Selective Positioning of Different Cell Types on 3D Scaffolds via DNA Hybridization.

Three-dimensional (3D) microscaffolds for cell biology have shown their potential in mimicking physiological environments and simulating complex multicellular constructs. However, controlling the localization of cells precisely on microfabricated structures is still complex and usually limited to two-dimensional assays. Indeed, the implementation of an efficient method to selectively target different cell types to specific regions of a 3D microscaffold would represent a decisive step toward cell-by-cell assembly of complex cellular arrangements. Here, we use two-photon lithography (2PL) to fabricate 3D microarchitectures with functional photoresists. UV-mediated click reactions are used to functionalize their surfaces with single-stranded DNA oligonucleotides, using sequential repetition to decorate different scaffold regions with individual DNA addresses. Various immortalized cell lines and stem cells modified by grafting complementary oligonucleotides onto the phospholipid membranes can then be immobilized onto complementary regions of the 3D structures by selective hybridization. This allows controlled cocultures to be established with spatially separated arrays of eukaryotic cells in 3D.

Intriguing Heteroleptic ZnII bis(dipyrrinato) Emitters in the Far-Red Region With Large Pseudo-Stokes Shift for Bioimaging.

Novel heteroleptic ZnII bis(dipyrrinato) complexes were prepared as intriguing emitters. With our tailor-made design, we achieved far-red emissive complexes with a photoluminescence quantum yield up to 45% in dimethylsulfoxide and 70% in toluene. This means that heteroleptic ZnII bis(dipyrrinato) complexes retain very intense emission also in polar solvents, in contrast to their homoleptic counterparts, which we prepared for comparing the photophysical properties. It is evident from the absorption and excitation spectra that heteroleptic complexes present the characteristic features of both ligands: the plain dipyrrin (Lp) and the π-extended dipyrrin (Lπ). On the contrary, the emission comes exclusively from the π-extended dipyrrin Lπ, suggesting an interligand nonradiative transition that causes a large pseudo-Stokes shift (up to 4,600 cm-1). The large pseudo-Stokes shifts and the emissive spectral region of these novel heteroleptic ZnII bis(dipyrrinato) complexes are of great interest for bioimaging applications. Thus, their high biocompatibiliy with four different cell lines make them appealing as new fluorophores for cell imaging.