Soumya Bhattacharya

Comparison study of ferrofluid and powder iron oxide nanoparticle permeability across the blood–brain barrier

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 blood–brain barrier, and deserve further investigation for a wide range of applications.

Controlling ferrofluid permeability across the blood-brain barrier model

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).

Comparative Study of Biomimetic Iron Oxides Synthesized Using Microwave Induced and Conventional Method

Aqueous ferrofluids having high steric stability were prepared biomimetically by chemical co-precipitation of iron salts in poly (vinyl) alcohol. Both conventional and microwave heating modes were used for the synthesis of the fluids; the bottleneck of conventional heating being low saturation magnetization. The uniqueness of this work lies in the fact that for the same initial constituents, microwave irradiation enhances saturation magnetization without compensating stability. Superparamagnetic iron oxide nanoparticles with a narrow size distribution were formed, and structural investigations of the dried fluid revealed that microwave irradiation increased the polydispersity and the average particle size of the nanocomposites which led to a loss of long-range ordering. X-ray diffraction patterns of the synthesized ferrofluids showed an increase in crystallinity for the microwave irradiated sample. All these structural rearrangements affected the saturation magnetization (Ms) which more than doubled from 12.97 to 27.07 kAm-1 with microwave irradiation.

Colloidal graphite/graphene nanostructures using collagen showing enhanced thermal conductivity

In the present study, the exfoliation of natural graphite (GR) directly to colloidal GR/graphene (G) nanostructures using collagen (CL) was studied as a safe and scalable process, akin to numerous natural processes and hence can be termed “biomimetic”. Although the exfoliation and functionalization takes place in just 1 day, it takes about 7 days for the nano GR/G flakes to stabilize. The predominantly aromatic residues of the triple helical CL forms its own special micro and nanoarchitecture in acetic acid dispersions. This, with the help of hydrophobic and electrostatic forces, interacts with GR and breaks it down to nanostructures, forming a stable colloidal dispersion. Surface enhanced Raman spectroscopy, X-ray diffraction, photoluminescence, fluorescence, and X-ray photoelectron spectroscopy of the colloid show the interaction between GR and CL on day 1 and 7. Differential interference contrast images in the liquid state clearly reveal how the GR flakes are entrapped in the CL fibrils, with a corresponding fluorescence image showing the intercalation of CL within GR. Atomic force microscopy of graphene-collagen coated on glass substrates shows an average flake size of 350 nm, and the hexagonal diffraction pattern and thickness contours of the G flakes from transmission electron microscopy confirm ≤ five layers of G. Thermal conductivity of the colloid shows an approximate 17% enhancement for a volume fraction of less than approximately 0.00005 of G. Thus, through the use of CL, this new material and process may improve the use of G in terms of biocompatibility for numerous medical applications that currently employ G, such as internally controlled drug-delivery assisted thermal ablation of carcinoma cells.

Liquid phase collagen modified graphene that induces apoptosis

Direct exfoliation of graphite (GR) to collagen modified graphene (G) flakes using acylated collagen has been studied. The chemical structure of collagen (CL) and all liquid exfoliants studied so far have striking similarity, namely, the hydrocarbon chain length, aromatic residues and polarity. Here, CL dispersed in acetic (AA), succinic (SA) and propionic (PA) acid behaves as three different surfactants which have been used to simultaneously exfoliate and disperse nano G platelets to a colloidal form. Transmission electron microscopy micrographs show average dimensions of ∼500 × 200 nm; Moire patterns observed at several places in all the three samples indicate periodic perturbations in the graphitic stacking and selected area electron diffraction confirms graphene formation. AFM images confirmed the same lateral dimensions with an average thickness of 1.2 nm. The Raman spectra revealed strain dependent splitting and a red shift of 2D bands, a maximum in G-PA and minimum in G-AA. X-ray photoelectron spectroscopy showed a decrease of the sp2/sp3 ratio GR post CL interaction indicating an interaction. The zeta potential, fluorescence and luminescence values changed in G, with maximum variation in G-PA; suggesting that CL dispersed in PA is the best. The bioactivity of colloidal G-PA was studied in solid, hematological and neuronal cancer cell lines. It induced reactive oxygen species and cell death in cancer cell lines and altered membrane integrity while sparing normal cells, underscoring its possible utility in cancer therapy.

