Pulsed laser assisted high-throughput intracellular delivery in hanging drop based three dimensional cancer spheroids.

Targeted intracellular delivery of biomolecules and therapeutic cargo enables the controlled manipulation of cellular processes. Laser-based optoporation has emerged as a versatile, non-invasive technique that employs light-based transient physical disruption of the cell membrane and achieves high transfection efficiency with low cell damage. Testing of the delivery efficiency of optoporation-based techniques has been conducted on single cells in monolayers, but its applicability in three-dimensional (3D) cell clusters/spheroids has not been explored. Cancer cells grown as 3D tumor spheroids are widely used in anti-cancer drug screening and can be potentially employed for testing delivery efficiency. Towards this goal, we demonstrated the optoporation-based high-throughput intracellular delivery of a model fluorescent cargo (propidium iodide, PI) within 3D SiHa human cervical cancer spheroids. To enable this technique, nano-spiked core-shell gold-coated polystyrene nanoparticles (ns-AuNPs) with a high surface-to-volume ratio were fabricated. ns-AuNPs exhibited high electric field enhancement and highly localized heating at an excitation wavelength of 680 nm. ns-AuNPs were co-incubated with cancer cells within hanging droplets to enable the rapid aggregation and assembly of spheroids. Nanosecond pulsed-laser excitation at the optimized values of laser fluence (45 mJ cm-2), pulse frequency (10 Hz), laser exposure time (30 s), and ns-AuNP concentration (5 × 1010 particles per ml) resulted in the successful delivery of PI dye into cancer cells. This technique ensured high delivery efficiency (89.6 ± 2.8%) while maintaining high cellular viability (97.4 ± 0.4%), thereby validating the applicability of this technique for intracellular delivery. The optoporation-based strategy can enable high-throughput single cell manipulation, is scalable towards larger 3D tissue constructs, and may provide translational benefits for the delivery of anti-cancer therapeutics to tumors.

Rapid Production of Cell-Laden Microspheres Using a Flexible Microfluidic Encapsulation Platform.

This study establishes a novel microfluidic platform for rapid encapsulation of cells at high densities in photocrosslinkable microspherical hydrogels including poly(ethylene glycol)-diacrylate, poly(ethylene glycol)-fibrinogen, and gelatin methacrylate. Cell-laden hydrogel microspheres are advantageous for many applications from drug screening to regenerative medicine. Employing microfluidic systems is considered the most efficient method for scale-up production of uniform microspheres. However, existing platforms have been constrained by traditional microfabrication techniques for device fabrication, restricting microsphere diameter to below 200 µm and making iterative design changes time-consuming and costly. Using a new molding technique, the microfluidic device employs a modified T-junction design with readily adjustable channel sizes, enabling production of highly uniform microspheres with cell densities (10-60 million cells mL-1 ) and a wide range of diameters (300-1100 µm), which are critical for realizing downstream applications, through rapid photocrosslinking (≈1 s per microsphere). Multiple cell types are encapsulated at rates of up to 1 million cells per min, are evenly distributed throughout the microspheres, and maintain high viability and appropriate cellular activities in long-term culture. This microfluidic encapsulation platform is a valuable and readily adoptable tool for numerous applications, including supporting injectable cell therapy, bioreactor-based cell expansion and differentiation, and high throughput tissue sphere-based drug testing assays.

Proteomic characterization of macro-, micro- and nano-extracellular vesicles derived from the same first trimester placenta: relevance for feto-maternal communication.

