Vaibhav Pandit

Design and analysis of a novel mechanical loading machine for dynamic in vivo axial loading.

This paper describes the construction of a loading machine for performing in vivo, dynamic mechanical loading of the rodent forearm. The loading machine utilizes a unique type of electromagnetic actuator with no mechanically resistive components (servotube), allowing highly accurate loads to be created. A regression analysis of the force created by the actuator with respect to the input voltage demonstrates high linear correlation (R(2) = 1). When the linear correlation is used to create dynamic loading waveforms in the frequency (0.5-10 Hz) and load (1-50 N) range used for in vivo loading, less than 1% normalized root mean square error (NRMSE) is computed. Larger NRMSE is found at increased frequencies, with 5%-8% occurring at 40 Hz, and reasons are discussed. Amplifiers (strain gauge, linear voltage displacement transducer (LVDT), and load cell) are constructed, calibrated, and integrated, to allow well-resolved dynamic measurements to be recorded at each program cycle. Each of the amplifiers uses an active filter with cutoff frequency at the maximum in vivo loading frequencies (50 Hz) so that electronic noise generated by the servo drive and actuator are reduced. The LVDT and load cell amplifiers allow evaluation of stress-strain relationships to determine if in vivo bone damage is occurring. The strain gauge amplifier allows dynamic force to strain calibrations to occur for animals of different sex, age, and strain. Unique features are integrated into the loading system, including a weightless mode, which allows the limbs of anesthetized animals to be quickly positioned and removed. Although the device is constructed for in vivo axial bone loading, it can be used within constraints, as a general measurement instrument in a laboratory setting.

Combinatorial therapy using negative pressure and varying lithium dosage for accelerated wound healing

In this work, we investigated the effects of negative pressure, applied using a pump designed for Negative Pressure Wound Therapy (NPWT), on the process of wound healing in vitro via initiation of the Wnt signaling pathway. Results indicate that negative pressure enhanced Wnt signaling and migration into a simulated wound in vitro in NIH-3T3 murine fibroblast cells. Increasing doses of lithium (upto 15 mM) increased basal Wnt signaling and enhanced cell migration into the simulated wound site. A combination of negative pressure and increased doses of lithium synergistically increased Wnt signaling and demonstrated further enhanced cell migration into simulated wound sites, with maximal filling of the simulated wound observed at lithium concentrations of at least 10mM.

Multifunctional Polysaccharide Hydrogels Capable of Mineralization, Vascularization, and Anti-bacterial Efficacy

The use of hydrogels in bone regeneration research has shown to provide a variety of benefits. Hydrogels can be modified to optimize their rheological and mechanical properties for improved bone formation and vascularization at defect sites. Hydrogels are a type of hydrated polymeric materials with properties similar to those of natural tissue as a result of their ample water constituents. The hydrogels used in this study were modified derivatives of methylcellulose, agarose, and chitosan blends capable of rapid transition from sols to gels [Zuidema 2011]. A natural chemical compound, genipin, was added to induce cross-linking in the chitosan component of the hydrogels. The added control of cross-linking enabled the increased manipulation of hydrogel stiffness without alterations in polysaccharide constituents. The ability to create multiple hydrogels with varying stiffness allowed for the determination of an optimal hydrogel stiffness for the support of mineralization and vascularization in bone defects. Hydrogel stiffness is an essential factor in cell adhesion and function, with low-stiffness gels favoring vascularization and high-stiffness gels favoring mineralization. This study aimed to determine an optimal gel stiffness that could promote both mineralization and vascularization to encourage the formation of healthy mineralized bone in defect sites. In addition, the inherent anti-bacterial efficacy of the hydrogels was evaluated as it pertained to the issue of sterilization in bone defects. In this study, we designed multifunctional hydrogels with varied stiffness and assessed their anti-bacterial efficacy and ability to promote mineralization and vascularization for eventual use in bone defect healing.

Optimizing Polymeric Nanoparticle Core Designs for Gene Delivery

Polymeric nanoparticles offer extraordinary promise as gene delivery vehicles, and recent advances in their designs have allowed for targeted deliveries with multi-stage releases of payloads. Despite these advances, delivery efficiency can still be improved. Namely, the core of a multilayered particle may be designed in such a way as to facilitate unloading once within the cell, with minimized electrostatic binding and waste of genes following endocytotic burst. Through creating a core particle that is semi-stable, further layers may functionally stabilize the polymeric complex until intracellular delivery is achieved, at which point the semistable configuration may promote payload release.

Genipin crosslinked polysaccharide hydrogels as rheologically enhanced osteoblast growth substrates

This paper aims to demonstrate how differences in rheological properties of the hydrogels affect cell growth, morphology and rates of mineralization of MC3T3-E1 osteoblast cells. To this end we developed hydrogels of varying degrees of crosslinking as determined by the ninhydrin assay. The hydrogels were made of Methylcellulose (75% w/w) Agarose (15% w/w) and Chitosan (10% w/w). The crosslinking was carried out using a naturally occurring Chitosan crosslinker, Genipin.

Relationship between deformation and electrical impedance in Mouse skin

Skin impedance is an excellent surrogate marker of skin permeability. Physical and chemical modalities that serve to increase skin permeability have direct applications in transdermal drug delivery. We have shown that the electrical impedance of skin, and consequently its permeability, can be changed by up to 60% by uniaxial stretching. This is of significant because electrical impedance has been directly correlated to skins permeability.

Reprogramming of cells using modified mRNA

Reprogramming of cells for delivery of proteins at specific sites holds great promise for future clinical applications. Chitosan delivery agents in form of nano-spheres presents a readily available biodegradable option for controlled release of mRNA in the cytosol of the cells. In this work we are using Enhanced Green Fluorescent protein as a proof of concept to show for transfection of osteoblast cells with modified mRNA. Transfection was carried out using lipofectaime RNAiMAX.