Langmuir

Artificial lipid droplets (aLDs) provide a controllable platform for studying lipid biochemistry, but their use is limited by contamination with other membrane structures and the lack of quantitative methods to assess sample purity. Here, we establish dithionite quenching of NBD-labeled lipids as a simple approach to evaluate aLD purity. The approach relies on dithionite's ability to selectively quench NBD fluorophores exposed in the phospholipid monolayer of aLDs and in the outer leaflet of liposome bilayers, but not those protected within the inner leaflet of liposome bilayers. Consistent with liposome contamination, bulk aLD preparations exhibit incomplete quenching, which can be separated by sucrose gradient centrifugation into liposome-like and droplet-enriched populations based on quenching behavior. Guided by this assay, sonication conditions were optimized to increase aLD purity and reduce liposome contamination. A biotin-streptavidin immobilization strategy further enabled stable imaging of individual aLDs. Finally, we applied this method to probe the accessibility of neutral lipids within aLDs. This revealed hydrophobicity-dependent quenching kinetics of neutral lipids, with less hydrophobic diacylglycerols showing greater surface exposure within aLDs than more hydrophobic triacylglycerols and cholesterol esters. Taken together, these establish dithionite quenching of NBD-labeled lipids as a simple quantitative method for assessing aLD purity and demonstrate its utility for studying lipid accessibility.

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

Lipid nanoparticles (LNPs) are conventionally produced through mixing of lipids dissolved in ethanol against a buffer containing RNA. An alternative strategy offering improved cold-chain stability involves formulating empty LNPs (eLNPs), removing ethanol, and post hoc loading (PHL) RNA into the aqueous eLNPs. The kinetics of this approach remain unknown. Here, we employ a flowthrough small-angle X-ray scattering (SAXS) setup based on a confined impinging jets (CIJ) mixer to probe PHL kinetics. We show that RNA PHL in a scalable CIJ mixer is efficient and reproducible, and that SAXS data confirms that this process concludes within ~12 ms under favorable conditions in rapid turbulent micromixing, suggesting a diffusion-limited aggregation mechanism. Favorable conditions were identified as an acidic pH 5.5 buffer combined with turbulent CIJ mixing. In contrast, PHL performed with a neutral pH 7.4 buffer using a CIJ mixer or under laminar flow with a pH 5.5 buffer resulted in inefficient PHL.

Fluorescent dyes are critical to visualizing nucleic acids in many applications. SYTOX Orange and SYTOX Green are cyanine dyes, used in dead cell staining and increasingly in single-molecule assays to probe DNA supercoiling and processing. However, their structures and effects on DNA mechanics are not or only partially known. We determine the structure of SYTOX Orange to be (E)-2-((2-(4 ((diethyl(methyl)ammonio)methyl)phenyl)-6-methoxy-1-methylquinolin-4(1H)-ylidene)methyl)-4-methyloxazolo[4,5-b]pyridin-4-ium, identical to SYBR Gold except for an aza-benzoxazol core that is fundamentally different from other dyes in the SYTOX and SYBR families. We report SYTOX Green to be (Z)-2-(bis(3-(trimethylammonio)propyl)amino)-4-((3-methylbenzo[d]thiazol-2(3H)-ylidene)methyl)-1-phenylquinolin-1-ium, similar to PicoGreen. Using magnetic tweezers, we characterize the effect of SYTOX Orange and SYTOX Green on DNA mechanics. They lengthen and unwind DNA consistent with intercalation and the DNA unwinding angles per dye are 21.1(1) degree and 20.5(1) degree for SYTOX Orange and Green, respectively. Both dyes leave the DNA bending persistence length and plectoneme size almost unaltered (<10% change up to 1 uM), which is advantageous in assays probing DNA supercoiling. Their photophysical properties reveal close agreement between single-molecule manipulation and optical absorbance and fluorescence spectroscopy. Our comprehensive set of complementary measurements relates mechanical and optical properties to the molecular structures and provides recommendations for their use in applications.

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.

