Influence of Topography and Composition of Commercial Titanium Dental Implants on Cell Adhesion of Human Gingiva-Derived Mesenchymal Stem Cells: An In Vitro Study.

The topography and composition of dental implant surfaces directly impact mesenchymal cell adhesion, proliferation, and differentiation, crucial aspects of achieving osseointegration. However, cell adhesion to biomaterials is considered a key step that drives cell proliferation and differentiation. The aim of this study was to characterize characterize the topography and composition of commercial titanium dental implants manufactured with different surface treatments (two sandblasted/acid-etched (SLA) (INNO Implants, Busan, Republic of Korea; BioHorizonsTM, Oceanside, CA, USA) and two calcium phosphate (CaP) treated (Biounite®, Berazategui, Argentina; Zimmer Biomet, Inc., Warsaw, IN, USA)) and to investigate their influence on the process of cell adhesion in vitro. A smooth surface implant (Zimmer Biomet, Inc.) was used as a control. For that, high-resolution methodologies such as scanning electron microscopy (SEM), X-ray dispersive spectroscopy (EDX), laser scanning confocal microscopy (LSCM), and atomic force microscopy (AFM) were employed. Protein adsorption and retromolar gingival mesenchymal stem cells (GMSCs) adhesion to the implant surfaces were evaluated after 48 h. The adherent cells were examined by SEM and LSCM for morphologic and quantitative analyses. ANOVA and Tukey tests (α = 0.05) were employed to determine statistical significance. SEM revealed that INNO, BioHorizonsTM, and Zimmer implants have an irregular surface, whereas Biounite® has a regular topography consisting of an ordered pattern. EDX confirmed a calcium and phosphate layer on the Biounite® and Zimmer surfaces, and AFM exhibited different roughness parameters. Protein adsorption and cell adhesion were detected on all the implant surfaces studied. However, the Biounite® implant with CaP and regular topography showed the highest protein adsorption capacity and density of adherent GMSCs. Although the Zimmer implant also had a CaP treatment, protein and cell adhesion levels were lower than those observed with Biounite®. Our findings indicated that the surface regularity of the implants is a more determinant factor in the cell adhesion process than the CaP treatment. A regular, nanostructured, hydrophilic, and moderately rough topography generates a higher protein adsorption capacity and thus promotes more efficient cell adhesion.

The Adsorption of P2X2 Receptors Interacting with IgG Antibodies Revealed by Combined AFM Imaging and Mechanical Simulation.

The adsorption of proteins onto surfaces significantly impacts biomaterials, medical devices, and biological processes. This study aims to provide insights into the irreversible adsorption process of multiprotein complexes, particularly focusing on the interaction between anti-His6 IgG antibodies and the His6-tagged P2X2 receptor. Traditional approaches to understanding protein adsorption have centered around kinetic and thermodynamic models, often examining individual proteins and surface coverage, typically through Molecular Dynamics (MD) simulations. In this research, we introduce a computational approach employing Autodesk Maya 3D software for the investigation of multiprotein complexes' adsorption behavior. Utilizing Atomic Force Microscopy (AFM) imaging and Maya 3D-based mechanical simulations, our study yields real-time structural and kinetic observations. Our combined experimental and computational findings reveal that the P2X2 receptor-IgG antibody complex likely undergoes absorption in an 'extended' configuration. Whereas the P2X2 receptor is less adsorbed once is complexed to the IgG antibody compared to its individual state, the opposite is observed for the antibody. This insight enhances our understanding of the role of protein-protein interactions in the process of protein adsorption.

Physicochemical and biological properties of nanohydroxyapatite grafted with star-shaped poly(ε-caprolactone).

