The nucleation and growth of hydroxyapatite is closely associated with the extracellular matrix environment. Bovine Serum Albumin, Collagen and poly vinyl alcohol were used to mimic the extracellular matrix. An attempt to understand the role of these matrices on the synthesis and function of Hydroxyapatite has been made. XRD, FT-IR, XPS, TG-DTA, SEM and TEM confirmed the formation of hydroxyapatite synthesized by the biomimetic route. Further the role of organic matrix in controlling the nucleation and growth of hydroxyapatite particles in the nano level is understood by the in-depth analysis of the XPS spectra. The in vitro release of the anti-cancer drug methotrexate, in aqueous solution was studied and the in vitro release profile was assayed by elution in phosphate buffered saline with pH 7.4 and pH 5 at 37 º C. The percentage of loading and release profiles of drug were evaluated. The results show that the use of matrix increased the drug release efficiency from 44.5% to 66% at pH 7.4 and 78% to 98.92% at pH 5. These results suggest that the synthesized hydroxyapatite can be used as a pH responsive vehicle for delivering drugs. Further the release profile was predicted by Higuchi and Peppas model. The results suggested that the release mechanism was governed by the Fickian diffusion for initial 8 hrs followed by anomalous transport for longer time. The cytocompatibility of the materials was evaluated by in vitro cytotoxicity test. Both MTT and live/dead assay observations indicated that the material had no adverse impact on the cell proliferation. The results imply these composites to be bioactive having a good cytocompatibility. Although all the matrices showed good results, the one with poly vinyl alcohol exhibited higher biocompatibility and drug release efficiency. A plausible explanation was proposed for the enhanced drug delivery efficiency of these materials.

For the first time, the heat dried biomass of a newly isolated fungus Arthrinium malaysianum was studied for the toxic Cr(VI) adsorption, involving more than one mechanism like physisorption, chemisorption, oxidation-reduction and chelation. The process was best explained by the pseudo-second order kinetic model and Redlich-Peterson isotherm with maximum predicted biosorption capacity (Q m) of 100.69 mg g−1. Film-diffusion was the rate-controlling step and the adsorption was spontaneous, endothermic and entropy-driven. The mode of interactions between Cr(VI) ions and fungal biomass were investigated by several methods [Fourier Transform-Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD) and Energy-Dispersive X-ray spectroscopy (EDX)]. X-ray Photoelectron Spectroscopy (XPS) studies confirmed significant reduction of Cr(VI) into non-toxic Cr(III) species. Further, a modified methodology of Atomic Force Microscopy was successfully attempted to visualize the mycelial ultra-structure change after chromium adsorption. The influence of pH, biomass dose and contact time on Cr(VI) depletion were evaluated by Response Surface Model (RSM). FESEM-EDX analysis also exhibited arsenic (As) and lead (Pb) peaks on fungus surface upon treating with synthetic solutions of NaAsO2 and Pb(NO3)2 respectively. Additionally, the biomass could also remove chromium from industrial effluents, suggesting the fungal biomass as a promising adsorbent for toxic metals removal.

Controlled size, shape and dispersibility of superparamagnetic iron oxide nanoparticles (SPIONs), has been achieved in a protein-polymer colloidal dispersion. Stable ferrofluid (FF) is synthesized in an aqueous medium of collagen, bovine serum albumin and poly(vinyl) alcohol that equilibrates with time, at ambient conditions, into an organized matrix with iron oxide particles sterically caged at defined sites. It mimics a biomineralization system; hence the process is termed biomimetics. Though the exact mechanism is not understood at this stage, we have established, with serial dilution of the protein-polymer solution that the SPIONs are formed inside the self-contained clusters of the two proteins and the polymer, which show a tendency to self assemble. More than the interparticle dipolar attractions of magnetic particles, electrostatic interactions play a role in cluster formation and collagen is responsible for the overall stability, supported by systematic dynamic light scattering data. The basic aim of this study was to increase magnetization of a previously synthesized ferrofluid without hampering stability, by reducing the total macromolecular concentration. Thrice the magnetization was achieved and in addition, the synthesized FFs exhibited very high transverse relaxivity and showed good contrast in mice liver, in the in vivo studies.

Heuristic picture connoting the green synthesis of iron substituted hydroxyapatite nanoparticles having versatile properties.