Anomalously Augmented Charge Transport Capabilities of Biomimetically Transformed Collagen Intercalated Nanographene-Based Biocolloids

Collagen microfibrils biomimetically intercalate graphitic structures in aqueous media to form graphene nanoplatelet-collagen complexes (G-Cl). Synthesized G-Cl-based stable, aqueous bionanocolloids exhibit anomalously augmented charge transportation capabilities oversimple collagen or graphene based colloids. The concentration tunable electrical transport properties of synthesized aqueous G-Cl bionanocolloids has been experimentally observed, theoretically analyzed, and mathematically modeled. A comprehensive approach to mathematically predict the electrical transport properties of simple graphene and collagen based colloids has been presented. A theoretical formulation to explain the augmented transport characteristics of the G-Cl bionanocolloids based on the physicochemical interactions among the two entities, as revealed from extensive characterizations of the G-Cl biocomplex, has also been proposed. Physical interactions between the zwitterionic amino acid molecules within the collagen triple helix with the polar water molecules and the delocalized π electrons of graphene and subsequent formation of partially charged entities has been found to be the crux mechanism behind the augmented transport phenomena. The analysis has been observed to accurately predict the degree of enhancement in transport of the concentration tunable composite colloids over the base colloids. The electrically active G-Cl bionanocolloids with concentration tunability promises find dual utility in novel gel bioelectrophoresis-based protein separation techniques and advanced surface charge modulated drug delivery using biocolloids.

Multi-functional biomimetic graphene induced transformation of Fe3O4 to ε-Fe2O3 at room temperature

Epsilon-iron oxide (e-Fe2O3) has been synthesized in large yields (≈73.7%) in a colloidal form at ambient conditions. Being embedded in biomimetic graphene, the synthesized thermodynamically unstable monoclinic phase is prevented from transforming to other phases. We have used the same protein–polymer mixture both for exfoliating natural graphite and as templating agents for iron oxide nanoparticles. X-ray diffraction of the composites confirms the formation of the e-Fe2O3 phase with minor quantities (≈26.3%) of cubic magnetite (Fe3O4). The particle size and distribution was studied using high resolution transmission electron microscopy which clearly shows self-assembled dense nanoparticles on graphene sheets. This exercises strain on graphene; evident from the highly broadened D and G bands of Raman measurements and the blue shifting of the G band. X-ray photoelectron spectra shows signatures of iron oxide, graphene and protein in the sample; deconvoluted C1s, O1s and N1s core level peaks confirm both the attachment of the nanoparticles with the substrate and Fe2p core level peaks reveal the high spin oxidation state of Fe3+ ions. Magnetic measurements confirm the superparamagnetic nature of the composites; the lack of coercivity unexpected of this polymorph may be explained by the low magnetocrystalline anisotropy of the randomly oriented graphene sheets. We suspect that graphene attracts the maximum ferric (Fe3+) ions of the mixed ferrous/ferric ions in the system resulting in ferrous (Fe2+) cation substitution which also results in the reduction of coercivity. Exchange bias was also observed at low temperature in this antiferro–ferrimagnetic hybrid film.

Fluorimetric assay of interaction of protein with ferrofluids

Magnetic iron oxide nanoparticles are inherently biocompatible and are amenable to post synthesis surface modification, making them excellent candidates for many important applications. If the above can be achieved in a single-step i.e., in situ synthesis and functionalization, the results are expected to be more dramatic for sensitive detection of biomolecules. For any application, it is necessary to confer a high level of binding specificity through surface chemistry, which can be introduced by using biological moieties that possess lock-and-key interactions, like those observed in antibody-antigen and enzyme-substrate recognition. In this paper, we have synthesized water based ferrofluids with serum albumin, the major protein component of blood. A series of other ferrofluids using different biocompatible polymers have also been studied with respect to their size determined by transmission electron microscopy, magnetic behavior with the aid of vibrating sample magnetometry and binding capability to bovine serum albumin by quenching of its native fluorescence. From our results, it can be inferred that binding has taken place between magnetic particles and biomolecules, the binding constants of which indirectly reveal the efficiency of the interaction.

Optimizing superparamagnetic iron oxide nanoparticles as drug carriers using an in vitro blood–brain barrier model

In the current study, an optimized in vitro blood–brain barrier (BBB) model was established using mouse brain endothelial cells (b.End3) and astrocytes (C8-D1A). Before measuring the permeability of superparamagnetic iron oxide nanoparticle (SPION) samples, the BBB was first examined and confirmed by an immunofluorescent stain and evaluating the transendothelial electrical resistance. After such confirmation, the permeability of the following five previously synthesized SPIONs was determined using this optimized BBB model: 1) GGB (synthesized using glycine, glutamic acid, and bovine serum albumin [BSA]), 2) GGC (glycine, glutamic acid, and collagen), 3) GGP (glycine, glutamic acid, and polyvinyl alcohol), 4) BPC (BSA, polyethylene glycol, and collagen), and 5) CPB (collagen, polyvinyl alcohol, and BSA). More importantly, after the permeability test, transmission electron microscopy thin section technology was used to investigate the mechanism behind this process. Transmission electron microscopy thin section images supported the hypothesis that collagen-coated CPB SPIONs displayed better cellular uptake than glycine and glutamine acid-coated GGB SPIONs. Such experimental data demonstrated how one can modify SPIONs to better deliver drugs to the brain to treat a wide range of neurological disorders.

Two-dimensional collagen-graphene as colloidal templates for biocompatible inorganic nanomaterial synthesis

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 sp2/sp3 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.