Soham Ghosh

Multifaceted transport characteristics of nanomedicine: needs for characterization in dynamic environment.

Nanomedicine for cancer, where nanoparticles (NPs) are used to deliver drugs, imaging agents, and heat to tumors, shows great potential of improved therapeutic outcomes. In spite of promising early stage results, its clinical efficacy is still significantly limited due to complex transport barriers in vivo. These transport barriers are associated with tumor microenvironment, which is highly complex and heterogeneous and varies spatiotemporally. Thus, in order to improve the in vivo efficacy of nanomedicine, NPs need to be designed and characterized considering their interaction with these complex transport barriers. In this article, thus, we discuss the multifaceted transport characteristics of NPs and their interaction mechanisms with the tumor microenvironment. We also illustrated that NPs have highly spatiotemporal and multiscale distribution around tumor. This dynamic and complex nature of NP transport needs to be taken into consideration in design strategies and evaluation criteria for successful delivery of cancer nanomedicine.

Probing nanoantenna-directed photothermal destruction of tumors using noninvasive laser irradiation

Plasmonicnanomaterials have tremendous potential to improve the tumor specificity of traditional cancerablation practices, yet little effort has been directed toward quantitatively understanding their photothermal energy conversion in tumortissues. In the present work, we develop a predictive model for plasmonicnanomaterial assisted tumor destruction under extracorporeal laser irradiation. Instead of appealing to heuristically based laser intensification models with tunable, tissue absorption and scattering coefficients, we consider fundamental characteristics of optoelectrothermal energy conversion and heat dissipation for plasmonicnanomaterials within living tumortissues to construct a simulation tool that accurately reproduces our experimental findings, including aspects of delayed time-temperature characteristics. We believe the comprehensive modeling strategy outlined here provides a groundwork for the development of anticipatory therapeutic planning tools with individually tailored treatment plans, resulting in an ultimate benefit to ailing cancer patients.

Thermomechanical analysis of freezing-induced cell–fluid–matrix interactions in engineered tissues

Successful cryopreservation of functional engineered tissues (ETs) is significant to tissue engineering and regenerative medicine, but it is extremely challenging to develop a successful protocol because the effects of cryopreservation parameters on the post-thaw functionality of ETs are not well understood. Particularly, the effects on the microstructure of their extracellular matrix (ECM) have not been well studied, which determines many functional properties of the ETs. In this study, we investigated the effects of two key cryopreservation parameters--(i) freezing temperature and corresponding cooling rate; and (ii) the concentration of cryoprotective agent (CPA) on the ECM microstructure as well as the cellular viability. Using dermal equivalent as a model ET and DMSO as a model CPA, freezing-induced spatiotemporal deformation and post-thaw ECM microstructure of ETs was characterized while varying the freezing temperature and DMSO concentrations. The spatial distribution of cellular viability and the cellular actin cytoskeleton was also examined. The results showed that the tissue dilatation increased significantly with reduced freezing temperature (i.e., rapid freezing). A maximum limit of tissue deformation was observed for preservation of ECM microstructure, cell viability and cell-matrix adhesion. The dilatation decreased with the use of DMSO, and a freezing temperature dependent threshold concentration of DMSO was observed. The threshold DMSO concentration increased with lowering freezing temperature. In addition, an analysis was performed to delineate thermodynamic and mechanical components of freezing-induced tissue deformation. The results are discussed to establish a mechanistic understanding of freezing-induced cell-fluid-matrix interaction and phase change behavior within ETs in order to improve cryopreservation of ETs.

Effects of light–tissue interaction on quantum dot mediated fluorescence thermometry

Thermal therapy is emerging as an effective treatment option for benign localized tumors. However, lack of reliable intraoperative monitoring techniques of the thermal lesion impedes more widespread application of thermal therapy in clinical settings. In order to address this challenge, a thermometry technique using temperature dependent fluorescence of quantum dots was proposed and its feasibility was also demonstrated with an in vitro cell system. In the present study, light–tissue interaction relevant to applying this quantum dot (QD) thermometry to a tissue system was characterized both experimentally and computationally. In the experiments, QD fluorescence was quantified through tissue phantom while varying QD temperature and phantom thickness. The results showed that QD fluorescence became diffused due to light–tissue interaction, but the QD fluorescence was still correlated to the temperature at any given phantom thickness studied. In the computations, an inverse solution algorithm was developed to estimate the QD fluorescence underneath the tissue phantom from the fluorescence through the phantom. This algorithm is to inversely solve the diffusion approximation of the radiative transfer equation. The developed algorithm was verified using the experimental results. In addition, the effects of relevant optical and thermal parameters on the accuracy of the inverse solution were characterized. The results suggest that the developed algorithm is capable of estimating the QD fluorescence considering light–tissue interaction in the range of tissue phantom thickness studied. The results were further discussed for implications to the application of QD thermometry in vivo.

Measurement of spatiotemporal intracellular deformation of cells adhered to collagen matrix during freezing of biomaterials.

