Journal of Colloid and Interface Science

PURPOSEBenzalkonium chloride (BAK), a common preservative in eye drops, has a major side effect of dry eye. The mechanisms are typically attributed to BAK cytotoxicity. However, due to its surfactant properties, BAK can disrupt the tear film lipid layer (TFLL), leading to dry eye. This study examined the stability and compressibility of the TFLL and the impact of the presence of BAK. METHODSMeibomian gland secretion (meibum, source of the TFLL) was collected from sacrificed cows eyelids. Lipids were extracted by dissolving meibum in chloroform to a final concentration of 1 mg/mL, with one solution additionally containing 0.1 mg/mL BAK. Each solution was overlaid on a water subphase in a Langmuir Trough-Blodgett trough. The changes of surface pressure ({pi}) with area (A) for the lipid film upon compression were monitored, and the corresponding compression modulus (Cs-1) at each data point was determined. RESULTSThe {pi}-A isotherms for meibum lipid monolayers exhibited near-reversible behavior with a smooth profile with a maximum {pi} of approximately 32 mN/m. The Cs-1-{pi} isotherms of the meibum lipid monolayer show that the films are gel-like with a constant compressive modulus of 24-32 mN/m within the surface pressure range of 8-30 mN/m. In contrast, adding BAK dramatically decreased the maximum surface pressure to only 10 mN/m and the compressive modulus to only 2-10 mN/m. CONCLUSIONSThis study demonstrated that BAK disrupts the meibum lipid layer by forming a monolayer with decreased stability and reduced compressive resistance, a mechanism that may underlie its dry-eye side effect yet has largely been neglected.

Underwater adhesion research increasingly draws on bioinspired systems to uncover the molecular mechanisms that enable strong interfacial binding in aqueous environments. The biofilm adhesin Bap1 from Vibrio cholerae contains a short peptide motif, SYWFFGWHTK (CP), which exhibits exceptional adhesive performance, surpassing mussel foot protein mfp5 under comparable conditions. Despite its promise, the roles of ionic environments and aggregation behavior in governing CP adhesion remain unclear. In this study, we investigate how ion identity influences CP aggregation, film formation, and interfacial properties. Using dynamic light scattering, we identify the formation of micron-scale assemblies of aggregated molecular clusters (AAMCs), with size distributions modulated by salt type. Quartz crystal microbalance with dissipation and liquid atomic force microscopy reveal that CP film formation is both surface- and ion-dependent. On gold substrates, AAMCs preferentially adsorb and collapse into rigid, smooth nanofilms, consistent with hydrophobic-driven compaction. In contrast, silicate surfaces inhibit such collapse, yielding distinct morphologies and interfacial energetics. These findings demonstrate that surface chemistry and ionic conditions jointly regulate peptide aggregation and adhesion. This work provides mechanistic insight into hydrophobic-rich peptide systems and informs the rational design of next-generation wet adhesives, with broader implications for biomaterials and peptide-based formulations. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=130 SRC="FIGDIR/small/733527v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@1bd012aorg.highwire.dtl.DTLVardef@1977892org.highwire.dtl.DTLVardef@16cf79borg.highwire.dtl.DTLVardef@f405bf_HPS_FORMAT_FIGEXP M_FIG C_FIG