STUDY QUESTION: What proteins are carried by extracellular vesicles (EVs) released from normal first trimester placentae? SUMMARY ANSWER: One thousand five hundred and eighty-five, 1656 and 1476 proteins were characterized in macro-, micro- and nano-vesicles, respectively, from first trimester placentae, with all EV fractions being enriched for proteins involved in vesicle transport and inflammation. WHAT IS KNOWN ALREADY: Placental EVs are being increasingly recognized as important mediators of both healthy and pathological pregnancies. However, current research has focused on detecting changes in specific proteins in particular fractions of vesicles during disease. This is the first study to investigate the full proteome of different-sized fractions of EVs from the same first trimester placenta and highlights the differences/similarities between the vesicle fractions. STUDY DESIGN, SIZE, DURATION: A well-established ex vivo placental explant culture model was used to generate macro-, micro- and nano-vesicles from 56 first trimester placentae. Vesicle fractions were collected by differential ultracentrifugation, quantified and characterized. PARTICIPANTS/MATERIALS, SETTING, METHODS: Placental macro-, micro- and nano-vesicles were characterized by microscopy, dynamic light scattering and nanoparticle tracking analysis. The proteome of each EV fraction was interrogated using liquid chromatography-coupled tandem mass spectrometry. Results were validated by semi-quantitative western blotting. MAIN RESULTS AND THE ROLE OF CHANCE: A total of 1585, 1656 and 1476 proteins were identified in macro-, micro- and nano-vesicles, respectively. One thousand one hundred and twenty-five proteins were shared between all three fractions while up to 223 proteins were unique to each fraction. Gene Ontology pathway analysis showed an enrichment of proteins involved in vesicle transport and inflammation in all three fractions of EVs. The expression levels of proteins involved in internalization of vesicles (annexin V, calreticulin, CD31, CD47), the complement pathway [C3, decay-accelerating factor (DAF), membrane cofactor protein (MCP), protectin] and minor histocompatibility antigens [ATP-dependent RNA helicase (DDX3), ribosomal protein S4 (RPS4)] were different between different-sized EVs. LIMITATIONS, REASONS FOR CAUTION: This study is largely hypothesis-generating in nature. It is important to validate these findings using EVs isolated from maternal plasma and the function of the different EV fractions would need further investigation. WIDER IMPLICATIONS OF THE FINDINGS: Our results support the concept that various EV factions can interact with different maternal cells and have unique effects to mediate feto-maternal communication during early pregnancy. This study also provides a list of candidate proteins, which may inform the identification of robust markers that can be used to isolate placental vesicles from the maternal blood in the future. STUDY FUNDING/COMPETING INTERESTS: M.T. is a recipient of the University of Auckland Health Research Doctoral Scholarship and the Freemasons Postgraduate Scholarship. This project was supported by a School of Medicine Performance-based research fund (PBRF) grant awarded to L.W.C. No authors have any conflicts of interest to disclose.

Dual-phase, surface tension-based fabrication method for generation of tumor millibeads.

Numerous methods have been developed for the fabrication of poly(ethylene glycol)-based hydrogel microstructures for drug-delivery and tissue-engineering applications. However, present methods focus on the fabrication of submicrometer scale hydrogel structures which have limited applications in creating larger tissue constructs, especially in recreating cancer tissue microenvironments. We aimed to establish a platform where cancer cells can be cultured in a three-dimensional (3D) environment, which closely replicates the native cancer microenvironment and facilitates efficient testing of anticancer drugs. This study demonstrated a novel surface tension-based fabrication technique for the generation of millimeter-scale hydrogel beads using a liquid-liquid dual phase system. The "hydrogel millibeads" obtained by this method were larger than previously reported, highly uniform in shape and size with better ease of size control and a high degree of consistency and reproducibility between batches. In addition, human breast cancer cells were encapsulated within these hydrogel constructs to generate "tumor millibeads", which were subsequently maintained in long-term 3D culture. Microscopic visualization using fluorescence imaging and microstructure analysis showed the morphology and uniform distribution of the cells within the 3D matrix and arrangement of cells with the surrounding scaffold material. Cell viability analysis revealed the creation of a core region of dead cells surrounded by healthy, viable cell layers at the periphery following long-term culture. These observations closely matched with those of native and in vivo tumors. Based on these results, this study established a rapidly reproducible surface tension-based fabrication technique for making spherical hydrogel millibeads and demonstrated the potential of this method in creating engineered 3D tumor tissues. It is envisioned that the developed hydrogel millibead system will facilitate the formation of physiologically relevant in vitro tumor models which will closely simulate the native tumor microenvironmental conditions and could enable future high-throughput testing of different anticancer drugs in preclinical trials.

