Development of iodine based sustained release antimicrobial coatings for polyurethane voice prostheses

Voice prostheses are known to fail in few weeks to several months of implantation due to the clogging mainly caused by microbial biofilm formation, which is a cause of concern. Iodine is a known broad-spectrum biocide and is reported to easily form complexes with various polymers. For long term device disinfection, strong iodine complexation that offers sustained iodine release for a prolonged period is essential. The present research work deals with the synthesis of a poly(methyl methacrylate-n-butyl acrylate-N-vinyl-2-pyrrolidone) (poly[MMA-BA-NVP]) tercopolymer through free radical polymerization for surface coating thermoplastic polyurethane (TPU) based voice prostheses. The NVP content in the tercopolymer was varied from 20% to 50% to optimise iodine loading and subsequent release. Base TPU coated with the tercopolymer was treated with 4% aqueous iodine solution at room temperature (28 ± 3 °C) for two hours. It was observed that the tercopolymer containing 35% N-vinyl-2-pyrrolidone (NVP), 32.5% methyl methacrylate (MMA) and 32.5% butyl acrylate (nBA) gave a stable coating on TPUs together with sustained iodine release for a prolonged period. Furthermore, the tercopolymer coated and iodine loaded TPUs exhibited excellent antimicrobial activity against Candida albicans, Staphylococcus aureus and Escherichia coli.

pH- and Thermo-Responsive Water-Soluble Smart Polyion Complex (PIC) Vesicle with Polyampholyte Shells

A diblock copolymer (P(VBTAC/NaSS)17-b-PAPTAC50; P(VS)17A50) composed of amphoteric random copolymer, poly(vinylbenzyl trimethylammonium chloride-co-sodium p-styrensunfonate) (P(VBTAC/NaSS); P(VS)) and cationic poly(3-(acrylamidopropyl) trimethylammonium chloride) (PAPTAC; A) block, and poly(acrylic acid) (PAAc49) were prepared via a reversible addition-fragmentation chain transfer radical polymerization. Scrips V, S, and A represent VBTAC, NaSS, and PAPTAC blocks, respectively. Water-soluble polyion complex (PIC) vesicles were formed by mixing P(VS)17A50 and PAAc49 in water under basic conditions through electrostatic interactions between the cationic PAPTAC block and PAAc49 with the deprotonated pendant carboxylate anions. The PIC vesicle collapsed under an acidic medium because the pendant carboxylate anions in PAAc49 were protonated to delete the anionic charges. The PIC vesicle comprises an ionic PAPTAC/PAAc membrane coated with amphoteric random copolymer P(VS)17 shells. The PIC vesicle showed upper critical solution temperature (UCST) behavior in aqueous solutions because of the P(VS)17 shells. The pH- and thermo-responsive behavior of the PIC vesicle were studied using 1H NMR, static and dynamic light scattering, and percent transmittance measurements. When the ratio of the oppositely charged polymers in PAPTAC/PAAc was equal, the size and light scattering intensity of the PIC vesicle reached maximum values. The hydrophilic guest molecules can be encapsulated into the PIC vesicle at the base medium and released under acidic conditions. It is expected that the PIC vesicles will be applied as a smart drug delivery system.

Recent Advances in the Synthesis of Complex Macromolecular Architectures Based on Poly(N-vinyl pyrrolidone) and the RAFT Polymerization Technique

Recent advances in the controlled RAFT polymerization of complex macromolecular architectures based on poly(N-vinyl pyrrolidone), PNVP, are summarized in this review article. Special interest is given to the synthesis of statistical copolymers, block copolymers, and star polymers and copolymers, along with graft copolymers and more complex architectures. In all cases, PNVP is produced via RAFT techniques, whereas other polymerization methods can be employed in combination with RAFT to provide the desired final products. The advantages and limitations of the synthetic methodologies are discussed in detail.

Synthesis, Structure, Hydrodynamics and Thermoresponsiveness of Graft Copolymer with Aromatic Polyester Backbone at Poly(2-isopropyl-2-oxazoline) Side Chains

New thermoresponsive graft copolymers with an aromatic polyester backbone and poly(2-isopropyl-2-oxazoline) (PiPrOx) side chains are synthesized and characterized by NMR and GPC. The grafting density of side chains is 0.49. The molar masses of the graft-copolymer, its backbone, side chains, and the modeling poly-2-isopropyl-2-oxaziline are 74,000, 19,000, 4300, and 16,600 g·mol⁻¹, respectively. Their conformational properties in nitropropane as well as thermoresponsiveness in aqueous solutions are studied and compared with that of free side chains, i.e., linear PiPrOx with a hydrophobic terminal group. In nitropropane, the graft-copolymer adopts conformation of a 13-arm star with a core of a collapsed main chain and a PiPrOx corona. Similarly, a linear PiPrOx chain protects its bulky terminal group by wrapping around it in a selective solvent. In aqueous solutions at low temperatures, graft copolymers form aggregates due to interaction of hydrophobic backbones, which contrasts to molecular solutions of the model linear PiPrOx. The lower critical solution temperature (LCST) for the graft copolymer is around 20 °C. The phase separation temperatures of the copolymer solution were lower than that of the linear chain counterpart, decreasing with concentration for both polymers.