Staphyloxanthin (STX) is a carotenoid synthesized by the human pathogen Staphylococcus aureus. The golden color of this bacterium is due to this carotenoid. STX protects Staphylococcus aureus from oxidative stress by scavenging free radical species. Furthermore, STX has been shown to mechanically strengthen the Staphylococcus aureus membrane and to form microdomains that recruit antibiotic-resistance factors. Thus, inhibition of STX is a promising strategy for intervening against multidrug-resistant strains of this pathogen. However, the molecular mechanisms by which STX regulates the membrane structure and function of Staphylococcus aureus remain unclear. More specifically, the localization of STX within phosphatidylglycerol (PG) bilayers, the primary phospholipid of this bacteriums membrane, and how this localization drives macroscopic biophysical changes remain unresolved questions. Here, we addressed this issue by integrating molecular dynamics (MD) simulations, X-ray scattering experiments, and fluorescence spectroscopy. We developed an atomistic model of STX, which was validated against X-ray scattering data and which is suitable for all-atom MD simulations. We demonstrate that STX significantly increases lipid packing and acyl chain order of STX-PG bilayer mixtures. In addition, STX self-assembles into clusters, where the long and rigid conjugated triterpenoid chain interdigitates across both leaflets, modifying locally the density of the surrounding PG molecules. These findings provide a molecular explanation to the reduced headgroup spacing and core dynamics observed in fluorescence experiments and are consistent with the formation of structurally-distinct STX-enriched microdomains. Notably, STX reduces the gel-to-liquid crystalline phase transition temperature, indicating a general stabilizing effect for the fluid phase of PG lipids of varying length. Overall, our findings provide molecular insights into how STX enhances membrane mechanical integrity. It will be highly interesting to establish how the membrane remodeling effects observed here connect with STXs dual roles, acting as an antioxidant and preventing pore formation and other mechanical perturbations induced by antimicrobial molecules.

The growing number of approved nucleic acid therapeutics illustrates the potential to treat diseases by targeting their genetic blueprints in vivo. The 10-23 DNAzyme is capable of cleaving a wide range of target RNA with high selectivity. However, its poor performance in vivo restricts its therapeutic application as gene silencing agent. Studies on ribozymes have shown that the crowded environment in cells and associated effects can impact ribozyme folding and thermostability, resulting in a change in activity. This opens up the question whether DNAzymes are also affected by molecular crowding. Here, we investigate the functional and structural influence of molecular crowding conditions on the 10-23 DNAzyme. The stability and activity of a PrP-specific 10-23 DNAzyme were examined in presence of PEG, dextran, and osmolytes. Our results indicate that osmolytes decrease DNAzyme activity in a concentration-dependent manner, while certain PEG and dextran concentrations promote activity. To rationalize our observations, we studied the cosolutes effect on physicochemical solution properties and the structure of the DNAzyme:RNA complex using FCS and SAXS. The data reveal that enhanced activity is observed under conditions where a combination of physiochemical properties matches an optimum that seems to be dependent on the metal ion cofactor. Structural influence under such conditions is indicated less. We propose that a certain degree of molecular crowding is required to favor a state, which allows for higher catalytic turnover. In addition, we show that the requirement for magnesium and manganese as a cofactor remains unchanged under the conditions applied. Our work contributes to a better understanding of how the cellular environment affects DNAzyme structure and function.

Control of fluids is a hallmark of microfluidic systems and fundamental for the successful application of microfluidic devices. Trigger valves use geometric features to autonomously control the release of fluids in microfluidic devices. Our previous work has adapted geometries used in closed trigger valve systems to enable use in open systems, allowing for open microfluidic devices with up to three trigger valves. Here, we focus on the parallel co-flows produced by sequential release of trigger valves and present a model that predicts their layer widths as a function of the geometric characteristics of the different side channels of each trigger valve. We show layered co-flows with widths as low as 50 microns. Additionally, we expand the use of trigger valves in open microfluidic devices by incorporating 1) varied step heights, 2) devices with up to seven trigger valves, and 3) use of varied fluids and plastics. To validate the implementation and use of these trigger valves in open systems, we have developed a theoretical framework to compare predicted outcomes (i.e., fluid travel distance, velocity, and layering width) with our experimental values. This theoretical work offers applications in various fields, including hydrogel patterning for 3D cell culture, organ-on-a-chip models, at-home sample preparation, and autonomous microfluidic systems for biosensing.

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.