Droplet Microfluidics-Based Fabrication of Monodisperse Poly(ethylene glycol)-Fibrinogen Breast Cancer Microspheres for Automated Drug Screening Applications.

Spheroidal cancer microtissues are highly advantageous for a wide range of biomedical applications, including high-throughput drug screening, multiplexed target validation, mechanistic investigation of tumor-extracellular matrix (ECM) interactions, among others. Current techniques for spheroidal tissue formation rely heavily on self-aggregation of single cancer cells and have substantial limitations in terms of cell-type-specific heterogeneities, uniformity, ease of production and handling, and most importantly, mimicking the complex native tumor microenvironmental conditions in simplistic models. These constraints can be overcome by using engineered tunable hydrogels that closely mimic the tumor ECM and elucidate pathologically relevant cell behavior, coupled with microfluidics-based high-throughput fabrication technologies to encapsulate cells and create cancer microtissues. In this study, we employ biosynthetic hybrid hydrogels composed of poly(ethylene glycol diacrylate) (PEGDA) covalently conjugated to natural protein (fibrinogen) (PEG-fibrinogen, PF) to create monodisperse microspheres encapsulating breast cancer cells for 3D culture and tumorigenic characterization. A previously developed droplet-based microfluidic system is used for rapid, facile, and reproducible fabrication of uniform cancer microspheres with either MCF7 or MDA-MB-231 (metastatic) breast cancer cells. Cancer cell-type-dependent variations in cell viability, metabolic activity, and 3D morphology, as well as microsphere stiffness, are quantified over time. Particularly, MCF7 cells grew as tight cellular clusters in the PF microspheres, characteristic of their epithelial morphology, while MDA-MB-231 cells displayed elongated and invasive morphology, characteristic of their mesenchymal and metastatic nature. Finally, the translational potential of the cancer microsphere platform toward high-throughput drug screening is also demonstrated. With high uniformity, scalability, and control over engineered microenvironments, the established cancer microsphere model can be potentially used for mechanistic studies, fabrication of modular cancer microtissues, and future drug-testing applications.

The Influence of Ligand Density and Degradability on Hydrogel Induced Breast Cancer Dormancy and Reactivation.

The role of hydrogel properties in regulating the phenotype of triple negative metastatic breast cancer is investigated using four cell lines: the MDA-MB-231 parental line and three organotropic sublines BoM-1833 (bone-tropic), LM2-4175 (lung-tropic), and BrM2a-831 (brain-tropic). Each line is encapsulated and cultured for 15 days in three poly(ethylene glycol) (PEG)-based hydrogel formulations composed of proteolytically degradable PEG, integrin-ligating RGDS, and the non-degradable crosslinker N-vinyl pyrrolidone. Dormancy-associated metrics including viable cell density, proliferation, metabolism, apoptosis, chemoresistance, phosphorylated-ERK and -p38, and morphological characteristics are quantified. A multimetric classification approach is implemented to categorize each hydrogel-induced phenotype as: 1) growth, 2) balanced tumor dormancy, 3) balanced cellular dormancy, or 4) restricted survival, cellular dormancy. Hydrogels with high adhesivity and degradability promote growth. Hydrogels with no adhesivity, but high degradability, induce restricted survival, cellular dormancy in the parental line and balanced cellular dormancy in the organotropic lines. Hydrogels with reduced adhesivity and degradability induce balanced cellular dormancy in the parental and lung-tropic lines and balanced tumor mass dormancy in bone- and brain-tropic lines. The ability to induce escape from dormancy via dynamic incorporation of RGDS is also presented. These results demonstrate that ECM properties and organ-tropism synergistically regulate cancer cell phenotype and dormancy.

