Abshar Hasan

Kinetic studies of attachment and re-orientation of octyltriethoxysilane for formation of self-assembled monolayer on a silica substrate

The present study deals with kinetic studies of the chemical modification for synthesizing a hydrophobic silica surface. Surface silanization (modification) via formation of Self-Assembled Monolayer (SAM) using a short chain triethoxyoctylsilane (TEOS) was carried out under inert atmosphere at room temperature. Fourier transmission infrared (FTIR) spectroscopy, water contact angle (WCA) and atomic force microscopy (AFM) were employed to investigate surface modification. FTIR analysis in the range from 900-1200cm(-1) and 2850-3000cm(-1) confirmed surface modification and re-orientation of the attached molecules. Kinetic studies of TEOS SAM formation were fitted by Exponential Association function. Kinetic fitting of FTIR data in the range from 900-1200cm(-1) revealed a very fast attachment of TEOS molecules resulting in total surface coverage within 16min whereas re-orientation rate was slow and continued till 512min. Further, change in orientation from lying-down to standing-up state was supported by contact angle analysis. AFM images initially showed small islands of ~20nm, which in-fill with time indicating formation of a smooth monolayer. Our findings indicate that formation of octyl SAM is fast process and completes within 8.5h in contrary to reported 24h in conventional SAM formation protocols. The kinetic fitting data can be explored to design a nanopatterned surface for a specific application.

Fabrication and characterization of Chitosan, polyvinylpyrrolidone and cellulose nanowhiskers nanocomposite films for wound healing drug delivery application

This study describes the preparation of composite film using chitosan (CS) and polyvinylpyrrolidone (PVP) with incorporated cellulose nanowhiskers (CNWs) for drug delivery application. CNWs were prepared by acid hydrolysis of cellulose with sulfuric acid. Field emission scanning electron microscopy studies revealed nanofibrous morphology of CNWs with 20-30 nm diameter and 200-250 nm in length. X-ray powder diffraction analysis confirmed highly crystalline nature of CNWs with 92.81% crystallinity. Incorporation of CNWs enhanced the thermal and mechanical properties of films. Fourier transform infrared spectroscopy data showed physical interactions between polymer-polymer and polymer-drug. Films prepared with CNWs showed improved swelling behavior which resulted in sustained drug release from polymeric matrix. In vitro curcumin release data were fitted with two-step release model; Step 1 as desorption from the outer surface of the film, and Step 2 as diffusion from within the film and subsequent desorption. The release kinetics confirmed biphasic release profile with different release rates along with diffusion controlled curcumin release. Prepared films showed high biocompatibility with excellent antibacterial activities. Overall, the performed studies confirmed CS-PVP-CNWs based release system can as a potential candidate for wound dressing applications with sustained drug release.

Review: Polymers, Surface-Modified Polymers, and Self Assembled Monolayers as Surface-Modifying Agents for Biomaterials

Biocompatibility and nontoxicity of biomaterials are of utmost importance when foreign bodies come in contact with a biological system. Irrespective of the nature of material, nonspecific protein adsorption is the first process observed at surface–biological system interfaces followed by cellular processes. Nonspecific protein adsorption leads to deleterious cellular processes such as biofouling and finally immunological host response. Hence, surface modification becomes mandatory for preventing undesirable implant failure and inflammatory responses. Various polymers, surface-modified polymers and surfaces withself assembled monolayers, have been tested to tune surface properties for a given application. Surface functional groups and surface structures of polymers and copolymers regulate surface hydrophobicity, nonspecific protein adsorption, biomaterial stability, and antifouling property, etc. Self assembled monolayers are formed by covalent linkage with more controlled surface structure and smoothness. Mixed and hybrid self assembled monolayers containing both hydrophilic and hydrophobic groups result in moderate wettability. Further, we have discussed different methods of surface modification using polymers, modified polymers, and self assembled monolayers for improved surface biocompatibility and nonfouling properties. GRAPHICAL ABSTRACT

Edible oil nanoemulsion: An organic nanoantibiotic as a potential biomolecule delivery vehicle

ABSTRACT Water-insoluble bioactive compounds typically require the formulation of lipophilic, antimicrobial delivery system to enhance their bio accessibility. Edible delivery system, in this contrast, plays an important role in food and medical industry. In the present study, an attempt has been made to increase the bioavailability of a model bioactive compound α-tocopherol as a food supplement through edible (coconut) oil nanoemulsion. A 9.5 mg mL−1 of encapsulation capacity was obtained with almost 100% release of the loaded α-tocopherol within 24 h. The nanoemulsions were analyzed for various physical and chemical stability parameters, namely, solvent, ionic concentration, temperature, rotatory motion, and various gastrointestinal pH zones. The prepared nanoemulsions were found stable to these parameters. The synthesized nanoemulsions were also evaluated for their biocompatibility and antimicrobial activity. The result showed reasonable cell viability (biocompatibility) with apposite antimicrobial activity confirming the synthesized nanoemulsion as a potential delivery vehicle. Experimental release data were fitted by combining a diffusion-controlled (Higuchi model) and a kinetic-controlled (first-order kinetics) models. The contribution of kinetic-controlled release was found about 70% and that of diffusion-controlled release was found about 30%. The present study reveals plausible application of edible oil nanoemulsion in food, beverages, and health care industries. GRAPHICAL ABSTRACT

