Although metallic biomaterials find numerous biomedical applications, their inherent low bioactivity and poor osteointegration had been a great challenge for decades. Surface modification via silanization can serve as an attractive method for improving the aforementioned properties of such substrates. However, its effect on protein adsorption/conformation and subsequent cell adhesion and spreading has rarely been investigated. This work reports the in-depth study of the effect of Ti6Al4V surface functionalization on protein adsorption and cell behavior. We prepared self-assembled monolayers (SAMs) of five different surfaces (amine, octyl, mixed [1:1 ratio of amine:octyl], hybrid, and COOH). Synthesized surfaces were characterized by Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy, contact angle goniometry, profilometry, and field emission scanning electron microscopy (FESEM). Quantification of adsorbed mass of bovine serum albumin (BSA) and fibronectin (FN) was determined on different surfaces along with secondary structure analysis. The adsorbed amount of BSA was found to increase with an increase in surface hydrophobicity with the maximum adsorption on the octyl surface while the reverse trend was detected for FN adsorption, having the maximum adsorbed mass on the COOH surface. The α-helix content of adsorbed BSA increased on amine and COOH surfaces while it decreased for other surfaces. Whereas increasing β-turn content of the adsorbed FN with the increase in the surface hydrophobicity was observed. In FN, RGD loops are located in the β-turn and consequently the increase in Δ adhered cells (%) was predominantly increased with the increasing Δ β-turn content (%). We found hybrid surfaces to be the most promising surface modifier due to maximum cell adhesion (%) and proliferation, larger nuclei area, and the least cell circularity. Bacterial density increased with the increasing hydrophobicity and was found maximum for the amine surface (θ = 63 ± 1°) which further decreased with the increasing hydrophobicity. Overall, modified surfaces (in particular hybrid surface) showed better protein adsorption and cell adhesion properties as compared to unmodified Ti6Al4V and can be potentially used for tissue engineering applications.

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In recent years, water pollution and pesticide accumulation in the food chain have become a serious environmental and health hazard problem. Direct determination of these contaminants is a difficult task due to their low concentration level and the matrix interferences. Therefore, an efficient separation and preconcentration procedure is often required prior to the analysis. With the advancement in nanotechnology, various types of magnetic core-shell nanoparticles have successfully been synthesized and received considerable attention as sorbents for decontamination of diverse matrices. Magnetic core-shell nanoparticles with surface modifications have the advantages of large surface-area-to-volume ratio, high number of surface active sites, no secondary pollutant, and high magnetic properties. Due to their physicochemical properties, surface-modified magnetic core-shell nanoparticles exhibit high adsorption efficiency, high rate of removal of contaminants, and easy as well as rapid separation of adsorbent from solution via external magnetic field. Such facile separation is essential to improve the operation efficiency. In addition, reuse of nanoparticles would substantially reduce the treatment cost. In this review article, we have attempted to summarize recent studies that address the preconcentration methods of pesticide residue analysis and removal of toxic contaminants from aquatic systems using magnetic core-shell nanoparticles as adsorbents.

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Surface modification plays a vital role in regulating protein adsorption and subsequently cell adhesion. In the present work, we prepared nanoscaled modified surfaces using silanization and characterized them using Fourier-transform infrared spectroscopy (FTIR), water contact angle (WCA), and atomic force microscopy (AFM). Five different (amine, octyl, mixed, hybrid, and COOH) surfaces were prepared based on their functionality and varying wettability and their effect on protein adsorption and initial cell adhesion was investigated. AFM analysis revealed nanoscale roughness on all modified surfaces. Fetal bovine serum (FBS) was used for protein adsorption experiment and effect of FBS was analyzed on initial cell adhesion kinetics (up to 6 h) under three different experimental conditions: (a) with FBS in media, (b) with preadsorbed FBS on surfaces, and (c) incomplete media, i.e., without FBS. Various cell features such as cell morphology/circularity, cell area and nuclei size were also studied for the above stated conditions at different time intervals. The cell adhesion rate as well as cell spread area were highest in the case of surfaces with preadsorbed FBS. We observed higher surface coverage rate by adhering cells on hybrid (rate, 0.073 h–1) and amine (0.072 h–1) surfaces followed by COOH (0.062 h–1) and other surfaces under preadsorbed FBS condition. Surface treated with cells in incomplete media exhibited least adhesion rate, poor cell spreading and improper morphology. Furthermore, we found that initial cell adhesion rate and Δadhered cells (%) linearly increased with the change in α-helix content of adsorbed FBS on surfaces. Among all the modified surfaces and under all three experimental conditions, hybrid surface exhibited excellent properties for supporting cell adhesion and growth and hence can be potentially used as surface modifiers in biomedical applications to design biocompatible surfaces.