The Influence of Matrix-Induced Dormancy on Metastatic Breast Cancer Chemoresistance.

Metastasis remains the leading cause of cancer-associated death worldwide. Disseminated tumor cells can undergo dormancy upon infiltration of secondary organs, and chemotherapeutics fail to effectively eliminate dormant populations. Mechanistic understanding of dormancy-associated chemoresistance could lead to development of targeted therapeutic strategies. Toward this goal, we implemented three poly(ethylene glycol) (PEG)-based hydrogel formulations fabricated from proteolytically degradable PEG (PEG-PQ), integrin ligating PEG-RGDS, and the non-degradable cross-linker N-vinylpyrrolidone (NVP) to induce three distinct phenotypes in triple negative MDA-MB-231 breast cancer cells. With constant 5% w/v PEG-PQ, PEG-RGDS and NVP concentrations were tuned to induce (i) a growth state characterized by high proliferation, high metabolic activity, significant temporally increased cell density, and an invasive morphology; (ii) a balanced dormancy state characterized by a temporal balance (~1:1 ratio) in new live and dead cell density and a non-invasive morphology; and (iii) a cellular dormancy state characterized by rounded, solitary quiescent cells with low viability, proliferation, and metabolic activity. The cellular responses to doxorubicin (DOX), paclitaxel (PAC), and 5-fluorouracil (5-FU) in the three phenotypic states were quantified. Under DOX treatment, cells in dormant states demonstrated increased chemoresistance with a 1.4- to 1.8-fold increase in half maximal effective concentration (EC50) and 1.3- to 1.8-fold increase in half maximal inhibitory concentration (IC50) compared to cells in the growth state. PAC and 5-FU treatment led to similar results. To mechanistically investigate the role of dormancy in conferring DOX resistance, cytoplasmic and nuclear accumulation of DOX was measured. The results indicated comparable DOX accumulation between all three phenotypic states; however, the intracellular to intranuclear distribution indicated a ~1.5 fold increase in DOX nuclear accumulation in cells in the growth state compared to the two dormant states. These results further validate the utility of implementing engineered hydrogels as in vitro platforms of breast cancer dormancy for the development of anti-dormancy therapeutic strategies.

Biofabrication Strategies and Engineered In Vitro Systems for Vascular Mechanobiology.

The vascular system is integral for maintaining organ-specific functions and homeostasis. Dysregulation in vascular architecture and function can lead to various chronic or acute disorders. Investigation of the role of the vascular system in health and disease has been accelerated through the development of tissue-engineered constructs and microphysiological on-chip platforms. These in vitro systems permit studies of biochemical regulation of vascular networks and parenchymal tissue and provide mechanistic insights into the biophysical and hemodynamic forces acting in organ-specific niches. Detailed understanding of these forces and the mechanotransductory pathways involved is necessary to develop preventative and therapeutic strategies targeting the vascular system. This review describes vascular structure and function, the role of hemodynamic forces in maintaining vascular homeostasis, and measurement approaches for cell and tissue level mechanical properties influencing vascular phenomena. State-of-the-art techniques for fabricating in vitro microvascular systems, with varying degrees of biological and engineering complexity, are summarized. Finally, the role of vascular mechanobiology in organ-specific niches and pathophysiological states, and efforts to recapitulate these events using in vitro microphysiological systems, are explored. It is hoped that this review will help readers appreciate the important, but understudied, role of vascular-parenchymal mechanotransduction in health and disease toward developing mechanotherapeutics for treatment strategies.

Datasets describing hydrogel properties and cellular metrics for modeling of tumor dormancy.

