Mesenchymal stem cell (MSC)-based biomimetic delivery has been actively explored for drug accumulation and penetration into tumors by taking advantage of the tumor-tropic and penetration properties of MSCs. In this work, we further demonstrated the feasibility of MSC-mediated nano drug delivery, which was characterized by the “Trojan horse”-like transport via an endocytosis–exocytosis–endocytosis process between MSCs and cancer cells. Chlorin e6 (Ce6)-conjugated polydopamine nanoparticles (PDA-Ce6) were developed and loaded into the MSCs. Phototherapeutic agents are safe to the MSCs, and their very low dark toxicity causes no impairment of the inherent properties of MSCs, including tumor-homing ability. The MSCs loaded with PDA-Ce6 (MSC-PDA-Ce6) were able to target and penetrate into tumors and exocytose 60% of the payloads in 72 h. The released PDA-Ce6 NPs could penetrate deep and be re-endocytosed by the cancer cells. MSC-PDA-Ce6 tended to accumulate in the lungs and delivered PDA-Ce6 into the tumors after intravenous injection in the mouse model with lung melanoma metastasis. Phototoxicity can be selectively triggered in the tumors by sequentially treating with near-infrared irradiation to induce photodynamic therapy (PDT) and photothermal therapy (PTT). The MSC-based biomimetic delivery of PDA-Ce6 nanoparticles is a potential method for dual phototherapy against lung melanoma metastasis.

The last few decades have been plagued by viral outbreaks that present some of the biggest challenges to public safety. The current coronavirus (COVID-19) disease pandemic has exponentiated these concerns. Increased research on diagnostic tools is currently being implemented in order to assist with rapid identification of the virus, as mass diagnosis and containment is the best way to prevent the outbreak of the virus. Accordingly, there is a growing urgency to establish a point-of-care device for the rapid detection of coronavirus to prevent subsequent spread. This device needs to be sensitive, selective, and exhibit rapid diagnostic capabilities. Electrochemical biosensors have demonstrated these traits and, hence, serve as promising candidates for the detection of viruses. This review summarizes the designs and features of electrochemical biosensors developed for some past and current pandemic or epidemic viruses, including influenza, HIV, Ebola, and Zika. Alongside the design, this review also discusses the detection principles, fabrication techniques, and applications of the biosensors. Finally, research and perspective of biosensors as potential detection tools for the rapid identification of SARS-CoV-2 is discussed.

Cell-based impedance spectroscopy (CBI) is a powerful tool that uses the principles of electrochemical impedance spectroscopy (EIS) by measuring changes in electrical impedance relative to a voltage applied to a cell layer. CBI provides a promising platform for the detection of several properties of cells including the adhesion, motility, proliferation, viability and metabolism of a cell culture. This review gives a brief overview of the theory, instrumentation, and detection principles of CBI. The recent applications of the technique are given in detail for research into cancer, neurodegenerative diseases, toxicology as well as its application to 2D and 3D in vitro cell cultures. CBI has been established as a biophysical marker to provide quantitative cellular information, which can readily be adapted for single-cell analysis to complement the existing biomarkers for clinical research on disease progression.

Understanding the factors that give rise to tau aggregation and reactive oxygen species (ROS) is the key aspect in Alzheimer’s disease pathogenesis. Microtubule (MT) binding repeats of tau protein were suggested to play a critical role in tau aggregation. Here, we show that the interaction of Cu²⁺ with full-length MT binding repeats R1–R4 leads to the aggregation, and a Cys-based redox chemistry is critically involved in tau aggregation leading to disulfide-bridge dimerization of R2 and R3 and further aggregation into a fibrillar structure. Notably, ascorbate and glutathione, the most abundant antioxidants in neurons, cannot prevent the effect of Cu²⁺ on R2 and R3 aggregation. Detailed ESI-MS and NMR experiments demonstrate the interaction of Cu²⁺ with MT binding repeats. We show that redox activity of copper increases when bound to the MT repeats leading to ROS formation, which significantly contribute to cellular damage and neuron death. Results presented here provide new insights into the molecular mechanism of tau aggregation and ROS formation and suggest a new target domain for tau aggregation inhibitors.