Sanjib Bhattacharyya

Carbon Nanotubes as Structural Nanofibers for Hyaluronic Acid Hydrogel Scaffolds

We have successfully dispersed functionalized single-walled carbon nanotubes (SWNTs) within hyaluronic acid-water solutions. Hybrid hyaluronic acid (HA) hydrogels with SWNTs were then formed by cross-linking with divinyl sulfone. We have found a considerable change in the morphology of the lyophilized hybrid hydrogels compared to HA hydrogels. The high water uptake capacity, an important property of HA hydrogels, remained almost unchanged after 2 wt % SWNT (vs HA) incorporation, despite a dramatic enhancement in the dynamic mechanical properties of the hybrid hydrogels compared to native ones. We have found a 300% enhancement in the storage modulus of hybrid hydrogel with only 2 wt % of SWNTs vs HA (0.06 wt % vs total weight including water content). This apparent contradiction can be explained by a networking effect between SWNTs, mediated by HA chains. As in biological tissue, HA plays a dual role of matrix and linker for the rigid reinforcing nanofibers.

Polymer-coated mesoporous silica nanoparticles for the controlled release of macromolecules.

With the goal of achieving constant release of large biological molecules over an extended period of time we focused on hybrid inorganic/organic nanoparticles. We synthesized poly(ethylene glycol) (PEG)-coated mesoporous silica nanoparticles (MSNs) with incorporated trypsin inhibitor (TI), a model protein molecule for growth factors. Due to the goal of incorporating large protein molecules the pore size of the as-synthesized MSNs was expanded by a hydrothermal treatment prior to TI incorporation. In vitro release from the MSNs without the thin polymer film shows an initial burst followed by continuous release. In the case of polymer-coated MSNs the initial burst release was completely suppressed and approximate zero order release was achieved for 4 weeks.

Measurement of interfacial shear strength in single wall carbon nanotubes reinforced composite using Raman spectroscopy

A novel method of measuring interfacial shear strength using Raman peak shift is reported. Carbon nanotubes (CNT) functionalized with biomolecules have been used to form a composite with polyvinyl alcohol. Type I collagen has proven to improve the load transfer from the matrix to the tubes leading to improvement of interfacial shear strength. Collagen interacts with single wall CNTs and probably wraps around it. When a composite structure is formed with the collagen, load transfer takes place through the collagen molecule. The interfacial strength of the nanotubes-matrix interface was found to be larger than 160 MPa, which is significantly higher than that observed before. A similar shear strength is estimated using a simple analytical calculation.

Sol–gel silica controlled release thin films for the inhibition of methicillin-resistant Staphylococcus aureus

The incidence of methicillin-resistant Staphylococcus aureus (MRSA) infection has significantly increased. Generally, the success of this bacterium as a pathogen is attributed to its ability to adhere to surfaces and remain there, under the protection of an extracellular matrix known as biofilm. To combat MRSA with regular doses of vancomycin, efforts are continuously underway to increase its effectiveness. A promising technique is to use combinational therapeutics. In vitro experiments showed that farnesol can be used as an adjuvant with conventional antibiotics. Farnesol is a natural sesquiterpenoid and quorum-sensing molecule. The biggest obstacle to using this concept is that farnesol is highly water insoluble. This compromises its bioavailability if it were to be used along with vancomycin at the site of infection when the treatment needs to be administered in vivo. Herein we designed an efficient therapeutic strategy for the simultaneous delivery of both antibiotic and adjuvant in order to treat MRSA infections. We demonstrate that sufficient quantities of both vancomycin and farnesol can be incorporated into sol-gel silica applied as thin films on an implant surface. The incorporation of the hydrophobic farnesol does not affect the stability of the thin films and neither does it affect the controlled release of vancomycin. The data demonstrate the potent adjuvant effect of farnesol on vancomycin in inhibiting MRSA infection. In vitro experiments show the complete inhibition (10(6) fold reduction in growth compared to control) of methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) when the ratio of vancomycin to farnesol in the sol-gel silica films is optimized. The local delivery of antibiotics minimizes the need for systemic antibiotics. The incorporation of vancomycin and farnesol into thin sol-gel films represents a new treatment paradigm for the topical delivery of antibiotics with adjuvant. The potential clinical benefits are significant and include avoiding the need for revision surgery, preventing surgical site infection and controlling healthcare costs.