To overcome the disadvantages generated by the lack of interfacial bonding between hydroxyapatite nanocrystals (HAPN) and agglomeration of particles in the development of biodegradable nanocomposites a chemical grafting method was applied to modify the surface of HAPN through grafting of the three-arms star-shaped poly(ε-caprolactone) (SPCL) onto the nanoparticles. The chemical grafting of SPCL onto HAPN (SPCL-g-HAPN) has been investigated using Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy (TEM), photoelectron spectroscopy, X-ray diffraction, zeta potential (ZP) and contact angle (CA). TEM micrographs of the SPCL-g-HAPN revealed the existence of hybrid organic/inorganic (O/I) nanoscale domains. The results of albumin (HSA) and fibrinogen (HFb) adsorption indicate resistance to HFb adsorption by SPCL-g-HAPN relatively to unmodified HAPN. The ZP and CA measurement suggest a heterogeneous topology for SPCL-g-HAPN likely due to the existence of hydrophobic-hydrophilic regions on the nanocomposite surface. The enzyme degradation by cholesterol esterase and lipase indicates that the rates of hydrolysis for SPCL-g-HAPN were very slow relative to the SPCL/HAPN blends. The in vitro biological studies showed that the human osteoblast-like cells (MG-63) cells had normal morphology and they were able to attach and spread out on SPCL-g-HAPN surfaces. A higher overall cellular proliferation was observed on SPCL-g-HAPN scaffolds compared to pure HAPN or SPCL materials.

Blood-Vessel-Inspired Hierarchical Trilayer Scaffolds: PCL/Gelatin-Driven Protein Adsorption and Cellular Interaction.

Fabrication of scaffolds with hierarchical structures exhibiting the blood vessel topological and biochemical features of the native extracellular matrix that maintain long-term patency remains a major challenge. Within this context, scaffold assembly using biodegradable synthetic polymers (BSPs) via electrospinning had led to soft-tissue-resembling microstructures that allow cell infiltration. However, BSPs fail to exhibit the sufficient surface reactivity, limiting protein adsorption and/or cell adhesion and jeopardizing the overall graft performance. Here, we present a methodology for the fabrication of three-layered polycaprolactone (PCL)-based tubular structures with biochemical cues to improve protein adsorption and cell adhesion. For this purpose, PCL was backbone-oxidized (O-PCL) and cast over a photolithography-manufactured microgrooved mold to obtain a bioactive surface as demonstrated using a protein adsorption assay (BSA), Fourier transform infrared spectroscopy (FTIR) and calorimetric analyses. Then, two layers of PCL:gelatin (75:25 and 95:5 w/w), obtained using a novel single-desolvation method, were electrospun over the casted O-PCL to mimic a vascular wall with a physicochemical gradient to guide cell adhesion. Furthermore, tensile properties were shown to withstand the physiological mechanical stresses and strains. In vitro characterization, using L929 mouse fibroblasts, demonstrated that the multilayered scaffold is a suitable platform for cell infiltration and proliferation from the innermost to the outermost layer as is needed for vascular wall regeneration. Our work holds promise as a strategy for the low-cost manufacture of next-generation polymer-based hierarchical scaffolds with high bioactivity and resemblance of ECM's microstructure to accurately guide cell attachment and proliferation.

Competitive protein adsorption on charge regulating silica-like surfaces: the role of protonation equilibrium.

We develop a molecular thermodynamic theory to study the interaction of some proteins with a charge regulating silica-like surface under a wide range of conditions, including pH, salt concentration and protein concentration. Proteins are modeled using their three dimensional structure from crystallographic data and the average experimental pKa of amino acid residues. As model systems, we study single-protein and binary solutions of cytochrome c, green fluorescent protein, lysozyme and myoglobin. Our results show that protonation equilibrium plays a critical role in the interactions of proteins with these type of surfaces. The terminal hydroxyl groups on the surface display considerable extent of charge regulation; protein residues with titratable side chains increase protonation according to changes in the local environment and the drop in pH near the surface. This behavior defines protein-surface interactions and leads to the emergence of several phenomena: (i) a complex non-ideal surface charge behavior; (ii) a non-monotonic adsorption of proteins as a function of pH; and (iii) the presence of two spatial regions, a protein-rich and a protein-depleted layer, that occur simultaneously at different distances from the surface when pH is slightly above the isoelectric point of the protein. In binary mixtures, protein adsorption and surface-protein interactions cannot be predicted from single-protein solution considerations.

