Photoinduced atom transfer radical polymerization in a polar solvent to synthesize a water-soluble poly(2-methacryloyloxyethyl phosphorylcholine) and its block-type copolymers

Biomimetic materials based on zwitterionic polymers toward human-friendly medical devices

This review summarizes recent research on the design of polymer material systems based on biomimetic concepts and reports on the medical devices that implement these systems. Biomolecules such as proteins, nucleic acids, and phospholipids, present in living organisms, play important roles in biological activities. These molecules are characterized by heterogenic nature with hydrophilicity and hydrophobicity, and a balance of positive and negative charges, which provide unique reaction fields, interfaces, and functionality. Incorporating these molecules into artificial systems is expected to advance material science considerably. This approach to material design is exceptionally practical for medical devices that are in contact with living organisms. Here, it is focused on zwitterionic polymers with intramolecularly balanced charges and introduce examples of their applications in medical devices. Their unique properties make these polymers potential surface modification materials to enhance the performance and safety of conventional medical devices. This review discusses these devices; moreover, new surface technologies have been summarized for developing human-friendly medical devices using zwitterionic polymers in the cardiovascular, cerebrovascular, orthopedic, and ophthalmology fields.

Determination of non-freezing water in different nonfouling materials by differential scanning calorimetry

Nonfouling materials have attracted increasing interest for their excellent biocompatibility and low immunogenicity. Strong hydration is believed to be the key reason for their resisting capability to nonspecific protein adsorption. However, little attention has been paid to quantifying their strong water binding capacity. In this study, we synthesized four zwitterionic polymers, including poly(sulfobetaine methacrylate) (pSBMA), poly(carboxybetaine methacrylate) (pCBMA), poly(carboxybetaine acrylamide) (pCBAA) and poly(2-methacryloyloxyethyl phosphorylcholine) (pMPC), and compared non-freezing water of these zwitterionic polymers with typical antifouling polymer poly(ethylene glycol) (PEG) using differential scanning calorimetry (DSC). Non-freezing water of their monomers was also investigated. The non-freezing water of the polymers (per unit) is pMPC (10.7 ± 1.4) ≈ pCBAA (10.8 ± 1.5) > pCBMA (9.0 ± 0.6) > pSBMA (6.6 ± 0.4) > PEG20000 (0.60 ± 0.04). Similar trend is observed for their monomers. For all studied zwitterionic materials, they showed higher binding capacity than PEG. We attribute the stronger hydration of zwitterionic polymers to their strong electrostatic interactions.

Recent Advances on Visible Light Metal-Based Photocatalysts for Polymerization under Low Light Intensity

In recent years, polymerization processes activated by light have attracted a great deal of interest due to the wide range of applications in which this polymerization technique is involved. Parallel to the traditional industrial applications ranging from inks, adhesives, and coatings, the development of high-tech applications such as nanotechnology and 3D-printing have given a revival of interest to this polymerization technique known for decades. To initiate a photochemical polymerization, the key element is the molecule capable to interact with light, i.e., the photoinitiator and more generally the photoinitiating system, as a combination of several components is often required to create the reactive species responsible for the polymerization process. With the aim of reducing the photoinitiator content while optimizing the polymerization yield and/or the polymerization speed, photocatalytic systems have been developed, enabling the photosensitizer to be regenerated during the polymerization process. In this review, an overview of the photocatalytic systems developed for polymerizations carried out under a low light intensity and visible light is provided. Over the years, a wide range of organometallic photocatalysts has been proposed, addressing both the polymerization efficiency and/or the toxicity, as well as environmental issues.

Externally controlled atom transfer radical polymerization

ATRP can be externally controlled by electrical current, light, mechanical forces and various chemical reducing agents. The mechanistic aspects and preparation of polymers with complex functional architectures and their applications are critically reviewed.

Novel 'schizophrenic' diblock copolymer synthesized via RAFT polymerization: poly(2-succinyloxyethyl methacrylate)-b-poly[(N-4-vinylbenzyl),N,N-diethylamine]