Breast cancer dormancy is an underlying challenge toward targeting and controlling metastatic recurrence and disease progression. Development of engineered, well-defined in vitro models is necessary to systematically recapitulate tumor dormancy and investigate potential therapeutic strategies. Toward this end, a set of sixteen hydrogel formulations with varying degrees of adhesivity and crosslink density was developed for encapsulation, three-dimensional (3D) culture, and phenotypic assessment of MDA-MB-231 breast cancer cells. The hydrogel adhesivity was regulated by incorporation of RGDS peptide conjugated to acrylate poly(ethylene glycol) (PEG-RGDS) and the crosslink density by incorporation of N-vinyl pyrrolidinone (NVP). Here, we present data concerning the characterization of hydrogel properties (PEG-RGDS incorporation, hydrogel crosslink density, and hydrogel diffusivity as a function of NVP concentration) and phenotypic metrics (viability, early apoptosis, proliferation, metabolic activity, viable cell density, and morphological features) of encapsulated MDA-MB-231s over 15 days in culture. Interpretation of this data can be found in a research article titled "Tunable Hydrogels for Controlling Phenotypic Cancer Cell States to Model Breast Cancer Dormancy and Reactivation" (Pradhan et al., 2019) [1].

Fabrication, characterization, and implementation of engineered hydrogels for controlling breast cancer cell phenotype and dormancy.

A better understanding of how microenvironmental factors regulate cancer dormancy is needed for development of new therapeutic strategies to control metastatic recurrence and disease progression. Modeling cancer dormancy using engineered, in vitro platforms is necessary for investigation under well-defined and well-controlled microenvironments. We present methods and protocols to fabricate, characterize, and implement engineered hydrogels with well-defined biochemical and physical properties for control over breast cancer cell phenotype in three-dimensional (3D) culture. Changes in hydrogel adhesivity, crosslink density, and degradability induce a range of phenotypic behaviors in breast cancer cells including: (1) high growth, (2) moderate growth, (3) single cell, restricted survival dormancy, and (4) balanced dormancy. We describe a method of classifying hydrogel formulations that support each of these phenotypic states. We also describe a method to phenotypically switch cancer cells from single cell dormancy to high growth by dynamically modulating ligand density, thereby recapitulating reactivation and metastatic recurrence.

Tunable hydrogels for controlling phenotypic cancer cell states to model breast cancer dormancy and reactivation.

During metastasis, disseminated tumor cells (DTCs) from the primary tumor infiltrate secondary organs and reside there for varying lengths of time prior to forming new tumors. The time delay between infiltration and active proliferation, known as dormancy, mediates the length of the latency period. DTCs may undergo one of four fates post-infiltration: death, cellular dormancy, dormant micrometastasis, or invasive growth which, is in part, mediated by extracellular matrix (ECM) properties. Recapitulation of these cell states using engineered hydrogels could facilitate the systematic and controlled investigation of the mechanisms by which ECM properties influence DTC fate. Toward this goal, we implemented a set of sixteen hydrogels with systematic variations in chemical (ligand (RGDS) density and enzymatic degradability) and mechanical (elasticity, swelling, mesh size) properties to investigate their influence on the fate of encapsulated metastatic breast cancer cells, MDA-MB-231. Cell viability, apoptosis, proliferation, metabolic activity, and morphological measurements were acquired at five-day intervals over fifteen days in culture. Analysis of the phenotypic metrics indicated the presence of four different cell states that were classified as: (1) high growth, (2) moderate growth, (3) single cell, restricted survival, dormancy, or (4) balanced dormancy. Correlating hydrogel properties with the resultant cancer cell state indicated that ligand (RGDS) density and enzymatic degradability likely had the most influence on cell fate. Furthermore, we demonstrate the ability to reactivate cells from the single cell, dormant state to the high growth state through a dynamic increase in ligand (RGDS) density after forty days in culture. This tunable engineered hydrogel platform offers insight into matrix properties regulating tumor dormancy, and the dormancy-proliferation switch, and may provide future translational benefits toward development of anti-dormancy therapeutic strategies.