Double hydrophilic block copolymers self-assemblies in biomedical applications

Double-hydrophilic block copolymers (DHBCs), consisting of at least two different water-soluble blocks, are an alternative to the classical amphiphilic block copolymers and have gained increasing attention in the field of biomedical applications. Although the chemical nature of the two blocks can be diverse, most classical DHBCs consist of a bioeliminable non-ionic block to promote solubilization in water, like poly(ethylene glycol), and a second block that is more generally a pH-responsive block capable of interacting with another ionic polymer or substrate. This second block is generally non-degradable and the presence of side chain functional groups raises the question of its fate and toxicity, which is a limitation in the frame of biomedical applications. In this review, following a first part dedicated to recent examples of non-degradable DHBCs, we focus on the DHBCs that combine a biocompatible and bioeliminable non-ionic block with a degradable functional block including polysaccharides, polypeptides, polyesters and other miscellaneous polymers. Their use to design efficient drug delivery systems for various biomedical applications through stimuli-dependent self-assembly is discussed along with the current challenges and future perspectives for this class of copolymers.

Application of asymmetric flow field-flow fractionation (AF4) and multiangle light scattering (MALS) for the evaluation of changes in the product molar mass during PVP-b-PAMPS synthesis

The use of polymers for the delivery of drugs has increased dramatically in the last decade. To ensure the desired properties and functionality of such substances, adequate characterization in terms of the molar mass (M) and size is essential. The aim of this study was to evaluate the changes in the M and size of PVP-b-PAMPS when the amounts of the synthesis reactants in the two-step radical reaction were varied. The determination of the M and size distributions was performed by an asymmetric flow field-flow fractionation (AF4) system connected to multiangle light scattering (MALS) and differential refractive index (dRI) detectors. The results show that the M of the polymers varies depending on the relative amounts of the reactants and that AF4-MALS-dRI is a powerful characterization technique for analyzing polymers. Using AF4, it was possible to separate the product of the first radical reaction (PVP-CTA) into two populations. The first population had an elongated, rod-like or random coil conformation, and the second had a conformation corresponding to homogeneous spheres or a microgel structure. PVP-b-PAMPS had only one population, which had a rod-like conformation. The molar masses of PVP-CTA and PVP-b-PAMPS found in this study were higher than those reported in previous studies.

Porous membranes based on poly(ether imide)-graft-poly(vinyl acetate) as a scaffold for cell growth

A series of poly(ether imide)-graft-poly(vinyl acetate) copolymers with different molecular weights were synthesized successfully and characterized using Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, proton nuclear magnetic resonance, gel permeation chromatography, differential scanning calorimeter, thermogravimetric analysis, and X-ray photoelectron spectroscopy analyses. These copolymers were used to fabricate honeycomb-structured porous films using the breath figure templating technique. The surface topology and composition of the highly ordered pattern film were further characterized using a scanning electron microscopy. The results indicated that the poly(ether imide)-graft-poly(vinyl acetate) graft molecular weight ratio influenced the breath figure film surface topology. A model was proposed to elucidate the stabilization process of the poly(ether imide)-graft-poly(vinyl acetate)-aggregated architecture on the water droplet–based templates. In addition, cell viability has been investigated via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test, and the cell morphology on the honeycomb-structured poly(ether imide)-graft-poly(vinyl acetate) porous film has been evaluated using a fluorescence microscope. This porous film is shown to be suitable as a matrix for cell growth.

Thermo/pH Dual Responsive Mixed-Shell Polymeric Micelles Based on the Complementary Multiple Hydrogen Bonds for Drug Delivery

Thermo/pH dual responsive mixed-shell polymeric micelles based on multiple hydrogen bonding were prepared by self-assembly of diaminotriazine-terminated poly(ɛ-caprolactone) (DAT-PCL), uracil-terminated methoxy poly(ethylene glycol) (MPEG-U), and uracil-terminated poly(N-vinylcaprolactam) (PNVCL-U) at room temperature. PCL acted as the core and MPEG/PNVCL as the mixed shell. Increasing the temperature, PNVCL collapsed and enclosed the PCL core, while MPEG penetrated through the PNVCL shell, thereby leading to the formation of MPEG channels on the micelles surface. The low cytotoxicity of the mixed micelles was confirmed by an MTT assay against BGC-823 cells. Studies on the in vitro drug release showed that a much faster release rate was observed at pH 5.0 compared to physiological pH, owing to the dissociation of hydrogen bonds. Therefore, the mixed-shell polymeric micelles would be very promising candidates in drug delivery systems.