The COVID-19 pandemic has imposed a reevaluation of safety protocols across various sectors, including the arts. This study addresses a critical gap in understanding SARS-CoV-2 persistence on materials commonly associated with musical instruments and scores, such as alloys, varnishes, reeds, and paper. While previous research has explored viral survival on various surfaces, limited data exists for materials specific to musical contexts. In this work, we investigate the efficacy of quarantine as a non-destructive method for inactivating SARS-CoV-2 on 16 materials, including brass, silver plating, ABS plastic, ebonite, and various varnishes and paper types. Results revealed significant variability in viral persistence across materials. Non-porous surfaces like metals and ABS plastic cleared infectivity within 3 days, while porous materials such as reeds and music scores required up to 7 days. Gold-plated brass and certain varnishes showed intermediate persistence, with infectivity clearing after 4 days. These findings are in agreement with prior studies indicating that SARS-CoV-2 survival is highly dependent on surface composition, with porous and organic-coated materials retaining viable virus longer due to reduced environmental stress. Our results highlight the feasibility of stratified quarantine protocols based on material type, offering practical guidelines for musicians and institutions and provides critical insights for mitigating SARS-CoV-2 transmission risks in musical settings.

The glycocalyx of red blood cells (RBCs), a negatively charged surface layer rich in sialic acid residues, plays a crucial role in modulating RBC aggregation. In pathological conditions such as diabetes and sepsis, glycocalyx degradation is often observed along with abnormal RBC aggregation. However, the mechanistic relationship between these phenomena remains poorly defined. In this study, we investigate the effects of enzymatic glycocalyx degradation on RBC aggregation under physiologically relevant flow conditions. Using neuraminidase from Clostridium perfringens (C. welchii) at varying concentrations, we selectively removed sialic acid residues from the RBC glycocalyx, simulating different levels of desialylation observed in health and disease. Confocal microscopy confirmed the dose-dependent depletion of membrane sialic acid, while microfluidic experiments revealed a significant increase in both the size and stability of the RBC aggregates after enzymatic treatment. Our findings suggest that glycocalyx integrity is a crucial biophysical determinant of RBC aggregation, likely influencing both electrostatic repulsion and hydrodynamic forces. This study provides new insights into how the enzymatic modification of the glycocalyx contributes to pathological hemorheology and may inform future strategies for the diagnosis or treatment of vascular diseases.

Potent antineoplastics, such as afatinib and freebase doxorubicin, are associated with systemic toxicity. To address this issue, we developed a carrier that releases drugs, including afatinib and doxorubicin, specifically at the focus of low-intensity ultrasound. This remotely triggered and focal approach enables the release of drugs specifically at the ultrasound focus, thus mitigating undesirable off-target effects, and at concentrations governed by the duration of the applied ultrasound. We produced ultrasound-sensitive microdroplets with high encapsulation efficiencies (39.6% for afatinib and 46.6% for doxorubicin). The microdroplets consist of an ultrasound-sensitive drug delivery system based on a methoxy poly(ethylene glycol)-poly(D, L-lactide) diblock copolymer (mPEG-PDLLA) and perfluorooctyl bromide (PFOB). Antineoplastic agents were encapsulated within these microdroplets via co-evaporation during particle synthesis. The microdroplets released doxorubicin and afatinib in an ultrasound-pressure-dependent manner, with fitted half-maximal release pressures (P50) of 0.61 MPa and 0.72 MPa, respectively. Together, the effective encapsulation of hydrophobic antineoplastic agents and the dose-dependent ultrasound-triggered release provide a new method for targeted drug delivery and a foundation for future targeted chemotherapies.

Lipid droplets (LDs) are cellular organelles responsible for lipid storage and metabolism. The mechanism of biogenesis of LDs involves phase separation of neutral lipids from the surrounding phospholipids, which generates oil lenses embedded in lipid bilayers, also known as nascent LDs. As nascent LDs grow, at some point they bud out of the bilayer, forming nearly spherical droplets. Nascent LDs have different propensity to bud, and it has been proposed that their shape provides information on such propensity; however, LD shape is difficult to determine experimentally. Here we studied the shape of lipid droplets using MD simulations at the coarse-grained level, and compared it to the predictions by an established theory. Our general system setup features an oil lens embedded into a flat, periodic bilayer. We found that the shape of simulated nascent LDs resembles a spherical cap (i.e., it has constant curvature over most of the surface), in excellent agreement with the theory, already for very small droplet sizes. The aspect ratio (height/radius) of nascent LDs increases with increasing LD volume, increasing membrane softness, and increasing surface tension between oil and water, also in agreement with theoretical predictions; however, it remains lower than 1 (i.e., the ratio for a sphere) for LDs of up to 40 nm in diameter. Fitting the simulated LD shapes with a theoretical shape equation suggests that a non-zero surface tension is present in both the monolayer and in the bilayer region. The existence of a relatively high surface tension in the bilayer region is confirmed by local stress calculations, and indicates that the periodic system setup does not reproduce the properties of nascent LDs in the endoplasmic reticulum, where the bilayer tension is two orders of magnitude lower. However, the simulations provide a microscopic view into the properties of droplet embedded vesicles.