This study presents the development and spectroscopic characterization of an erlotinib-functionalized gold nanoparticle (erlotinib:AuNP) nanosystem designed for targeted delivery to metastatic non-small cell lung cancer H1299 cells. Initial MTS assays demonstrated that free erlotinib induced a concentration-dependent reduction in cell viability, while 0.1 {micro}M erlotinib exhibited negligible cytotoxicity and was therefore selected for nanosystem fabrication. AuNPs alone showed minimal toxicity toward H1299 cells over the investigated concentration range. Following conjugation of erlotinib with AuNPs, the resulting nanosystems reduced cell viability to approximately 60%, indicating enhanced biological activity of the drug after nanoparticle-assisted delivery. Fluorescence microscopy confirmed the intracellular internalization of the nanosystems in H1299 cells, with nanoparticle aggregates predominantly localized in the perinuclear and perimitochondrial regions. Three-dimensional Raman spectroscopy (3D RS) mapping further verified the intracellular localization of the conjugates through characteristic Raman signatures of erlotinib:AuNPs. Importantly, 3D RS enabled detection of nanosystems at concentrations below the sensitivity limit of fluorescence imaging, demonstrating superior analytical performance for intracellular nanosystem tracking. Atomic force microscopy-infrared (AFM-IR) spectroscopy coupled with principal component analysis (PCA) demonstrated substantial biochemical modifications induced by the erlotinib:AuNP nanosystems, including enhanced lipid-related spectral features and significant alterations in protein secondary structure, particularly the increased contribution of unordered and antiparallel {beta}-turn conformations. The obtained results demonstrate that combining plasmonic nanocarriers with advanced vibrational spectroscopy enables highly sensitive monitoring of intracellular drug delivery and nanosystem-induced biochemical responses in cancer cells.

Nile Red is widely used for the detection of microplastics because its fluorescence emission is sensitive to local polarity and can distinguish hydrophobic plastics from hydrophilic ones. The fluorescence of the molecular rotor, 9-(dicyanovinyl)-julolidine (DCVJ) is less sensitive to polarity but more to viscosity. DCVJ is less widely used for microplastic analysis, although it has been used to detect polystyrene nanobeads. Here, we compared these dyes with standard samples from the Hawaii Pacific University Polymer Kit 1.0 and confirmed that Nile Red, in general, was better for the detection and identification of microplastics. Fluorescence emission was analyzed using photography, as well as spectroscopy. The color and peak emission wavelength of some stained environmental microplastics were affected by additives. Raman spectroscopy was used to confirm the chemical identity of such samples. Although DCVJ emits green fluorescence on binding to some microplastics, a peak at 620 nm has been reported with polystyrene nanobeads, attributed to dimer/excimer formation. We confirmed this property and directly observed diffraction-limited spots using fluorescence microscopy, attributed to single or just a few nanobeads. Nile Red also stains polystyrene nanobeads and gave stronger signals than with DCVJ, but Nile Red was prone to false positives due to dye aggregation in aqueous solutions.

Water-soluble polymers commonly interact with cell membranes, but their interactions are poorly understood. Here, we investigate polyethylene glycol (PEG) and dextran (DEX) interactions with different model lipid membranes. Using total internal reflection fluorescence microscopy, we observe that PEG and DEX trigger strikingly different membrane responses - DEX induces extensive membrane remodeling, including localized multilamellar domain formation, while PEG does not. Combining fluorescence spectroscopy, fluorescence anisotropy, and vibrational sum frequency spectroscopy, we show that DEX perturbs lipid headgroup hydration by displacing interfacial water with minimal effects on lipid packing, while PEG largely preserves this hydration layer. We find that membrane binding affinity alone does not determine the extent to which hydrophilic polymers perturb membrane structure and interfacial properties; and that lipid headgroup hydration, rather than lipid charge, is a general regulator of hydrophilic polymer-membrane interactions. This work gives mechanistic insights into how neutral polymers interact with cells and vesicles, with relevance to cell biology and drug delivery. O_FIG O_LINKSMALLFIG WIDTH=169 HEIGHT=200 SRC="FIGDIR/small/739366v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@1d1c6corg.highwire.dtl.DTLVardef@135361corg.highwire.dtl.DTLVardef@73970corg.highwire.dtl.DTLVardef@c19615_HPS_FORMAT_FIGEXP M_FIG C_FIG