This article describes the synthesis and characterization of a novel 'schizophrenic' diblock copolymer [poly(2-succinyloxyethyl methacrylate)-b-poly[(N-4-vinylbenzyl),N,N-diethylamine)]; PSEMA-b-PVEA] via reversible addition of fragmentation chain transfer (RAFT) polymerization technique. The chemical structures of all samples as representatives were characterized by means of Fourier transform infrared (FTIR), and 1H nuclear magnetic resonance (NMR) spectroscopies. The molecular weights of PHEMA and PVEA segments were calculated to be 9770 and 12,630 gmol-1, respectively, from 1H NMR spectroscopy. The self-assembly behavior of the synthesized PSEMA-b-PVEA diblock copolymer was investigated by means of 1H NMR spectroscopy, dynamic light scattering (DLS) measurements, and transmission electron microscopy (TEM) observation. The average sizes of the PSEMA-b-PVEA micelles at pHs 3.0, 6.0, and 10.0 were obtained to be 294, 237, and 201 nm, respectively, from DLS analysis. The zeta potential measurements at various pHs demonstrated that the synthesized PSEMA-b-PVEA diblock copolymer has zwitterionic properties, and the range of isoelectric point's (IEP's) was determined as 5.8-7.3. It is expected that the synthesized PSEMA-b-PVEA diblock copolymer considered as a prospective candidate in nanomedicine applications such as drug delivery, mainly due to its excellent 'schizophrenic' micellization behavior.

Photoinduced inhibition of DNA unwinding in vitro with water-soluble polymers containing both phosphorylcholine and photoreactive groups

Nile blue (NB)-tagged DNA helix-targeting amphiphilic photoreactive 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer, poly(MPC-co-3-methacryloyloxy-2-hydroxypropyl-4-oxybenzophenone-co-2-trimethylammonium ethyl methacrylate chloride) (PMHT-NB), containing a cationic group to facilitate cell membrane penetration and a benzophenone (BP) group to promote photoinduced conjugation with DNA helix was synthesized using radical polymerization method. Ultraviolet light (UV)-visible light absorption spectra of PMHT-NB showed absorption peaks at wavelengths 254, 289, and 600nm, suggesting successful incorporation of BP and NB groups. PMHT-NB was highly sensitive to photoirradiation with UV irradiation at the second level, as confirmed based on the degradation spectra of UV absorption peaks for the BP group in PBS (pH=7.4). PMHT-NB showed good solubility in both aqueous solution and in ethanol. In a cell culture medium containing 10mg/mL PMHT-NB, the NB group showed fluorescence peaks at an emission wavelength of 650nm and excitation wavelength of 633nm. PMHT-NB also showed low cytotoxicity and good cell membrane permeability toward cancerous HeLa cells. Further, photoinduced PMHT-NB effectively inhibited the unwinding of a molecular beacon with a hairpin structure, indicating that synthetic photoreactive MPC polymers photoregulated the unwinding of DNA.

STATEMENT OF SIGNIFICANCE

Natural and synthetic genetic hybrid biomaterials consisting of well-designed polymers loaded with oligonucleotide fragments are considered as an attractive alternative to conventional transgene systems and chemical methods for precisely and rapidly modulation of intracellular gene expression. Containing versatile functional moieties, the effectiveness of well-designed cytocompatible polymers themselves without oligonucleotide fragments on gene regulation is rarely investigated. In the present study, a 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer composed of a tumor/DNA-targeting moiety and photo-controllable unit demonstrated low cytotoxicity, rapid cell membrane permeability and effective inhibitive ability on DNA unwinding under a light irradiation. The synthetic polymer was considered as promising material to effectively inhibit intracellular partial DNA unwinding for cancer/gene therapy.

Photoinduced Electron Transfer Reactions for Macromolecular Syntheses

Photochemical reactions, particularly those involving photoinduced electron transfer processes, establish a substantial contribution to the modern synthetic chemistry, and the polymer community has been increasingly interested in exploiting and developing novel photochemical strategies. These reactions are efficiently utilized in almost every aspect of macromolecular architecture synthesis, involving initiation, control of the reaction kinetics and molecular structures, functionalization, and decoration, etc. Merging with polymerization techniques, photochemistry has opened up new intriguing and powerful avenues for macromolecular synthesis. Construction of various polymers with incredibly complex structures and specific control over the chain topology, as well as providing the opportunity to manipulate the reaction course through spatiotemporal control, are one of the unique abilities of such photochemical reactions. This review paper provides a comprehensive account of the fundamentals and applications of photoinduced electron transfer reactions in polymer synthesis. Besides traditional photopolymerization methods, namely free radical and cationic polymerizations, step-growth polymerizations involving electron transfer processes are included. In addition, controlled radical polymerization and "Click Chemistry" methods have significantly evolved over the last few decades allowing access to narrow molecular weight distributions, efficient regulation of the molecular weight and the monomer sequence and incredibly complex architectures, and polymer modifications and surface patterning are covered. Potential applications including synthesis of block and graft copolymers, polymer-metal nanocomposites, various hybrid materials and bioconjugates, and sequence defined polymers through photoinduced electron transfer reactions are also investigated in detail.

