Radio-frequency plasma treatment improves the growth and attachment of endothelial cells on poly(methyl methacrylate) substrates: implications in tissue engineering

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.

Molecular Dynamics Insights into Water-Parylene C Interface: Relevance of Oxygen Plasma Treatment for Biocompatibility

Solid-water interfaces play a vital role in biomaterials science because they provide a natural playground for most biochemical reactions and physiological processes. In the study, fully atomistic molecular dynamics simulations were performed to investigate interactions between water molecules and several surfaces modeling for unmodified and modified parylene C surfaces. The introduction of -OH, -CHO, and -COOH to the surface and alterations in their coverage significantly influence the energetics of interactions between water molecules and the polymer surface. The theoretical studies were complemented with experimental measurements of contact angle, surface free energy, and imaging of osteoblast cells adhesion. Both MD simulations and experiments demonstrate that the optimal interface, in terms of biocompatibility, is obtained when 60% of native -Cl groups of parylene C surface is exchanged for -OH groups. By exploring idealized models of bare and functionalized parylene C, we obtained a unique insight into molecular interactions at the water-polymer interface. The calculated values of interaction energy components (electrostatic and dispersive) correspond well with the experimentally determined values of surface free energy components (polar and dispersive), revealing their optimal ratio for cells adhesion. The results are discussed in the context of controllable tuning and functionalization of implant polymeric coating toward improved biocompatibility.

Polydopamine-Gelatin as Universal Cell-Interactive Coating for Methacrylate-Based Medical Device Packaging Materials: When Surface Chemistry Overrules Substrate Bulk Properties

Despite its widespread application in the fields of ophthalmology, orthopedics, and dentistry and the stringent need for polymer packagings that induce in vivo tissue integration, the full potential of poly(methyl methacrylate) (PMMA) and its derivatives as medical device packaging material has not been explored yet. We therefore elaborated on the development of a universal coating for methacrylate-based materials that ideally should reveal cell-interactivity irrespective of the polymer substrate bulk properties. Within this perspective, the present work reports on the UV-induced synthesis of PMMA and its more flexible poly(ethylene glycol) (PEG)-based derivative (PMMAPEG) and its subsequent surface decoration using polydopamine (PDA) as well as PDA combined with gelatin B (Gel B). Successful application of both layers was confirmed by multiple surface characterization techniques. The cell interactivity of the materials was studied by performing live-dead assays and immunostainings of the cytoskeletal components of fibroblasts. It can be concluded that only the combination of PDA and Gel B yields materials possessing similar cell interactivities, irrespective of the physicochemical properties of the underlying substrate. The proposed coating outperforms both the PDA functionalized and the pristine polymer surfaces. A universal cell-interactive coating for methacrylate-based medical device packaging materials has thus been realized.

Surface modification of several dental substrates by non-thermal, atmospheric plasma brush

OBJECTIVE

The purpose of this study was to reveal the effectiveness of non-thermal atmospheric plasma brush in surface wettability and modification of four dental substrates.

METHODS

Specimens of dental substrates including dentin, enamel, and two composites Filtek Z250, Filtek LS Silorane were prepared (∼2mm thick, ∼10mm diameter). The prepared surfaces were treated for 5-45s with a non-thermal atmospheric plasma brush working at temperatures from 36 to 38°C. The plasma-treatment effects on these surfaces were studied with contact-angle measurement, X-ray photoemission spectroscopy (XPS) and scanning electron microscopy (SEM).

RESULTS

The non-thermal atmospheric argon plasma brush was very efficient in improving the surface hydrophilicity of four substrates studied. The results indicated that water contact angle values decreased considerably after only 5s plasma treatment of all these substrates. After 30s treatment, the values were further reduced to <5°, which was close to a value for super hydrophilic surfaces. XPS analysis indicated that the percent of elements associated with mineral in dentin/enamel or fillers in the composites increased. In addition, the percent of carbon (%C) decreased while %O increased for all four substrates. As a result, the O/C ratio increased dramatically, suggesting that new oxygen-containing polar moieties were formed on the surfaces after plasma treatment. SEM surface images indicated that no significant morphology change was induced on these dental substrates after exposure to plasmas.

