Ozone-induced grafting phosphorylcholine polymer onto silicone film grafting 2-methacryloyloxyethyl phosphorylcholine onto silicone film to improve hemocompatibility

Zwitterionic Polymer-Grafted Polylactic Acid Vascular Patches Based on a Decellularized Scaffold for Tissue Engineering

More than 10 million people suffer from cardiovascular diseases, and diseased blood vessels need to be treated with vascular patches. For a vascular patch, good affinity for endothelial progenitor cells is a key factor in promoting the formation of endothelial tissue-endothelialization. To construct such a vascular patch with good cell affnity, in this work, we first synthesized a reactive zwitterionic organophosphate containing a phosphorylcholine headgroup: 6-(acryloyloxy)hexyl-2-(N-isopropyl-N,N-dimethylammonio)ethyl phosphate (AHEP). We then grafted AHEP onto a polylactic acid (PLA)-coated decellularized scaffold to obtain a vascular patch. Its hydrophilicity and biocompatibility were investigated. Its in vivo performance was also examined in a pig model with B-ultrasonography, Doppler spectra, and computed tomography angiography. The vascular patch demonstrated a nonhemolytic property, noncytotoxicity, long in vitro coagulation times, the strong ability to resist platelet adhesion, and a good affinity for endothelial progenitor cells. The vascular patch was able to maintain the long-term patency (5 months) of surgical arteries. Hence, the zwitterionic polymer-grafted PLA vascular patch may be a promising candidate for vascular tissue engineering.

Modification of Ti6Al4V Titanium Alloy Surface Layer in the Ozone Atmosphere

The paper reports the results of a study on the Ti6Al4V titanium alloy involving the XPS (X-ray photoelectron spectroscopy) photoelectron spectroscopy method. The position of bands in the viewing spectrum serves as a basis for the qualitative identification of atoms forming the surface layer, while their intensity is used to calculate the aggregate concentration of these atoms in the analyzed layer. High-resolution spectra are used to determine the type of chemical bonds based on characteristic numerical values of the chemical shift. The paper also presents the 3D results of surface roughness measurements obtained from optical profiling, as well as the results of energy state measurements of the Ti6Al4V titanium alloy surface layer after ozone treatment. It was shown that the ozone treatment of the Ti6Al4V titanium alloy removes carbon and increases concentrations of Ti and V ions at higher oxidation states at the expense of metal atoms and lower valence ions. The modification of the surface layer in ozone atmosphere caused a 30% increase in the Ti element concentration in the surface layer compared to the samples prior to ozone treatment. The carbon removal rate from the Ti6Al4V titanium alloy samples amounted to 35%, and a 13% increase was noted in oxides. The tests proved that the value of the surface free energy of the Ti6Al4V titanium alloy increased as a result of ozone treatment. The highest increase in the surface free energy was observed for Variant 4 samples, and amounted to 17% compared to the untreated samples, while the lowest increase was equal to 14%. For the analyzed data, the maximum value of standard deviation was 0.99 [mJ/m²].

Surface grafting techniques on the improvement of membrane bioreactor: State-of-the-art advances

Membrane bioreactor (MBR) is regarded as the state-of-the-art technology in separation processes. Surface modification techniques play a critical role in improving the conventional membrane system which is mostly hydrophobic in nature. The hydrophobic nature of membranes is known to cause fouling, resulting in high maintenance costs and shorter lifespan of MBR. Thus, surface grafting aims to improve the hydrophilicity of bio-based membrane systems. This review describes the major surface grafting techniques currently used in membranes, including photo induced grafting, plasma treatment and plasma induced grafting, radiation induced grafting, thermal induced grafting and ozone induced grafting. The advantages and disadvantages of each method is discussed along with their parametric studies. The potential applications of MBR are very promising, but some integral membrane properties could be a major challenge that hinders its wider reach. The fouling issue could be resolved with the surface grafting techniques to achieve better performance of MBRs.

