Mitigation of Cellular and Bacterial Adhesion on Laser Modified Poly (2-Methacryloyloxyethyl Phosphorylcholine)/Polydimethylsiloxane Surface

Nowadays, using polymers with specific characteristics to coat the surface of a device to prevent undesired biological responses can represent an optimal strategy for developing new and more efficient implants for biomedical applications. Among them, zwitterionic phosphorylcholine-based polymers are of interest due to their properties to resist cell and bacterial adhesion. In this work, the Matrix-Assisted Laser Evaporation (MAPLE) technique was investigated as a new approach for functionalising Polydimethylsiloxane (PDMS) surfaces with zwitterionic poly(2-Methacryloyloxyethyl-Phosphorylcholine) (pMPC) polymer. Evaluation of the physical-chemical properties of the new coatings revealed that the technique proposed has the advantage of achieving uniform and homogeneous stable moderate hydrophilic pMPC thin layers onto hydrophobic PDMS without any pre-treatment, therefore avoiding the major disadvantage of hydrophobicity recovery. The capacity of modified PDMS surfaces to reduce bacterial adhesion and biofilm formation was tested for Gram-positive bacteria, Staphylococcus aureus (S. aureus), and Gram-negative bacteria, Escherichia coli (E. coli). Cell adhesion, proliferation and morphology of human THP-1 differentiated macrophages and human normal CCD-1070Sk fibroblasts on the different surfaces were also assessed. Biological in vitro investigation revealed a significantly reduced adherence on PDMS-pMPC of both E. coli (from 29 × 10 ⁶ to 3 × 10² CFU/mL) and S. aureus (from 29 × 10⁶ to 3 × 10² CFU/mL) bacterial strains. Additionally, coated surfaces induced a significant inhibition of biofilm formation, an effect observed mainly for E. coli. Moreover, the pMPC coatings improved the capacity of PDMS to reduce the adhesion and proliferation of human macrophages by 50% and of human fibroblast by 40% compared to unmodified scaffold, circumventing undesired cell responses such as inflammation and fibrosis. All these highlighted the potential for the new PDMS-pMPC interfaces obtained by MAPLE to be used in the biomedical field to design new PDMS-based implants exhibiting long-term hydrophilic profile stability and better mitigating foreign body response and microbial infection.

A Uniform and Robust Bioinspired Zwitterion Coating for Use in Blood-Contacting Catheters with Improved Anti-Inflammatory and Antithrombotic Properties

Inflammation and thrombosis are two major complications of blood-contacting catheters that are used as extracorporeal circuits for hemodialysis and life-support systems. In clinical applications, complications can lead to increased mortality and morbidity rates. In this work, a biomimetic erythrocyte membrane zwitterion coating based on poly(2-methacryloyloxyethyl phosphorylcholine-co-dopamine methacrylate) (pMPCDA) copolymers is uniformly and robustly modified onto a polyvinyl chloride (PVC) catheter via mussel-inspired surface chemistry. The zwitterionic pMPCDA coating exhibits excellent antifouling activity and resists bacterial adhesion, fibrinogen adsorption, and platelet adhesion/activation. The material also demonstrates great hemocompatibility, cytocompatibility, and anticoagulation properties in vitro. Additionally, this biocompatible pMPCDA coating reduces in vivo foreign-body reactions by mitigating inflammatory response and collagen capsule formation, due to its outstanding ability to resist nonspecific protein adsorption. More importantly, when compared with a bare PVC catheter, the pMPCDA coating exhibits outstanding antithrombotic properties when tested in an ex vivo rabbit perfusion model. Thus, it is envisioned that this biomimetic erythrocyte membrane surface strategy will provide a promising way to mitigate inflammation and thrombosis caused by the use of blood-contacting catheters.

Influence of UV-irradiation intensity and exposure duration on the hemobiocompatibility enhancement of a novel synthesized phosphobetaine zwitterions polyethersulfone clinical hemodialysis membranes

To improve the biocompatibility of polyethersulfone (PES) membranes utilized for biomedical hemodialysis (HD) applications, surface grafting with hydrophilic polymers has become a reliable modification strategy. Like most photochemical catalyzed reactions, UV-assisted grafting is distinctly advantageous for inducing permanent surface chemistry, enhancing hydrophilicity, improving morphology, and surface charge of membranes. PES membranes may be hydrophilic and chemically stable; however, they also have low protein-binding capacity and very susceptible to fouling and target analyte binding. In this study, novel zwitterionic polymers (PVP-ZW) have been synthesized by UV-assisted grafting PVP to a phosphobetaine monomer in a reaction involving dimethylamino and dioxaphospholane-2-oxide terminal groups in an NVP monomer solution at varying UV exposure conditions. The highlight of the present study is the investigation of the hemocompatibility of coated PES HD membranes at varying UV exposure conditions with respect to membrane chemistry and morphology and its influence on human serum protein adsorption. A clinical investigation of inflammatory biomarker release from incubated coated membranes within uremic blood samples of HD patients reveals they are weak complement and coagulation activators compared to bare PES membrane. The trend of fibrinogen adsorption on coated PES membranes was observed to increase with reducing UV intensity and exposure duration. Fibrinogen adhesion only increased with roughened membrane surfaces, and this also led to the formation of biological activation pathways hindering biocompatibility. Resistance against fibrinogen absorption on zwitterionic modified PES membrane could be linked with the creation of electrostatically induced neutral zwitterionic PVP-phosphobetaine hydration layer with hydrophilic character. Experimental results are accompanied by spectroscopic and morphological imaging evidence. Zwitterion coated PES membranes (PES-PVP-ZW) fabricated from higher UV intensities through longer exposure durations showed significant presence of surface deformations in the forms of inherent exfoliations due to harsh UV reaction conditions. The zeta potential and surface roughness of coated membranes also played significant role in the fibrinogen adsorption on PES membranes during ultrafiltration.

Synergistic prevention of biofouling in seawater desalination by zwitterionic surfaces and low-level chlorination

Smooth, durable, ultrathin antifouling layers are deposited onto commercial reverse osmosis membranes without damaging them and they exhibit a fouling reduction. A new synergistic approach to antifouling, by coupling surface modification and drinking-water-level chlorination is enabled by the films' unique resistance against chlorine degradation. This approach substantially enhances longer-term fouling resistance compared with surface modification or chlorination alone, and can reduce freshwater production cost and its collateral toxicity to marine biota.