Fabrication of electrospun poly(lactic acid) nanoporous membrane loaded with niobium pentoxide nanoparticles as a potential scaffold for biomaterial applications

Probing the interaction between niobium pentoxide nanoparticles and serum albumin proteins by Spectroscopic approaches

Nanoparticles (NPs) can directly or indirectly enter into the body because of their small size; then they tend to alter the conformation and function of proteins upon interaction with them. Thus, it is crucial to understand the impact of NPs in a biological medium. Recently, niobium pentoxide nanoparticles (Nb2O5 NPs) are finding increasing applications in the biological system, for example, bone tissue and dental material, matrix for biosensing of proteins, etc. In all such applications, the Nb2O5 NP interacts with proteins and other biomolecules. Hence, the study of such interactions is of considerable importance. Here in this work, we present the impact of Nb2O5 NP on the structure, stability and activity of blood proteins, bovine serum albumin (BSA) and human serum albumin (HSA) by means of various spectroscopic approaches. Steady-state fluorescence studies indicated that intrinsic fluorescence intensities of both serum albumin proteins got quenched upon their interaction with NP. The nature of the quenching was elucidated by time-resolved fluorescence and absorption measurements. Using circular dichroism (CD) and synchronous fluorescence spectroscopy (SFS), the structural perturbations of the protein molecules after interaction with NP were investigated. Moreover, the role of temperature on protein stability upon complexation with NP was also explored. In addition, the effect of NP on protein functionality was probed by esterase-like activity assays.Communicated by Ramaswamy H. Sarma.

An in vivo toxicity assessment of piezoelectric sodium potassium niobate [NaxK1-xNbO3 (x = 0.2-0.8)] nanoparticulates towards bone tissue engineering approach

One of the recent challenges in the design/development of prosthetic orthopedic implants is to address the concern of local/systemic toxicity of debris particles, released due to wear or degradation. Such debris particles often lead to inflammation at the implanted site or aseptic loosening of the prosthesis which results in failure of the implant during long run. Several in vitro studies demonstrated the potentiality of piezoelectric sodium potassium niobate [Na_xK_1-xNbO₃ (x = 0.2, 0.5, 0.8), NKN] as an emerging next-generation polarizable orthopedic implant. In this perspective, we performed an in vivo study to examine the local and systemic toxicity of NKN nanoparticulates, as a first report. In the present study, male Wistar rats were intra-articularly injected to the knee joint with 100 μl of NKN nanoparticulates (25 mg/ml in normal saline). After 7 days of exposure, the histopathological analyses demonstrate the absence of any inflammation or dissemination of nanoparticulates in vital organs such as heart, liver, kidney and spleen. The anti-inflammatory cytokines (IL-4 and IL-10) profile analyses suggest the increased anti-inflammatory response in the treated rats as compared to non-injected (control) rats, preferably for the sodium and potassium rich NKN i.e., Na_0.8K_0.2NbO₃ and Na_0.2K_0.8NbO₃. The biochemical analyses revealed no pathological changes in the liver and kidney of particulate treated rats. The present study is the first proof to confirm the non-toxic nature of NKN nanoparticulates which provides a step forward towards the development of prosthetic orthopedic implants using biocompatible piezoelectric NKN ceramics.

Interplay of surface polarization charge, dynamic electrical stimulation and compositional modification towards accelerated osteogenic response of NaxK1-xNbO3 piezo-bioceramics

Bone remodeling processes involve endogenous bioelectrical signals such as piezoelectric charges. Moreover, external electrical stimulation helps in improving the healing capability of injured tissues by modulating the metabolic signaling pathways of cells. Towards this end, the present study reveals the influence of the combined action of electrostatic surface polarization charge and dynamic pulsed electrical stimulation alongwith compositional modification towards improving the osteogenic response of emerging piezo-bioceramics, sodium potassium niobate [Na_xK_1-xNbO₃ (x = 0.2-0.8), NKN]. The dependence of crystal structure on compositions (x) was retrieved by Rietveld refinement and X-ray peak profile analyses. The surface charge, stored in the polarized (@ 25 kV at 500 °C) Na_xK_1-xNbO₃ (x = 0.2, 0.5, 0.8) samples were measured to be 0.52, 0.50 and 0.47 μC/cm², respectively, using thermally stimulated depolarized current (TSDC). X-ray photoelectron spectroscopy (XPS) survey scan spectra revealed that the polarization process does not alter the surface chemistry of NKN. Negatively charged surfaces are observed to accelerate early-stage adhesion of osteoblast-like cells which further results in enhanced spreading of adhered cells. Subsequently, the dynamic pulsed electrical stimulation of 1 V/cm with the pulse duration of 400 μs was applied, while the cells were being adhered on electrostatically charged surfaces. The quantitative and qualitative analyses revealed that the synergistic action of electrostatic surface polarization charge and dynamic pulsed electrical stimulation further accelerates cell proliferation and differentiation on negatively charged surfaces of Na and K-rich compositions of NKN. The mechanism of augmented cellular activity was analyzed using intracellular Ca²⁺ measurement.

Use of supercritical carbon dioxide technology for fabricating a tissue engineering scaffold for anterior cruciate ligament repair

Tissue-engineered grafts may be useful in Anterior Cruciate Ligament (ACL) repair and provide a novel, alternative treatment to clinical complications of rupture, harvest site morbidity and biocompatibility associated with autografts, allografts and synthetic grafts. We successfully used supercritical carbon dioxide (Sc-CO₂) technology for manufacturing a “smart” biomaterial scaffold, which retains the native protein conformation and tensile strength of the natural ACL but is decellularized for a decreased immunogenic response. We designed and fabricated a new scaffold exhibiting (1) high tensile strength and biomechanical properties comparable to those of the native tissue, (2) thermodynamically-stable extra-cellular matrix (ECM), (3) preserved collagen composition and crosslinking, (4) a decellularized material milieu with potential for future engineering applications and (5) proven feasibility and biocompatibility in an animal model of ligament reconstruction. Because of the “smart” material ECM, this scaffold may have the potential for providing a niche and for directing stem cell growth, differentiations and function pertinent to new tissue formation. Sc-CO₂-related technology is advanced and has the capability to provide scaffolds of high strength and durability, which sustain a lifetime of wear and tear under mechanical loading in vivo.