Altug Ozcelikkale

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.

In vitro microfluidic models of tumor microenvironment to screen transport of drugs and nanoparticles

Advances in nanotechnology have enabled numerous types of nanoparticles (NPs) to improve drug delivery to tumors. While many NP systems have been proposed, their clinical translation has been less than anticipated primarily due to failure of current preclinical evaluation techniques to adequately model the complex interactions between the NP and physiological barriers of tumor microenvironment. This review focuses on microfluidic tumor models for characterization of delivery efficacy and toxicity of cancer nanomedicine. Microfluidics offer significant advantages over traditional macroscale cell cultures by enabling recapitulation of tumor microenvironment through precise control of physiological cues such as hydrostatic pressure, shear stress, oxygen, and nutrient gradients. Microfluidic systems have recently started to be adapted for screening of drugs and NPs under physiologically relevant settings. So far the two primary application areas of microfluidics in this area have been high-throughput screening using traditional culture settings such as single cells or multicellular tumor spheroids, and mimicry of tumor microenvironment for study of cancer-related cell-cell and cell-matrix interactions. These microfluidic technologies are also useful in modeling specific steps in NP delivery to tumor and characterize NP transport properties and outcomes by systematic variation of physiological conditions. Ultimately, it will be possible to design drug-screening platforms uniquely tailored for individual patient physiology using microfluidics. These in vitro models can contribute to development of precision medicine by enabling rapid and patient-specific evaluation of cancer nanomedicine. WIREs Nanomed Nanobiotechnol 2017, 9:e1460. doi: 10.1002/wnan.1460 For further resources related to this article, please visit the WIREs website.

Least-squares spectral element solution of incompressible Navier-Stokes equations with adaptive refinement

Least-squares spectral element solution of steady, two-dimensional, incompressible flows are obtained by approximating velocity, pressure and vorticity variable set on Gauss-Lobatto-Legendre nodes. Constrained Approximation Method is used for h- and p-type nonconforming interfaces of quadrilateral elements. Adaptive solutions are obtained using a posteriori error estimates based on least squares functional and spectral coefficient. Effective use of p-refinement to overcome poor mass conservation drawback of least-squares formulation and successful use of h- and p-refinement together to solve problems with geometric singularities are demonstrated. Capabilities and limitations of the developed code are presented using Kovasznay flow, flow past a circular cylinder in a channel and backward facing step flow.

Thermal Destabilization of Collagen Matrix Hierarchical Structure by Freeze/Thaw.

This study aims to characterize and understand the effects of freezing on collagen structures and functionality. Specifically, thermodynamic destabilization of collagen at molecular- and fibril-levels by combination of low temperatures and freezing were experimentally characterized using modulated differential scanning calorimetry. In order to delineate the effects of sub-zero temperature and water-ice phase change, we hypothesized that the extent of destabilization can be determined based on post-thaw heat induced thermal denaturation of collagen. It is found that thermal denaturation temperature of collagen in hydrogel decreases by 1.4–1.6°C after freeze/thaw while no such decrease is observed in the case of molecular solution. The destabilization is predominantly due to ice formation. Exposure to low temperatures in the absence of ice has only minimal effect. Calorimetry measurements combined with morphological examination of collagen matrices by scanning electron microscopy suggest that freezing results in destabilization of collagen fibrils due to expansion of intrafibrillar space by ice formation. This fibril-level damage can be alleviated by use of cryoprotectant DMSO at concentrations as low as 0.5 M. A theoretical model explaining the change in collagen post-thaw thermal stability by freezing-induced fibril expansion is also proposed.

Role of Cells in Freezing-Induced Cell-Fluid-Matrix Interactions Within Engineered Tissues

During cryopreservation, ice forms in the extracellular space resulting in freezing-induced deformation of the tissue, which can be detrimental to the extracellular matrix (ECM) microstructure. Meanwhile, cells dehydrate through an osmotically driven process as the intracellular water is transported to the extracellular space, increasing the volume of fluid for freezing. Therefore, this study examines the effects of cellular presence on tissue deformation and investigates the significance of intracellular water transport and cell-ECM interactions in freezing-induced cell-fluid-matrix interactions. Freezing-induced deformation characteristics were examined through cell image deformetry (CID) measurements of collagenous engineered tissues embedded with different concentrations of MCF7 breast cancer cells versus microspheres as their osmotically inactive counterparts. Additionally, the development of a biophysical model relates the freezing-induced expansion of the tissue due to the cellular water transport and the extracellular freezing thermodynamics for further verification. The magnitude of the freezing-induced dilatation was found to be not affected by the cellular water transport for the cell concentrations considered; however, the deformation patterns for different cell concentrations were different suggesting that cell-matrix interactions may have an effect. It was, therefore, determined that intracellular water transport during freezing was insignificant at the current experimental cell concentrations; however, it may be significant at concentrations similar to native tissue. Finally, the cell-matrix interactions provided mechanical support on the ECM to minimize the expansion regions in the tissues during freezing.

