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Mimicking the diverse glyco-conjugate structures in nature is always the dream of scientists. Right now, hierarchical self-assembled structures of natural conjugates of peptides and sugars could not easily be achieved via linear glycopolypeptide with monosaccharides as attachments. In this work, by using a series of well-designed alternating amphiphilic glycopolypeptide brushes (AAGBs) with pendants of glycodendrons and short peptides, various self-assembled morphologies were achieved, including nanowires, nanoribbon, and compound micelles mainly depending on the number ratio of the sugar units to the amino acids species (S/F). Among these morphologies, nanowire attracted our great attention. TEM studies demonstrated that it is formed via a hierarchical self-assembly, i.e., a series of successive processes, including micellization, micelles alignment forming nanofilament, branching of the nanofilaments by micelles, and finally nanowire formation. As far as we know, such hierarchical self-assembly process with high complexity has not been observed in literature for glycopolypeptides even polypeptides, which will deepen our understanding on self-assembly mechanism of natural glyco-conjugates and expand the library of biomimetic materials.

The capability of monitoring the differentiation process in living stem cells is crucial to the understanding of stem cell biology and the practical application of stem-cell-based therapies, yet conventional methods for the analysis of biomarkers related to differentiation require a large number of cells as well as cell lysis. Such requirements lead to the unavoidable loss of cell sources and preclude real-time monitoring of cellular events. In this work, we report the detection of microRNAs (miRNAs) in living human mesenchymal stem cells (hMSCs) by using polydopamine-coated gold nanoparticles (Au@PDA NPs). The PDA shell facilitates the immobilization of fluorescently labeled hairpin DNA strands (hpDNAs) that can recognize specific miRNA targets. The gold core and PDA shell quench the fluorescence of the immobilized hpDNAs, and subsequent binding of the hpDNAs to the target miRNAs leads to their dissociation from Au@PDA NPs and the recovery of fluorescence signals. Remarkably, these Au@PDA-hpDNA nanoprobes can naturally enter stem cells, which are known for their poor transfection efficiency, without the aid of transfection agents. Upon cellular uptake of these nanoprobes, we observe intense and time-dependent fluorescence responses from two important osteogenic marker miRNAs, namely, miR-29b and miR-31, only in hMSCs undergoing osteogenic differentiation and living primary osteoblasts but not in undifferentiated hMSCs and 3T3 fibroblasts. Strikingly, our nanoprobes can afford long-term tracking of miRNAs (5 days) in the differentiating hMSCs without the need of continuously replenishing cell culture medium with fresh nanoprobes. Our results demonstrate the capability of our Au@PDA-hpDNA nanoprobes for monitoring the differentiation status of hMSCs (i.e., differentiating versus undifferentiated) via the detection of specific miRNAs in living stem cells. Our nanoprobes show great promise in the investigation of the long-term dynamics of stem cell differentiation, identification and isolation of specific cell types, and high-throughput drug screening.