Thermo-triggered drug delivery from polymeric micelles of poly(N-isopropylacrylamide-co-acrylamide)-b-poly(n-butyl methacrylate) for tumor targeting

Novel temperature-sensitive micelles, possessing a core-shell structure, were successfully fabricated and evaluated as possible systems for targeting anticancer drugs to solid tumors. The amphiphilic block copolymer poly( N-isopropylacrylamide- co-acrylamide)-b-poly( n-butyl methacrylate) was used to achieve a stimuli-responsive on/off release and spatial specificity. The anticancer drug methotrexate, which is poorly water soluble, was used as the model. Fourier transform–infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, gel-permeation chromatography, and critical micelle concentration were used to evaluate the successful synthesis of block copolymers with a lower critical solution temperature ~40°C. Based on transmission electron microscope images, the micelles are spherical particles with narrow size distribution. The thermally triggered release of methotrexate was observed in vitro. Quartz crystal microbalance with dissipation was used to investigate the interactions of the polymeric micelles with bovine serum albumin, to illustrate protein adsorption and cell attachment. Cytotoxicity studies were conducted on Lewis lung carcinoma cells, and the anticancer activity of methotrexate-loaded micelles was significantly enhanced in combination with hyperthermia. The thermo-sensitive characteristics of the micelles make them applicable as smart drug delivery systems, when combined with localized hyperthermia.

Antimicrobial polyurethane thermosets based on undecylenic acid: synthesis and evaluation

In the present study, plant oil-derived surface-modifiable polyurethane thermosets are presented. Polyol synthesis is carried out taking advantage of thiol-yne photopolymerization of undecylenic acid derivatives containing methyl ester or hydroxyl moieties. The prepared methyl ester-containing polyurethanes allow surface modification treatment to enhance their hydrophilicity and impart antimicrobial activity through the following two steps: i) grafting poly(propylene glycol) monoamine (Jeffamine M-600) via aminolysis and ii) Jeffamine M-600 layer complexation with iodine. The antimicrobial activity of the iodine-containing polyurethanes is demonstrated by its capacity to inhibit the growth of Staphylococcus aureus, and Candida albicans in agar media.

Succinylated polysaccharide-based thermosensitive polyelectrostatic complex for protein drug delivery

The objective of this study was to develop a thermosensitive polyelectrostatic complex, based on polysaccharides, as carriers for long-term protein delivery. We developed a thermosensitive polyelectrostatic complex formed through combined electrostatic and hydrophobic interactions. The copolymer (succinylated pullulan -poly(l-lactide)) showed thermosensitivity in aqueous solution and complexed with protein (lysozyme) via electrostatic attractions and hydrophobic interactions at physiological temperature which formed a thermosensitive polyelectrostatic complex. The particle size of the thermosensitive polyelectrostatic complex was decreased from ~520 nm at 4°C to ~190 nm at 37.5°C. These thermosensitive polyelectrostatic complexes were stable in serum and salt conditions, and maintained the bioactivity of encapsulated protein for 36 days. The thermosensitive polyelectrostatic complex had prolonged in vivo stability that was greater than the polyelectrostatic complex. Based on stability and bioactivity tests for the lysozyme-loaded thermosensitive polyelectrostatic complexes, the potential of the long-term protein delivery carrier in physiological conditions was confirmed.

Smart drug delivery systems: from fundamentals to the clinic

Smart materials can endow implantable depots, targetable nanocarriers and insertable medical devices with activation-modulated and feedback-regulated control of drug release.

Synthesis and characterization of a pH- and enzyme-sensitive poly(ethylene glycol)–hyaluronic acid–melphalan prodrug

Prodrug development is an important strategy for improving tumor cell targeting and the selectivity of anticancer drugs. In this study, poly(ethylene glycol) and melphalan, an anticancer drug, were linked to the backbone of hyaluronic acid via amide bonds using carbodiimide chemistry to synthesize a poly(ethylene glycol)–hyaluronic acid–melphalan prodrug. The physicochemical properties of the prodrug were characterized by Fourier transform infrared, proton nuclear magnetic resonance, ultraviolet–visible spectroscopy, and dynamic light scattering and transmission electron microscopy. The in vitro drug release profiles and the corresponding in vitro cell evaluation of the prodrug were investigated. The poly(ethylene glycol)–hyaluronic acid–melphalan prodrug was successfully synthesized and self-assembled into 116.4-nm nanoparticles. The release profiles demonstrated that controlled release of the prodrug could be achieved with a sensitive property involving both pH and enzymatic degradation. The poly(ethylene glycol)–hyaluronic acid–melphalan prodrug was more effectively transferred into the ovarian tumor cell (SKOV3) than into human ovarian fibroblast (HOF) cells. It also had a higher inhibition effect on SKOV3 and a lower inhibition effect on HOF than melphalan. This poly(ethylene glycol)–hyaluronic acid–melphalan prodrug, with its controlled release properties and selectivity, is a promising drug delivery system for cancer therapy.