1.Surface functionality and pH play a decisive role in governing the structural dynamics, hydration, and drug-binding behaviour of dendrimers. Here, all-atom molecular dynamics (MD) simulations were performed on five generations of PAMAM (G1-G5) and PETIM (G2-G6) dendrimers with O-core and N-core architectures, functionalized with amine, carboxylic acid, or sugar terminal groups under different protonation states. Protonation of the tertiary branch-point amines expands the dendrimer structure, increases internal porosity and hydration, and enhances structural fluctuations across both families. In contrast, non-protonated amine -NH2 (NP) and carboxylic acid -COOH (NP) terminated dendrimers, together with deprotonated carboxylate-COO- (DeP) systems, retain comparatively compact conformations. Sugar-functionalized dendrimers ({beta}-galactose-terminated PETIM and D-glucose-terminated PAMAM) are most hydrated and structurally rigid, whereas amine-terminated dendrimers exhibit the greatest conformational dynamics. PAMAM dendrimers with -NH2, -NH3+, and -COO- terminal groups are generally more hydrated than their PETIM counterparts. However, {beta}-galactose-terminated PETIM dendrimers are more hydrophilic than D-glucose-terminated PAMAM dendrimers. N-core PETIM dendrimers also adopt more compact and spherical conformations than equivalent O-core PETIM dendrimers. Drug-binding MD simulations show that curcumin binding is dominated by van der Waals (vdW) interactions, whereas doxorubicin complexation is primarily driven by electrostatic interactions. Among the investigated surface functionalities, -NH2 (NP), -NH3+ (P), -COOH (NP), and -COO- (DeP) terminations exhibit the most favourable drug-binding characteristics. Except for deprotonated carboxylate systems, curcumin binds more strongly than doxorubicin. Overall, these findings establish molecular-level relationships between surface functionality, protonation state, dendrimer architecture, and drug-binding behaviour, providing design principles for pH-responsive dendrimer nanocarriers with enhanced drug-loading and controlled-release performance. TOC O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=75 SRC="FIGDIR/small/742721v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@119bf29org.highwire.dtl.DTLVardef@1554d86org.highwire.dtl.DTLVardef@154a254org.highwire.dtl.DTLVardef@16d5c5b_HPS_FORMAT_FIGEXP M_FIG C_FIG

Small molecules regulate biomolecular condensates in a biphasic manner, promoting liquid-liquid phase separation (LLPS) at low concentrations while suppressing it at higher concentrations. Despite increasing experimental evidence for such re-entrant behavior, a unified physical description remains lacking. Here, we identify a minimal thermodynamic mechanism for re-entrant LLPS by coupling Cahn-Hilliard dynamics to a concentration-dependent Flory interaction parameter containing competing LLPS-promoting and inhibitory contributions. The resulting model reproduces experimentally observed nonmonotonic condensate formation in Tau-tannic acid and TDP-43-bis-ANS systems, including the concentration-dependent emergence and dissolution of protein-rich domains. Spinodal analysis reveals finite concentration windows for phase instability and demonstrates that re-entrant mixing is encoded directly in the free-energy landscape. The framework further captures morphology transitions and diffusive coarsening within the phase-separated regime. These results establish a general mesoscale description of chemically regulated condensates and provide design principles for controlling phase separation through small-molecule modulators.

An e-GLUE is a polymer network containing interpenetrating polycations, which can bond the anionic network of mucosa through interfacial polycation bridging under an electric field. Such an electroadhesion involves electrophoresis of polycations, ionic complexation between polycations and the anionic network, and polycation-network entanglement, yet their quantitative understanding is lacking. Here, we formulate a theoretical model to describe electroadhesion of polymer networks by polycation interfacial bridging. We use a diffusion-drift model coupled with a Bell-like field-dependent chain friction to describe the sticky electrophoresis of polycations in an anionic sea. The formation of ionic bonds is determined by local availability of cations and anions over the penetration depth. To debond, a force must either pull polycations out from the e-GLUE network or first dissociate them from ionic complexes and then pull out from the anionic network. We model chain pullout from the bulk networks to the interface as a viscous drag against water. The adhesion strength is calculated by summing the debonding force for each polycation per unit area across all chains. Our model quantitatively links electric field strength, applied duration, polycation chain length, and cation concentration to polycation electrophoresis kinetics, ionic bond formation, and adhesion strength. We further conduct electroadhesion tests, and our model predicts well with the experimental data. Lastly, we discuss the use of the model to guide the e-GLUE design. TOC graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=90 SRC="FIGDIR/small/730541v1_ufig1.gif" ALT="Figure 1"> View larger version (45K): org.highwire.dtl.DTLVardef@16524c6org.highwire.dtl.DTLVardef@15163aeorg.highwire.dtl.DTLVardef@673949org.highwire.dtl.DTLVardef@e207a0_HPS_FORMAT_FIGEXP M_FIG C_FIG For Table of Contents use only