In the present study, an in vitro blood–brain barrier model was developed using murine brain endothelioma cells (b.End3 cells). Confirmation of the blood–brain barrier model was completed by examining the permeability of FITCDextran at increasing exposure times up to 96 h in serum-free medium and comparing such values with values from the literature. After such confirmation, the permeability of five novel ferrofluid (FF) nanoparticle samples, GGB (ferrofluids synthesized using glycine, glutamic acid and BSA), GGC (glycine, glutamic acid and collagen), GGP (glycine, glutamic acid and PVA), BPC (BSA, PEG and collagen) and CPB (collagen, PVA and BSA), was determined using this blood–brain barrier model. All of the five FF samples were characterized by zeta potential to determine their charge as well as TEM and dynamic light scattering for determining their hydrodynamic diameter. Results showed that FF coated with collagen passed more easily through the blood–brain barrier than FF coated with glycine and glutamic acid based on an increase of 4.5% in permeability. Through such experiments, diverse magnetic nanomaterials (such as FF) were identified for: (1) MRI use since they were less permeable to penetrate the blood–brain barrier to avoid neural tissue toxicity (e.g. GGB) or (2) brain drug delivery since they were more permeable to the blood–brain barrier (e.g. CPB).

In this study, natural graphite was first converted to collagen-graphene composites and then used as templates for the synthesis of nanoparticles of silver, iron oxide, and hydroxyapatite. X-ray diffraction did not show any diffraction peaks of graphene in the composites after inorganic nucleation, compared to the naked composite which showed (002) and (004) peaks. Scanning electron micrographs showed lateral gluing/docking of these composites, possibly driven by an electrostatic attraction between the positive layers of one stack and negative layers of another, which became distorted after inorganic nucleation. Docking resulted in single layer-like characteristics in certain places, as seen under transmission electron microscopy, but sp 2 /sp 3 ratios from Raman analysis inferred three-layer composite formation. Strain-induced folding of these layers into uniform clusters at the point of critical nucleation, revealed beautiful microstructures under scanning electron microscopy. Lastly, cell viability studies using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays showed the highest cell viability for the collagen-graphene-hydroxyapatite composites. In this manner, this study provided – to the field of nanomedicine – a new process for the synthesis of several nanoparticles (with low toxicity) of high interest for numerous medical applications.

This paper describes a simple method for the room temperature synthesis of magnetite/hydroxyapatite composite nanocomposites using ferrofluids. The in situ synthesis of magnetic-hydroxyapatite results in a homogenous distribution of the two phases as seen both in transmission electron micrographs and assembled to a micron range in the confocal micrographs. The selected area diffraction pattern analysis shows the presence of both phases of iron oxide and hydroxyapatite. To the dialyzed ferrofluid, the constituents of hydroxyapatite synthesis was added, the presence of the superparamagnetic iron oxide particles imparts directionality to the hydroxyapatite crystal growth. Electron probe microanalysis confirms the co-existence of both iron and calcium atoms. Vibrating Sample magnetometer data shows magnetization three times more than the parent ferrofluid, the local concentration of iron oxide nanoparticles affects the strength of dipolar interparticle interactions changing the energy barrier for determining the collective magnetic behavior of the sample. The limitations inherent to the use of external magnetic fields which can be circumvented by the introduction of internal magnets located in the proximity of the target by a minimal surgery or by using a superparamagnetic scaffold under the influence of externally applied magnetic field inspires us to increase the magnetization of our samples. The composite in addition shows anti-bacterial properties against the two gram (-ve) bacteria tested. This work is significant as magnetite-hydroxyapatite composites are attracting a lot of attention as adsorbents, catalysts, hyperthermia agents and even as regenerative medicine.

Abstract:In the present study, the permeability of 11 different iron oxide nanoparticle (IONP) samples (eight fluids and three powders) was determined using an in vitro blood-brain barrier model. Importantly, the results showed that the ferrofluid formulations were statistically more permeable than the IONP powder formulations at the blood-brain barrier, suggesting a role for the presently studied in situ synthesized ferrofluid formulations using poly(vinyl) alcohol, bovine serum albumin, collagen, glutamic acid, graphene, and their combinations as materials which can cross the blood-brain barrier to deliver drugs or have other neurological therapeutic efficacy. Conversely, the results showed the least permeability across the blood-brain barrier for the IONP with collagen formulation, suggesting a role as a magnetic resonance imaging contrast agent but limiting IONP passage across the blood-brain barrier. Further analysis of the data yielded several trends of note, with little correlation between permeability and fluid zeta potential, but a larger correlation between permeability and fluid particle size (with the smaller particle sizes having larger permeability). Such results lay the foundation for simple modification of iron oxide nanoparticle formulations to either promote or inhibit passage across the bloodbrain barrier, and deserve further investigation for a wide range of applications.