Cell Sheet Engineering: Thermoresponsive Harvest

Culture Dish

Culture time 36 h

Dish temperature 37.0 °C

Harvest Method

Culturing at 37.0 °C — grow the sheet, then cool below the LCST and harvest.

Live Readouts

Confluence

Polymer hydration

ECM / junction integrity

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Cell viability

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How it works

Cell sheet engineering grows cells on a dish coated with poly(N-isopropylacrylamide), PNIPAAm — a polymer with a lower critical solution temperature (LCST) of about 32 °C:

Hydration:  H(T) = 1 / (1 + exp((T - Tc) / w))
            Tc ≈ 32 °C,  w ≈ 1.2 °C

Confluence: C(t) = K / (1 + ((K-C0)/C0)·e^(-r t))
            logistic growth, r ≈ 0.11 /h, K = 100%

Above 32 °C the polymer chains are collapsed and hydrophobic — cells attach, spread and form a confluent sheet with intact cell–cell junctions and secreted extracellular matrix (ECM). Cool the dish below Tc and the chains hydrate and swell (H → 1), the surface turns hydrophilic, and adhesion energy collapses — the entire monolayer detaches as one contiguous sheet with its junctions, ECM and basal proteins preserved.

Thermal harvest — only works once hydration is high (T well below 32 °C); the sheet lifts off intact, ECM/junction integrity stays high (~90%+).
Enzymatic harvest (trypsin) — works at any temperature but proteolytically cleaves the surface adhesion proteins and cadherin junctions holding the sheet together, so cells detach individually; ECM/junction integrity collapses (~20–30%) and the tissue architecture is lost.

This is why thermoresponsive culture is used clinically for corneal epithelial sheets, cardiomyocyte patches and periodontal ligament grafts — the harvested construct keeps the cell-to-cell wiring a scaffold-based or enzymatically dissociated graft cannot.

Healthy cell / intact sheet PNIPAAm brush layer Detached / damaged cell

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