Insight into the role of cholesterol in modulation of morphology and mechanical properties of CHO-K1 cells: An in situ AFM study

In Situ Heterodyne-Detected Second-Harmonic Generation Study of the Influence of Cholesterol on Dye Molecule Adsorption on Lipid Membrane

Cholesterol plays an essential role in regulating the functionality of biomembranes. This study employed in situ second-harmonic generation (SHG) to investigate the adsorption behavior of the dye molecule 4-(4-(diethylamino)styryl)-N-methyl-pyridinium iodide (D289) on a biomimic membrane composed of 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (sodium salt) (DPPG) and cholesterol. The time-dependent polarization SHG intensity exhibited an initial rapid increase, followed by a subsequent decline. The initial increased SHG intensity is responsible for the electrostatic interaction-driven adsorption of D289 onto the membrane, while the decrease in the SHG signal results from the broadening of the orientation distribution within the membrane. Heterodyne-detected SHG (HD-SHG) measurements demonstrated that the adsorption of dye molecules influenced the phase of the induced electric field. The interfacial potential Φ(0) as a function of time was measured, and we found that even after reaching a stable Stern layer state, the diffusion layer continued to exhibit a dynamic change. This study offers a comprehensive understanding of the influence of cholesterol on adsorption, reorientation dynamics, and dynamic changes in the reorientation of water in the diffusion layer.

Protein and Peptide-Based Nanotechnology for Enhancing Stability, Bioactivity, and Delivery of Anthocyanins

Anthocyanin, a unique natural polyphenol, is abundant in plants and widely utilized in biomedicine, cosmetics, and the food industry due to its excellent antioxidant, anticancer, antiaging, antimicrobial, and anti-inflammatory properties. However, the degradation of anthocyanin in an extreme environment, such as alkali pH, high temperatures, and metal ions, limits its physiochemical stabilities and bioavailabilities. Encapsulation and combining anthocyanin with biomaterials could efficiently stabilize anthocyanin for protection. Promisingly, natural or artificially designed proteins and peptides with favorable stabilities, excellent biocapacity, and wide sources are potential candidates to stabilize anthocyanin. This review focuses on recent progress, strategies, and perspectives on protein and peptide for anthocyanin functionalization and delivery, i.e., formulation technologies, physicochemical stability enhancement, cellular uptake, bioavailabilities, and biological activities development. Interestingly, due to the simplicity and diversity of peptide structure, the interaction mechanisms between peptide and anthocyanin could be illustrated. This work sheds light on the mechanism of protein/peptide-anthocyanin nanoparticle construction and expands on potential applications of anthocyanin in nutrition and biomedicine.

Peptide-modified bioresponsive chondroitin sulfate micelles for targeted doxorubicin delivery in triple-negative breast cancer

Triple-negative breast cancer is an offensive tumor that is highly challenging to cure. In this study, we developed novel polymeric nanoparticles that target dual receptors and respond to reducing conditions for chemotherapeutic drug release in the treatment of triple-negative breast cancer. Then we synthesized and characterized a targeted peptide-grafted chondroitin sulfate A-ss-deoxycholic acid (TCSSD) copolymer and prepare doxorubicin (DOX)-loaded TCSSD (TCSSD-D) micelles high-loading content. The bioresponsive drug release of TCSSD-D nanoparticles was demonstrated in a glutathione-containing phosphate buffer solution. We found that TCSSD-D effectively targeted CD44 and P-selectin receptors both in vitro and in vivo. TCSSD-D micelles were higher cytotoxicity and cellular uptake than unmodified DOX-containing micelles in MDA-MB-231 cells. Furthermore, TCSSD-D micelles showed the strongest suppression of tumor growth among three DOX-based formulations in triple-negative MDA-MB-231-bearing nude mice. These results suggest that amphiphilic TCSSD nanoparticles can serve as a targeted and intelligent delivery vehicle for triple-negative breast cancer therapy.

Membrane Internalization Mechanisms and Design Strategies of Arginine-Rich Cell-Penetrating Peptides

Cell-penetrating peptides (CPPs) have been discovered to deliver chemical drugs, nucleic acids, and macromolecules to permeate cell membranes, creating a novel route for exogenous substances to enter cells. Up until now, various sequence structures and fundamental action mechanisms of CPPs have been established. Among them, arginine-rich peptides with unique cell penetration properties have attracted substantial scientific attention. Due to the positively charged essential amino acids of the arginine-rich peptides, they can interact with negatively charged drug molecules and cell membranes through non-covalent interaction, including electrostatic interactions. Significantly, the sequence design and the penetrating mechanisms are critical. In this brief synopsis, we summarize the transmembrane processes and mechanisms of arginine-rich peptides; and outline the relationship between the function of arginine-rich peptides and the number of arginine residues, arginine optical isomers, primary sequence, secondary and ternary structures, etc. Taking advantage of the penetration ability, biomedical applications of arginine-rich peptides have been refreshed, including drug/RNA delivery systems, biosensors, and blood-brain barrier (BBB) penetration. Understanding the membrane internalization mechanisms and design strategies of CPPs will expand their potential applications in clinical trials.

