Abstract
Upper Critical Solution Temperature (UCST)-type thermally responsive polypeptides (TRPs) with phase transition temperatures around 37 °C in phosphate-buffered saline (PBS) buffer (pH 7.4, 100 mM) were prepared from poly(l-ornithine) hydrobromide and coated on non-tissue culture-treated plastic plates (nTCP). Cell adhesion was observed at temperatures above the phase transition temperature of the coating polymer (39 °C), while cell release was triggered when the culture temperature was switched to 37 °C. Approximately 65% of the attached cells were released from the surface within 6 h after changing the temperature, and more than 96% of the released cells were viable. Water contact angle measurements performed at 39 and 37 °C demonstrated that the surface hydrophobicity of the new TRP coatings changed in response to applied temperature. The cell attachment varied with the presence of serum in the media, suggesting that the TRP coatings mediated cell attachment and release as the underlying polymer surface changed conformation and consequently the display of adsorbed protein. These new TRP coatings provide an additional means to mediate cell attachment for application in cell-based tissue regeneration and therapies.
Highlights
Controlled delivery of specific cells to correct defective or damaged tissue has become a significant research goal in tissue regenerative therapies
The reaction contents were maintained with stirring at 50 ◦ C, which is higher than the phase transition temperatures of all the target polymers in this study, to avoid polymer phase separation during the reaction time
The modified POC product was characterized by 1 H-Nuclear Magnetic Resonance (NMR) spectroscopy (400 Hz, D2 O at 70 ◦ C). (Figure S2 for Polymer 2 and Figure 1b for Polymer 3, and Table 1) δ: 4.68, 3.58–3.61, 3.42, 3.14, 2.33 (NHCHCH2 CH2 CH2 ) and 2.02–2.09
Summary
Controlled delivery of specific cells to correct defective or damaged tissue has become a significant research goal in tissue regenerative therapies. Design of supports to promote cell attachment is highly complex and the determinants of cell adhesion range from surface charge [1,2], hydrophilic/hydrophobic balance [1,3,4,5,6,7], functional group type and content [1,7,8,9], to surface roughness and topology [10,11]. For cell culture and delivery applications, it is usually important to generate materials which exhibit high cellular affinity during the cell growth and transport stages, but low affinity when the cells are in their desired site of action or expansion. It is desirable to be able to switch on or off these cell surface interactions via a simple stimulus, as traditional cell harvesting methods (e.g., high shear or proteases) are not applicable in vivo. Certain polymers exhibit changes of solubility in aqueous solutions in response to changes in temperature, and those
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