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Mesenchymal stem cells are multipotent adult stem cells capable of generating bone, cartilage and fat, and are thus currently being exploited for regenerative medicine. When considering osteogenesis, developments have been made with regards to chemical induction (e.g. differentiation media) and physical induction (e.g. material stiffness, nanotopography), targeting established early transcription factors or regulators such as runx2 or bone morphogenic proteins and promoting increased numbers of cells committing to osteo-specific differentiation. Recent research highlighted the involvement of microRNAs in lineage commitment and terminal differentiation. Herein, gold nanoparticles that confer stability to short single stranded RNAs were used to deliver MiR-31 antagomiRs to both pre-osteoblastic cells and primary human MSCs in vitro. Results showed that blocking miR-31 led to an increase in osterix protein in both cell types at day 7, with an increase in osteocalcin at day 21, suggesting MSC osteogenesis. In addition, it was noted that antagomiR sequence direction was important, with the 5 prime reading direction proving more effective than the 3 prime. This study highlights the potential that miRNA antagomiR-tagged nanoparticles offer as novel therapeutics in regenerative medicine. [ABSTRACT FROM AUTHOR]

Nanotechnology plays an increasingly important role in the biomedical arena. In particular, magnetic nanoparticles (mNPs) have become important tools in molecular diagnostics, in vivo imaging and improved treatment of disease, with the ultimate aim of producing a more theranostic approach. Due to their small sizes, the nanoparticles can cross most of the biological barriers such as the blood vessels and the blood brain barrier, thus providing ubiquitous access to most tissues. In all biomedical applications maximum nanoparticle uptake into cells is required. Two promising methods employed to this end include functionalization of mNPs with cell-penetrating peptides to promote efficient translocation of cargo into the cell and the use of external magnetic fields for enhanced delivery. This study aimed to compare the effect of both penetratin and a static magnetic field with regards to the cellular uptake of 200 nm magnetic NPs and determine the route of uptake by both methods. Results demonstrated that both techniques increased particle uptake, with penetratin proving more cell specific. Clathrinmedicated endocytosis appeared to be responsible for uptake as shown via PCR and western blot, with Pitstop 2 (known to selectively block clathrin formation) blocking particle uptake.Interestingly, it was further shown that a magnetic field was able to reverse or overcome the blocking, suggesting an alternative route of uptake. [ABSTRACT FROM AUTHOR]

Nanoparticle entry into the cell depends on the surface charge and also on their size. Here, we report the entry of large magnetic nanoparticles (500 nm mean diameter) into the cell, being mediated by a mechanical stimulus supplied to the culture flasks. Investigations were carried out at 2-10 Hz frequency range with the vertical excursions ranging from 5 to 20 nm. Mechanical stimulation was found to aid the entry of both positive and negatively charged nanoparticles over a frequency range of 2-10 Hz. Transmission electron microscopy analysis indicated that, the stimulated samples could possibly mediate particle uptake through membrane invaginations, while the control samples indicated particles at the cell periphery, just outside the cell membrane. Mechanical stimulation had no significant effect on the cell morphology. Bromodeoxyuridine incorporation resulted in an increase in the proportion of S-phase in the stimulated samples compared with the controls, suggesting a reduction in the cell cycle duration. Mechanical stimulation could very well extend its effects to nanoscale cellular movements, and also facilitate the entry of large magnetic nanoparticle. This could be an interesting prospect for nanoparticle mediated drug delivery. [ABSTRACT FROM AUTHOR]