower values in alkaline solutions. The Cp was measured at different concentrations of Hofmeister kosmotropic and chaotropic anion salt solutions in a range of pH solutions for the terpolymers. It demonstrated the same behavior as mentioned in pH solutions besides the effect of salt ions. By measuring the Tc and Cp of these polymers, we can exploit various applications of stimuli-responsive materials for sensors and biomedical technology.

Two-step grafting of 2-hydroxyethyl methacrylate (HEMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) onto a polyethylene plate for enhancement of Cr(VI) ion adsorption

Polyethylene (PE) plates grafted with a neutral monomer, 2-hydroxyethyl methacrylate (HEMA), and a cationic monomer, 2-(dimethylamino)ethyl methacrylate (DMAEMA), (PE-g-PHEMA)-g-PDMAEMA plates were prepared by the two-step photografting. The Cr(VI) ion adsorption behavior of the (PE-g-PHEMA)-g-PDMAEMA plates was investigated as a function of the amounts of grafted HEMA, amount of grafted DMAEMA, initial pH value, and temperature. The adsorption capacity of the DMAEMA-grafted PE (PE-g-PDMAEMA) and (PE-g-PHEMA)-g-PDMAEMA plates had the maximum value at the initial pH value of 3.0, independent of the temperature. The adsorption capacity of (PE-g-PHEMA)-g-PDMAEMA plates increased with the amount of grafted HEMA (G_HEMA) in the first-step grafting. The increase in the water absorptivity of the grafted layers and thereby the increase in the degree of protonation of dimethylamino groups on grafted PDMAEMA chains were found to lead to the increase in the adsorption capacity. This adsorption capacity was higher than or comparable to those of other polymeric adsorbents for Cr(VI) ions. The Cr(VI) ion adsorption behavior on both PE-g-DMAEMA and (PE-g-PHEMA)-g-PDMAEMA plates obeyed the mechanism of the pseudo-second-order kinetic model and was well expressed by Langmuir isotherm. The high values of the Langmuir constant suggest that the adsorption of Cr(VI) ions occurs through an electrostatic interaction between protonated dimethylamino groups on grafted PDMAEMA chains and HCrO4- ions. Cr(VI) ions were successfully desorbed from PE-g-PDMAEMA and (PE-g-PHEMA)-g-PDMAEMA plates in eluents such as NaCl, NaCl containing NaOH, NH₄Cl, NH₄Cl containing NaOH, and NaOH.

Karaya gum-graft-poly(2-(dimethylamino)ethyl methacrylate) gel: An efficient adsorbent for removal of ionic dyes from water

In the present study, a novel hydrogel based on the polysaccharide, 'Karaya gum' has been synthesised by graft copolymerization and evaluated as an adsorbent for the removal of ionic dyes from aqueous solution. The hydrogel was made by simultaneous grafting and cross linking of Karaya gum using 2-(dimethylamino)ethyl methacrylate (DMAEMA) and N,N'-methylene-bis-acrylamide via microwave irradiation. The graft copolymer gel was characterized by FTIR, TGA, SEM techniques. The swelling of the gel studied in buffer media of varying pH revealed a pH responsive behaviour with a maximum swelling in neutral pH and a minimum swelling at pH 1.2. The temperature dependent swelling study indicated 40 °C as the lowest critical solution temperature. Kinetic studies indicated the swelling to be a second order process with Fickian diffusion as the water transport mechanism. The adsorption studies indicated maximum adsorption capacity of 89.28 and 101.42 mg/g towards methylene blue and indigo carmine respectively. The dye adsorption data is found to fit well with pseudo- second order kinetic model and the Freundlich adsorption isotherm model. The adsorption was found to be a multistep process with surface adsorption followed by intraparticle diffusion. Thermodynamic studies revealed the adsorption of dyes to be spontaneous.

Binary graft modification of polypropylene for anti-inflammatory drug-device combo products

Temperature- and pH-responsive copolymers were γ-ray grafted onto polypropylene (PP) to provide its surface with capability to load and to control the release of nonsteroidal anti-inflammatory drugs (NSAIDs) with the aim of being useful as component of drug-eluting medical devices. Poly(N,N'-dimethylaminoethylmethacrylate) (PDMAEMA) or poly(4-vinylpyridine) (P4VP) were grafted onto PP films via a direct method, and then poly(N-isopropylacrylamide) (PNIPAAm) was grafted applying a preirradiation method. The binary graft copolymers showed hemocompatibility and certain capability to adsorb albumin. (PP-g-DMAEMA)-g-NIPAAm exhibited higher affinity for ibuprofen and, particularly, diclofenac than (PP-g-4VP)-g-NIPAAm. Sustained release was observed under physiological conditions. Cytotoxicity and anti-inflammatory activity of NSAID-eluting (PP-g-DMAEMA)-g-NIPAAm films were evaluated on RAW 264.7 macrophage cells. First, dose dependence of anti-inflammatory activity and cytotoxicity of ibuprofen and diclofenac on RAW 264.7 cells were investigated to elucidate the ranges of drug concentration that the graft copolymers should provide. Optimal concentrations of diclofenac and ibuprofen at which they reduce inflammation while maintaining cell viability were determined to be 200 μg/mL and above 400 μg/mL in culture medium. Sequential grafting of DMAEMA and NIPAAm made PP surface to exhibit remarkably high affinity to diclofenac, being able to load and to regulate drug release fulfilling in vitro requirements to avoid inflammatory response.

Drug/Medical Device Combination Products with Stimuli-responsive Eluting Surface

Drug-eluting medical devices are designed to improve the primary function of the device and at the same time offer local release of drugs which otherwise might find it difficult to reach the insertion/implantation site. The incorporation of the drug enables the tuning of the host/microbial responses to the device and the management of device-related complications. On the other hand, the medical device acts as platform for the delivery of the drug for a prolonged period of time just at the site where it is needed and, consequently, the efficacy and the safety of the treatment, as well as its cost-effectiveness are improved. This chapter begins with an introduction to the combination products and then focuses on the techniques available (compounding, impregnation, coating, grafting of the drug or of polymers that interact with it) to endow medical devices with the ability to host drugs/biological products and to regulate their release. Furthermore, the methods for surface modification with stimuli-responsive polymers or networks are analyzed in detail and the performance of the modified materials as drug-delivery systems is discussed. A wide range of chemical-, irradiation- and plasma-based techniques for grafting of brushes and networks that are sensitive to changes in temperature, pH, light, ionic strength or concentration of certain biomarkers, from a variety of substrate materials, is currently available. Although in vivo tests are still limited, such a surface functionalization of medical devices has already been shown useful for the release on-demand of drugs and biological products, being switchable on/off as a function of the progression of certain physiological or pathological events (e.g. healing, body integration, biofouling or biofilm formation). Improved knowledge of the interactions among the medical device, the functionalized surface, the drug and the body are expected to pave the way to the design of drug-eluting medical devices with optimized and novel performances.