Thermosensitive poly(N-isopropyl acrylamide-co-N,N-dimethyl acryl amide)-block-poly(d,l-lactide) amphiphilic block copolymer micelles for prednisone drug release

Novel amphiphilic block copolymers consisting of hydrophobic poly(D,L-lactide) segments and hydrophilic poly( N-isopropylacrylamide- co- N, N-dimethylacrylamide) blocks were designed and synthesized through a simple free radical copolymerization route based on a bifunctional initiator, followed by the ring-opening polymerization of D,L-lactide. The copolymers self-assembled into thermosensitive spherical-nanosized core–shell micelles in aqueous solution in the presence or the absence of the model drug prednisone. The chemical and physical characterizations of drug-loaded and unloaded micelles revealed a lower critical solution temperature of 40°C–47°C, and a critical micelle concentration less than 7.20 mg L−1, a transmission electron microscope mean particle size from 50 to 75 nm, and a narrow dynamic light scattering diameter below 180 nm. The prepared blank and drug-loaded micellar nanoparticles were thermodynamically stabile and employed in targeted drug delivery by responding to the higher temperature of the local microenvironment. Based on prednisone release kinetic studies, structural changes of the self-assembled micelles as well as temperature- or environment-induced diffusion controlled drug release and improved bioavailability. The copolymer micelles exhibited good biocompatibility as established by the MTT cytotoxicity assay. Therefore, an effective target therapy against lesion tissues is feasible using these polymeric micelles.

Synthesis and characterization of antibacterial polyurethane coatings from quaternary ammonium salts functionalized soybean oil based polyols

In this study, a simple and versatile synthetic approach was developed to prepare bactericidal polyurethane coatings. For this purpose, introduction of both quaternary ammonium salts (QASs), with well-known antibacterial activity, and reactive hydroxyl groups on to the backbone of soybean oil was considered. Epoxidized soybean oil was reacted with diethylamine and the intermediate tertiary amine containing polyol was reacted with two different alkylating agents, methyl iodide and benzyl chloride, to produce MQAP and BQAP, respectively. These functional polyols were reacted with different diisocyanate monomers to prepare polyurethane coatings. Depending on the structure of monomers used for the preparation of polyurethane coatings, initial modulus, tensile strength and elongation at break of samples were in the ranges of 122-339 MPa, 4.6-12.4 MPa and 8.4-46%, respectively. Polyurethane coatings based on isophorone diisocyanate showed proper mechanical properties and adhesion strength (0.41 MPa) for coating application. Study of fibroblast cells interaction with prepared polyurethanes showed promising cells viability in the range of 78-108%. Meanwhile, MQAP based samples with higher concentration of QASs showed better adhesion strength, surface hydrophilicity and antibacterial activity (about 95% bacterial reduction). Therefore, these materials can find applications as bactericidal coating for biomedical devices and implants.

Self-assembled polyion complex micelles for sustained release of hydrophilic drug

Graft copolymer polyethylenimine-graft-poly(N-vinylpyrrolidone) (PEI-g-PVP) was prepared by coupling mono carboxyl-terminated PVP (PVP-COOH) with PEI using N,N'-dicyclohexylcarbodiimide (DCC) and N-hydroxysuccinimide (NHS) as coupling agents. In aqueous medium, PVP-g-PEI can self-assemble into stable polyion complex micelles with an oppositely charged block copolymer, poly(N-vinylpyrrolidone)-block-poly(2-acrylamido-2-methyl-1-propanesulphonic acid) (PVP-b-PAMPS). Transmission electron microscopy images showed that these micelles were regularly spherical in shape. The micelle size determined by size analysis was around 142 nm. To estimate their feasibility as vehicles for drugs, the model drug folic acid (FA) was incorporated into the cores of the micelles via electrostatic interactions. In vitro release test of FA showed that the drug-release rates are dependent on the pH value of the release media. Based on these results, we can conclude that the polyion complex micelles prepared from the PEI-g-PVP/PVP-b-PAMPS copolymers have great potential as drug delivery nanocarriers.