Super-assembly platform for diverse nanoparticles with tunable topological architectures and surface morphologies.

Self-assembly leveraged by nature enables the sophisticated generation of a wide range of nanoparticles (NPs) with rich architectures and morphologies. However, existing artificial self-assembly platforms largely only allow for the fabrication of single type of NPs with limited structures, due to their inability to define interfacial interaction between seeds and growth materials, which is critically important to gain controllable growth patterns of the grown materials on the seeds' surface. Here, we report a versatile super-assembly platform that shows the capabilities to fabricate diverse NPs with tunable topological architectures and surface morphologies, e.g., molecular-like NPs, hollow asymmetric NPs, patchy NPs, etc. We unprecedentedly discovered the powerful functions of polyvinylpyrrolidone (PVP), which enable us to well define interfacial interaction between growth materials and seeds to achieve the controllable and tunable generation of various complex topological growth patterns. Moreover, the nucleation pattern (island nucleation or layered nucleation) of the patches can be thermodynamically modulated via the polarity of the solvent, while the number and size of the patches can be kinetically tuned by the ratio of polystyrene (PS), precursor, and catalyst. Interestingly, the hollow NPs can be generated by single-one processing step in our platform, unlike the multiple steps laboriously and widely employed by previously reported fabrication platforms. In addition, we demonstrate that our annealed NPs can not only selectively reflect visible light, and show well-controlled colors from gray, blue, to green, but also exhibit excellent photothermal conversion performances with a high photothermal conversion efficiency of 68.7% that are superior to currently routinely reported of 40%. This super-assembly platform can serve as a powerful toolset to sophisticatedly create varied NPs with tunable hierarchical architectures and controllable surface morphologies, which would significantly benefit the development of drug delivery, nanomaterial assembly, nano pigments, nanoreactors, and beyond.

The modulatory effects of bHLH transcription factors with the Wnt/beta-catenin pathway on differentiation of neural progenitor cells derived from neonatal mouse anterior subventricular zone.

The subventricular zone (SVZ) located adjacent to the lateral ventricles is the major site where neural progenitor cells (NPCs) are concentrated in the adult brain. NPCs in the anterior subventricular zone (SVZa) generate neuronal precursors and migrate along a highly localized pathway--the rostral migratory stream (RMS) to the olfactory bulb (OB), where they differentiate into interneurons. To investigate the modulatory effects of basic helix-loop-helix (bHLH) transcription factors on differentiation from SVZa NPCs, we firstly examined the distribution of bHLH family members (Mash1, Id2, and Hes1) in cultured mouse SVZa NPCs and evaluated their regulatory effects on differentiation by transfection with Mash1, Id2, or Hes1 eukaryotic expression plasmid. Furthermore, we assessed the effects of bHLH transcription factors on the expression of downstream molecules of the Wnt/beta-catenin pathway, beta-catenin and (Glycogen synthase kinase-3beta). Our results demonstrated that Mash1, Id2, Hes1 were all widely expressed in in vitro progenies from mouse SVZa NPCs. Analyses of SVZa NPCs transfected with eukaryotic expression plasmids showed that Mash1 promoted neuronal differentiation from SVZa NPCs, while Id2 and Hes1 repressed neuronal differentiation. In addition, we found that Id2 and Hes1 simulated expression of beta-catenin and GSK-3beta, while Mash1 inhibited their expression. Our results suggest that the classic bHLH transcription factors, Mash1, Id2 and Hes1, play important roles in the regulation of differentiation from SVZa NPCs. This modulation is possibly mediated by a coordination of bHLH and Wnt/beta-catenin signaling.

SVZa neural stem cells differentiate into distinct lineages in response to BMP4.

Neural stem cells (NSCs) reside in the anterior portion of the forebrain subventricular zone (SVZa) and generate the progenitors which will differentiate into neurons, and via a tangential migratory pathway, known as the rostral migratory stream (RMS), migrate to the olfactory bulbs (OB). Bone morphogenetic proteins (BMPs) play significant roles in neural development at different stages and locations, but their roles have not been determined in the SVZa. To explore possible roles of BMPs in SVZa NSCs, BMP4 at various concentrations were tested for their capacity to induce SVZa NSCs. The expression of BMP4 was also examined in living cells using a reportor vector, in which the BMP4 promotor was conjugated with red fluorescent protein (RFP). In the meantime, the differentiation of SVZa NSCs was dynamically monitored by using reportor vectors of the Nestin enhancer and the promoters of TH and GFAP. In the OB, high expression of BMP4 was found using both promoter activity analysis and in situ hybridization. However, low BMP4 expression was found in the RMS and only moderate expression of BMP4 was displayed in the SVZa. The results also demonstrated that low concentrations (1-5 ng/ml) of BMP4 promoted the proliferation of SVZa NSCs but high concentrations (10-100 ng/ml) of BMP4 inhibited this proliferation. BMP4 enhanced neuron commitment before 4 days but inhibited it after 4 days. As the antagonist of BMP4, Noggin almost completely blocked all these BMP4 responses. Thus, our findings indicate that BMP4 promotes the exit from the cell cycle and triggers the differentiation of neuron progenitors in the OB. BMP4 also promotes the proliferation of the committed neuron progenitors in the RMS, but in the SVZa, BMP4 may facilitate the commitment of NSCs into astrocytes.