PAMAM dendrimers are distinguished by their capacity for functionalization, which enhances the properties of the compounds they transport, rendering them highly versatile nanoparticles with extensive applications in the biomedical domain, including drug, vaccine, and gene delivery. These dendrimers can be internalized into cells through various endocytic mechanisms, such as passive diffusion, clathrin-mediated endocytosis, and caveolae-mediated endocytosis, allowing them to traverse the cytoplasm and reach intracellular targets, such as the mitochondria or nucleus. Despite the significant challenge posed by the cytotoxicity of these nanoparticles, which is contingent upon the dendrimer size, surface charge, and generation, numerous strategies have been documented to modify the dendrimer surface using polyethylene glycol and other chemical groups to temporarily mitigate their cytotoxic effects. The potential of PAMAM dendrimers in cancer therapy and other biomedical applications is substantial, owing to their ability to enhance bioavailability, pharmacokinetics, and pharmacodynamics of active ingredients within the body. This underscores the necessity for further investigation into the optimization of internalization pathways and cytotoxicity of these nanoparticles. This review offers a comprehensive synthesis of the current literature on the diverse cellular internalization pathways of PAMAM dendrimers and their cargo molecules, emphasizing the mechanisms of entry, intracellular trafficking, and factors influencing these processes.

Neurotransmission is critical for brain function, allowing neurons to communicate through neurotransmitters and neuropeptides. RVD-hemopressin (RVD-Hp), a novel peptide identified in noradrenergic neurons, modulates cannabinoid receptors CB1 and CB2. Unlike hemopressin (Hp), which induces anxiogenic behaviors via transient receptor potential vanilloid 1 (TRPV1) activation, RVD-Hp counteracts these effects, suggesting that it may block TRPV1. This study investigates RVD-Hp’s role as a TRPV1 channel blocker using HEK293 cells expressing TRPV1-GFP. Calcium imaging and patch-clamp recordings demonstrated that RVD-Hp reduces TRPV1-mediated calcium influx and TRPV1 ion currents. Molecular docking and dynamics simulations indicated that RVD-Hp interacts with TRPV1’s selectivity filter, forming stable hydrogen bonds and van der Waals contacts, thus preventing ion permeation. These findings highlight RVD-Hp’s potential as a therapeutic agent for conditions involving TRPV1 activation, such as pain and anxiety.

Oxidative stress on the mitochondria in a human cell is attributed to several life-risking conditions, and as such, the importance of molecular structures packed with antioxidant properties and structural characteristics to enter the cell to help prevent such stress has been substantially relevant in recent years. In this study, we investigated the antioxidant properties of triphenylphosphonium (TPP)-conjugated phenolic acids encapsulated in β-cyclodextrin (β-CD). We synthesized TPP conjugates of caffeic, coumaric, and cinnamic acids and formed inclusion complexes with β-CD. Our results showed successful encapsulation of TPP conjugates in β-CD with high efficiency. The TPP conjugates maintained antioxidant activity, with slight reductions observed in β-CD complexes. Furthermore, cell viability studies showed low cytotoxicity of the dds. Computational analyses revealed that TPP conjugation preserved the chemical reactivity of the phenolic acids. Molecular dynamics simulations demonstrated stable inclusion complexes with β-CD and the free energy calculations indicated that TPP conjugation significantly enhanced the ability of caffeic acid to translocate across mitochondrial membranes. These results highlight the potential of TPP-conjugated phenolic acids encapsulated in β-CD as effective antioxidants with improved mitochondrial targeting capabilities.

Thyroxine (T4) is a drug extensively utilized for the treatment of hypothyroidism. However, the oral absorption of T4 presents certain limitations. This research investigates the efficacy of CO₂ nanobubbles in water as a potential oral carrier for T4 administration to C57BL/6 hypothyroid mice. Following 18 h of fasting, the formulation was administered to the mice, demonstrating that the combination of CO₂ nanobubbles and T4 enhanced the drug’s absorption in blood serum by approximately 40%. To comprehend this observation at a molecular level, we explored the interaction mechanism through which T4 engages with the CO₂ nanobubbles, employing molecular simulations, semi-empirical quantum mechanics, and PMF calculations. Our simulations revealed a high affinity of T4 for the water–gas interface, driven by additive interactions between the hydrophobic region of T4 and the gas phase and electrostatic interactions of the polar groups of T4 with water at the water–gas interface. Concurrently, we observed that at the water–gas interface, the cluster of T4 formed in the water region disassembles, contributing to the drug’s bioavailability. Furthermore, we examined how the gas within the nanobubbles aids in facilitating the drug’s translocation through cell membranes. This research contributes to a deeper understanding of the role of CO₂ nanobubbles in drug absorption and subsequent release into the bloodstream. The findings suggest that utilizing CO₂ nanobubbles could enhance T4 bioavailability and cell permeability, leading to more efficient transport into cells. Additional research opens the possibility of employing lower concentrations of this class of drugs, thereby potentially reducing the associated side effects due to poor absorption.

Mechanosensitive ion channels such as OSCA1.2 enable cells to sense and respond to mechanical forces by translating membrane tension into ionic flux. While lipid rearrangement in the inter-subunit cleft has been proposed as a key activation mechanism, the contributions of other domains to OSCA gating remain unresolved. Here, we combined the genetic encoding of the photoactivatable crosslinker p-benzoyl-L-phenylalanine (BzF) with functional Ca²⁺ imaging and molecular dynamics simulations to dissect the roles of specific residues in OSCA1.2 gating. Targeted UV-induced crosslinking at positions F22, H236, and R343 locked the channel in a non-conducting state, indicating their functional relevance. Structural analysis revealed that these residues are strategically positioned: F22 interacts with lipids near the activation gate, H236 lines the lipid-filled cavity, and R343 forms cross-subunit contacts. Together, these results support a model in which mechanical gating involves a distributed network of residues across multiple channel regions, allosterically converging on the activation gate. This study expands our understanding of mechanotransduction by revealing how distant structural elements contribute to force sensing in OSCA channels.

Cold environments challenge the structural and functional integrity of membrane proteins, requiring specialized adaptations to maintain activity under low thermal energy. Here, we investigate the molecular basis of cold tolerance in the peptide transporter PepT1 from the Antarctic icefish (Chionodraco hamatus, ChPepT1) using molecular dynamics simulations, binding free energy calculations (MM/GBSA), and dynamic network analysis. We compare ChPepT1 to its human ortholog (hPepT1), a non-cold-adapted variant, to reveal key features enabling psychrophilic function. Our simulations show that ChPepT1 displays enhanced global flexibility, particularly in domains adjacent to the substrate-binding site and the C-terminal domain (CTD). While hPepT1 loses substrate binding affinity as temperature increases, ChPepT1 maintains stable peptide interactions across a broad thermal range. This thermodynamic buffering results from temperature-sensitive rearrangement of hydrogen bond networks and more dynamic lipid interactions. Importantly, we identify a temperature-responsive segment (TRS, residues 660–670) within the proximal CTD that undergoes an α-helix to coil transition, modulating long-range coupling with transmembrane helices. Dynamic cross-correlation analyses further suggest that ChPepT1, unlike hPepT1, reorganizes its interdomain communication in response to temperature shifts. Our findings suggest that cold tolerance in ChPepT1 arises from a combination of structural flexibility, resilient substrate binding, and temperature-sensitive interdomain dynamics. These results provide new mechanistic insight into thermal adaptation in membrane transporters and offer a framework for engineering proteins with enhanced functionality in extreme environments.