Nano-biocomposite scaffolds of chitosan, carboxymethyl cellulose and silver nanoparticle modified cellulose nanowhiskers for bone tissue engineering applications

In the present work, we aimed to synthesize highly efficient nano-composite polymeric scaffolds with controllable pore size and mechanical strength. We prepared nanocomposite (CCNWs-AgNPs) of silver nanoparticles (AgNPs) decorated on carboxylated CNWs (CCNWs) which serves dual functions of providing mechanical strength and antimicrobial activity. Scaffolds containing chitosan (CS) and carboxymethyl cellulose (CMC) with varying percent of nanocomposite were fabricated using freeze drying method. XRD and FESEM analysis of nanocomposite revealed highly crystalline structure with AgNPs (5.2 nm dia) decorated on ~200 nm long CCNWs surface. FTIR analysis confirmed the interaction between CCNWs and AgNPs. Incorporation of nanocomposite during scaffolds preparation helped in achieving the desirable 80-90% porosity with pore diameter ranging between 150 and 500 μm and mechanical strength was also significantly improved matching with the mechanical strength of cancellous bone. The swelling capacity of scaffolds decreased after the incorporation of nanocomposite. In turn, scaffold degradation rate was tuned to support angiogenesis and vascularization. Scaffolds apart from exhibiting excellent antimicrobial activity, also supported MG63 cells adhesion and proliferation. Incorporation of CCNWs also resulted in improved biomineralization for bone growth. Overall, these studies confirmed excellent properties of fabricated scaffolds, making them self-sustained and potential antimicrobial scaffolds (without any loaded drug) to overcome bone related infections like osteomyelitis.

Surface Functionalization of Ti6Al4V via Self-assembled Monolayers for Improved Protein Adsorption and Fibroblast Adhesion

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.

Recent advances in conventional and contemporary methods for remediation of heavy metal-contaminated soils

Remediation of heavy metal-contaminated soils has been drawing our attention toward it for quite some time now and a need for developing new methods toward reclamation has come up as the need of the hour. Conventional methods of heavy metal-contaminated soil remediation have been in use for decades and have shown great results, but they have their own setbacks. The chemical and physical techniques when used singularly generally generate by-products (toxic sludge or pollutants) and are not cost-effective, while the biological process is very slow and time-consuming. Hence to overcome them, an amalgamation of two or more techniques is being used. In view of the facts, new methods of biosorption, nanoremediation as well as microbial fuel cell techniques have been developed, which utilize the metabolic activities of microorganisms for bioremediation purpose. These are cost-effective and efficient methods of remediation, which are now becoming an integral part of all environmental and bioresource technology. In this contribution, we have highlighted various augmentations in physical, chemical, and biological methods for the remediation of heavy metal-contaminated soils, weighing up their pros and cons. Further, we have discussed the amalgamation of the above techniques such as physiochemical and physiobiological methods with recent literature for the removal of heavy metals from the contaminated soils. These combinations have showed synergetic effects with a many fold increase in removal efficiency of heavy metals along with economic feasibility.

Effect of Zn/ZnO integration with hydroxyapatite: a review

Abstract Hydroxyapatite (HAp) is one of the most studied ceramic for various biomedical applications such as bone tissue engineering, biologicals delivery systems and bioactive coatings. It owns extensive biocompatibility. However, lower mechanical properties for load bearing applications, lower antimicrobial activity and lower biological interaction rates are the major lags for biomedical applications of HAp. Various researchers have tried to integrate HAp with various metals and metal ions to overcome these holdups. In this review, we have described the crystal structure of both HAp and zinc oxide (ZnO) and have majorly focused on the zinc and ZnO integration with HAp. Zn/ZnO offer several physical and biological properties. We have evaluated the effect of zinc integration over physical state and mechanical properties of HAp with latest research examples. We have appraised the additional biological properties provided by the incorporation zinc into the HAp through recent examples of researchers with varying degree of successes.

Conformational and organizational insights of serum proteins during competitive adsorption on self-assembled monolayers

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.

Synthesis, characterization and in vitro analysis of α-Fe2O3-GdFeO3 biphasic materials as therapeutic agent for magnetic hyperthermia applications

The use of gadolinium orthoferrite for biomedical application like as contrast agents for magnetic resonance imaging (MRI) has been found to be very promising due to its fascinating properties. The present study focuses on the determination of the effect of the gadolinium concentration in the formation biphasic α-Fe2O3-GdFeO3 for hyperthermia applications. An in-situ sol-gel technique was adopted for the synthesis of biphasic orthoferrites with four different gadolinium concentrations. The XRD analysis confirmed the formation of gadolinium orthoferrites after heat treatment at 1000 °C, 1100 °C, and 1200 °C. The presence of α-Fe2O3 in trace amounts was observed in the materials with low gadolinium concentrations. VSM (Vibrating-sample magnetometer) analysis was performed to ensure the magnetic properties of the materials, which were found to be weakly ferromagnetic. The biocompatibility of the materials was investigated through MTT assay and no cytotoxic effect was observed. The assessment of heating ability of the materials was performed under an alternating magnetic field using an induction heating instrument and all the samples showed temperature rise in the range of hyperthermia temperature with a maximum temperature of 55.71 °C in 6 min. The heating experiments at 44 °C in the absence of samples established the vulnerability of cancer cells as compared to normal cells.