(650c) Photolithographically Assembled Polyelectrolyte Complexes As Shape-Directing Templates for Thermoreversible Gels

Generation of soft materials with diverse, application-specific shapes has been a topic of intense research interest.^1-3 To this end, we have recently demonstrated photodirected assembly as an approach to customizing polyelectrolyte complex (PEC) shape. This process involves highly localized in situ photopolymerization of an anionic monomer in the presence of a cationic polymer, which drives rapid photolithographic assembly of custom-shaped PECs at the irradiation sites.⁴ Here, we show how these photolithographically generated PECs can serve as structure-directing templates for shaping thermoreversible gels. These custom-shaped gels are formed through the addition of a thermosensitive gelling polymer (agarose) to the anionic monomer/cationic polymer/photoinitiator precursor solutions so that, upon irradiation, PECs form within agarose gel matrices. Upon forming custom-shaped PECs, the surrounding agarose gels are melted (through heating) and washed away, leaving behind interpenetrating PEC/agarose gel networks. Dissolving the sacrificial PEC templates in 3.5 M NaCl solutions then produces custom-shaped agarose gels, whose shapes and dimensions match those of their PEC templates. Besides their tailored shapes and sizes, the mechanical properties of these PEC-templated gels can be readily tuned by varying the initial agarose concentrations used during PEC formation. Moreover, like agarose gels formed through traditional methods, these custom-shaped gels are compatible with mammalian cells. Though here we focus only on agarose gels, this gel templating strategy can also likely be extended to other thermoreversible gel networks (e.g., those based on methylcellulose, Poloxamers or thermoresponsive chitosan derivatives) and, because this strategy can simultaneously tune the size, shape and mechanical properties of widely used cytocompatible materials, it could have many potential applications, ranging from drug delivery and tissue engineering to sensing and bioseparations.

References:

(1) Hanson Shepherd, J. N.; Parker, S. T.; Shepherd, R. F.; Gillette, M. U.; Lewis, J. A.; Nuzzo, R. G. Adv. Funct. Mater. 2011, 21, 47.

(2) Heintz, K.A.; Bregenzer, M.E.; Mantle, J.L.; Lee, K.H.; West, J.L.; Slater, J.H. Adv. Healthc. Mater. 2016, 5, 2153.

(3) Skoog, S.A.; Goering, P.L.; Narayan, R.J. J. Mater. Sci. Mater. Med. 2014, 25, 845.

(4) de Silva, U.K.; Choudhuri, K.; Bryant-Friedrich, A.C.; Lapitsky, Y. Soft Matter 2018, 14, 521.