SIGNIFICANCE

Without affecting the bulk properties, a super-hydrophilic surface could be easily achieved by the plasma brush treatment regardless of original hydrophilicity/hydrophobicity of dental substrates tested.

Films of dextran-graft-polybutylmethacrylate to enhance endothelialization of materials

We have synthesized new structures obtained from amphiphilic copolymers of dextran and polybutylmethacrylate with the aim of endothelialization of biomaterials. Grafting of butylmethacrylate onto dextran has been carried out using ceric ammonium nitrate as initiator. Three copolymers were obtained (11, 30 and 37 wt.% dextran) and homogeneous thin films were successfully prepared. In contrast to dextran, the resulting films were stable in water, and copolymers characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry and dynamic mechanical analysis showed evidence of hybrid properties between the parent homopolymers. Surfaces of films were smooth when analyzed by atomic force microscopy (roughness 2+/-1 nm) but greatly differed in their hydrophilicity by increasing the dextran content (water contact angle from 99 degrees to 57 degrees). In contrast to polybutylmethacrylate, where the proliferation of vascular smooth muscle cells (VSMCs) was excellent but that of endothelial cells was very low, the copolymer containing 11% of dextran was excellent for endothelial cells but very limited for VSMCs. An in vitro wound assay demonstrated that copolymer with 11% dextran is even more favorable for endothelial cell migration than tissue-culture polystyrene. Increasing the dextran content in the copolymers decreased the proliferation for both vascular cell types. Altogether, these results show that transparent and water-insoluble films made from copolymers of dextran and butylmethacrylate copolymers with an appropriate composition could enhance endothelial cell proliferation and migration. Therefore, a potential benefit of this approach is the availability of surfaces with tunable properties for the endothelialization of materials.

The role of surface energy of technical polymers in serum protein adsorption and MG-63 cells adhesion

Polymeric materials are widely used as supports for cell culturing in medical implants and as scaffolds for tissue regeneration. However, novel applications in the biosensor field require materials to be compatible with cell growth and at the same time be suitable for technological processing. Technological polymers are key materials in the fabrication of disposable parts and other sensing elements. As such, it is essential to characterize the surface properties of technological polymers, especially after processing and sterilization. It is also important to understand how technological polymers affect cell behavior when in contact with polymer materials. Therefore, the aim of this research was to study how surface energy and surface roughness affect the biocompatibility of three polymeric materials widely used in research and industry: poly(methyl methacrylate), polystyrene, and poly(dimethylsiloxane). Glass was used as the control material.

FROM THE CLINICAL EDITOR

Polymeric materials are widely used as supports for cell culturing in medical implants and as scaffolds for tissue regeneration. The aim of this research is to study how surface energy and surface roughness affect the biocompatibility of three polymeric materials widely used in research and industry: poly(methylmethacrylate) (PMMA), polystyrene (PS), and poly(dimethylsiloxane) (PDMS).

Argon-Oxygen Post-Discharge Treatment of Hexatriacontane: Heat Transfer between Gas Phase and Sample

Characterization of the interaction between an argon-oxygen post-discharge and hexatriacontane (C36H74) is carried out. Optical emission spectroscopy using the atmospheric band O2 (b1Σg +, v=0 X3Σg −, v’=0) at 760 nm gives simultaneously the evolution of the O(3P) concentration above the surface and the gas temperature by simulation of the rotational spectrum of the transition. Surface reactions contribute to the heating in the sample and to a substantial increase in the gas temperature. Finally, a strong correlation between the time evolutions of the transition intensity and the sample temperature is observed, suggesting that O(3P) is the main reactive species that produces the heating and the chemical changes in the HTC.

Transparent polymeric cell culture chip with integrated temperature control and uniform media perfusion

Modern microfabrication and microfluidic technologies offer new opportunities in the design and fabrication of miniaturized cell culture systems for online monitoring of living cells. We used laser micromachining and thermal bonding to fabricate an optically transparent, low-cost polymeric chip for long-term online cell culture observation under controlled conditions. The chip incorporated a microfluidic flow equalization system, assuring uniform perfusion of the cell culture media throughout the cell culture chamber. The integrated indium-tin-oxide heater and miniature temperature probe linked to an electronic feedback system created steady and spatially uniform thermal conditions with minimal interference to the optical transparency of the chip. The fluidic and thermal performance of the chip was verified by finite element modeling and by operation tests under fluctuating ambient temperature conditions. HeLa cells were cultured for up to 2 weeks within the cell culture chip and monitored using a time-lapse video recording microscopy setup. Cell attachment and spreading was observed during the first 10-20 h (lag phase). After approximately 20 h, cell growth gained exponential character with an estimated doubling time of about 32 h, which is identical to the observed doubling time of cells grown in standard cell culture flasks in a CO2 incubator.