Chronic cholesterol depletion increases F-actin levels and induces cytoskeletal reorganization via a dual mechanism

Previous work from us and others has suggested that cholesterol is an important lipid in the context of the organization of the actin cytoskeleton. However, reorganization of the actin cytoskeleton upon modulation of membrane cholesterol is rarely addressed in the literature. In this work, we explored the signaling crosstalk between cholesterol and the actin cytoskeleton by using a high-resolution confocal microscopic approach to quantitatively measure changes in F-actin content upon cholesterol depletion. Our results show that F-actin content significantly increases upon chronic cholesterol depletion, but not during acute cholesterol depletion. In addition, utilizing inhibitors targeting the cholesterol biosynthetic pathway at different steps, we show that reorganization of the actin cytoskeleton could occur due to the synergistic effect of multiple pathways, including prenylated Rho GTPases and availability of membrane phosphatidylinositol 4,5-bisphosphate. These results constitute one of the first comprehensive dissections of the mechanistic basis underlying the interplay between cellular actin levels and cholesterol biosynthesis. We envision these results will be relevant for future understating of the remodeling of the actin cytoskeleton in pathological conditions with altered cholesterol.

Targeted delivery of cancer drug paclitaxel to chordomas tumor cells via an RNA nanoparticle harboring an EGFR aptamer

Paclitaxel has been extensively used in clinics for cancer treatment. However, its limited solubility in aqueous solution and high occurrence of side effects have also been widely reported. In this study, we constructed a biocompatible RNA nanoparticle delivery system (3WJ-EGFR_apt) that includes 3WJ (3-way junction) nanoparticle with a size of 4.85 ± 0.59 nm as a backbone and an EGFR (epidermal growth factor receptor) aptamer for specific targeting to chordomas cells, which owns the encapsulation ability of drug paclitaxel (PTX) for cancer therapy. Confocal microscopy and flow cytometry results confirmed 3WJ-EGFR_apt nanoparticle exhibited excellent specific targeting to chordomas cell U-CH2 which is an EGFR(+) cell line; while the 3WJ nanoparticle lose the targeted ability. Both of the two nanoparticles own no sensitivity to lung cancer cell H520 which is an EGFR(-) cell line. Moreover, the 3WJ-EGFR_apt nanoparticle encapsulated drug PTX could enhance the inhibition efficiency of chordomas tumor cells U-CH2 as compared to free PTX alone. This work demonstrates that RNA-3WJ constructed with a targeting aptamer provides a compromising targeted drug delivery ability on chordomas cells for therapeutics.

Phospholipid exchange shows insulin receptor activity is supported by both the propensity to form wide bilayers and ordered raft domains

Insulin receptor (IR) is a membrane tyrosine kinase that mediates the response of cells to insulin. IR activity has been shown to be modulated by changes in plasma membrane lipid composition, but the properties and structural determinants of lipids mediating IR activity are poorly understood. Here, using efficient methyl-alpha-cyclodextrin mediated lipid exchange, we studied the effect of altering plasma membrane outer leaflet phospholipid composition upon the activity of IR in mammalian cells. After substitution of endogenous lipids with lipids having an ability to form liquid ordered (Lo) domains (sphingomyelins) or liquid disordered (Ld) domains (unsaturated phosphatidylcholines (PCs)), we found that the propensity of lipids to form ordered domains is required for high IR activity. Additional substitution experiments using a series of saturated PCs showed that IR activity increased substantially with increasing acyl chain length, which increases both bilayer width and the propensity to form ordered domains. Incorporating purified IR into alkyl maltoside micelles with increasing hydrocarbon lengths also increased IR activity, but more modestly than by increasing lipid acyl chain length in cells. These results suggest that the ability to form Lo domains as well as wide bilayer width contributes to increased IR activity. Inhibition of phosphatases showed that some of the lipid dependence of IR activity upon lipid structure reflected protection from phosphatases by lipids that support Lo domain formation. These results are consistent with a model in which a combination of bilayer width and ordered domain formation modulates IR activity via IR conformation and accessibility to phosphatases.

Development of Hydrophilic Drug Encapsulation and Controlled Release Using a Modified Nanoprecipitation Method

The improvement of the loading content of hydrophilic drugs by polymer nanoparticles (NPs) recently has received increased attention from the field of controlled release. We developed a novel, simply modified, drop-wise nanoprecipitation method which separated hydrophilic drugs and polymers into aqueous phase (continuous phase) and organic phase (dispersed phase), both individually and involving a mixing process. Using this method, we produced ciprofloxacin-loaded NPs by Poly (d,l-lactic acid)-Dextran (PLA-DEX) and Poly lactic acid-co-glycolic acid-Polyethylene glycol (PLGA-PEG) successfully, with a considerable drug-loading ability up to 27.2 wt% and an in vitro sustained release for up to six days. Drug content with NPs can be precisely tuned by changing the initial drug feed concentration of ciprofloxacin. These studies suggest that this modified nanoprecipitation method is a rapid, facile, and reproducible technique for making nano-scale drug delivery carriers with high drug-loading abilities