Infectious pathogens cause severe threats to public health due to their frightening infectivity and lethal capacity. Rapid and accurate detection of pathogens is of great significance for preventing their infection. Gold nanoparticles have drawn considerable attention in colorimetric biosensing during the past decades due to their unique physicochemical properties. Colorimetric diagnosis platforms based on functionalized AuNPs are emerging as a promising pathogen-analysis technique with the merits of high sensitivity, low-cost, and easy operation. This review summarizes the recent development in this field. We first introduce the significance of detecting pathogens and the characteristics of gold nanoparticles. Four types of colorimetric strategies, including the application of indirect target-mediated aggregation, chromogenic substrate-mediated catalytic activity, point-of-care testing (POCT) devices, and machine learning-assisted colorimetric sensor arrays, are systematically introduced. In particular, three biomolecule-functionalized AuNP-based colorimetric sensors are described in detail. Finally, we conclude by presenting our subjective views on the present challenges and some appropriate suggestions for future research directions of colorimetric sensors.

Iron oxide nanoparticles (IONPs) have been extensively studied in different biomedical fields. Recently, the non-cytotoxic concentration of IONPs induced cell-specific response raised concern of their safety. Endothelial cell exposure was unavoidable in their applications, while whether IONPs affect the phenotype of vascular endothelial cells is largely unknown. In this work, the effect of IONPs on endothelial-to-mesenchymal transition (EndMT) was investigated in vitro and in vivo. The incubation with γ-Fe2O3 nanoparticles modified with polyglucose sorbitol carboxymethyether (PSC-Fe2O3) at non-cytotoxic concentration induced morphological changes of human umbilical vein endothelial cells (HUVECs) from cobblestone-like to spindle mesenchymal-like morphology, while PSC-Fe2O3 mostly stay in the culture medium and intercellular space. At the same time, the endothelial marker CD31 and VE-cadherin was decreased along with the inhibitory of angiogenesis properties of HUVEC. Meanwhile, the mesenchymal marker α-smooth muscle actin (α-SMA) and fibroblast specific protein (FSP) was up regulated significantly, and the migration ability of the cells was enhanced. When ROS scavenger mannitol or AA was supplemented, the EndMT was rescued. Results from the in vivo study showed that, expression of CD31 was decreased and α-SMA increased in the liver, spleen and kidney of mice given PSC-Fe2O3, and the density of collagen fibers in the liver sinusoid of mice was increased. The supplementary mannitol or AA could reverse the degree of EndMT in the tissues. Mechanistic study in vitro indicated that the level of extracellular hydroxyl radicals (·OH) was up regulated significantly by PSC-Fe2O3, which induced the response of intracellular ROS and resulted in the EndMT effect on HUVECs. The PSC-Fe2O3 was capable of inducing EndMT in the endothelial cells at acutely non-cytotoxic dose due to its intrinsic peroxidase-like activity, though they were few taken up by endothelial cell. The EndMT effect on HUVEC can be rescued by ROS scavenger in vitro and in vivo.

Objective: The interaction between superparamagnetic iron oxide (SPIO) nanoparticles and mesenchymal stem cells (MSCs) in the presence of pulsed magnetic field (PMF) has become important areas of research in recent years. Methods: A parameter-adjustable pulsed magnetic field was developed based on the principle of insulated gate bipolar translator (IGBT) transistor-controlled discharge of large capacitances. The internalizations of SPIO nanoparticles by MSCs were investigated under the treatment of PMF in both intermittent stimulation mode and continuous stimulation mode. Results: The intensities and frequencies of pulsed magnetic field can be adjustable in the range of 1.9-4.6mT and 3-5 kHz, respectively. This PMF was safe to the MSCs. However, the uptake of SPIO nanoparticles by MSCs was significantly prohibited under the treatment of KHz-ranged PMF while the 10Hz PMF enhanced the cellular uptake of nanoparticles. This phenomenon was relative with the magnetic effect of the PMF with different frequency. Conclusion: The PMF can be used to effectively regulate the cellular uptake of SPIO nanoparticles and the mechanism lies in the magnetic effect. Significance: The interaction between SPIO nanoparticles and the MSCs is a fundamental and important issue for nanomedicine and stem cell research. Our results demonstrated the external magnetic field can be used to regulate their interaction. We believed that this safe, facile and flexible method will greatly promote the development and clinical translation of regenerative medicine and nanomedicine.

Anoikis resistance constitutes a critical pathophysiological mechanism driving metastatic progression in colorectal cancer. While in vitro models are essential for mechanistic studies, conventional 2D cultures inadequately replicate tumor microenvironment (TME) complexity. In this study, we developed a biomimetic composite hydrogel (GHP_4a) composed of 4-arm-PEGDA, Gelatin Methacryloyl, and Hyaluronic acid Methacryloyl to establish compact 3D cell spheres that mimic TME. The GHP_4a demonstrates superior biocompatibility, suitable mechanical strength at 600-700 Pa, and biomimetic properties that promote cell proliferation and differentiation when co-culturing Caco-2 cells. The cell anchorage and survival for anoikis resistance are enhanced compared to traditional 2D cell incubation due to a well-organized 3D formation akin to the extracellular matrix (ECM). The biomimetic mechanism may be attributed to the fact that the GHP_4a promoted the activation of key pro-survival pathways, including FAK and PI3K/Akt signaling, and suppressed caspase-mediated apoptosis. Single-cell RNA sequencing revealed distinct transcriptional profiles within the proliferating T cell population, suggesting a novel regulatory mechanism of T cell-mediated anti-tumor immunity in the TME. Additionally, radiomic analysis identified significant differences in tumor heterogeneity and texture between GHP_4a-based 3D cultures and traditional 2D models. These findings established the GHP_4a as an effective candidate for the in vitro tumor anoikis resistance model, providing a unique approach for studying anoikis resistance in colorectal cancer and offering a robust tool for the development of advancing cancer diagnosis and therapy strategies.