Urea, salts, and Tween 20 influence on adsorption of IgG and Leishmania rNTPDase2 to nitrocellulose.

Lateral flow immunochromatography is a widely used technique for immunological assays. Construction of test and control lines is mostly done by antigen adsorption to nitrocellulose membranes, a process not fully understood. This study aimed to evaluate the influence of urea, salts, and Tween 20, on adsorption. The performance of canine IgG in water and in buffer containing urea and salts (pH 8.3) were compared to observe if the interferents would lead to protein stripping when challenged with increasing concentrations of Tween 20 in the lateral flow buffer. Immobilization of the rLiNTPDase2, an antigen for Canine Leishmaniasis diagnosis, was evaluated and compared to the rLbNTPDase2 by the same method. There were no differences between adsorption coefficients of IgG in water and in buffer, but high salt and urea concentrations seems to stabilize and enhance IgG immobilization. Adsorption performance between canine IgG and rNTPDases had different patterns, but was highly similar between rNTPDases, indicating that protein identity may have an important role. Also, low concentrations of Tween 20 in the flow solution may aid the maintenance of rNTPDase2 on the strips. Our results bring insights about protein adsorption and perspectives about the influence of urea, salts and Tween 20 on this process.

Antifouling PVC Catheters by Gamma Radiation-Induced Zwitterionic Polymer Grafting.

In medical environments, polymeric surfaces tend to become contaminated, hindering the treatment and recovery from diseases. Biofouling-resistant materials, such as zwitterionic polymers, may mitigate this problem. In this work, the modification of PVC catheters with a binary graft of 4-vinylpyridine (4VP) and sulfobetaine methacrylate (SBMA) by the oxidative pre-irradiation method is proposed to develop pH-responsive catheters with an antifouling capacity. The ionizing radiation allowed us to overcome limitations in the synthesis associated with the monomer characteristics. In addition, the grafted materials showed a considerable increase in their hydrophilic character and antifouling capacity, significantly decreasing the protein adsorption compared to the unmodified catheters. These materials have potential for the development of a combined antimicrobial and antifouling capabilities system to enhance prophylactic activity or even to help treat infections.

Proteins Adsorbing onto Surface-Modified Nanoparticles: Effect of Surface Curvature, pH, and the Interplay of Polymers and Proteins Acid-Base Equilibrium.

Protein adsorption onto nanomaterials is a process of vital significance and it is commonly controlled by functionalizing their surface with polymers. The efficiency of this strategy depends on the design parameters of the nanoconstruct. Although significant amount of work has been carried out on planar surfaces modified with different types of polymers, studies investigating the role of surface curvature are not as abundant. Here, we present a comprehensive and systematic study of the protein adsorption process, analyzing the effect of curvature and morphology, the grafting of polymer mixtures, the type of monomer (neutral, acidic, basic), the proteins in solution, and the conditions of the solution. The theoretical approach we employed is based on a molecular theory that allows to explicitly consider the acid-base reactions of the amino acids in the proteins and the monomers on the surface. The calculations showed that surface curvature modulates the molecular organization in space, but key variables are the bulk pH and salt concentration (in the millimolar range). When grafting the NP with acidic or basic polymers, the surface coating could disfavor or promote adsorption, depending on the solution's conditions. When NPs are in contact with protein mixtures in solution, a nontrivial competitive adsorption process is observed. The calculations reflect the balance between molecular organization and chemical state of polymers and proteins, and how it is modulated by the curvature of the underlying surface.

Reduced cytotoxicity of nanomaterials driven by nano-bio interactions: Case study of single protein coronas enveloping polymersomes.