Electrospun nanofibres: Biomedical applications

Synthetic and semi-synthetic polymeric materials were originally developed for their durability and resistance to all forms of degradation, including biodegradation. Nanotechnology has the potential to revolutionize many sectors, including pharmaceuticals, information technology, medical devices, materials science, chemicals, and energy. Nanofibres provide a connection between the nanoscale world and the macroscale world, since their diameters are in the range of 1 to 100 nanometres and several metres in length. Therefore, the current emphasis of research is to exploit such properties and focus on determining appropriate conditions for electrospinning various polymers and biopolymers for eventual applications including: multifunctional membranes; biomedical structural elements (scaffolds used in tissue engineering, wound dressing, drug delivery, artificial organs, vascular grafts); protective shields in specialty fabrics; and filter media for submicron particles in the separation industry. This paper reviews the research on recent biomedical applications of electrospun nanofibres.

Synthesis and characterization of acrylic terpolymers with RGD peptides for biomedical applications

The goal of this research was to design a biomaterial, using acrylic terpolymers, which could support endothelial cells and function in small diameter vascular graft applications. Hexyl methacrylate (HMA) and octyl methacrylate (OMA) were used as comonomers to produce a material with a low glass transition temperature (T(g)). Methacrylic acid (MAA) was used to provide ionic character, and methyl methacrylate (MMA) was selected because of its wide usage in biomedical applications. Cation neutralization was employed to modify the mechanical properties. RGD-based peptide sequences were attached to promote endothelial cell adhesion, because vascular grafts seeded with endothelial cells have fewer problems with thrombosis. The two methods used to incorporate peptide sequences were a chain transfer reaction during polymerization, and a coupling reaction attaching the peptides to carboxyl groups on the polymer after polymerization. The compositions that produced T(g)s of approximately 0 degrees C were 75 mol% OMA and 92 mol% HMA. The Young's modulus of the HMA copolymer was approximately 0.37 MPa, well below the desired value of 0.9 MPa. Likewise, the Young's modulus of approximately 0.50 MPa for the OMA copolymer was also below the desired value. After partial neutralization with sodium cations, the Young's moduli increased to approximately 0.93 and 0.99 MPa, respectively. The chain transfer reaction lowered the molecular weights and mechanical properties of the copolymers, while the coupling reaction method had little effect on these properties. The chain transfer method appears to be a promising one-step method to produce polymers with a wide range of peptide concentrations.

Endothelial cell adhesion on RGD-containing methacrylate terpolymers

Hexyl methacrylate (HMA), methyl methacrylate (MMA), and methacrylic acid (MAA) were used as comonomers to produce a low glass transition temperature material, potentially useful in fabricating a small diameter vascular graft. Because it has been shown that grafts seeded with endothelial cells have better resistance to thrombosis, RGD-based peptide sequences were incorporated into the terpolymer. The two methods used for incorporating peptide sequences were a chain transfer reaction during polymerization, and a coupling reaction between the amine terminus of the peptide and the carboxyl groups of the MAA. Polymers were synthesized using the chain transfer reaction with peptide concentrations ranging from 1.7 to 7.0 micromol/g. Weight-average molecular weights decreased with increasing peptide concentration from 310,000 g/mol for the terpolymer without peptide, to 110,000 g/mol for a peptide concentration of 7.0 micromol/g. As a result, Young's modulus decreased with increasing peptide concentration. Terpolymers with peptides attached through a coupling reaction showed no decrease in molecular weight or mechanical properties. Confocal microscopy showed cells seeded on the RGD surfaces adhered and spread, while terpolymers with RGE sequences showed cells that were rounded and not spreading. Cell density on RGD surfaces increased with increasing peptide concentration up to a bulk peptide concentration of approximately 5 micromol/g and reached a plateau, which indicated the minimum peptide concentration necessary for maximum cell adhesion.