PhD Thesis Colloquium: Mr. Sriram Bharath (23/12/25)
Thesis title:
Engineering 3D/4D Bioprinted Tissue Scaffolds for Triple Negative Breast Cancer Disease Modeling and Drug Screening
Faculty advisor(s):
Prof. Kaushik Chatterjee
When?
23rd December, 2025 (Tuesday), 3:00 PM (India Standard Time)
Where
KPA Auditorium, Department of Materials Engineering
Abstract:
Triple Negative Breast Cancer (TNBC), an aggressive breast cancer subtype lacking targeted therapies, is poorly represented by conventional two-dimensional (2D) cultures and animal models, which are limited in their ability to reproduce human-relevant tissue stiffness, geometry, and microenvironmental dynamics. To address these gaps, visible-light–based digital light processing (DLP) bioprinting of gelatin methacryloyl (GelMA) or its blend with poly(ethylene glycol) dimethacrylate (PEGDM) hydrogels is employed to generate cytocompatible, mechanically tunable, and shape-morphing constructs. Across three interconnected chapters, the work progresses from static three dimensional (3D)-bioprinted, mechanomimetic metastatic niche models to stimulus-responsive two-dimensional (4D) sheets, and finally to self-folding, duct-like tubular scaffolds under both static and dynamic culture conditions, providing an advanced in vitro, non-animal platform for TNBC disease modeling and preclinical drug screening.
The first chapter focuses on engineering DLP-based GelMA or GelMA–PEGDM scaffolds that emulate the stiffness of common TNBC metastatic targets such as lung, liver, and cancellous bone. Two formulations were used to prepare 3D-bioprinted , yielding soft gels with a compressive modulus of about 6.7 ± 2.5 kPa and stiffer gels with a modulus of about 43.8 ± 18.4 kPa. These scaffolds show good print fidelity and support cell viability and proliferation. MDA‑MB‑231 cells in the soft gels adopt a spindle-like morphology by Day 14 and show an approximately 3.8-fold increase in metabolic activity relative to Day 1. In contrast, cells in the stiff scaffolds remain more spherical and maintain relatively constant metabolic activity over the same period. Cells retrieved from both 3D scaffolds exhibit higher elastic moduli than cells grown on 2D tissue culture polystyrene, indicating changes consistent with mechanical adaptation. Treatment of Day 14 constructs with 1 µM doxorubicin for 48 h results in about 45% cell death in the soft scaffolds and about 7% in the stiff scaffolds. These results highlight the importance of metastatic site–specific biophysical cues in regulating TNBC behavior and demonstrate that DLP-printed mechanomimetic hydrogels can serve as robust, high-throughput alternatives to animal models for probing drug response and resistance.
The second chapter establishes a 4D bioprinting strategy in which a flat sheet printed with visible light 405 nm based DLP using GelMA and PEGDM based bioink is programmed to undergo rapid, predictable shape transformation upon exposure to cell‑compatible stimuli such as hydration. By incorporating a photoabsorber to induce controlled light attenuation, spatially graded crosslinking is achieved within the printed sheets, creating internal anisotropy that drives bending and curvature. The extent and direction of this shape change can be tuned through parameters such as sheet thickness and strand orientation, enabling the generation of complex, three-dimensional forms from simple planar precursors within minutes. Importantly, the resulting hydrogels maintain NIH/3T3 cells cytocompatibility, supporting the viability and proliferation of encapsulated cells. This chapter, therefore, introduces a versatile, visible-light crosslinkable bioink for producing tubular geometry mimetic scaffolds. These cell-laden constructs bridge the gap between static 3D bioprinted scaffolds and dynamic, tissue-like architectures suitable for tissue engineering and disease modeling.
Building on this foundation, the third chapter applies 4D bioprinting to create self-folding tubular constructs that mimic the geometry of mammary ducts for TNBC modeling under both static and rocker-based dynamic culture conditions. Systematic variation of photoinitiator concentration, strand dimensions, solvent conditions, and encapsulated MDA-MB-231 cell density identifies printing regimes that reliably produce closed tubes with internal diameters on the order of those found in mammary ducts (2.15 ± 0.5 mm). Under dynamic culture, which introduces shear stresses analogous to interstitial fluid flow, the constructs support high cell viability, elevated metabolic activity (1.4-fold) compared with static conditions, and accelerated acquisition of mesenchymal-like, spindle-shaped morphology and multicellular aggregation. When treated with doxorubicin, dynamically cultured tubes display slightly greater chemoresistance than their statically cultured counterparts, underscoring the role of fluid-mediated mechanical cues and duct-like architecture in shaping TNBC therapeutic responses. Overall, this thesis presents a set of 3D and 4D-bioprinted TNBC models that capture key metastatic mechanics and duct-like microenvironments. These in vitro systems provide a scalable, animal-free platform for mechanistic studies and the exploration of anti-metastatic and precision treatment strategies.