The protein adsorption onto poly(acrylic acid)-block-polystyrene (PAA22-b-PS144) polymersomes has been investigated with regard to structural features, thermodynamic aspects and biological consequences. The light scattering measurements revealed the formation of protein coronas enveloping the polymeric capsules regardless of the chemical nature of the biomacromolecules. The experiments were conducted by using lysozyme, immunoglobulin G - IgG and bovine serum albumin - BSA as model proteins due to their differences concerning size and residual surface charge at physiological pH. The protein adsorption was further confirmed by isothermal titration calorimetry, and the experimental data suggest that the phenomenon is mainly governed by hydrogen bonding and van der Waals interactions. The pre-existing protein layer via the pre-incubation in protein environments notably attenuates the cytotoxicity of the nanomaterial compared to the pristine counterparts. This approach can possibly be extended to different types of assemblies when intermolecular interactions are able to induce protein adsorption and the development of protein coronas around nanoparticles. Such fairly simple method may be convenient to engineer safer nanomaterials towards a variety of biomedical applications when the nanotoxicity is an issue. Additionally, the strategy can possibly be used to tailor the surface properties of nanoparticles by adsorbing specific proteins for targeting purposes.

Computational Characterization of Mechanical, Hemodynamic, and Surface Interaction Conditions: Role of Protein Adsorption on the Regenerative Response of TEVGs.

Currently available small diameter vascular grafts (<6 mm) present several long-term limitations, which has prevented their full clinical implementation. Computational modeling and simulation emerge as tools to study and optimize the rational design of small diameter tissue engineered vascular grafts (TEVG). This study aims to model the correlation between mechanical-hemodynamic-biochemical variables on protein adsorption over TEVG and their regenerative potential. To understand mechanical-hemodynamic variables, two-way Fluid-Structure Interaction (FSI) computational models of novel TEVGs were developed in ANSYS Fluent 2019R3® and ANSYS Transient Structural® software. Experimental pulsatile pressure was included as an UDF into the models. TEVG mechanical properties were obtained from tensile strength tests, under the ISO7198:2016, for novel TEVGs. Subsequently, a kinetic model, linked to previously obtained velocity profiles, of the protein-surface interaction between albumin and fibrinogen, and the intima layer of the TEVGs, was implemented in COMSOL Multiphysics 5.3®. TEVG wall properties appear critical to understand flow and protein adsorption under hemodynamic stimuli. In addition, the kinetic model under flow conditions revealed that size and concentration are the main parameters to trigger protein adsorption on TEVGs. The computational models provide a robust platform to study multiparametrically the performance of TEVGs in terms of protein adsorption and their regenerative potential.

Toxicity of engineered nanomaterials with different physicochemical properties and the role of protein corona on cellular uptake and intrinsic ROS production.

The Organisation for Economic Co-operation and Development has listed thirteen engineered nanomaterials (ENM) in order to investigate their toxicity on human health. Silicon dioxide (SiO2) and titanium dioxide (TiO2) are included on that list and we added indium tin oxide (ITO) nanoparticles (NPs) to our study, which is not listed on OECD suggested ENM to be investigated, however ITO NPs has a high potential of industrial production. We evaluate the physicochemical properties of SiO2 NPs (10-20 nm), TiO2 nanofibers (NFs; 3 µm length) and ITO NPs (<50 nm) and the impact of protein-corona formation on cell internalization. Then, we evaluated the toxicity of uncoated ENM on human lung epithelial cells exposed to 10 and 50 µg/cm2 for 24 h. TiO2 NFs showed the highest capability to adsorb proteins onto the particle surface followed by SiO2 NPs and ITO NPs after acellular incubation with fetal bovine serum. The protein adsorption had no impact on Alizarin Red S conjugation, intrinsic properties for reactive oxygen (ROS) formation or cell uptake for all types of ENM. Moreover, TiO2 NFs induced highest cell alterations in human lung epithelial cells exposed to 10 and 50 µg/cm2 while ITO NPs induced moderated cytotoxicity and SiO2 NPs caused even lower cytotoxicity under the same conditions. DNA, proteins and lipids were mainly affected by TiO2 NFs followed by SiO2 NPs with toxic effects in protein and lipids while limited variations were detected after exposure to ITO NPs on spectra analyzed by Fourier Transform Infrared Spectroscopy.