Atomically precise gold nanoclusters (AuNCs) are ultra-small particles composed of ten to hundreds gold atoms and exhibit unique photophysical properties. Significant progress has been made in tuning and extending their luminescence in the near-infrared window through the design of AuNC assemblies. Herein, we report a straightforward method for synthesizing highly pure, programmable DNA tetrahedra functionalized with a controlled number of AuNCs (from one up to four AuNCs). Using ligand exchange chemistry, AuNCs bearing a single grafted ssDNA onto them were produced. These constructs then served as building blocks for synthesizing tetrahedra through DNA hybridization. Products obtained at each stage of the synthesis were thoroughly characterized using a range of complementary technics. Notably, mass spectrometry in native mode provided novel insights into the accurate composition and stoichiometry of these architectures. This study paves the way for the synthesis and the characterization of a variety of new three-dimensional, DNA-guided AuNC assemblies that may serve as powerful theranostics and biophotonic tools.

The tomato leafminer, Tuta absoluta, poses a severe global agricultural threat due to its rapid leaf-mining behavior and swift development of resistance to conventional chemical pesticides. While microbial chitinases are potent biopesticides, their field efficacy is limited by environmental degradation and the short exposure window before larvae penetrate leaf tissues. This study evaluates a stimuli-responsive, controlled-release nanobiopesticide system utilizing a novel chitinase from newly characterized Serratia marcescens GBS19. A 61.1 kDa chitinase (GBS19_ChiA) was heterologously expressed in Escherichia coli and purified to a specific activity of 215.01 U/mg. The enzyme was immobilized onto starch-coated silica nanoparticles designed for target-triggered release via host alpha-amylase. Genomic profiling and R-based kinetic modeling were integrated to evaluate the efficacy of purified and immobilized forms against T. absoluta. Immobilization enhanced thermal and pH stability, with the nanocarrier maintaining 85% activity over 10 weeks. In larval bioassays, immobilization increased mortality from 21.9% to 59.4% (5000 U/mL) by day 3, reaching 62.5% by day 6. Genomic analysis identified an expansive secretome and a Type VI Secretion System (T6SS), characterizing GBS19 as a multi-pronged pathogen. Kinetic modeling established that while immobilized enzymes are effective, the 2.5-hour exposure time on T. absoluta requires the synergistic action of chitinases (ChiA/B/C) to reach the lethal desiccation threshold before larvae establish protective mines. Starch-coated silica nanoparticles significantly improve chitinase stability and delivery. However, overcoming the rapid penetration of T. absoluta necessitates a whole-cell or multi-enzyme synergistic approach to outpace larval behavioural defences.