Silicon oxide based materials for controlled release in orthopedic procedures.

By virtue of excellent tissue responses in bone tissue, silicon oxide (silica) based materials have been used for bone tissue engineering. Creating nanoscale porosity within silica based materials expands their applications into the realm of controlled release area. This additional benefit of silica based materials widens their application in the orthopedic fields in a major way. This review discusses the various chemical and physical forms of silica based controlled release materials, the release mechanisms, the applications in orthopedic procedures and their overall biocompatibility.

Self-assembled lamellar structures with functionalized single wall carbon nanotubes

Highly ordered self-assembled multi-layer structures with denatured collagen wrapped single wall carbon nanotubes and surfactant systems were obtained through bioinspired methodology.

4.34 Sol–Gel Processed Oxide Controlled Release Materials☆

In this chapter, we focus extensively on sol–gel processed silica to illustrate the benefits and to elucidate the structure–property-processing relationships of sol–gel oxides as controlled release system. We discuss the general sol–gel process and the biocompatibility of the sol–gel oxides. As a control release system, the release kinetics of the incorporated molecules is discussed. Following the discussion regarding the effect of physical and chemical processing parameters of sol–gel derived oxides on drug release kinetics, we review the applications potential of these materials in the controlled release arena. In a last section, we also summarize the various applications that are being pursued with sol–gel oxides as controlled release system for pharmaceutics and biological molecules.

Increase in the Curie temperature and magnetic anisotropy in FePd/Pt-iron oxide core-shell nanoparticles

Partially oxidized fcc FePd and FePt nanoparticles with mean diameters of 5 and 3 nm, respectively, were synthesized by a reverse micelle polyol process. In situ measurements of magnetic and structural properties during annealing showed a large increase in the magnetocrystalline anisotropy and in the Curie temperature of the nanoparticles due to (i) a phase transition from A1 to L1(0) and (ii) a simultaneous phase separation between a metallic core and an iron oxide shell. These occurred at 675 K in the FePd nanoparticles and at above 850 K for the FePt. The Curie temperature of the nanoparticles was found to be about 850 K, an increase of more than 100 K from the bulk L10 phase. The ferromagnetic resonance results are discussed and compared with a phenomenological model that makes it possible to estimate the magnetocrystalline anisotropy as 1.6 X 10(5) and 1.5 X 10(6) J m(-3) in FePd and FePt, respectively. Exchange coupling between the core and the shell explains both the high magnetocrystalline anisotropy of the core and the high Curie temperature of the shell. (c) 2009 American Institute of Physics. [doi:10.1063/1.3233936]

4.36 Silica Based Mesoporous Nanospheres

Since the independent discovery of the formation of mesostructured silica using surfactants as structure directing agents by several groups in the early 1990s, these materials have found important application in the area of catalysis, separation technology and, most recently, as biomaterials. Among all the silica based materials that have been investigated, mesoporous silica nanospheres with well-defined structures and surface properties are very promising for various biomedical applications. In this chapter we first provide a brief history along with the general synthesis procedure of mesoporous silica materials. This is followed by a description of the synthesis to obtain the mesoporous silica based microspheres and nanospheres. We also discuss the physical and chemical properties along with the general characterization techniques used for these materials. Particular attention is paid towards the applications as biomaterials.

Silica-Based Mesoporous Nanospheres

Since the independent discovery of the formation of mesostructured silica using surfactants as structure-directing agents by several groups in the early 1990s, these materials have found important applications in the areas of catalysis and separation technology and, most recently, as biomaterials. Among all the silica-based materials that have been investigated, mesoporous silica nanospheres (MSNs) promise to have great potential for various biomedical applications because of their well-defined structures and surface properties. In this chapter, we first provide a brief history of mesoporous silica materials along with the general synthesis procedure of these materials. This is followed by a description of the synthesis to obtain the mesoporous silica-based microspheres and nanospheres. We also discuss the physical and chemical properties of these materials along with the general techniques used for characterizing them. Particular attention is given to their applications as biomaterials.