Nanosensors for regenerative medicine

Assessing biodistribution, fate, and function of implanted therapeutic cells in preclinical animal experiments is critical to realize safe, effective and efficient treatments for subsequent implementation within the clinic. Currently, tissue histology, the most prevalent analytical technique to meet this need, is limited by end-point analysis, high cost and long preparation time. Moreover, it is disadvantaged by an inability to monitor in real-time, qualitative interpretation and ethical issues arising from animal sacrifice. While genetic engineering techniques allow cells to express molecules with detectable signals (e.g., fluorescence, luminescence, T1 (spin–lattice)/T2 (spin–spin) contrast in magnetic resonance imaging, radionuclide), concerns arise regarding technical complexity, high-cost of genetic manipulation, as well as mutagenic cell dysfunction. Alternatively, cells can be labeled using nanoparticle-sensors—nanosensors that emit signals to identify cell location, status and function in a simple, cost-effective, and non-genetic manner. This review article provides the definition, classification, evolution, and applications of nanosensor technology and focuses on how they can be utilized in regenerative medicine. Several examples of direct applications include: (1) monitoring post-transplantation cell behavior, (2) revealing host response following foreign biomaterial implantation, and (3) optimization of cell bioprocess operating conditions. Incorporating nanosensors is expected to expedite the development of cell-based regenerative medicine therapeutics

Interference-free Micro/nanoparticle Cell Engineering by Use of High-Throughput Microfluidic Separation

Engineering cells with active-ingredient-loaded micro/nanoparticles is becoming increasingly popular for imaging and therapeutic applications. A critical yet inadequately addressed issue during its implementation concerns the significant number of particles that remain unbound following the engineering process, which inadvertently generate signals and impart transformative effects onto neighboring nontarget cells. Here we demonstrate that those unbound micro/nanoparticles remaining in solution can be efficiently separated from the particle-labeled cells by implementing a fast, continuous, and high-throughput Dean flow fractionation (DFF) microfluidic device. As proof-of-concept, we applied the DFF microfluidic device for buffer exchange to sort labeled suspension cells (THP-1) from unbound fluorescent dye and dye-loaded micro/nanoparticles. Compared to conventional centrifugation, the depletion efficiency of free dyes or particles was improved 20-fold and the mislabeling of nontarget bystander cells by free particles was minimized. The microfluidic device was adapted to further accommodate heterogeneous-sized mesenchymal stem cells (MSCs). Complete removal of unbound nanoparticles using DFF led to the usage of engineered MSCs without exerting off-target transformative effects on the functional properties of neighboring endothelial cells. Apart from its effectiveness in removing free particles, this strategy is also efficient and scalable. It could continuously process cell solutions with concentrations up to 10⁷ cells·mL^–1 (cell densities commonly encountered during cell therapy) without observable loss of performance. Successful implementation of this technology is expected to pave the way for interference-free clinical application of micro/nanoparticle engineered cells