Concentration-dependent effects of latex F1-protein fraction incorporated into deproteinized bovine bone and biphasic calcium phosphate on the repair of critical-size bone defects.

F1-protein fraction (F1) is a natural bioactive compound extracted from the rubber tree, Hevea brasiliensis, and has been recently studied for its therapeutic potential in wound healing. In this study, we investigated the concentration-dependent effects of F1 (0.01%, 0.025%, 0.05%, and 0.1%) incorporated into deproteinized bovine bone (DBB) and porous biphasic calcium phosphate (pBCP), on the repair of rat calvarial critical-size bone defects (CSBD). The defects were analyzed by 3D-microtomography and 2D-histomorphometry at 12 weeks postsurgery. The binding efficiency of F1 to pBCP (96.3 ± 1.4%) was higher than that to DBB (67.7 ± 3.3%). In vivo analysis showed a higher bone volume (BV) gain in all defects treated with DBB (except in 0.1% of F1) and pBCP (except in 0.05% and 0.1% of F1) compared to the CSBD without treatment/control group (9.96 ± 2.8 mm3 ). DBB plus 0.025% F1 promoted the highest BV gain (29.7 ± 2.2 mm3 , p < .0001) compared to DBB without F1 and DBB plus 0.01% and 0.1% of F1. In the pBCP group, incorporation of F1 did not promote bone gain when compared to pBCP without F1 (15.9 ± 4.2 mm3 , p > .05). Additionally, a small BV occurred in defects treated with pBCP plus 0.1% F1 (10.4 ± 1.4 mm3, p < .05). In conclusion, F1 showed a higher bone formation potential in combination with DBB than with pBCP, in a concentration-dependent manner. Incorporation of 0.25% F1 into DBB showed the best results with respect to bone formation/repair in CSBD. These results suggest that DBB plus 0.25% F1 can be used as a promising bioactive material for application in bone tissue engineering.

Suppressing Non-Specific Binding of Proteins onto Electrode Surfaces in the Development of Electrochemical Immunosensors.

Electrochemical immunosensors, EIs, are systems that combine the analytical power of electrochemical techniques and the high selectivity and specificity of antibodies in a solid phase immunoassay for target analyte. In EIs, the most used transducer platforms are screen printed electrodes, SPEs. Some characteristics of EIs are their low cost, portability for point of care testing (POCT) applications, high specificity and selectivity to the target molecule, low sample and reagent consumption and easy to use. Despite all these attractive features, still exist one to cover and it is the enhancement of the sensitivity of the EIs. In this review, an approach to understand how this can be achieved is presented. First, it is necessary to comprise thoroughly all the complex phenomena that happen simultaneously in the protein-surface interface when adsorption of the protein occurs. Physicochemical properties of the protein and the surface as well as the adsorption phenomena influence the sensitivity of the EIs. From this point, some strategies to suppress non-specific binding, NSB, of proteins onto electrode surfaces in order to improve the sensitivity of EIs are mentioned.

Effects of calcium and phosphorus incorporation on the properties and bioactivity of TiO2 nanotubes.