Nisin is a promising antimicrobial peptide widely used in food preservation due to its efficacy against Gram-positive spoilage and pathogenic bacteria. Although Nisin is increasingly applied in the food sector, the biopeptide suffers from instability within food matrixes and can rapidly lose its antimicrobial potential following interaction with food biomolecules. Thus, it is necessary to investigate approaches that can be employed to extend the stability and activity of Nisin. Hence, the aim of this study was to develop and characterise a chitosan-alginate polyelectrolyte microencapsulation system capable of enhancing Nisin stability while retaining antimicrobial activity. The microencapsulation of Nisin was achieved by pre-gelation of alginate using calcium chloride and subsequent direct electrostatic interaction between cationic Nisin and chitosan with pre-gelled anionic alginate at pH 5.0. Following microcapsule formation, physicochemical and structural characterisation was performed using Zeta potential determination and measurement of the polydispersity index (PDI) via dynamic light scattering. SEM micrographs were used to confirm morphology, while Fourier-transform infrared (FTIR) spectroscopy and high-performance liquid chromatography (HPLC) were utilised to assess chemical integrity and functional group preservation of encapsulated Nisin. Following this, stable microcapsules with diameters ranging from 150-200 nm and smooth surface morphology were obtained. Microcapsule formation was strongly influenced by formulation parameters, particularly pH, calcium ion concentration, and chitosan content, with deviations from optimal acidic conditions (< pH 5.0) resulting in aggregation, increased polydispersity, and reduced encapsulation efficiency. The microcapsules were monodispersed (PDI {approx} 0.30) and electrostatically stable, exhibiting a Zeta potential of approximately +36 mV. These microcapsules remained stable over a prolonged storage period of 21 days under refrigerated conditions while retaining antimicrobial activity against Bacillus cereus. Encapsulation efficiency reached approximately 65%, confirming effective retention of Nisin within the polymer matrix. Overall, the findings demonstrate that chitosan-alginate ionic gelation is a non-denaturing and effective encapsulation strategy for extending the functional stability of Nisin. These microcapsules show strong potential as natural antimicrobial delivery systems for food and beverage applications, particularly in acidic food matrices, with implications for improved food safety and shelf-life extension.

Live cell plasma membranes show spatially heterogeneous liquid-ordered (Lo)-like and liquid-disordered (Ld)-like regions similar to the co-existing Lo/Ld phases observed in lipid vesicles. The Lo-like regions are relatively less hydrated and less polar due to tight packing of the membrane components compared to the Ld-like regions. The steady-state fluorescence spectra of Di-4-ANEPPDHQ (Di-4), a widely used polarity-sensitive probe, is blue or red shifted when solvated in less polar (Ld- like) or more polar (Lo-like) regions respectively. However, quantification of Di-4 fluorescence in blue and red channels for the evaluation of membrane phase state suffers from the lack of specific wavelength choice for these two channels and Di-4s relatively higher concentration in Ld phase (red channel) due to its partitioning preference. To address these issues, we employed fluorescence lifetime of Di-4, a concentration independent photophysical parameter, to understand membrane biophysical properties. The fluorescence lifetime of Di-4 in lipid vesicles exhibits Arrhenius-like temperature dependence. Centred around this energetic feature of Di-4 photophysics, we developed a novel analytical module, namely excited state relaxation activation energy (ESRAct), that serves as an intrinsic descriptor of the membrane nano-environment sensed by this probe. We show that the ESRAact value scales with increasing disorder in nanoscale phase separation (i.e., ESRAct of pure Ld > mixed Ld/Lo > pure Lo phase). We then extended its applications to giant plasma membrane vesicles (GPMVs) isolated from MCF-7 cells and found that these vesicles exhibit nanoscale Lo/Ld co-existing phase within 16-37{degrees}C. We envisage wide applications of ESRAct to delineate plasma membrane phase behavior as well as general photophysical studies on other newly designed polarity-sensitive probes.

Online structural characterization during microfluidic lipid self-assembly is important for understanding and controlling the formation of nonlamellar liquid crystalline nanodispersions. Here, we report a 3D-printed, X-ray-compatible hydrodynamic flow-focusing microfluidic chip with variable channel dimensions, integrated with synchrotron small-angle X-ray scattering (SAXS), for position-resolved SAXS-on-chip monitoring of Ca2+-triggered hexosome formation. Hexosomes were produced under continuous flow by mixing ethanolic solutions of docosahexaenoic acid monoglyceride (MAG-DHA), the negatively charged phosphatidylglycerol DOPG, and -tocopherol with Ca2+-containing PIPES buffer. Online SAXS-on-chip measurements detected three Bragg reflections characteristic of the internal inverse hexagonal (H2) phase on a tens-of-milliseconds residence-time scale, revealing rapid structural evolution during microfluidic mixing. Complementary ex situ SAXS identified the DOPG/Ca2+ molar ratio as a key parameter modulating the direct vesicle-to-hexosome transformation and the compactness of the internal H2 nanostructures. Dynamic light scattering showed that the flow-rate ratio modulated nanoparticle size, yielding hexosomes with mean hydrodynamic diameters in the range of approximately 120-175 nm and polydispersity index values down to 0.14 at a total flow rate of 200 {micro}L min-1. Cryo-TEM revealed coexistence of hexosomes and vesicular nanostructures, highlighting morphological heterogeneity, while Coarse-Grained Molecular Dynamics simulations supported a central role of Ca2+-DOPG association in promoting a direct lamellar-H2 phase transition. Overall, this work shows that 3D-printed SAXS-compatible microfluidics can integrate continuous production with online structural characterization, providing a basis for future formulation and process optimization of drug-loaded cubosomes, hexosomes, and related nonlamellar liquid crystalline nanodispersions.

