Tuhin Subhra Santra

Bio: Tuhin Subhra Santra is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Electroporation & Materials science. The author has an hindex of 16, co-authored 69 publications receiving 676 citations. Previous affiliations of Tuhin Subhra Santra include Indian Institutes of Technology & Tsinghua University.

Infrared Pulse Laser-Activated Highly Efficient Intracellular Delivery Using Titanium Microdish Device.

Abstract: We report infrared (IR) pulse laser-activated highly efficient parallel intracellular delivery by using an array of titanium microdish (TMD) device. Upon IR laser pulse irradiation, a two-dimensional array of TMD device generated photothermal cavitation bubbles to disrupt the cell membrane surface and create transient membrane pores to deliver biomolecules into cells by a simple diffusion process. We successfully delivered the dyes and different sizes of dextran in different cell types with variations of laser pulses. Our platform has the ability to transfect more than a million cells in a parallel fashion within a minute. The best results were achieved for SiHa cells with a delivery efficiency of 96% and a cell viability of around 98% for propidium iodide dye using 600 pulses, whereas a delivery efficiency of 98% and a cell viability of 100% were obtained for dextran 3000 MW delivery using 700 pulses. For dextran 10,000 MW, the delivery efficiency was 92% and the cell viability was 98%, respectively. The device is compact, easy-to-use, and potentially applicable for cellular therapy and diagnostic purposes.

Nano-localized single-cell nano-electroporation.

Abstract: The ability to deliver foreign cargos into single living cells is of great interest in cell biology and therapeutic research. Here, we have reported a single or multiple position based nano-localized single-cell nano-electroporation platform. The device consists of an array of triangular shape ITO nano-electrodes with a 70 nm gap between two nano-electrodes, each having a 40 nm tip diameter. The voltage is applied between nano-electrodes to generate an intense electric field, which electroporates multiple nano-localized regions of the targeted single-cell membrane, and biomolecules are gently delivered into cells by pressurizing pump flow, without affecting cell viability. The platform successfully delivers dyes, QDs, and plasmids into different cell types with the variation of field strength, pulse duration, and the number of pulses. This new approach allows us to analyze delivery of different biomolecules into single living cells with high transfection efficiency (>96%, for CL1-0 cells) and high cell viability (∼98%), which are potentially beneficial for cellular therapy and diagnostic purposes.

Dielectric passivation layer as a substratum on localized single-cell electroporation

Abstract: Single-cell electroporation is a powerful technique to understand cellular behavior with heterogeneity, which might be impossible based on bulk measurements of millions of cells together. In this study, a dielectric passivation layer was deposited on top of an indium-tin oxide micro-electrode-based transparent chip surface using a plasma enhanced chemical vapour deposition technique. We theoretically and experimentally investigated the key effects of the dielectric passivation layer on localized single-cell electroporation for different cancer cells, which were randomly distributed with a high density throughout the chip surface as a monolayer. The passivation layer not only prevented the conventional or bulk electroporation with bubble and ion generation, but also provide an intense electric field in-between electrode gap for localized single-cell electroporation with high cell viability. Thus, devices with dielectric passivation layers are potentially applicable for single-cell studies.

Physical approaches for drug delivery: an overview

Abstract: Delivery of exogenous materials or cargo such as drugs, proteins, peptides, and nucleic acids into cells is a vital segment in molecular and cellular biology for potential cellular therapy and drug-discovery applications contributing toward personalization of medicine. Over the years, drug-delivery techniques have been developed in order to gain more control over the drug dosage, targeted delivery, and to minimize side effects. The major drug-delivery techniques can be classified as viral, chemical, and physical methods. Viral vectors are prominently used for gene therapy; however, they are cell-specific and have an immune response with high toxicity. Chemical methods are often limited by the low efficiency of plasmid delivery into different cell types due to plasmid degradation and toxicity. Considering these limitations, different physical methods such as photoporation, gene gun, hydrodynamic injection, electroporation, and mechanoporation, etc., are being widely developed for highly efficient cargo delivery with low toxicity. These methods are able to create transient hydrophilic membrane pores to deliver cargos into cells using different physical energies. Currently, ex vivo cargo delivery is widely studied while few in vivo applications have been developed. Concerning several obstacles to cargo delivery into cells, this chapter mainly focuses on different physical drug-delivery techniques such as electroporation, optoporation, mechanoporation, magnetoporation, and hybrid techniques along with their working mechanisms, advantages, disadvantages, and limitations. An insight into the future prospects and real-time applications of these techniques is also discussed.

Self-Supported Interconnected Pt Nanoassemblies as Highly Stable Electrocatalysts for Low-Temperatur

Abstract: In it for the long haul: Clusters of Pt nanowires (3D Pt nanoassemblies, Pt NA) serve as an electrocatalyst for low-temperature fuel cells. These Pt nanoassemblies exhibit remarkably high stability following thousands of voltage cycles and good catalytic activity, when compared with a commercial Pt catalyst and 20 % wt Pt catalyst supported on carbon black (20 % Pt/CB).

One Bacterial Cell, One Complete Genome

Abstract: While the bulk of the finished microbial genomes sequenced to date are derived from cultured bacterial and archaeal representatives, the vast majority of microorganisms elude current culturing attempts, severely limiting the ability to recover complete or even partial genomes from these environmental species. Single cell genomics is a novel culture-independent approach, which enables access to the genetic material of an individual cell. No single cell genome has to our knowledge been closed and finished to date. Here we report the completed genome from an uncultured single cell of Candidatus Sulcia muelleri DMIN. Digital PCR on single symbiont cells isolated from the bacteriome of the green sharpshooter Draeculacephala minerva bacteriome allowed us to assess that this bacteria is polyploid with genome copies ranging from approximately 200-900 per cell, making it a most suitable target for single cell finishing efforts. For single cell shotgun sequencing, an individual Sulcia cell was isolated and whole genome amplified by multiple displacement amplification (MDA). Sanger-based finishing methods allowed us to close the genome. To verify the correctness of our single cell genome and exclude MDA-derived artifacts, we independently shotgun sequenced and assembled the Sulcia genome from pooled bacteriomes using a metagenomic approach, yielding a nearly identical genome. Four variations we detected appear to be genuine biological differences between the two samples. Comparison of the single cell genome with bacteriome metagenomic sequence data detected two single nucleotide polymorphisms (SNPs), indicating extremely low genetic diversity within a Sulcia population. This study demonstrates the power of single cell genomics to generate a complete, high quality, non-composite reference genome within an environmental sample, which can be used for population genetic analyzes.