Preservation of structural integrity inside cells and at cell-extracellular matrix (ECM) interfaces is a key challenge during freezing of biomaterials. Since the post-thaw functionality of cells depends on the extent of change in the cytoskeletal structure caused by complex cell-ECM adhesion, spatiotemporal deformation inside the cell was measured using a newly developed microbead-mediated particle tracking deformetry (PTD) technique using fibroblast-seeded dermal equivalents as a model tissue. Fibronectin-coated 500 nm diameter microbeads were internalized in cells, and the microbead-labeled cells were used to prepare engineered tissue with type I collagen matrices. After a 24 h incubation the engineered tissues were directionally frozen, and the cells were imaged during the process. The microbeads were tracked, and spatiotemporal deformation inside the cells was computed from the tracking data using the PTD method. Effects of particle size on the deformation measurement method were tested, and it was found that microbeads represent cell deformation to acceptable accuracy. The results showed complex spatiotemporal deformation patterns in the cells. Large deformation in the cells and detachments of cells from the ECM were observed. At the cellular scale, variable directionality of the deformation was found in contrast to the one-dimensional deformation pattern observed at the tissue scale, as found from earlier studies. In summary, this method can quantify the spatiotemporal deformation in cells and can be correlated to the freezing-induced change in the structure of cytosplasm and of the cell-ECM interface. As a broader application, this method may be used to compute deformation of cells in the ECM environment for physiological processes, namely cell migration, stem cell differentiation, vasculogenesis, and cancer metastasis, which have relevance to quantify mechanotransduction.

Predicting DNA-mediated drug delivery in interior carcinoma using electromagnetically excited nanoparticles

Tumor-site-specific delivery of anti-cancer drugs remains one of the most prevailing problems in cancer treatment. While conventional means of chemo-delivery invariably leave different degrees of side-effects on healthy tissues, in recent times, intelligent chemical designs have been exploited to reduce the cross-consequences. In particular, the strategies involving superparamaganetic nanoparticles with surface assembled oligonucleotides as therapeutic carrier have raised affirmative promises. Process is designed in such a way that the therapeutic molecules are released preferentially at target site as the complementary oligonucleotide chains dissociate over the heat generated by the nanoparticles under the excitation of low frequency electromagnetic energy. In spite of the preliminary demonstrations, analytical comprehension of the entire process especially on the purview of non-trivial interactions between stochastic phase-transition phenomena of oligonucleotide chains and hierarchical organization of in vivo transport processes remains unknown. Here, we propose an integrated computational predictive model to interpret the efficacy of drug delivery in the aforementioned process. The basic physics of heat generation by superparamagnetic nanoparticles in presence of external electromagnetic field has been coupled with transient biological heat transfer model and the statistical mechanics based oligonucleotide denaturation dynamics. Conjunctionally, we have introduced a set of hierarchically appropriate transport processes to mimic the in vivo drug delivery system. The subsequent interstitial diffusion and convection of the various species involved in the process over time was simulated assuming a porous media model of the carcinoma. As a result, the model predictions exhibit excellent congruence with available experimental results. To delineate a broader spectrum of a priori speculations, we have investigated the effects of different tunable parameters such as magnetizing field strength, nanoparticle size, diffusion coefficients, porous media parameters and different oligonucleotide sequences on temperature rise and site-specific drug release. The proposed model, thus, provides a generic framework for the betterment of nanoparticle mediated drug delivery, which is expected to impart significant impact on cancer therapy.

Role of intracellular poroelasticity on freezing-induced deformation of cells in engineered tissues

Freezing of biomaterials is important in a wide variety of biomedical applications, including cryopreservation and cryosurgeries. For the success of these applications to various biomaterials, biophysical mechanisms, which determine freezing-induced changes in cells and tissues, need to be well understood. Specifically, the significance of the intracellular mechanics during freezing is not well understood. Thus, we hypothesize that cells interact during freezing with the surroundings such as suspension media and the extracellular matrix (ECM) via two distinct but related mechanisms—water transport and cytoskeletal mechanics. The underlying rationale is that the cytoplasm of the cells has poroelastic nature, which can regulate both cellular water transport and cytoskeletal mechanics. A poroelasticity-based cell dehydration model is developed and confirmed to provide insight into the effects of the hydraulic conductivity and stiffness of the cytoplasm on the dehydration of cells in suspension during freezing. We further investigated the effect of the cytoskeletal structures on the cryoresponse of cells embedded in the ECM by measuring the spatio-temporal intracellular deformation with dermal equivalent as a model tissue. The freezing-induced change in cell, nucleus and cytoplasm volume was quantified, and the possible mechanism of the volumetric change was proposed. The results are discussed considering the hierarchical poroelasticity of biological tissues.

Spatiotemporal intracellular deformation of cells during freezing-induced cell-fluid-matrix interactions

Freezing of biomaterials is emerging as one of the key biotechnologies in cell/tissue engineering, medicine and biology. Its applications include — 1) preservation of cell/tissue engineering products, 2) quality control of biospecimens cryopreserved in tissue banks and repositories, and 3) synthesis procedures of biomaterials such as decellularization of native tissues to create acellular (i.e., cell-free) complex three-dimensional extracellular matrices (ECMs). Traditionally, research efforts have focused on determining optimal freeze/thaw (F/T) protocols with chemical additives, so called cryoprotective agents, for a given cell/tissue-type by comparing the outcomes of F/T protocols, which are mainly gauged by cell viability. Although cell viability is the major constituent, it has recently been recognized that other features beyond viability are also critical to the functionality of biomaterials, including the microstructure of the ECM, the status of cell-matrix adhesion, and the cytoskeletal structure and organization [1, 2, 3].Copyright