Chronic wounds (principally pressure sores, venous leg ulcers and diabetic foot ulcers) are a drain on global health services and remain a major area of unmet clinical need. Chronic wounds are characterised by a bacterial biofilm (densely aggregated colonies of bacteria encased by a matrix of extracellular polymeric substances), which hinders innate immune response and can prevent wound healing. Bioactive glass (BG) fibres doped with antimicrobial metal ions, such as silver, can offer a promising treatment for chronic wound infections, where silver is well known for its antimicrobial activity against a range of pathogens and is commonly used in wound dressings. We first present a system of non-linear partial differential equations to model the treatment of a chronic wound biofilm infection with BG fibres. The BG fibres are assumed to have two mechanisms of action against the biofilm: physical disruption of the top layers of the biofilm by the BG fibres; and release of antimicrobial silver ions from the BG fibres, which then diffuse into the biofilm and can kill the bacteria. Treatment-associated parameters are estimated from in vitro experimental data using a combination of least-squares minimisation and Approximate Bayesian Computation (ABC). Sensitivity investigations are performed on other parameters that cannot currently be calculated experimentally to investigate their influence on treatment efficacy. We thus predict key parameter regimes that should lead to biofilm eradication, crucially informing the future design of metal-doped BG fibres to maximise treatment efficacy. Author summaryChronic wounds are a huge drain on global health services and will become even more problematic due to an ageing population. Current treatment methods are often unsuccessful, where treatment failure is exacerbated by the presence of a biofilm infection. Biofilms consist of communities of bacteria that adhere to the wound surface and produce extracellular polymeric substances, which can protect the bacteria by acting as both a physical and chemical barrier. More recently, there has been a focus on biofilm-based wound care, where the aim is to firstly eradicate the biofilm infection, which then enables wound healing to occur naturally. Our aim is to produce a novel treatment that can target and eradicate the biofilm infection, followed by directly assisting the wound healing. Bioactive glass (BG) fibres doped with silver offer a promising treatment as they have both anti-biofilm effects and can also stimulate the wound healing process. Here, we restrict attention to their anti-biofilm properties. By developing a mathematical model, we can predict treatment outcomes under several different scenarios, the results of which can then be utilised during design of the BG fibres. Using this combination of computational and experimental approaches, we reduce both the cost and time of optimising this promising treatment.

The multivalent display of surface glycoprotein hemagglutinin (HA) on Influenza A viruses (IAVs) enhances the overall binding avidity to sialylated glycans on host cell surfaces. While precomplexing HA trimers with antibodies increases multivalency and avidity, this method does not replicate the virions geometry and limits insights into the multivalent binding process. Here, we use perfectly controllable icosahedral protein nanoparticles to examine the multivalent HA receptor-binding properties. We compare three HA presentation systems with varying degrees of multivalency: single HA trimers, antibody-precomplexed HA trimers, and HA trimers on nanoparticles. Our results indicate that increasing HA valency enhances binding avidity across various glycan surfaces, including erythrocytes, cells, and lipid bilayers with varying glycan densities, while maintaining receptor specificity. By combining functional and non-functional HA trimers during nanoparticle formation, we create statistical mixtures of nanoparticles with varying valencies. At high receptor densities, nanoparticles with few functional trimers still bind strongly, whereas at low receptor densities, a patch of five HA trimers appears necessary for binding. As a key finding, we observe that such a statistical mixture of nanoparticles with functional and nonfunctional HAs binds to glycan surfaces in a stronger density-dependent manner than fully functional particles. We also observe differences in binding modes that correlate with the number of functional trimers, the glycan structure (linear vs branched), and the densities achievable with these glycans. Overall, our findings demonstrate that the presentation of multivalent HA plays an enormous role in the response to glycan receptor type and density, with implications for the future design of virus monitoring, viral inhibitors, and targeting vectors.