Selective laser melted titanium alloys for hip implant applications: Surface modification with new method of polymer grafting

A significant number of hip replacements (HR) fail permanently despite the success of the medical procedure, due to wear and progressive loss of osseointegration of implants. An ideal model should consist of materials with a high resistance to wear and with good biocompatibility. This study aims to develop a new method of grafting the surface of selective laser melted (SLM) titanium alloy (Ti-6Al-4V) with poly (2-methacryloyloxyethyl phosphorylcholine) (PMPC), to improve the surface properties and biocompatibility of the implant. PMPC was grafted onto the SLM fabricated Ti-6Al-4V, applying the following three techniques; ultraviolet (UV) irradiation, thermal heating both under normal atmosphere and UV irradiation under N₂ gas atmosphere. Scanning electron microscopy (SEM), 3D optical profiler, energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) were used to characterise the grafted surface. Results demonstrated that a continuous PMPC layer on the Ti-6Al-4V surface was achieved using the UV irradiation under N₂ gas atmosphere technique, due to the elimination of oxygen from the system. As indicated in the results, one of the advantages of this technique is the presence of phosphorylcholine, mostly on the surface, which reveals the existence of a strong chemical bond between the grafted layer (PMPC) and substrate (Ti-6Al-4V). The nano-scratch test revealed that the PMPC grafted surface improves the mechanical strength of the surface and thus, protects the underlying implant substrate from scratching under high loads.

Preparation of anti-fouling silicone elastomers by covalent immobilization of carboxybetaine

The surface-grafted carboxybetaine (CB) layer could enhance the biocompatibility of polydimethylsiloxane (PDMS) and reduce the adsorption of protein and adhesion of bacteria efficiently.

Grafting copolymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) onto pre-irradiated cellulose films

Grafting of 2-methacryloyloxyethyl phosphorylcholine (MPC) and poly(ethylene glycol mathacrylate) (PEGMA) onto cellulose films was performed using the pre-irradiation grafting method. The effects of monomer concentration, solvent system and co-solvent composition, and reaction time on the degree of grafting were determined. The grafted samples were confirmed by FT-IR-ATR spectra. The blood compatibilities of the grafted cellulose were evaluated by platelet-rich plasma contact studies and viewed by scanning electron microscopy; non-grafted cellulose film sample was used as references. As a result, MPC and MPC/PEGMA were grafted on the surface of cellulose films. It was found that fewer platelets adhered to the MPC-grafted surfaces and that they showed less shape variation than the ungrafted references.

An implantable biochip to influence patient outcomes following trauma-induced hemorrhage

Following hemorrhage-causing injury, lactate levels rise and correlate with the severity of injury and are a surrogate of oxygen debt. Posttraumatic injury also includes hyperglycemia, with continuously elevated glucose levels leading to extensive tissue damage, septicemia, and multiple organ dysfunction syndrome. A temporary, implantable, integrated glucose and lactate biosensor and communications biochip for physiological status monitoring during hemorrhage and for intensive care unit stays has been developed. The dual responsive, amperometric biotransducer uses the microdisc electrode array format upon which were separately immobilized glucose oxidase and lactate oxidase within biorecognition layers, 1.0-5.0 μm thick, of 3 mol% tetraethyleneglycol diacrylate cross-linked p(HEMA-co-PEGMA-co-HMMA-co-SPA)-p(Py-co-PyBA) electroconductive hydrogels. The device was then coated with a bioactive hydrogel layer containing phosphoryl choline and polyethylene glycol pendant moieties [p(HEMA-co-PEGMA-co-HMMA-co-MPC)] for indwelling biocompatibility. In vitro cell proliferation and viability studies confirmed both polymers to be non-cytotoxic; however, PPy-based electroconductive hydrogels showed greater RMS 13 and PC12 proliferation compared to controls. The glucose and lactate biotransducers exhibited linear dynamic ranges of 0.10-13.0 mM glucose and 1.0-7.0 mM and response times (t(95)) of 50 and 35-40 s, respectively. Operational stability gave 80% of the initial biosensor response after 5 days of continuous operation at 37 °C. Preliminary in vivo studies in a Sprague-Dawley hemorrhage model showed tissue lactate levels to rise more rapidly than systematic lactate. The potential for an implantable biochip that supports telemetric reporting of intramuscular lactate and glucose levels allows the refinement of resuscitation approaches for civilian and combat trauma victims.

