Thermal-controlled cellular uptake of "hot" nanoparticles

Energy and Speed Landscapes of the Membrane Internalization Behavior of Soft Nanoparticles

The cellular endocytosis of nanoparticles (NPs) is a fundamental biological process with significant potential in biomedical applications. However, a comprehensive understanding of the mechanistic aspects of endocytosis and the impact of particle properties on this process remains elusive. In this study, we investigated the membrane-wrapping behavior of soft NPs (SNPs) with varying rigidities using theoretical calculations. Our findings reveal that the membrane-wrapping process of SNPs involves a complex energy change including the possible existence of an energy barrier; moreover, it is found that the location and height of this barrier strongly depend on the mechanistic properties of the NPs and membranes. Additionally, by considering force balance in the membrane-wrapping process, we calculated the speed at which NP is internalized by the membrane, showing a nonmonotonic dependence on particle rigidity and/or wrapping degree. These phenomena can be attributed to competition between different energy components associated with NP-membrane binding, membrane tension, and deformations occurring during SNP-membrane interaction processes. Our results contribute to a deeper understanding of cellular-level endocytosis mechanisms and offer potential applications for soft NPs in biomedicine.

Asymmetric disturbance and permeabilization of bilayer membranes by 3-nm carbon dots

Small-sized fluorescent carbon dots (CDs) are gaining increasing attention in the field of biomedical applications. The environmental and biological compatibility of positively charged CDs has been extensively investigated; however, the potential cytotoxicity caused by negatively and particularly neutrally charged small CDs has been significantly overlooked. In this study, we conducted a comprehensive investigation into the cellular membrane disruption effect of weakly negatively charged 3-nm CDs using a combination of various biophysical techniques. Our findings demonstrate that even at a low concentration of 0.5 μg mL-1, these CDs induce significant perturbations on the cellular membrane, resulting in increased membrane permeability due to asymmetric disruption of the bilayer structure. Furthermore, CDs exhibit distinct mechanisms at different concentrations, including prompt insertion into the bilayer at low concentrations (<20 μg mL-1) and a synergistic effect after a threshold time at high concentrations (e.g., 25-200 μg mL-1). Moreover, these CDs possess specific antibacterial properties against Acinetobacter baumannii (with a minimum inhibitory concentration of 50 μg mL-1) while showing minimal hemolytic or cytotoxic effects on mammalian cells. This study provides comprehensive insights into the biophysical aspects of cellular membrane toxicity caused by small weakly negatively charged CDs and contributes to assessing their potential biomedical applications.

Cholesterol Depletion and Membrane Deformation by MeβCD and the Resultant Enhanced T Cell Killing

Recent studies have demonstrated the crucial role of cholesterol (Chol) in regulating the mechanical properties and biological functions of cell membranes. Methyl-β-cyclodextrin (MeβCD) is commonly utilized to modulate the Chol content in cell membranes, but there remains a lack of a comprehensive understanding. In this study, using a range of different techniques, we find that the optimal ratio of MeβCD to Chol for complete removal of Chol from a phosphocholine (PC)/Chol mixed membrane with a 1:1 mol ratio is 4.5:1, while the critical MeβCD-to-Chol ratio for membrane permeation falls within the range between 1.5 and 2.4. MeβCD at elevated concentrations induces the formation of fibrils or tubes from a PC membrane. Single lipid tracking reveals that removing Chol restores the diffusion of lipid molecules in the PC/Chol membrane to levels observed in pure PC membranes. Exposure to 5 mM MeβCD for 30 min effectively eliminates Chol from various cell lines, leading to an up to 8-fold enhancement in melittin cytotoxicity over Hela cells and an up to 3.5-fold augmentation of T cell cytotoxicity against B16F10-OVA cells. This study presents a diagram that delineates the concentration- and time-dependent distribution of MeβCD-induced Chol depletion and membrane deformation, which holds significant potential for modulating the mechanical properties of cellular membranes in prospective biomedical applications.

Biological Applications of Thermoplasmonics

Thermoplasmonics has emerged as an extraordinarily versatile tool with profound applications across various biological domains ranging from medical science to cell biology and biophysics. The key feature of nanoscale plasmonic heating involves remote activation of heating by applying laser irradiation to plasmonic nanostructures that are designed to optimally convert light into heat. This unique capability paves the way for a diverse array of applications, facilitating the exploration of critical biological processes such as cell differentiation, repair, signaling, and protein functionality, and the advancement of biosensing techniques. Of particular significance is the rapid heat cycling that can be achieved through thermoplasmonics, which has ushered in remarkable technical innovations such as accelerated amplification of DNA through quantitative reverse transcription polymerase chain reaction. Finally, medical applications of photothermal therapy have recently completed clinical trials with remarkable results in prostate cancer, which will inevitably lead to the implementation of photothermal therapy for a number of diseases in the future. Within this review, we offer a survey of the latest advancements in the burgeoning field of thermoplasmonics, with a keen emphasis on its transformative applications within the realm of biosciences.