Engineered In Vitro Models of Tumor Dormancy and Reactivation.

Metastatic recurrence is a major hurdle to overcome for successful control of cancer-associated death. Residual tumor cells in the primary site, or disseminated tumor cells in secondary sites, can lie in a dormant state for long time periods, years to decades, before being reactivated into a proliferative growth state. The microenvironmental signals and biological mechanisms that mediate the fate of disseminated cancer cells with respect to cell death, single cell dormancy, tumor mass dormancy and metastatic growth, as well as the factors that induce reactivation, are discussed in this review. Emphasis is placed on engineered, in vitro, biomaterial-based approaches to model tumor dormancy and subsequent reactivation, with a focus on the roles of extracellular matrix, secondary cell types, biochemical signaling and drug treatment. A brief perspective of molecular targets and treatment approaches for dormant tumors is also presented. Advances in tissue-engineered platforms to induce, model, and monitor tumor dormancy and reactivation may provide much needed insight into the regulation of these processes and serve as drug discovery and testing platforms.

A Microvascularized Tumor-mimetic Platform for Assessing Anti-cancer Drug Efficacy.

Assessment of anti-cancer drug efficacy in in vitro three-dimensional (3D) bioengineered cancer models provides important contextual and relevant information towards pre-clinical translation of potential drug candidates. However, currently established models fail to sufficiently recapitulate complex tumor heterogeneity. Here we present a chip-based tumor-mimetic platform incorporating a 3D in vitro breast cancer model with a tumor-mimetic microvascular network, replicating the pathophysiological architecture of native vascularized breast tumors. The microfluidic platform facilitated formation of mature, lumenized and flow-aligned endothelium under physiological flow recapitulating both high and low perfused tumor regions. Metastatic and non-metastatic breast cancer cells were maintained in long-term 3D co-culture with stromal fibroblasts in a poly(ethylene glycol)-fibrinogen hydrogel matrix within adjoining tissue chambers. The interstitial space between the chambers and endothelium contained pores to mimic the "leaky" vasculature found in vivo and facilitate cancer cell-endothelial cell communication. Microvascular pattern-dependent flow variations induced concentration gradients within the 3D tumor mass, leading to morphological tumor heterogeneity. Anti-cancer drugs displayed cell type- and flow pattern-dependent effects on cancer cell viability, viable tumor area and associated endothelial cytotoxicity. Overall, the developed microfluidic tumor-mimetic platform facilitates investigation of cancer-stromal-endothelial interactions and highlights the role of a fluidic, tumor-mimetic vascular network on anti-cancer drug delivery and efficacy for improved translation towards pre-clinical studies.

Fundamentals of Laser-Based Hydrogel Degradation and Applications in Cell and Tissue Engineering.

The cell and tissue engineering fields have profited immensely through the implementation of highly structured biomaterials. The development and implementation of advanced biofabrication techniques have established new avenues for generating biomimetic scaffolds for a multitude of cell and tissue engineering applications. Among these, laser-based degradation of biomaterials is implemented to achieve user-directed features and functionalities within biomimetic scaffolds. This review offers an overview of the physical mechanisms that govern laser-material interactions and specifically, laser-hydrogel interactions. The influences of both laser and material properties on efficient, high-resolution hydrogel degradation are discussed and the current application space in cell and tissue engineering is reviewed. This review aims to acquaint readers with the capability and uses of laser-based degradation of biomaterials, so that it may be easily and widely adopted.

A three-dimensional spheroidal cancer model based on PEG-fibrinogen hydrogel microspheres.

