BioMIPs Biocompatible Biomimetics—Molecular Imprinting Ties the Know with Natural Polymers. Synthesis, Properties and Future Perspectives of Silk Molecularly Imprinted Nanoparticles.

The process of molecular imprinting allows to produce biomimetics of nanometric dimensions (nanoMIPs) by means of a template assisted synthesis [1]. NanoMIPs are gaining momentum for their outstanding recognition properties <i>in vitro</i> and <i>in vivo</i>, proving effective in cell imaging, tumor-cell targeting, drug delivery [2-5]. The expectations for nanoMIPs in medicine stake high. Yet, nanoMIPs are currently prepared starting from synthetic monomers (e.g. acrylamides), while focal point for their translation into clinical applications should be biocompatibility.<br/>In this framework, we imagined a possible breakthrough development, based on the original idea to synthesize fully biocompatible nanoMIPs starting from the natural polymer silk fibroin, that is characterized by non-toxicity and high biocompatibility. Given the natural origin, we named the silk imprinted nanoparticles bioMIPs.<br/>We investigated and optimized the synthesis of the bioMIPs by a three parameters (quantity of silk fibroin, pH, photoinitiator) response surface method (RSM) that enabled to model the landscape of the possible synthetic conditions. In set conditions, uniform (polydispersity index &lt; 0.25) nanometer sized populations of bioMIPs, with Z_average ~50 nm or Z_average~100 nm, were obtained.<br/>The possibility to imprint recognition cavities on the bioMIP and the ability of these bioMIPs to trap a defined target molecule was also studied. Target molecules of different sizes (i.e. a peptide and a protein) were chosen as templates, so to consider the effects of the template size on the imprinting process [6,7]. Both isothermal titration nanocalorimetry and fluorescence spectroscopy proved the molecular recognition abilities of the formed bioMIPs. The estimated dissociation constants of the bioMIPs for the targets were in the nanomolar range, moreover the bioMIPs had selectivity and specificity for the target and a quasi-single binding site per nanoparticle. Additionally, the bioMIPs proved to be nontoxic for cultured mouse embryonic fibroblasts even at significantly high concentrations (2 mg/mL). Finally, we produced functional biomaterials with tailored recognition by coupling the bioMIPs to silk micro- and nano-fibers. Such bioMIP-silk specialized functional fibers proved to selectively trap the targeted molecule [6].<br/>Hence, the unprecedented combination of silk fibroin building blocks to molecular imprinting appears as a compelling strategy to entail recognitive-functions to bio-nanoparticles. BioMIPs open for a new class of biomimetics that conjugate natural polymers to the custom design of molecular recognition abilities, with foreseen impact in precision medicine and instructive biomaterials.<br/><br/>References<br/>1. Y. Hoshino, T. Kodama, Y. Okahata, K.J. Shea J. Am. Chem. Soc. 2008, 130, 15242.<br/>2. S. Piletsky, F. Canfarotta, A. Poma, A.M. Bossi, S. Piletsky, Trends Biotechnol. 2020, 38, 368.<br/>3. A.M. Bossi, Nat. Chem., 2020, 12, 111.<br/>4. K. Haupt, P.X. Medina Rangel, B.T.S. Bui, Chem. Rev. 2021, 120, 9554.<br/>5. Y. Dong, W. Li, Z. Gu, R. Xing, Y. Ma, Q. Zhang, Z. Liu, Angew. Chem. Int. Ed. 2019, 58, 10621.<br/>6. A.M. Bossi, A. Bucciarelli, D. Maniglio, ACS Appl. Mater. Interfaces, 2021, 13, 312431.<br/>7. A.M. Bossi, D. Maniglio, Microchem. Acta, 2022, 189, 66.