Spatiotemporal Characterization of Extracellular Matrix Microstructures in Engineered Tissue: A Whole-Field Spectroscopic Imaging Approach

Quality and functionality of engineered tissues are closely related to the microstructures and integrity of their extracellular matrix (ECM). However, currently available methods for characterizing ECM structures are often labor-intensive, destructive, and limited to a small fraction of the total area. These methods are also inappropriate for assessing temporal variations in ECM structures. In this study, to overcome these limitations and challenges, we propose an elastic light scattering approach to spatiotemporally assess ECM microstructures in a relatively large area in a nondestructive manner. To demonstrate its feasibility, we analyze spectroscopic imaging data obtained from acellular collagen scaffolds and dermal equivalents as model ECM structures. For spatial characterization, acellular scaffolds are examined after a freeze/thaw process mimicking a cryopreservation procedure to quantify freezing-induced structural changes in the collagen matrix. We further analyze spatial and temporal changes in ECM structures during cell-driven compaction in dermal equivalents. The results show that spectral dependence of light elastically backscattered from engineered tissue is sensitively associated with alterations in ECM microstructures. In particular, a spectral decay rate over the wavelength can serve as an indicator for the pore size changes in ECM structures, which are at nanometer scale. A decrease in the spectral decay rate suggests enlarged pore sizes of ECM structures. The combination of this approach with a whole-field imaging platform further allows visualization of spatial heterogeneity of EMC microstructures in engineered tissues. This demonstrates the feasibility of the proposed method that nano- and micrometer scale alteration of the ECM structure can be detected and visualized at a whole-field level. Thus, we envision that this spectroscopic imaging approach could potentially serve as an effective characterization tool to nondestructively, accurately, and rapidly quantify ECM microstructures in engineered tissue in a large area.

Differential response to doxorubicin in breast cancer subtypes simulated by a microfluidic tumor model

ABSTRACT Successful drug delivery and overcoming drug resistance are the primary clinical challenges for management and treatment of cancer. The ability to rapidly screen drugs and delivery systems within physiologically relevant environments is critically important; yet is currently limited due to lack of appropriate tumor models. To address this problem, we developed the Tumor‐microenvironment‐on‐chip (T‐MOC), a new microfluidic tumor model simulating the interstitial flow, plasma clearance, and transport of the drug within the tumor. We demonstrated T‐MOCs capabilities by assessing the delivery and efficacy of doxorubicin in small molecular form versus hyaluronic acid nanoparticle (NP) formulation in MCF‐7 and MDA‐MB‐231, two cell lines representative of different molecular subtypes of breast cancer. Doxorubicin accumulated and penetrated similarly in both cell lines while the NP accumulated more in MDA‐MB‐231 than MCF‐7 potentially due to binding of hyaluronic acid to CD44 expressed by MDA‐MB‐231. However, the penetration of the NP was less than the molecular drug due to its larger size. In addition, both cell lines cultured on the T‐MOC showed increased resistance to the drug compared to 2D culture where MDA‐MB‐231 attained a drug‐resistant tumor‐initiating phenotype indicated by increased CD44 expression. When grown in immunocompromised mice, both cell lines exhibited cell‐type‐dependent resistance and phenotypic changes similar to T‐MOC, confirming its predictive ability for in vivo drug response. This initial characterization of T‐MOC indicates its transformative potential for in vitro testing of drug efficacy towards prediction of in vivo outcomes and investigation of drug resistance mechanisms for advancement of personalized medicine. Graphical abstract Figure. No caption available.

Enzyme-Induced Matrix Softening Regulates Hepatocarcinoma Cancer Cell Phenotypes

The progression of cancer is often accompanied by changes in the mechanical properties of an extracellular matrix. However, limited efforts have been made to reproduce these biological events in vitro. To this end, this study demonstrates that matrix remodeling caused by matrix metalloproteinase (MMP)-1 regulates phenotypic activities and modulates radiosensitivity of cancer cells exclusively in a 3D matrix. In this study, hepatocarcinoma cells are cultured in a collagen-based gel tailored to present an elastic modulus of ≈4.0 kPa. The subsequent exposure of the gel to MMP-1 decreases the elastic modulus from 4.0 to 0.5 kPa. In response to MMP-1, liver cancer cells undergo active proliferation, downregulation of E-cadherin, and the loss of detoxification capacity. The resulting spheroids are more sensitive to radiation than the spheroids cultured in the stiffer gel not exposed to MMP-1. Overall, this study serves to better understand and control the effects of MMP-induced matrix remodeling.

Effects of dynamic matrix remodelling on en masse migration of fibroblasts on collagen matrices

Fibroblast migration plays a key role during various physiological and pathological processes. Although migration of individual fibroblasts has been well studied, migration in vivo often involves simultaneous locomotion of fibroblasts sited in close proximity, so-called ‘en masse migration’, during which intensive cell–cell interactions occur. This study aims to understand the effects of matrix mechanical environments on the cell–matrix and cell–cell interactions during en masse migration of fibroblasts on collagen matrices. Specifically, we hypothesized that a group of migrating cells can significantly deform the matrix, whose mechanical microenvironment dramatically changes compared with the undeformed state, and the alteration of the matrix microenvironment reciprocally affects cell migration. This hypothesis was tested by time-resolved measurements of cell and extracellular matrix movement during en masse migration on collagen hydrogels with varying concentrations. The results illustrated that a group of cells generates significant spatio-temporal deformation of the matrix before and during the migration. Cells on soft collagen hydrogels migrate along tortuous paths, but, as the matrix stiffness increases, cell migration patterns become aligned with each other and show coordinated migration paths. As cells migrate, the matrix is locally compressed, resulting in a locally stiffened and dense matrix across the collagen concentration range studied.

DNA Walker-Regulated Cancer Cell Growth Inhibition.

We demonstrate a DNAzyme‐based walker system as a controlled oligonucleotide drug AS1411 release platform for breast cancer treatment. In this system, AS1411 strands are released from fuel strands as a walker moves along its carbon nanotube track. The release rate and amount of anticancer oligonucleotides are controlled by the walker operation. With a walker system embedded within the collagen extracellular matrix, we show that this drug release system can be used for in situ cancer cell growth inhibition.