Three-dimensional (3D) in vitro cancer models offer an attractive approach towards the investigation of tumorigenic phenomena and other cancer studies by providing dimensional context and higher degree of physiological relevance than that offered by conventional two-dimensional (2D) models. The multicellular tumor spheroid model, formed by cell aggregation, is considered to be the "gold standard" for 3D cancer models, due to its ease and simplicity of use. Although better than 2D models, tumor spheroids are unable to replicate key features of the native tumor microenvironment, particularly due to a lack of surrounding extracellular matrix components and heterogeneity in shape, size and aggregate forming tendencies. In order to address this issue, we have developed a 3D "tumor microsphere" model, formed by a dual-photoinitiator, aqueous-oil emulsion technique, for the encapsulation of cancer cells within PEG-fibrinogen hydrogel microspheres and for subsequent long-term 3D culture. In comparison to self-aggregated tumor spheroids, the tumor microspheres displayed a higher degree of size and shape homogeneity throughout long-term culture. In sharp contrast to cells in tumor spheroids, cells within tumor microspheres demonstrated significant loss in apico-basal polarity and cellular architecture, cellular and nuclear atypia, increased disorganization, elevated nuclear cytoplasmic ratio and nuclear volume density and reduction in cell-cell junction length, all of which are hallmarks of malignant transformation and tumorigenic progression. Additionally, the tumor microsphere model was extended for the 3D encapsulation and maintenance of a wide range of other cancer cell (metastatic and non-metastatic) types. Taken together, our results reinforce the importance of incorporating a biomimetic matrix in the cellular microenvironment of 3D tumor models and the influential effects of the matrix on the tumorigenic morphology of 3D cultured cells. The tumor microsphere system established in this study has the potential to be used in future investigations of 3D cancer cell-cell and cell-ECM interactions and in drug-testing applications.

PEG-fibrinogen hydrogels for three-dimensional breast cancer cell culture.

Tissue-engineered three-dimensional (3D) cancer models employing biomimetic hydrogels as cellular scaffolds provide contextual in vitro recapitulation of the native tumor microenvironment, thereby improving their relevance for use in cancer research. This study reports the use of poly(ethylene glycol)-fibrinogen (PF) as a suitable biosynthetic hydrogel for the 3D culture of three breast cancer cell lines: MCF7, SK-BR-3, and MDA-MB-231. Modification of the matrix characteristics of PF hydrogels was achieved by addition of excess poly(ethylene glycol) diacrylate, which resulted in differences in Young's moduli, degradation behavior, release kinetics, and ultrastructural variations in scaffold microarchitecture. Cancer cells were maintained in 3D culture with high viability within these hydrogels and resulted in cell-type dependent morphological changes over time. Cell proliferation and 3D morphology within the hydrogels were visualized through immunofluorescence staining. Finally, spatial heterogeneity of colony area within the hydrogels was quantified, with peripheral cells forming colonies of higher area compared to those in the interior regions. Overall, PF-based hydrogels facilitate 3D culture of breast cancer cells and investigation of cellular behavior in response to varying matrix characteristics. PF-based cancer models could be potentially used in future investigations of cancer biology and in anti-cancer drug-testing applications. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 236-252, 2017.

Polymeric Biomaterials for In Vitro Cancer Tissue Engineering and Drug Testing Applications.

Biomimetic polymers and materials have been widely used in tissue engineering for regeneration and replication of diverse types of both normal and diseased tissues. Cancer, being a prevalent disease throughout the world, has initiated substantial interest in the creation of tissue-engineered models for anticancer drug testing. The development of these in vitro three-dimensional (3D) culture models using novel biomaterials has facilitated the investigation of tumorigenic and associated biological phenomena with a higher degree of complexity and physiological context than that provided by established two-dimensional culture models. In this review, an overview of a wide range of natural, synthetic, and hybrid biomaterials used for 3D cancer cell culture and investigation of cancer cell behavior is presented. The role of these materials in modulating cell-matrix interactions and replicating specific tumorigenic characteristics is evaluated. In addition, recent advances in biomaterial design, synthesis, and fabrication are also assessed. Finally, the advantages of incorporating polymeric biomaterials in 3D cancer models for obtaining efficacy data in anticancer drug testing applications are highlighted.