Single-particle tracking (SPT) over time enables direct observation of molecular transport and interactions in living cells. Fluorescence-based SPT has provided insights into intracellular processes such as endocytosis, receptor signaling, and drug delivery. Extending the observation window to several hours and beyond is critical for capturing slow intracellular dynamics, including the full course of endosomal trafficking, the long-term accumulation of particles within subcellular compartments, and transitions between transport modes that occur on hour-scale timescales. However, long-term intracellular SPT under visible-wavelength excitation remains challenging because fluorescence probes generally suffer from photobleaching and phototoxicity. While near-infrared (NIR) excitation can simultaneously mitigate these issues, generally weak emission of NIR-emitting dyes has hindered its wide application in long-term SPT. Here, we demonstrate long-term NIR SPT using atomically precise gold quantum needles, Au42(PET)32 (PET = 2-phenylethanethiolate). Continuous tracking of intracellular particles in living HEK293 cells was achieved for up to 12 h. Trajectory analysis revealed temporal transitions between directional and diffusive transport, as well as the accumulation of multiple particles within localized intracellular domains over several-hour timescales. The high photostability of Au42, combined with low phototoxicity of NIR excitation, enables visualization of intracellular transport dynamics over timescales difficult to access using conventional visible fluorescent probes. These results establish Au42-based NIR imaging as a platform for long-term, low-phototoxicity intracellular SPT and provide a framework for investigating slow intracellular dynamics in living systems.

Hydrated extracellular polymeric phases (such as mucus, biofilms, and extracellular matrices) have traditionally been viewed as passive barriers. We complement and extend this view by analysing these systems through the murburn framework and liquid-liquid phase separation (LLPS) biophysics. Using quantitative modeling, we first demonstrate how frothy mucus in amphibian egg-masses enhances oxygen delivery while buffering diffusible reactive species (DRS), leading to improved developmental synchrony. We then model the human cervical mucus system, showing its cycle-dependent transitions between coherent barriers (pregnancy), active transduction media (ovulation), and controlled inflammatory remodeling (labor). Finally, we present thiolated polyglycerol sulfate (dPGS-SH) as a synthetic validation (another groups recently published work): this rationally designed mucolytic agent recapitulates native mucuss DRS-modulating properties and shows superior efficacy for addressing cystic fibrosis pathology. With such pan-systemic perspectives, we argue that phase-separated hydrated polymeric matrices represent one of evolutions most conserved solutions for regulating stochastic murburn chemistry, enabling organisms to exploit oxygen while preserving biological coherence. From biofilms to birth, this framework unifies the physicochemical basis of lifes most fundamental processes.

Bioelectrochemical reduction of dilute nitrate (NO-; sub-mM to low-mM range) to ammonium (NH) offers a promising route toward circular nitrogen management from contaminated groundwater and environmental waters. However, on-site application of bioelectrochemical systems remains challenging due to low reduction rates and poor electron transfer efficiency of naturally formed biofilm electrodes. Here, we constructed a hydrogel biocathode by applying a carbon black/riboflavin/sodium alginate/cellulose hydrogel incorporating Shewanella oneidensis MR-1 cells to a graphite felt electrode via brush coating. The hydrogel electrode achieved NH production rates of 0.16-0.19 mol m-3 h-{superscript 1} without NO2- accumulation, and these rates were maintained without significant performance loss across three consecutive cycles with medium exchange over 1.5 days of total operation. The hydrogel electrode increased the current density by more than 5-fold compared with a conventional S. oneidensis biofilm electrode, indicating enhanced electron transfer efficiency per unit biomass, which directly contributed to the high NH production rates. The electricity consumption for NH production of 1.68-2.39 x 10{superscript 2} kJ g-N-{superscript 1} was substantially lower than that of metal catalyst systems at comparable NO- concentrations (typically, >104 kJ g-N-{superscript 1}). These findings demonstrate that the hydrogel electrode design represents an energy-efficient, and readily fabricated platform for bioelectrochemical NH production from dilute NO-.