In this study, we investigate the formation of calcium and phosphorus-doped TiO2 nanotubes, produced by potentiostatic anodization of Ti in viscous electrolyte-containing HF and Ca/P ions. Characterization of the produced oxide layer was conducted using scanning electron microscopy, glancing-angle X-ray diffraction, X-ray photoelectron spectroscopy, contact angle, and protein adsorption measurements. Adipose-derived stem cells were used to study material cytotoxicity, cell viability and proliferation, and cell morphology and growth. To evaluate the adipose-derived stem-cell differentiation, we investigated the expression of osteocalcin and osteopontin by cells as well as calcium mineralization. Results show that it was possible to produce a superhydrophilic titanium oxide nanotube layer with incorporation of Ca and P ions. The presence of Ca and P in the oxide layer not only improved the cell adhesion and proliferation but also stimulated the production of key marker proteins indicating differentiation of cells.

Influence of buffer solutions in the adsorption of human serum proteins onto layered double hydroxide.

The adsorption of human immunoglobulin G (IgG) and human serum albumin (HSA) on a non-calcined Mg-Al layered double hydroxide (3:1 Mg-Al LDH) was studied in batch and fixed bed experiments, focusing on the effect of buffer solution and pH over sorbent uptake. Mg-Al LDH was synthesized and characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherms at -196°C, X-ray photoelectron spectroscopy (XPS), Zero point charge (pHzpc), particle size distribution and Fourier transform infra-red (FTIR). Batch adsorption experiments were performed in order to investigate the effects of pH on IgG and HSA adsorption with different buffers: sodium acetate (ACETATE), sodium phosphate (PHOSPHATE), 3-(N-morpholino) propanesulfonic acid (MOPS), 4-(2-Hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES) and trizma-hydrochloric acid (TRIS-HCl). Maximum adsorption capacities estimated by the Langmuir model were 239mgg-1 for IgG and 105mgg-1 for HSA in TRIS-HCl buffer. On the other hand, the highest selectivity for IgG adsorption over HSA was obtained with buffer PHOSPHATE (pH 6.5). The maximum IgG and HSA adsorption uptake in this case were 165 and 36mgg-1, respectively. Fixed bed experiments were carried out with both proteins using PHOSPHATE buffer (pH 6.5), which confirmed that IgG was more selectively adsorbed than HSA on Mg-Al LDH and both could be fully recovered by elution with sodium chloride (NaCl).

Sensitivity improvement of a sandwich-type ELISA immunosensor for the detection of different prostate-specific antigen isoforms in human serum using electrochemical impedance spectroscopy and an ordered and hierarchically organized interfacial supramolecular architecture.

A gold millielectrode (GME) functionalized with a mixed (16-MHA + EG3SH) self-assembled monolayer (SAM) was used to fabricate an indirect enzyme-linked immunosorbent assay (ELISA) immunosensor for the sensitive detection of prostate-specific antigen (PSA), a prostate cancer (PCa) biomarker, in human serum samples. To address and minimize the issue of non-specific protein adsorption, an organic matrix (amine-PEG3-biotin/avidin) was assembled on the previously functionalized electrode surface to build up an ordered and hierarchically organized interfacial supramolecular architecture: Au/16-MHA/EG3SH/amine-PEG3-biotin/avidin. The electrode was then exposed to serum samples at different concentrations of a sandwich-type immunocomplex molecule ((Btn)Ab-AgPSA-(HRP)Ab), and its interfacial properties were characterized using electrochemical impedance spectroscopy (EIS). Calibration curves for polarization resistance (RP) and capacitance (1/C) vs. total and free PSA concentrations were obtained and their analytical quality parameters were determined. This approach was compared with results obtained from a commercially available ELISA immunosensor. The results obtained in this work showed that the proposed immunosensor can be successfully applied to analyze serum samples of patients representative of the Mexican population.

A Note on the use of Steady-State Fluorescence Quenching to Quantify Nanoparticle-Protein Interactions.