Physicochemical interactions of proteins with surfaces mediate the interactions between the implant and the biological system. Surface chemistry of the implant is crucial as it regulates the events at the interface. The objective of this study was to explore the performance of modified surfaces for such interactions relevant to various biomedical applications. Because of a wide range of surface wettability, we aimed to study protein behavior (i.e., conformational changes and their packing) during competitive protein adsorption. Three serum proteins (bovine serum albumin, BSA; fibrinogen, FB; and immunoglobulin G, IgG) were tested for their conformational changes and orientation upon adsorption on hydrophilic (COOH and amine), moderately hydrophobic (mixed and hybrid), and hydrophobic (octyl) surfaces generated via silanization. Modified surfaces were characterized using Fourier-transform infrared spectroscopy, contact angle, and atomic force microscopy (AFM) techniques. Adsorbed masses of proteins from single and binary protein solutions on different surfaces were quantified along with their secondary structure analyses. Maximum adsorbed protein masses were found to be on negatively charged and hydrophobic (octyl) surfaces because of ionic and hydrophobic interactions between protein molecules and surfaces, respectively. Side-on and end-on orientations of adsorbed protein molecules were analyzed using theoretical and AFM analyses. We observed compact and elongated forms of BSA molecules on hydrophilic and hydrophobic surfaces, respectively. We further found a linear increase in the α-helix content of BSA and β-sheet contents of FB and IgG proteins with the increasing side-on (%)-oriented protein molecules on the surfaces. This indicates that side-on orientations of adsorbed FB and IgG lead to the formation of β-sheets. Sodium dodecyl sulfate polyacrylamide gel electrophoresis was employed to quantify the protein types and their ratio in competitively adsorbed proteins on different surfaces. A theoretical analysis was also used to determine the % secondary structures of competitively adsorbed proteins from BSA/FB and BSA/IgG solutions, which very well agreed with experimental results. The competitive protein adsorption from both BSA/FB and BSA/IgG solutions was found to be entropy-driven, as revealed by thermodynamic studies performed using isothermal titration calorimetry.

Synthetic osteo‐promoting materials that are able to stimulate and accelerate bone formation without the addition of exogenous cells or growth factors represent a major opportunity for an aging world population. A co‐assembling system that integrates hyaluronic acid tyramine (HA‐Tyr), bioactive peptide amphiphiles (GHK‐Cu2+), and Laponite (Lap) to engineer hydrogels with physical, mechanical, and biomolecular signals that can be tuned to enhance bone regeneration is reported. The central design element of the multicomponent hydrogels is the integration of self‐assembly and enzyme‐mediated oxidative coupling to optimize structure and mechanical properties in combination with the incorporation of an osteo‐ and angio‐promoting segments to facilitate signaling. Spectroscopic techniques are used to confirm the interplay of orthogonal covalent and supramolecular interactions in multicomponent hydrogel formation. Furthermore, physico‐mechanical characterizations reveal that the multicomponent hydrogels exhibit improved compressive strength, stress relaxation profile, low swelling ratio, and retarded enzymatic degradation compared to the single component hydrogels. Applicability is validated in vitro using human mesenchymal stem cells and human umbilical vein endothelial cells, and in vivo using a rabbit maxillary sinus floor reconstruction model. Animals treated with the HA‐Tyr‐HA‐Tyr‐GHK‐Cu2+ hydrogels exhibit significantly enhanced bone formation relative to controls including the commercially available Bio‐Oss.