Adsorption of fibrinogen and lysozyme on silicon grafted with poly(2-methacryloyloxyethyl phosphorylcholine) via surface-initiated atom transfer radical polymerization

Surfaces based on grafted poly(2-methacryloyloxyethyl phosphorylcholine) (poly(MPC)) "brushes" with a constant graft density of 0.39 chain/nm2 and chain length from 5 to 200 monomer units were prepared by surface-initiated atom transfer radical polymerization (ATRP) on silicon wafers. The chain length and layer thickness of the poly(MPC) grafts were varied via the ratio of MPC to sacrificial initiator. The surfaces were characterized by water contact angle, XPS, and AFM. The effect of poly(MPC) chain length on fibrinogen and lysozyme adsorption was studied in TBS buffer at pH 7.4. The adsorption of both proteins on the poly(MPC)-grafted surfaces was greatly reduced compared to the unmodified silicon. Adsorption decreased with increasing chain length of the poly(MPC) grafts. Grafts of chain length 200 (MW 59 000) gave adsorption levels of 7 and 2 ng/cm2, respectively, for fibrinogen and lysozyme at 1 mg/mL protein concentration, corresponding to reductions of greater than 98% compared to the unmodified silicon. Adsorption experiments using mixtures of the two proteins showed that the suppression of protein adsorption on the poly(MPC)-grafted surfaces was not strongly dependent on protein size or charge.

Novel Acrylonitrile-Based Copolymers Containing Phospholipid Moieties: Synthesis and Characterization

Novel acrylonitrile-based copolymers containing phospholipid moieties were synthesized by a three-step process, which included the copolymerization of acrylonitrile and 2-hydroxyethyl methacrylate (HEMA) in water and the reaction of the resulting poly[acrylonitrile-co-(2-hydroxyethyl methacrylate)]s (PANCHEMA) with 2-chloro-2-oxo-1,3,2-dioxaphospholane (COP) followed by the ring-opening reaction of COP with trimethylamine. The chemical structure of PANCHEMA and the phospholipid-containing acrylonitrile-based copolymers (PLCANCP) was analyzed with FT-IR spectroscopy, (1)H and (31)P NMR, and XPS. Surface properties of the studied copolymers were evaluated by the pure water contact angle, protein adsorption and platelets adhesion measurements. The water contact angle measured by sessile drop method decreased for the polymers in the following sequence: PAN, PANCHEMA, and PLCANCP. The adsorption amount of bovine serum albumin and the adhesive number of platelet followed the same decline sequence. These results demonstrate that the biocompatibility of the acrylonitrile-based copolymer membranes could be improved efficiently by the introduction of phospholipid moieties.

Various approaches to modify biomaterial surfaces for improving hemocompatibility

In this paper, the mechanism of thrombus formation on the surface of polymeric materials and the various approaches of modifying biomaterial surfaces to improve their hemocompatibility are reviewed. Moreover, the blood compatibility of the cellulose membrane grafted with O-butyrylchitosan (OBCS) by using a radiation grafting technique was studied. Surface analysis of grafted cellulose membrane was verified by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and electron spectroscopy for chemical analysis (ESCA), which confirmed that OBCS was successfully grafted onto the cellulose membrane surfaces. Blood compatibility of the grafted cellulose membranes was evaluated by platelet rich plasma (PRP) contacting experiments and protein adsorption experiments using blank cellulose membranes as the control. The blood compatibility of OBCS grafted cellulose membranes is better than that of blank cellulose membranes. These results suggest that the photocrosslinkable chitosan developed here has the potential of serving in blood-contacting applications in medical use.