Antithrombotic and hemocompatible properties of nanostructured coatings assembled from block copolymers

Preparation, Properties, and Bioapplications of Block Copolymer Nanopatterns

Block copolymer (BCP) self-assembly has emerged as a feasible method for large-scale fabrication with remarkable precision - features that are not common for most of the nanofabrication techniques. In this review, recent advancements in the molecular design of BCP along with state-of-the-art processing methodologies based on microphase separation alone or its combination with different lithography methods are presented. Furthermore, the bioapplications of the generated nanopatterns in the development of protein arrays, cell-selective surfaces, and antibacterial coatings are explored. Finally, the current challenges in the field are outlined and the potential breakthroughs that can be achieved by adopting BCP approaches already applied in the fabrication of electronic devices are discussed.

Antibacterial nanopatterned coatings for dental implants

Dental implants, usually made of titanium, are exposed to hostile oral microflora that facilitate bacterial infections and subsequent inflammation. To mitigate these processes, we coated titanium substrates with block copolymer nanopatterns and investigated the bactericidal effect of these coatings against Gram-positive and Gram-negative bacteria. We found that the bactericidal efficacy of the coatings depends on their morphology and surface chemistry as well as on the bacterial strain: an optimal combination can lead to significant bacterial death for a short time, i.e. 90% for 90 min. Human gingival fibroblasts in contact with the nanopatterned coatings showed similar cell attachment and morphology as on bare Ti. Immunostaining assays showed similar levels of CCR7 and CD206 in macrophages cultured over the nanopatterns and bare Ti, demonstrating adequate properties for tissue integration. The nanopatterns induced a small increase in macrophage aspect ratio, which might indicate early states of M2 polarization, given the absence of CD206.

Block copolymer nanopatterns affect cell spreading: Stem versus cancer bone cells

Bone healing after a tumor removal can be promoted by biomaterials that enhance the bone regeneration and prevent the tumor relapse. Herein, we obtained several nanopatterns by self-assembly of polystyrene-block-poly-(2-vinylpyridine) (PS-b-P2VP) with different molecular weights and investigated the adhesion and morphology of human bone marrow mesenchymal stem cells (BMMSC) and osteosarcoma cell line (SaOS-2) on these patterns aiming to identify topography and chemistry that promote bone healing. We analyzed > 2000 cells per experimental condition using imaging software and different morphometric descriptors, namely area, perimeter, aspect ratio, circularity, surface/area, and fractal dimension of cellular contour (FDC). The obtained data were used as inputs for principal component analysis, which showed distinct response of BMMSC and SaOS-2 to the surface topography and chemistry. Among the studied substrates, micellar nanopatterns assembled from the copolymer with high molecular weight promote the adhesion and spreading of BMMSC and have an opposite effect on SaOS-2. This nanopattern is thus beneficial for bone regeneration after injury or pathology, e.g. bone fracture or tumor removal.

Hyaluronic Acid-Grafted Bioprosthetic Heart Valves Achieved by Copolymerization Exhibited Improved Anticalcification and Antithrombogenicity

Bioprosthetic heart valves (BHVs) are widely used in clinic, but they still have problems of calcification, thrombogenicity, and cytotoxicity. The reported techniques based on glutaraldehyde (Glut) crosslinking have difficulty in solving these problems simultaneously. In this study, we grafted Glut-crosslinked porcine pericardium (GA) with hyaluronic acid (HA) by radical copolymerization to improve its anticalcification and antithrombotic properties. Partially methacrylated poly-ε-lysine was used to introduce methacryl groups into GA. Then, HA-grafted porcine pericardium (GA-HA) was obtained by radical copolymerization. Rat's subcutaneous implantation results showed that the calcium content of GA-HA was significantly lower than that of GA (37 ± 29 μg/mg vs 188 ± 7 μg/mg), and the platelets adhering to the surface of GA-HA decreased by approximately 41% compared with GA. In conclusion, grafting porcine pericardium with HA by copolymerization might be feasible to improve the anticalcification and antithrombotic properties of BHVs.