Sulalit Bandyopadhyay

L‐DOPA‐Coated Manganese Oxide Nanoparticles as Dual MRI Contrast Agents and Drug‐Delivery Vehicles

Manganese oxide nanoparticles (MONPs) are capable of time-dependent magnetic resonance imaging contrast switching as well as releasing a surface-bound drug. MONPs give T2/T2* contrast, but dissolve and release T1-active Mn(2+) and L-3,4-dihydroxyphenylalanine. Complementary images are acquired with a single contrast agent, and applications toward Parkinsons disease are suggested.

Controlling the self-assembly and optical properties of gold nanoclusters and gold nanoparticles biomineralized with bovine serum albumin

While the size-dependent optical properties of BSA-stabilized gold nanoclusters are well known, the time-dependent growth mechanism remains to be described. Herein, we systematically compare two synthesis methods with and without ascorbic acid, and show that tuning of BSA-stabilized gold nanoclusters (AuNCs) of different sizes can be performed without the aid of an extrinsic reducing agent and with good reproducibility. We also show that adding ascorbic acid yields larger BSA-stabilized gold nanoparticles (AuNPs), and that AuNPs can only form above a threshold gold precursor concentration. Using computed tomography, we describe how these biomineralized AuNPs show size-dependent X-ray attenuation. Growth of BSA-stabilized AuNCs and AuNPs, over a range of gold precursor concentrations, was followed with steady-state fluorescence and UV-vis spectroscopy for one week, constituting the first study of its kind. Based on our results, we propose a mechanism for BSA-stabilization of AuNCs and AuNPs that can further aid in selective growth of discrete AuNCs and AuNPs.

A robust method to calculate the volume phase transition temperature (VPTT) for hydrogels and hybrids

Here, we report three different methods to determine the volume phase transition temperature (VPTT) of various systems including poly(N-isopropylacrylamide) (pNIPAm) based nanogels, Au nanoclusters and a combination of inorganic and polymeric systems. Although all the methods reveal close VPTT values, we suggest that method III is the least computation dependent and most reliable. In an attempt to define the overall system reversibility, a predictive reversibility parameter (RP) was defined that explains the system behavior at each state point. RP takes into consideration all the system states during both heating and cooling cycles. Reversible systems were found to have RP values less than 1, while irreversible systems were observed to have RP values of 2. We predict that real systems will show RP values between 1 and 2. Thus, by knowing both the systems VPTT and its reversibility, a particular application can be designed or upgraded.

Synthesis, Characterization and Drug Loading of Multiresponsive p[NIPAm-co-PEGMA] (core)/p[NIPAm-co-AAc] (Shell) Nanogels with Monodisperse Size Distributions

We report the synthesis and properties of temperature- and pH-responsive p([NIPAm-co-PEGMA] (core)/[NIPAm-co-AAc] (shell)) nanogels with narrow size distributions, tunable sizes and increased drug loading efficiencies. The core-shell nanogels were synthesized using an optimized two-stage seeded polymerization methodology. The core-shell nanogels show a narrow size distribution and controllable physico-chemical properties. The hydrodynamic sizes, charge distributions, temperature-induced volume phase transition behaviors, pH-responsive behaviors and drug loading capabilities of the core-shell nanogels were investigated using transmission electron microscopy, zeta potential measurements, dynamic light scattering and UV-Vis spectroscopy. The size of the core-shell nanogels was controlled by polymerizing NIPAm with crosslinker poly(ethylene glycol) dimethacrylate (PEGDMA) of different molecular weights (Mn-200, 400, 550 and 750 g/mol) during the core synthesis. It was found that the swelling/deswelling kinetics of the nanogels was sharp and reversible; with its volume phase transition temperature in the range of 40–42 °C. Furthermore, the nanogels loaded with l-3,4-dihydroxyphenylalanine (L-DOPA), using a modified breathing-in mechanism, showed high loading and encapsulation efficiencies, providing potential possibilities of such nanogels for biomedical applications.

Growing gold nanostructures for shape-selective cellular uptake

With development in the synthesis of shape- and size-dependent gold (Au) nanostructures (NSs) and their applications in nanomedicine, one of the biggest challenges is to understand the interaction of these shapes with cancer cells. Herein, we study the interaction of Au NSs of five different shapes with glioblastoma-astrocytoma cells. Three different shapes (nanorods, tetrahexahedra, and bipyramids), possessing tunable optical properties, have been synthesized by a single-step seed-mediated growth approach employing binary surfactant mixtures of CTAB and a secondary surfactant. By the use of two-step seed-mediated approach, we obtained new NSs, named nanomakura (Makura is a Japanese word used for pillow) which is reported for the first time here. Spherical Au nanoparticles were prepared by the Turkevich method. To study NS-cell interactions, we functionalized the NSs using thiolated PEG followed by 11-Mercaptoundecanoic acid. The influence of shape and concentration of NSs on the cytotoxicity were assessed with a LIVE/DEAD assay in glioblastoma-astrocytoma cells. Furthermore, the time-dependent uptake of nanomakura was studied with TEM. Our results indicate that unlike the other shapes studied here, the nanomakura were taken up both via receptor-mediated endocytosis and macropinocytosis. Thus, from our library of different NSs with similar surface functionality, the shape is found to be an important parameter for cellular uptake.

The Influence of Differently Shaped Gold Nanoparticles Functionalized with NIPAM-Based Hydrogels on the Release of Cytochrome C

Here, we report the synthesis and functionalization of five different shapes of Au nanoparticles (NPs), namely nanorods, tetrahexahedral, bipyramids, nanomakura, and spheres with PEG and poly (N-isopropylacrylamide)-acrylic acid (pNIPAm-AAc) hydrogels. The anisotropic NPs are synthesized using seed-mediated growth in the presence of silver. The NPs have been characterized using Dynamic Light Scattering (DLS), zeta potential measurements, UV-Visible spectrophotometry (UV-Vis), and Scanning Transmission Electron Microscopy (S(T)EM). Cyt C was loaded into the PEG-hydrogel-coated AuNPs using a modified breathing-in method. Loading efficiencies (up to 80%), dependent on particle geometry, concentration, and hydrogel content, were obtained. Release experiments conducted at high temperature (40 °C) and acidic pH (3) showed higher release for larger sizes of PEG-hydrogel-coated AuNPs, with temporal transition from spherical to thin film release geometry. AuNP shape, size, number density, and hydrogel content are found to influence the loading as well as release kinetics of Cyt C from these systems.