Liquid crystalline mesophases exhibit structurally programmable internal architectures that enable co-loading of chemically orthogonal molecules within a single composite material. Realizing the potential of these materials for drug delivery requires a quantitative understanding of how tuning the composition affects internal mesophase architecture and consequently performance metrics such as payload release. Here, Flash NanoPrecipitation with hydrophobic ion pairing is used to prepare nanocarriers containing liquid crystalline mesophases co-encapsulating two compounds from widely different chemical classes: hydrophilic polymyxin B (logP -6) with one of four hydrophobic co-core materials (logP 7-11), achieving >75% encapsulation efficiency and up to 32% and 50% mass loadings for polymyxin and co-core. Synchrotron SAXS is used to quantify characteristic mesophase repeat spacing, which is found to be tunable as a function of composition. A strong correlation between d-spacing and polymyxin release rate is presented. Co-core chemistry and weight fraction jointly govern mesophase architecture, and repeat distance emerges as a structural metric linking these to the hydrophilic payload release kinetics. Mucus diffusivity and antibacterial efficacy are assessed as independent performance metrics, and results corroborate the release behavior. These findings establish a quantitative framework connecting material composition, mesophase architecture, and functional performance that can be applied toward rational co-formulation design. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=86 SRC="FIGDIR/small/734853v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@1d722eborg.highwire.dtl.DTLVardef@135adb7org.highwire.dtl.DTLVardef@11fe29eorg.highwire.dtl.DTLVardef@571165_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOToC Graphic TextC_FLOATNO Flash NanoPrecipitation yields liquid crystalline nanocarriers co-encapsulating with high efficiency payloads with widely distinct physicochemical properties. Synchrotron SAXS establishes characteristic repeat spacing as a quantitative structural metric directly governing hydrophilic release kinetics, providing a rational design framework linking mesophase architecture to functional performance across a range of payload structures. C_FIG

Auxetic metamaterials exhibit negative Poisson's ratio behaviors due to their architecture of periodically arranged unit cells. Although mechanical metamaterials are well established at the macroscale, programmable auxetic units remain scarce at the nanoscale. DNA origami offers a promising platform to bridge this gap, but design principles for dynamically deformable 3D auxetic nanostructures remain largely unexplored. Here, we develop design strategies for such 3D auxetic metastructures built from wireframe DNA origami. As a model system, we use a 3D re-entrant triangular unit composed of double-stranded DNA (dsDNA) bundle edges connected by single-stranded DNA (ssDNA) joints. Using coarse-grained molecular dynamics (MD) and umbrella-sampling free-energy simulations, we examine how edge design and joint-connection scheme govern auxetic responses and the energetics of the structural transformation. Our results show that auxetic performance and deformation energetics emerge from the coupled effects of DNA bundle rigidity and connector mechanics at the joints. This study provides mechanistic insights and design guidelines for programmable auxetic motion and energetics in 3D DNA origami metamaterials, advancing the development of stimuli-responsive nanomechanical devices.

Culture conditions were optimized for the production of melanin nanoparticle by the bacterial strain Pseudomonas stutzeri BTCZ 305. Response surface methodology was employed for determining the most significant fermentation conditions using variables including, pH, temperature and L-tyrosine concentration identified through one-factor-at-a time approach. Box-behnken design consisting of 17 different combinations of all these factors were performed. Using this methodology, a quadratic regression model was built and the optimal combinations of media constituents for maximum melanin production 1192.27 microg/mL were determined as temperature (32.5 degreeC), pH (8.5) and L-tyrosine concentration (7 g/L). Melanin production was obtained experimentally coincident with the predicted value and the model was proven to be adequate. The nanostructural distribution, its stability in colloidal suspension and particle size were also characterized with the help of TEM, particle size analysis and Zeta potential. The potent applicability of this molecule in anti-inflammation and wound healing was also elucidated.

