Cytocompatibility of poly(acrylonitrile-co-N-vinyl-2-pyrrolidone) membranes with human endothelial cells and macrophages

Structure and State of Water in Branched N-Vinylpyrrolidone Copolymers as Carriers of a Hydrophilic Biologically Active Compound

Hydrated copolymers of N-vinylpyrrolidone (VP) with triethylene glycol dimethacrylate as a promising platform for biologically active compounds (BAC) were investigated by different physical chemical methods (dynamic light scattering, infrared spectroscopy, thermal gravimetric analysis, and differential scanning calorimetry) and the quantum chemical modeling of water coordination by the copolymers in a solution. According to the quantum chemical simulation, one to two water molecules can coordinate on one O-atom of the lactam ring of VP units in the copolymer. Besides the usual terminal coordination, the water molecule can form bridges to bind two adjacent C=O groups of the lactam rings of VP units. In addition to the first hydration shell, the formation of a second one is also possible due to the chain addition of water molecules, and its structure depends on a mutual orientation of C=O groups. We showed that N,N-dimethylbiguanidine hydrochloride (metformin) as a frontline drug for the treatment of type 2 diabetes mellitus can be associated in aqueous solutions with free and hydrated C=O groups of the lactam rings of VP units in studied copolymers. Based on the characteristics of the H-bonds, we believe that the level of the copolymer hydration does not affect the behavior and biological activity of this drug, but the binding of metformin with the amphiphilic copolymer will delight in the penetration of a hydrophilic drug across a cell membrane to increase its bioavailability.

Influence of co-monomer ratio on the chemical properties and cytotoxicity of poly[acrylonitrile-co-(N-vinylpyrrolidone)] nanoparticles

PURPOSE

A system of nanoparticles with varying hydrophilicities may include promising biomaterial candidates as they offer various cellular uptake properties and a range of drug encapsulation efficacies, which would be advantageous in regenerative therapies. Therefore, a model system of nanoparticles with varying hydrophilicities was synthesized and assessed for its candidacy as a biomaterial.

METHODS

Here, acrylonitrile (AN) was copolymerized with N-vinylpyrrolidone (NVP) in a mini-emulsion to form a family of nanoparticles, thereby enabling the systematic variation of the copolymer hydrophilicity. The nanoparticles based on these copolymers were prepared and characterized using 1H-NMR, dynamic light scattering, differential scanning calorimetry, and thermal gravimetric analysis. Finally, the cytotoxicity of the nanoparticles was assessed by conducting indirect tests using L929 fibroblasts.

RESULTS

The nanoparticles showed well controlled NVP/AN molar ratios as determined by 1H NMR, well defined diameters ranging from approximately 100 nm to 200 nm, and increasing glass transition temperatures with increasing molar NVP content. Finally, L929 fibroblasts only slightly changed their morphology upon incubation with material eluates.

CONCLUSIONS

Poly[acrylonitrile-co-(N-vinylpyrrolidone)] nanoparticles with varying amounts of NVP were shown to be a promising model system for further biological assessment.

Cytotoxicity of bovine and porcine collagen membranes in mononuclear cells

This study compared the cytotoxicity and the release of nitric oxide induced by collagen membranes in human mononuclear cells. Peripheral blood was collected from each patient and the separation of mononuclear cells was performed by Ficoll. Then, 2x10(5) cells were plated in 48-well culture plates under the membranes in triplicate. The polystyrene surface was used as negative control. Cell viability was assessed by measuring mitochondrial activity (MTT) at 4, 12 and 24 h, with dosage levels of nitrite by the Griess method for the same periods. Data had non-normal distribution and were analyzed by the Kruskal-Wallis test (p<0.05). Statistically significant differences (p<0.05) were observed between the membranes and the control in the experimental period, although there was a significant reduction in viability over time (p<0.01). At 4 and 12 h, the porcine membrane induced a higher release of nitrite compared with the control and bovine membrane, respectively (p<0.01), and this difference was maintained at 24 h (p<0.05). This in vitro study showed that the porcine collagen membrane induces an increased production of proinflammatory mediators by mononuclear cells in the first hours of contact, decreasing with time.

Correlating macrophage morphology and cytokine production resulting from biomaterial contact

The morphological and inflammatory responses of adherent macrophages are correlated to evaluate the biocompatibility of surfaces. Monocyte-derived macrophage (MDM), THP-1, and THP-1 cells expressing GFP-actin chimeric protein were seeded onto glass, polyurethane (PU), and glass surface modified with quaternary ammonium salt functionalized chitosan (CH-Q) and hyaluronic acid (HA). Using confocal microscopy, the surface area, volume and 3D shape factor of adherent macrophages was quantified. For comparison, functional consequences of cell-surface interactions that activate macrophages and thereby elicit secretion of a proinflammatory cytokine were evaluated. Using an enzyme linked immune sorbent assay, tumor necrosis factor-alpha (TNF-α) was measured. On glass, macrophages exhibited mainly an amoeboid shape, exhibited the largest surface area, volume, and 3D shape factor and produced the most TNF-α. On PU, macrophages displayed mainly a hemispherical shape, exhibited an intermediate volume, surface area and 3D shape factor, and produced moderate TNF-α. In contrast, on CH-Q and HA surfaces, macrophages were spherical, exhibited the smallest volume, surface area, and 3D shape factor, and produced the least TNF-α. These studies begin to validate the use of GFP-actin-modified MDM as a novel tool to correlate cell morphology with inflammatory cell response.

Nanofibrous composites for tissue engineering applications

Development of artificial matrices for tissue engineering is a crucial area of research in the field of regenerative medicine. Successful tissue scaffolds, in analogy with the natural mammalian extracellular matrix (ECM), are multi-component, fibrous, and on the nanoscale. In addition, to this key morphology, artificial scaffolds must have mechanical, chemical, surface, and electrical properties that match the ECM or basement membrane of the specific tissue desired. In particular, these material properties may vary significantly for the four primary tissues in the body: nerve, muscle, epithelial, and connective. In order to address this complex array of attributes with a polymeric material, a nanocomposite approach, employing a blend of materials, addition of a particle to enhance particular properties, or a surface treatment, is likely to be required. In this review, we examine nanocomposite approaches to address these diverse needs as a function of tissue type. The review is intended as a bridge between material scientists and biomedical researchers to give basic background information on tissue biology to the former, and on material processing approaches to the latter, in a general manner, and specifically review fibrous nanocomposite materials that have previously been used for cell studies, either in vivo or in vitro.

Polymer surfaces structured with random or aligned electrospun nanofibers to promote the adhesion of blood platelets

Fibrous membranes (nonwoven meshes) prepared via electrospinning technique have great potential in tissue engineering. This work is the first study on the behaviors of blood platelets at the nanostructured surface generated by electrospinning. Poly[acrylonitrile-co-(N-vinyl-2-pyrrolidone)] (PANCNVP) that shows excellent antiplatelet adhesion ability was directly electrospun onto its dense membrane surface. Polyacrylonitrile (PAN) samples were used as controls. The depth as well as the density of the nanofibers can be easily controlled. The results showed that the PANCNVP dense membrane certainly suppressed the activation and adhesion of platelets. However, whether the nanofibers and underlying membranes were composed of PAN or PANCNVP, the nanostructured surfaces promoted the activation, adhesion, and orientation of platelets. It was also found that, if the space between fibers was too large or the depth of fibers was too small, the nanostructured surface did not change the property of antiplatelet adhesion of PANCNVP. The promotion of activation and adhesion of platelets was obviously due to the presence of nanofibers, which induced the changes of surface topography and charge.