Surface properties and cell adhesion onto allylamine-plasma and amine-plasma coated glass coverslips

Development of a super-hydrophilic anaerobic tube for the optimization of platelet-rich fibrin

Horizontal platelet-rich fibrin (H-PRF) contains a variety of bioactive growth factors and cytokines that play a key role in the process of tissue healing and regeneration. The blood collection tubes used to produce Solid-PRF (plasmatrix (PM) tubes) have previously been shown to have a great impact on the morphology, strength and composition of the final H-PRF clot. Therefore, modification to PM tubes is an important step toward the future optimization of PRF. To this end, we innovatively modified the inner wall surface of the PM tubes with plasma and adjusted the gas environment inside the PM tubes to prepare super-hydrophilic anaerobic plasmatrix tubes (SHAP tubes). It was made anaerobic for the preparation of H-PRF with the aim of improving mechanical strength and bioactivity. The findings demonstrated that an anaerobic environment stimulated platelet activation within the PRF tubes. After compression, the prepared H-PRF membrane formed a fibrous cross-linked network with high fracture strength, ideal degradation characteristics, in addition to a significant increase in size. Thereafter, the H-PRF membranes prepared by the SHAP tubes significantly promoted collagen synthesis of gingival fibroblast and the mineralization of osteoblasts while maintaining excellent biocompatibility, and advantageous antibacterial properties. In conclusion, the newly modified PRF tubes had better platelet activation properties leading to better mechanical strength, a longer degradation period, and better regenerative properties in oral cell types including gingival fibroblast and alveolar osteoblasts. It also improves the success rate of H-PRF preparation in patients with coagulation dysfunction and expands the clinical application scenario.

Adhesion and Proliferation of Mesenchymal Stem Cells on Plasma-Coated Biodegradable Nanofibers

Various biomedical applications of biodegradable nanofibers are a hot topic, as evidenced by the ever-increasing number of publications in this field. However, as-prepared nanofibers suffer from poor cell adhesion, so their surface is often modified. In this work, active polymeric surface layers with different densities of COOH groups from 5.1 to 14.4% were successfully prepared by Ar/CO2/C2H4 plasma polymerization. It has been shown that adhesion and proliferation of mesenchymal stem cells (MSCs) seeded onto plasma-modified PCL nanofibers are controlled by the CO2:C2H4 ratio. At a high CO2:C2H4 ratio, a well-defined network of actin microfilaments is observed in the MSCs. Nanofibers produced at a low CO2:C2H4 ratio showed poor cell adhesion and very poor survival. There were significantly fewer cells on the surface, they had a small spreading area, a poorly developed network of actin filaments, and there were almost no stress fibrils. The maximum percentage of proliferating cells was recorded at a CO2:C2H4 ratio of 35:15 compared with gaseous environments of 25:20 and 20:25 (24.1 ± 1.5; 8.4 ± 0.9, and 4.1 ± 0.4%, respectively). Interestingly, no differences were observed between the number of cells on the untreated surface and the plasma-polymerized surface at CO2:C2H4 = 20:25 (4.9 ± 0.6 and 4.1 ± 0.4, respectively). Thus, Ar/CO2/C2H4 plasma polymerization can be an excellent tool for regulating the viability of MSCs by simply adjusting the CO2:C2H4 ratio.

Biofunctionalization of Dental Abutment Surfaces by Crosslinked ECM Proteins Strongly Enhances Adhesion and Proliferation of Gingival Fibroblasts

To ensure the long-term success of dental implants, a functional attachment of the soft tissue to the surface of the implant abutment is decisively important in order to prevent the penetration of bacteria into the implant-bone interface, which can trigger peri-implant disease. Here a surface modification approach is described that includes the covalent immobilization of the extracellular matrix (ECM) proteins fibronectin and laminin via a crosslinker to silanized Ti6Al4V and Y-TZP surfaces. The surface properties are evaluated using static contact angle, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The interaction of human gingival fibroblasts (HGFs) with the immobilized ECM proteins is verified by analyzing the localization of focal contacts, cell area, cell morphology, proliferation rate, and integrin expression. It is observed in the presence of fibronectin and laminin an increased cellular attachment, proliferation, and integrin expression of HGFs accompanied by a significantly higher number of focal adhesions. The presented approach holds great potential to enable a stronger bond between soft tissue and implant abutment surface. This could potentially help to prevent the penetration of bacteria in an in vivo application and thus reduce the risk of periimplant disease.

Cost effective optimised synthetic surface modification strategies for enhanced control of neuronal cell differentiation and supporting neuronal and Schwann cell viability

Enriching a biomaterial surface with specific chemical groups has previously been considered for producing surfaces that influence cell response. Silane layer deposition has previously been shown to control mesenchymal stem cell adhesion and differentiation. However, it has not been used to investigate neuronal or Schwann cell responses in vitro to date. We report on the deposition of aminosilane groups for peripheral neurons and Schwann cells studying two chain lengths: (a) 3-aminopropyl triethoxysilane (short chain-SC) and (b) 11-aminoundecyltriethoxysilane (long chain-LC) by coating glass substrates. Surfaces were characterised by water contact angle, AFM and XPS. LC-NH₂ was produced reproducibly as a homogenous surface with controlled nanotopography. Primary neuron and NG108-15 neuronal cell differentiation and primary Schwann cell responses were investigated in vitro by S100β, p75, and GFAP antigen expression. Both amine silane surface supported neuronal and Schwann cell growth; however, neuronal differentiation was greater on LC aminosilanes versus SC. Thus, we report that silane surfaces with an optimal chain length may have potential in peripheral nerve repair for the modification and improvement of nerve guidance devices.