Visible-light induced controlled radical polymerization of methacrylates with Cu(dap)2Cl as a photoredox catalyst

Under visible light irradiation, block copolymers of PPEGMA-b-PMMA with high molecular weights and narrow molecular weight distributions are obtained starting from a PPEGMA macroinitiator in the presence of the Cu(dap)₂Cl/Me₆TREN catalytic system.

Synergetic effect of the epoxide functional groups in the photocatalyzed atom transfer radical copolymerization of glycidyl methacrylate

Methyl methacrylate (MMA) and glycidyl methacrylate (GMA) were copolymerized by photocatalyzed atom transfer radical polymerization under visible light irradiation. The polymerization was made faster by the epoxide group, which played the role of a reducing agent and thus favored the regeneration of the activator.

REDV/Rapamycin-loaded polymer combinations as a coordinated strategy to enhance endothelial cells selectivity for a stent system

A major challenge in the development of drug eluting stent platform is the sustained inhibition of smooth muscle cell (SMC) proliferation while endothelial cell (EC) coverage is promoted. We demonstrated in this study that the combination of rapamycin-loaded polymer base layer and Arg-Glu-Asp-Val (REDV) peptide tethered top layer is a coordinated strategy to enhance EC-specific selectivity. A 2-methacryloyloxyethyl phosphorylcholine(MPC)-co-n-stearyl methacrylate (SMA) [PMS] film was prepared as a base coating to load rapamycin. MPC-co-SMA-co-p-nitrophenyloxycarbonyl polyethyleneglycol methacrylate (MEONP) [PMSN] was synthesized to form the top layer, which conjugated the EC-specific ligand REDV peptide that promotes EC attachment. The top layer functioned as a diffusion barrier, and the polymer film can sustain the rapamycin release of for over 120 days. The In vitro cell behavior of EC and SMC indicated that the rapamycin loaded polymer film inhibited cell growth in the first few days of drug release. After 8 days of drug release, the composite coating consistently resisted the nonspecific adsorption of SMC, whereas REDV enhanced EC attachment specifically. A rabbit iliac injury model was used to evaluate the in vivo of the application of this kind of surface-modified stainless steel stent. The composite polymer coating approach could significantly promote re-endothelialization without causing neointimal hyperplasia. The combination of an EC-specific ligand with rapamycin-loaded polymeric coating may potentially be an effective therapeutic alternative to improve currently available drug-eluting stents.

Photoreactive Polymers Bearing a Zwitterionic Phosphorylcholine Group for Surface Modification of Biomaterials

Photoreactive polymers bearing zwitterionic phosphorylcholine and benzophenone groups on the side chain were synthesized and used as surface modification reagents for biomaterials. A photoreactive methacrylate containing the benzophenone group, 3-methacryloyloxy-2-hydroxypropyl-4-oxybenzophenone (MHPBP), was synthesized via a ring-opening and addition reaction between glycidyl methacrylate and 4-hydroxybenzophenone. Then, water-soluble, amphiphilic polymers poly(2-methacryloyloxyethyl phosphorylcholine (MPC)-co-MHPBP) (PMH) and poly(MPC-co-n-butyl methacrylate-co-MHPBP), with different monomer unit compositions, were synthesized through radical polymerization. Ultraviolet-visible (UV/vis) absorption spectra of these polymer solutions showed that these polymers have maximum absorption peaks at 254 and 289 nm that can be attributed to the benzophenone unit. The intensity of UV adsorption at 289 nm was decreased with increased UV irradiation time, and it was saturated within a few minutes, indicating that the polymers are highly sensitive to UV irradiation. A commercial material (i.e., cyclic polyolefin) was simply modified by a UV irradiation for 1.0 min. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis results indicated that the stability of the polymer on the surface was dramatically enhanced because of the photochemical reaction of the benzophenone moiety. The air contact angles of PMH surfaces measured in water were up to 160°. Thus, highly hydrophilic surfaces were obtained. The critical surface tension of the PMH-modified surface was 45.7 mN/m. By evaluating the biological reactivity of the treated surface, protein adsorption and cell adhesion were completely inhibited on the surface, which was prepared using a photopatterning procedure using PMH. In conclusion, photoreactive MPC polymers with a benzophenone moiety could be used as a novel and effective surface modifier.