RNA aptamers selected to bind fluorophores and activate their fluorescence offer a simple and modular way to visualize native RNAs in cells. Split aptamers which are inactive until the halves are brought within close proximity can become useful for visualizing the dynamic actions of RNA assemblies and their interactions in real time with low background noise and eliminated necessity for covalently attached dyes. Here, we design and test several sets of F30 Broccoli aptamer splits, that we call fluorets, to compare their relative fluorescence and physicochemical stabilities. We show that the splits can be simply assembled either through one-pot thermal annealing or co-transcriptionally, thus allowing for direct tracking of transcription reactions via the fluorescent response. We suggest a set of rules that enable for the construction of responsive biomaterials that readily change their fluorescent behavior when various stimuli such as the presence of divalent ions, exposure to various nucleases, or changes in temperature are applied. We also show that the strand displacement approach can be used to program the controllable fluorescent responses in isothermal conditions. Overall, this work lays a foundation for the future development of dynamic systems for molecular computing which can be used to monitor real-time processes in cells and construct biocompatible logic gates.

Spider silk is a natural material possessing unique properties such as biocompatibility, regenerative and antimicrobial activity, and biodegradability. It is broadly considered an attractive matrix for tissue regeneration applications. Optical monitoring and potential control over tissue regrowth are attractive tools for monitoring of this process. In this work, we show upconversion modification of natural spider silk fibers with inorganic nanoparticles. To achieve upconversion, metal oxide nanoparticles were doped with low concentrations of rare-earth elements, producing potentially biocompatible luminescent nanomaterials. The suggested approach to spider silk modification is efficient and easy to perform, opening up sensing and imaging possibilities of biomaterials in a noninvasive and real-time manner in bio-integration approaches.

Chitosan (Chi) is a biodegradable nontoxic polycation with multiple reactive groups that is easily used to obtain derivatives with a desired charge and hydrophobic properties. The aim of this work was to study the intracellular traffic of positively charged hexanoyl-chitosan (HC) or HC-based nanoparticles (HCNPs) and negatively charged succinoyl-chitosan (SC) and SCNPs in epithelial and macrophage cell lines. By using flow cytometry we demonstrated that positively charged HC adhered to cell membranes quicker and more efficiently than negatively charged SC or NPs. However confocal studies showed that SC and SCNPs penetrated cells much more efficiently than HC while HCNPs did not enter the epithelial cells. Macrophages also phagocyted better negatively charged material but were able to engulf both HC and HCNPs. Upon entering the cells, SC and SCNPs were co-localized with endosomes and lysosomes while HC was found in mitochondria and, to a lesser extent, in lysosomes of epithelial cells. Macrophages, RAW264.7, more efficiently transported all Chi samples to the lysosomal compartment while some positively charged material was still found in mitochondria. Incubation of Chi derivatives and ChiNPs at pH specific to mitochondria (8.0) and lysosomes (4.5) demonstrated the neutralization of Chi charge. We concluded that epithelial cells and, to a lesser extent, macrophages sort charged material to the organelles neutralizing Chi charge.

No abstract

Synthetic molecular machines have been explored to manipulate matter at the molecular level.