Polypropylene grafted with NIPAAm and APMA for creating hemocompatible surfaces that load/elute nalidixic acid

Polypropylene Graft Poly(methyl methacrylate) Graft Poly(N-vinylimidazole) as a Smart Material for pH-Controlled Drug Delivery

Surface modification of polypropylene (PP) films was achieved using gamma-irradiation-induced grafting to provide an adequate surface capable of carrying glycopeptide antibiotics. The copolymer was obtained following a versatile two-step route; pristine PP was exposed to gamma rays and grafted with methyl methacrylate (MMA), and afterward, the film was grafted with N-vinylimidazole (NVI) by simultaneous irradiation. Characterization included Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and physicochemical analysis of swelling and contact angle. The new material (PP-g-MMA)-g-NVI was loaded with vancomycin to quantify the release by UV-vis spectrophotometry at different pH. The surface of (PP-g-MMA)-g-NVI exhibited pH-responsiveness and moderate hydrophilicity, which are suitable properties for controlled drug release.

Stimuli-responsive polypropylene for the sustained delivery of TPGS and interaction with erythrocytes

Hemocompatibility and oxidative stress are significant for blood-contacting devices. In this study, N-isopropylacrylamide (NIPAAm) and N-(3-aminopropyl)methacrylamide hydrochloride (APMA) were cografted on polypropylene (PP) membrane using ultraviolet grafting to load antioxidative d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) and control the release of TPGS. The immobilization of NIPAAm and APMA onto PP membrane was confirmed by attenuated total reflectance Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Combined with data from platelet adhesion, red blood cell (RBC) attachment, and hemolysis rate, the hemocompatibility of PP was significantly improved. An in-depth characterization using hemolysis rate test, scanning electron microscopy, atomic force microscopy, and confocal laser scanning microscopy was conducted to confirm that the mechanism of the release of TPGS interacted with RBCs was different at different stages. The release of TPGS from the loading PP membranes affected hemolysis at different stages. At the early stage of release, TPGS maintained the tiny (nanometer-sized) tubers on the membrane surface and enhanced the membrane permeabilization by generating nanosized pores on the cell membranes. Afterward, the incorporated TPGS slowed the lipid peroxidation of erythrocytes and filled in the lipid bilayer of erythrocyte to prevent hemolysis. Thus, the approach implemented to graft NIPAAm and APMA and load TPGS was suitable to develop medical device with excellent hemocompatibility and antioxidative property.

Key parameters in blood-surface interactions of 3D bioinspired ceramic materials

Direct contact of materials with blood components may trigger numerous processes which ultimately lead to hemolysis, clot formation and recruitment of inflammatory cells. In this study, the blood-surface interactions for two inert bioinspired ceramic scaffolds obtained from natural resources; biomorphic carbon and silicon carbides (bioSiC) from different origins have been studied. The response of the blood in contact with carbon is well known, however little has been identified on the influence of their 3D porous structure. Moreover, to our knowledge, there is no reference in the literature about the hemocompatibility of biomorphic silicon carbide as a porous scaffold. The experimental results showed the surface energy to be crucial to evaluate the hemocompatibility of a material however the surface topography and material porosity are also parameters to be considered. Surface roughness modifies clot formation whereas for protein adsorption total sample porosity seems to be the key parameter to be considered for hydrophilic materials (biomorphic silicon carbides), while the size of the pores determines the hemolytic response.

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.

Surface functionalization of polypropylene devices with hemocompatible DMAAm and NIPAAm grafts for norfloxacin sustained release

To improve the hemocompatibility and elution of antimicrobial agents for medical devices, N,N′-dimethylacrylamide (DMAAm) and N-isopropylacrylamide (NIPAAm) were sequentially grafted onto polypropylene (PP) films. Various (PP-g-DMAAm)-g-NIPAAm grafts were prepared using different time periods of irradiation while keeping the radiation dose constant. The hydrogel layer that formed on the surface of the PP was temperature-responsive (shifted from 32°C for NIPAAm to 37°C for the copolymer). The (PP-g-DMAAm)-g-NIPAAm films adsorbed serum albumin but not fibrinogen and had significantly lower hemolytic and thrombogenic activity. The DMAAm promoted the loading of norfloxacin (13.3 μg cm—2) when the hydrogel layer was swollen; as the NIPAAm shrank, a sustained delivery (∼6 h) occurred at body temperature. These functionalized PP films have potential as hemo- and cyto-compatible materials for medical devices and drug delivery products.

Stimuli-responsive networks grafted onto polypropylene for the sustained delivery of NSAIDs

Co-polymers of N-isopropyl acrylamide (NIPAAm) and N-(3-aminopropyl) methacrylamide hydrochloride (APMA) were grafted on polypropylene (PP) films by means of a γ-ray pre-irradiation method, with the aim of developing medical devices able to load non-steroidal anti-inflammatory drugs (NSAIDs) and to control their release under physiological conditions. The NIPAAm/APMA molar ratios in the grafts, estimated by Fourier transform infrared attenuated total reflection spectroscopy and X-ray photoelectron spectroscopy analysis, were 4.76 and 1.23 for PP-g-(1M NIPAAm-r-0.5M APMA) and PP-g-(1M NIPAAm-r-1M APMA), respectively. By varying the reaction time, different degrees of grafting were achieved, while the monomer ratio was kept constant. PP-g-(NIPAAm-r-APMA) films showed temperature-responsive swelling, smaller friction coefficients, hemolysis and thrombogenicity and higher cell compatibility, did not elicit secretion of cytokines, and took up remarkable amounts of diclofenac and ibuprofen and sustained delivery for several hours in phosphate buffer, pH 7.4. Coating with carboxymethyl dextran of diclofenac-loaded PP-g-(NIPAAm-r-APMA) films caused a minor discharge of the drug but did not alter the drug release rate.

Biofilm inhibition and drug-eluting properties of novel DMAEMA-modified polyethylene and silicone rubber surfaces

Poly(2-(dimethylaminoethyl) methacrylate) (pDMAEMA) was grafted to low density polyethylene (LDPE) and silicone rubber (SR) in order to make them less susceptible to microbial biofilm formation. The direct grafting of DMAEMA using γ-rays was an efficient and fast procedure for obtaining modified materials, which could be quaternized in a second step using methyl iodide. Raman spectroscopy showed that the grafting occurred only at the surface of the LDPE, but both at the surface and in the bulk of the SR. Consequently, the grafted chains caused changes in the surface-related features of the LDPE (water contact angle and viscoelastic behavior in the dry state) and in the bulk-related properties of the SR (swelling and viscoelasticity in the swollen state). The microbiological assays revealed that the grafted DMAEMA reduced Candida albicans biofilm formation (almost no biofilm on SR), while the quaternized surfaces inhibited C. albicans and Staphylococcus aureus biofilm by more than 99% compared to pristine materials. Modified LDPE and SR were capable of holding considerable amounts of nalidixic acid, an anionic antimicrobial drug, and sustained the release for several hours. In addition, the grafted materials were cytocompatible (fibroblast cell survival > 70%). In conclusion, these materials have the ability to inhibit microbial biofilm formation and at the same time act as drug-eluting systems, and for that reason may hold great promise for anti-biofouling applications.