We present a comparative study of the inner membrane of three Gram-positive bacterial strains, namely S. aureus, S. epidermidis and N. lacusekhoensis. A lipidomics study is used to obtain the lipid architecture and composition for S. epidermidis found in the skin microbiome and N. lacusekhoensis, an extremophile present in halophilic and alkophilic environments. Differences between the strains arise from both the lipid architecture and the cardiolipin content varying from 5% in S. aureus to 85% in N. lacusekhoensis. We develop coarse grained (CG) Martini-3 membrane models which reproduce structural properties such as membrane area, thickness, density distributions as well as ion-correlations with all-atom models. Inter-lipid correlations reveal a homogeneous distribution of lipids in the membranes despite the wide variation in lipid types and composition. Mechanical properties such as the area stretch modulus increased with cardiolipin content, however the bending modulus has a more complex dependence on membrane charge and lipid type. Using the CG models we evaluate the insertion free energies for four widely used antimicrobial molecules. Entry barriers for thymol and methylparaben arise from the charge density modulation at the membrane headgroups due to counterion condensation. The entry mechanisms of the antimicrobial peptide cecropin-melittin-15 (CM15) and the preservative molecule ethyl-lauroyl-arginate (ELAR) are found to be similar across all three strains. We also illustrate the manner in which the extremophilic strain, N. lacusekhoensis with its high cardiolipin content, modulates the partitioning kinetics of the antimicrobial molecule thymol with pH and salt. Our study reveals that membrane properties are largely conserved across the three model membranes. The molecular models and insights emerging from the present work should aid in the development of novel antimicrobials against Gram-positive strains.

IntroductionMusculoskeletal disorders remain a major cause of disability worldwide and require non invasive regenerative strategies that support tissue repair. Green-synthesized zinc oxide nanoparticles (ZnONPs) have attracted interest because of their biocompatibility and biological activity. This study investigated the synthesis of Mimosa pudica-derived ZnONPs (ZnOMP) and evaluated their effects on human bone marrow mesenchymal stromal cells (BM-MSCs). MethodologyZnOMP were synthesized using an aqueous extract of Mimosa pudica leaves and characterized by UV-Vis spectroscopy, FTIR spectroscopy, powder X-ray diffraction, SEM, EDS, and TEM. BM-MSCs isolated from human bone marrow were exposed to ZnOMP, plant extract, and synthesized ZnO nanoparticles. Cell metabolic activity was assessed by MTT assay after 1, 3, and 5 days. Cytoskeletal and nuclear morphology were analyzed by fluorescence microscopy and CellProfiler-based morphometry. Osteogenic differentiation was evaluated after 21 days using Alizarin Red S staining and quantification. ResultsSpectroscopic and microscopic analyses confirmed the successful formation of phytochemical-capped ZnOMP nanoparticles with nanoscale dimensions and specific elemental composition. ZnOMP maintained significantly higher metabolic activity than Mimosa pudica extract or ZnO at both 150 and 300 g/mL. Morphometric profiling revealed that Mimosa pudica extract induced the most pronounced changes in nuclear morphology, reflecting enhanced nuclear plasticity and substantial remodeling of nuclear architecture, whereas ZnOMP preserved cellular and nuclear features closer to untreated controls. During osteogenic induction, ZnOMP did not impair matrix mineralization and preserved the ability of BM-MSCs to form a mineralized extracellular matrix. ConclusionMimosa pudica-mediated ZnO nanoparticles combine favorable biocompatibility with preservation of mesenchymal stem cell morphology and osteogenic competence. These findings support their potential use as bioactive nanomaterials for musculoskeletal tissue engineering and regenerative medicine.