Yung Hsiang (John) Lu and IBBME UofT

December 5, 2019 @ 12:30 pm – 1:00 pm
Red Seminar Room
Donnelly Building

Event Name: Graduate Seminar Series: Cell and Tissue Stream

Graduate Seminar Series for the Institute of Biomaterials and Biomedical Engineering (IBBME). This day is for cell and tissue stream presenters.

Location: Red Seminar Room – Donnelly Building

Presentation Title: A Platform To Recapitulate Dynamic Tissues: Engineered Hydrogels With Spatio-Temporal Control
Introduction: Hydrogels are traditionally designed as static systems for 3-dimensional (3D) cell culture as an improvement from culturing on mechanically stiff 2D tissue culture polystyrene. However, traditional hydrogels have been shown to be insufficient in modelling the dynamic nature of tissue during development and disease progression. Recently, research groups have developed bioengineered hydrogel systems which use photo-chemical methods to enable spatio-temporal control over mechanical properties or the presentation of biochemical signals to cells. However, most of these systems use bioinert materials, such as polyethylene glycol, that are not physiologically relevant to the body and/or focus on controlling the spatio-temporal removal rather than the activation of biochemical cues. The goal of this project is to develop a new, physiologically-relevant hydrogel system with spatio-temporal control over the activation of photocaged proteins. As a proof of concept study, we synthesized hyaluronan (HA)-based hydrogels with controlled activation of epidermal growth factor (EGF) and analysed the effect of EGF on encapsulated breast cancer spheroids. HA has been shown to be overexpressed in the breast cancer tumour microenvironment. EGF has previously been shown to differentially affect different breast cancer cell lines in terms of viability, invasion, and response to drug treatment. With photo-chemistry, we can control the spatio-temporal presentation of EGF to breast cancer spheroids. This study serves as a first step towards validating our hydrogel platform to dynamically present a diverse range of biochemical cues in a variety of in vitro biological models.

Materials and Methods: HA hydrogels were synthesized using oxime and Diels-Alder chemistry. MDA-MB-468 breast cancer cells were encapsulated and grown as spheroids for 14 days with or without EGF and assessed for: size using GelCount, viability using PrestoBlue Viability Assay and morphology by confocal microscopy. EGF was functionalized with both photolabile moieties to enable photochemical control and maleimide to attach to the hydrogel backbone.

Results and Discussion: Breast cancer spheroids grew well in HA-oxime hydrogels. Breast cancer spheroids grew in the absence but not the presence of soluble EGF over a period of 14 days (Fig 1a), verifying the activity of EGF in our model. Live/dead staining confirmed the effect of EGF, with large spheroids and few dead cells in cultures without EGF (Fig. 1b) versus small spheroids with numerous dead cells seen in cultures with EGF (Fig. 1c).

Conclusions: We have verified the bioactivity of EGF in our new hydrogel model. We are currently validating the photochemical method of inducing EGF activity in the hydrogels.

Acknowledgements: We thank NSERC (Discovery to MSS and CREATE in M3 to YHL) and CFREF / Medicine by Design for funding.

Supervisor Name: Molly Shoichet
Year of Study: 2
Program of Study: MASc

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