Steady-state fluorescence quenching is a commonly used technique to investigate the interactions between proteins and nanoparticles, providing quantitative information on binding affinity, stoichiometry and cooperativity. However, a failure to account for the limitations and pitfalls of the methodology can lead to significant errors in data analysis and interpretation. Thus, in this communication we first draw attention to a few common pitfalls in the use of fluorescence quenching to study nanoparticle-protein interactions. For example, we discuss a frequent mistake in the use of the Hill equation to determine cooperativity. We also test using both simulated and experimental data the application of a model-independent method of analysis to generate true thermodynamic nanoparticle-protein binding isotherms. This model-free approach allows for a quantitative description of the interactions independent of assumptions about the nature of the binding process [Bujalowski W, Lohman TM (1987) Biochemistry 26: 3099; Schwarz G (2000) Biophys. Chem. 86: 119].

Adhesion and proliferation of HeLa and fibroblast cells on chemically-modified gold surfaces.

The development of materials that allow proper functioning of cells on solid supports is directly relevant to the construction of living-cell biosensors. Both physical and chemical properties of the surfaces have been shown to be critical in this field. Our aim is to report correlations between chemical properties of surfaces and cell behavior by studying adhesion, viability and proliferation of fibroblasts and HeLa cells. Neither fibroblasts nor HeLa cells adhered to a hydrophobic surface. Fibroblasts were able to attach and proliferate well on all other surfaces tested. In contrast, on some surfaces where HeLa cells adhered and were viable, proliferation decreased by half while on others proliferation was not affected. Proliferation was significantly correlated with the level of adsorption of serum proteins on the surface (quantified by surface plasmon resonance), but not with surface wettability (water contact angle). Interestingly, surfaces modified with COOH and HSO3 groups were the ones that favored most protein adsorption and allowed the best measures for HeLa cell proliferation. The decrease of HeLa cell proliferation on surfaces covered with poly-L-lysine (PL) was related with the profile of integrin expression. Compared to a polystyrene control surface, there was an increase in αV and αVß3 and a decrease in α2 and α3, indicating that migration rather than proliferation could be favored on PL functionalized surfaces. These results indicate that charge is more important than wettability to determine biocompatibility.

Blood protein adsorption on sulfonated chitosan and κ-carrageenan films.

Many strategies have been reported to improve compatibility of biopolymers using chemical and physical modifications. One possibility is the introduction of sulfonate groups (R-SO3(-)) in the chitosan chain. Another biopolymer with similar characteristics to those of heparin is κ-carrageenan. This study proposed to investigate the application of these two polymers, based on their potential for globular protein adsorption (BSA and fibrinogen). Polymeric films of chitosan and κ-carrageenan were prepared; all films were characterized by elemental analyses, FTIR, XPS and SEM. Characterization techniques showed that the chitosan chain was modified and confirmed the existence of sulfonate groups, as well as in the κ-carrageenan chain, indicating surfaces with similar chemical properties to those of heparin. The effect of charge density was observed for each adsorption condition (BSA at pH 5.0 and 7.4). A more pronounced adsorption rate was observed at pH 5.0 than at pH 7.4 and equilibrium adsorption was achieved, in both cases, after approximately 20 min. The equilibrium data indicate a lower adsorption rate for the sulfonated chitosan film, in comparison to the other films. These results confirm the potential of modified chitosan for use in applications in which globular protein adsorption should be avoided.

BSA and fibrinogen adsorption on chitosan/κ-carrageenan polyelectrolyte complexes.

PECs of chitosan/κ-carrageenan are prepared in three different volumetric rations. The complex formation is characterized in order to evaluate the blending formation. Blood compatibility is evaluated by protein adsorption (BSA and fibrinogen) and PEC toxicities are determined with fibroblast cell viability and proliferation. The swelling degree of PECs decreases when the amount of chitosan increases. Due to the linked film formation, PECs decrease BSA adsorption and increase fibrinogen adsorption when compared to the pristine chitosan and κ-carrageenan films. Although pristine chitosan and κ-carrageenan films produced similar cell expansion and viability, the PEC 50:50 vol% chitosan/κ-carrageenan PEC may be acceptable as a new scaffold for cell therapies, due to their effect on cell survival.