Shourya Dutta-Gupta

Islet transplantation is emerging as a promising strategy for Type 1 Diabetes mellitus(T1DM). However, the limited extracellular matrix (ECM) support and insufficient microenvironments alter the beta cell function, thereby affecting insulin production and the longevity of islet function. In this study, a 3D-printed islet construct using MIN6 cell lines was bioengineered using a composite hydrogel comprising human umbilical cord-derived decellularized extracellular matrix (UdECM) and hyaluronic acid methacrylate (HAMA).The extracellular components of UdECM, including proteins and glycosaminoglycans, promoted enhanced cell viability, proliferation, cell adhesion, cellular connections, and also exhibited low immunogenicity with its highly enriched biochemical cues and its biomimetic milieu.HAMA,on the other hand, was used as the combination material along with UdECM to increase the mechanical properties of the hydrogel, and it has been proven to have an excellent cell viability, along with low immunogenicity. The 3D-bioprinted UdECM HAMA hydrogel exhibited superior structural stability, and it supported the assembly of MIN6 cells into multiple microspheroid-like structures, resulting in improved islet function and enhanced insulin secretion in vitro.This approach emphasizes the importance of human-derived extracellular matrix (ECM) in creating physiologically accurate islet transplant structures by providing a customized and promising platform to address significant shortcomings in the traditional islet encapsulation method.

Controlling the microstructure of thin films is of critical importance for various applications. We demonstrate a methodology for tuning the local microstructure through film-substrate interactions using Ag-Cu as a model system. Metastable single-phase Ag-Cu thin films are deposited on Si substrates pre-patterned by FIB milling. During post-deposition annealing, localized film-substrate reaction around the milled patterns produces a distinct microstructure termed as the ‘halo’. It consists of copper silicide and almost pure Ag, while the far-field film forms a random mixture of Cu and Ag-rich domains through phase separation. We show that the extent of the halo can be controlled by varying the temperature and duration of annealing. We present a semi-analytical kinetic model of product and halo growth that incorporates species balance, diffusional transport and a modified Stefan condition. Predictions from the model reveal two distinct growth regimes of the product with power law indices of 1/2 and 2/7 and experimental data fall into the latter regime. These regimes originate from the dimensionality of growth (2d or 3d) compared to that of solute transport (2d), which in turn depend on film thickness and species diffusivity. Using an inverse optimization procedure, we also estimate the diffusivity, which suggests grain boundary diffusion to be the dominant transport mechanism. This study provides an avenue and framework for microstructural engineering of alloy thin films through interfacial reaction.

Real-time in situ monitoring during chemical synthesis can provide vital clues for tracking nanoparticle synthesis, potentially leading to application-optimized reaction products with high yield and reproducibility. In this article, we demonstrate a homemade extinction spectroscopy platform that can track nanoparticle synthesis and chemical reactions with sub-ms time resolution. In the first part of the paper, we provide the various steps required for building and aligning the optical platform that can perform in situ extinction measurements. Subsequently, we employ the platform to study the growth of anisotropic gold bipyramids and nanorods. We show that adjusting the reaction temperature can significantly alter the synthesis rate. Thereafter, we use this system to track the photo-degradation of methylene blue dye using CeO2 nanoparticles and to track pH changes in solution. Finally, we have detailed the potential pitfalls that can arise while using the system and potential avenues for addressing them. In addition to the examples demonstrated here, the established platform can be used to study other reactions, including drug synthesis, protein aggregation, phase separation, and sol-gel synthesis by choosing an appropriate wavelength range of operation. The information extracted from this analysis can be used to modify the reaction conditions in real-time to obtain a pre-determined synthesis product, thereby making synthesis processes efficient and convenient.

We show a method for the integrated real-time optical monitoring and analysis of anisotropic gold nanoparticles in capsule shaped microdrops. We then use it for monitoring the growth kinetics of gold nanosphere synthesis in these drops.

Electrospun PDMS membranes with tailored solvent-responsive shrinkage and folding are demonstrated. The membranes are used as soft robotic traps, self-sealing membranes, and oxygen-permeable films to enhance photocatalytic H ₂ O ₂ generation.

Using in situ correlative micro-spectroscopy techniques, we study the temperature-directed shape change of anisotropic gold bipyramids (AuNBP), leading to localized plasmon resonance tunability of more than 250 nm.

Photoreduction of metallic nanoparticles can be used for localized and deterministic synthesis of nanostructures required for various applications. Specifically, in-situ photoreduction of silver nanoparticles (AgNPs) is a facile fabrication route that enables the fabrication of nanoplasmonic substrates. In the present work, we demonstrate an approach to fabricate hybrid plasmonic substrates using in-situ photoreduction of AgNPs within gold nanoapertures (NAs). The approach involves the top-down approach to fabricate NAs followed by a site-specific synthesis of AgNPs within the NAs. Furthermore, we use dark-field imaging to monitor and understand the photoreduction within the gold NAs in real time. We demonstrate that a careful selection of experiment parameters aid to synthesize the AgNPs within NAs and the scattered light intensity can be used to map the characteristics of the formed AgNPs. The illumination time, laser power and AgNO₃ concentration can be used to tune the AgNPs characteristics. The demonstrated strategy for realizing hybrid plasmonic substrates can be used for the fabrication of substrates for SERS based sensors, enhancing fluorescence of molecules, and photocatalytic applications.

Deformation induced modification of SERS response in polymer grafted plasmonic nanoparticle thin films yields insights into structure-function relationships in plasmonic networks.

Nanofabrication is an integral part of the realization of advanced functional devices ranging from optical displays to memory devices. Focused-ion beam (FIB) milling is one of the most widely used nanofabrication methods. Conventionally, FIB milling has been carried out for patterning single-phase stable thin films. However, the influence of FIB milling on the phase separation of metastable alloy films during subsequent treatments has not been reported. Here, we show how FIB milling of Ag–Cu thin films influences the separation process and microstructure formation during post-milling annealing. The phase-separated microstructure of the film consists of fine, randomly distributed Ag-rich and Cu-rich domains, whereas adjacent to milled apertures (cylindrical holes), we observe two distinctly coarser rings. A combination of imaging and analysis techniques reveals Cu-rich islands dispersed in Ag-rich domains in the first ring next to the aperture, while the second ring constitutes mostly of Ag-rich grains. Copper silicide is observed to form in and around apertures through reaction with the Si-substrate. This substrate interaction, in addition to known variables like composition, temperature, and capillarity, appears to be a key element in drastically changing the local microstructure around apertures. Thus, the current study introduces new avenues to locally modulate the composition and microstructure through an appropriate choice of the film-substrate system. Such an ability can be exploited further to tune device functionalities for possible applications in plasmonics, catalysis, microelectronics, and magnetics.