Behaviour of Vascular Smooth Muscle Cells on Amine Plasma-Coated Materials with Various Chemical Structures and Morphologies

Amine-coated biodegradable materials based on synthetic polymers have a great potential for tissue remodeling and regeneration because of their excellent processability and bioactivity. In the present study, we have investigated the influence of various chemical compositions of amine plasma polymer (PP) coatings and the influence of the substrate morphology, represented by polystyrene culture dishes and polycaprolactone nanofibers (PCL NFs), on the behavior of vascular smooth muscle cells (VSMCs). Although all amine-PP coatings improved the initial adhesion of VSMCs, 7-day long cultivation revealed a clear preference for the coating containing about 15 at.% of nitrogen (CPA-33). The CPA-33 coating demonstrated the ideal combination of good water stability, a sufficient amine group content, and favorable surface wettability and morphology. The nanostructured morphology of amine-PP-coated PCL NFs successfully slowed the proliferation rate of VSMCs, which is essential in preventing restenosis of vascular replacements in vivo. At the same time, CPA-33-coated PCL NFs supported the continuous proliferation of VSMCs during 7-day long cultivation, with no significant increase in cytokine secretion by RAW 264.7 macrophages. The CPA-33 coating deposited on biodegradable PCL NFs therefore seems to be a promising material for manufacturing small-diameter vascular grafts, which are still lacking on the current market.

Efficacy of Plasma-Polymerized Allylamine Coating of Zirconia after Five Years

Plasma-polymerized allylamine (PPAAm) coatings of titanium enhance the cell behavior of osteoblasts. The purpose of the present study was to evaluate a PPAAm nanolayer on zirconia after a storage period of 5 years. Zirconia specimens were directly coated with PPAAm (ZA0) or stored in aseptic packages at room temperature for 5 years (ZA5). Uncoated zirconia specimens (Zmt) and the micro-structured endosseous surface of a zirconia implant (Z14) served as controls. The elemental compositions of the PPAAm coatings were characterized and the viability, spreading and gene expression of human osteoblastic cells (MG-63) were assessed. The presence of amino groups in the PPAAm layer was significantly decreased after 5 years due to oxidation processes. Cell viability after 24 h was significantly higher on uncoated specimens (Zmt) than on all other surfaces. Cell spreading after 20 min was significantly higher for Zmt = ZA0 > ZA5 > Z14, while, after 24 h, spreading also varied significantly between Zmt > ZA0 > ZA5 > Z14. The expression of the mRNA differentiation markers collagen I and osteocalcin was upregulated on untreated surfaces Z14 and Zmt when compared to the PPAAm specimens. Due to the high biocompatibility of zirconia itself, a PPAAm coating may not additionally improve cell behavior.

Preparation of a Biofunctionalized Surface on Titanium for Biomedical Applications: Surface Properties, Wettability Variations, and Biocompatibility Characteristics

This study developed a promising approach (low-temperature plasma polymerization with allylamine) to modify the titanium (Ti) surface, which helps the damaged tissue to heal faster. The Ti surface was first cleaned by argon (Ar) plasma, and then the functional amino-groups were coated on the Ti surface via plasma polymerization. The topography characteristics, wettability, and optimal plasma modification parameters were investigated through atomic force spectroscopy, secondary ion mass spectroscopy, and response surface methodology (RSM). Analytical results showed that the formation of a porous surface was found on the Ar plasma-modified Ti surfaces after Ar plasma modification with different parameters. The Ar plasma modification is an effective approach to remove surface contaminants and generate a porous topography on the Ti surface. As the Ti with Ar plasma modification was at 100 W and 190 m Torr for 12 min, the surface exhibited the maximum hydrophilic performance. In the allylamine plasma modifications, the contact angle values of the allylamine plasma-modified Ti surfaces varied between 70.15° and 88.26° in the designed parameters. The maximum concentration of amino-groups (31.58 nmole/cm2) can be obtained from the plasma-polymerized sample at 80 W and 150 mTorr for 22 min. Moreover, the cell response also demonstrated that the allylamine plasma-modified Ti sample with an optimal modification parameter (80 W, 22 min, and 150 mTorr) possessed great potential to increase cell adhesion ability. Thus, the optimal parameters of the low-temperature plasma polymerization with allylamine can be harvested using the RSM design. These data could provide new scientific information in the surface modification of Ti implant.

Comparison of plasma and chemical modifications of poly-L-lactide-co-caprolactone scaffolds for heparin conjugation

Biodegradable polymers have potential as a scaffold material for making small diameter artery bypass grafts. To resist thrombosis, maintain biocompatibility and enhance the remodeling of the grafts, it is crucial to modify polymer scaffolds so that the grafts have antithrombogenic capacity and allow cell infiltration. In this study, two methods of aminolysis on electrospun poly-L-lactide-co-caprolactone (PLCL) microfiber vascular grafts are compared: plasma treatment method and Fmoc-PEG-diamine insertion method. Both methods successfully inserted amino groups on the polymer graft for heparin conjugation. However, plasma treatment resulted in significantly higher initial heparin density and higher heparin stability on PLCL microfibers than Fmoc-PEG-diamine treatment. In addition, mechanical testing demonstrated that the plasma treatment method maintained PLCL microfiber tensile strength after heparin conjugation. Fmoc-PEG-diamine insertion method compromised the mechanical property due to partial fiber melting and structure disruption. Subcutaneous implantation of the grafts in a rat model showed that heparin coating with both methods promoted cell infiltration. This study provides a rationale to optimize the biomolecule conjugation on electrospun PLCL scaffolds, and will have applications in tissue engineering vascular grafts and other tissues.