Past few decades witnessed a boom in pharmaceutical and bioproduct industry with the help of bioprocess technology. Industrially important bioproducts can be produced in large scale for commercialization with the help of fermenters. Here in, pharmaceutically valuable bioproduct melanin, synthesized from Pseudomonas stutzeri strain BTC109 by using two different sized bioreactors. Under controlled conditions the bacteria were allowed to synthesis melanin nanoparticles. The important parameters to be monitored here are pH, dissolved oxygen, agitation, aeration, melanin production and cell biomass concentration. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=163 SRC="FIGDIR/small/737634v1_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@d92fe5org.highwire.dtl.DTLVardef@d76c07org.highwire.dtl.DTLVardef@f5516forg.highwire.dtl.DTLVardef@1b5864b_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIPharmaceutical and bioproduct development industries witnessed a shoot up due to bioprocess technology. C_LIO_LIIndustrially important bioproduct like melanin can be produced in large scale with the help of industrial fermentation technology. C_LIO_LIThe product thus obtained was found to be nano sized and it can be commercialized. C_LI

Control over network dynamics at different length scales is a feature of natural materials challenging to replicate in synthetic hydrogels. Hydrogel viscoelasticity is commonly controlled by tuning the kinetics of reversible crosslinks; however, this strategy inherently links the resulting macroscale and nanoscale dynamics of the individual network components. Taking inspiration from biological materials that feature lipids as structural elements, we introduce Lipid Network Crosslinked (LINC) hydrogels that exploit the mobility of individual lipids within self-assembled liposomes as covalent, network-crosslinking points. These mobile, covalent crosslinks increase hydrogel stress relaxation rates over 20-fold compared to polymer-only hydrogels with equivalent crosslinking chemistries and stiffnesses. We demonstrate that liposome design parameters, including degree of surface functionalization and tail saturation, provide a means to independently control the macroscale storage moduli and stress relaxation behavior. Finally, as an application where control over network dynamics at different length scales is critical, we placed cell-adhesive ligands onto more mobile or less mobile network elements. Human neural progenitor cells cultured within LINC hydrogels of identical macroscale viscoelasticity significantly altered their phenotype in response to nanoscale ligand dynamics. These results establish LINC hydrogels as biomimetic materials that leverage nanoscale lipid mobility within a macroscale polymeric network to control dynamics at multiple length scales.

Lipid nanoparticles (LNPs) have become a clinical standard for systemically-administered nucleic acid drugs and vaccines, but the LNP pipeline for locally-delivered LNP therapies remains much less mature. Local delivery in lung represents a particularly compelling application space for DNA-LNP therapeutics, as local gene therapies could support sustained epithelial recovery and functional restoration in various lung diseases. However, locally-delivered DNA-LNPs face multiple barriers, including the limited availability of serum components that often support conventional LNP activity, and the additional delivery barriers posed by the nucleus. We generated hybrid peptide-lipid nanoparticles (hpLNPs) for pulmonary DNA delivery by using a core-shell assembly strategy to incorporate short histone-derived peptides, selected for their DNA-transport capacity, into a clinically inspired LNP formulation. In parallel, we evaluated serum pre-coating of LNPs as a strategy to boost hpLNP activity in the serum-poor airway environment. A peptide:DNA amine/phosphate (N/P) ratio of 0.9 was identified as the highest feasible ratio to permit peptide incorporation into hpLNPs while preserving DNA encapsulation efficiency at >90%, retaining hpLNP colloidal stability, and preserving the overall pKa for LNPs. At N/P = 0.9, hpLNPs showed markedly enhanced DNA delivery in alveolar lung cells, achieving up to a 17-fold increase in transgene expression compared to peptide-free LNPs. Transgene expression levels varied depending on serum concentration, with expression peaking in the presence of 6% serum. Furthermore, serum pre-coating was necessary to enable in vivo hpLNP activity following intratracheal administration in mice, yielding robust local GFP expression. Mechanistic studies in exosome-free serum revealed that peptide incorporation in the hpLNPs enhanced transgene delivery by increasing nanoparticle interactions with serum exosome components, resulting in significant enhancements to hpLNP uptake. Together, these findings identify nanoparticle- serum interactions as a critical determinant of LNP-mediated pulmonary DNA delivery and establish peptide incorporation and serum pre-coating as promising strategies to enable robust, localized gene transfer in serum-free environments.

Innate immune agonists are promising therapeutic agents to induce immune responses against cancer. However, these agents have been limited by toxicity associated with systemic accumulation and activity in off-target cells. In this work, a targeted nanoparticle (NP) platform to encapsulate and protect the Toll-like receptor 3 (TLR3) agonist polyinosinic-polycytidylic acid (poly(I:C)) and promote its specific delivery to antigen presenting cells (APCs), macrophages and dendritic cells, for activation of this cell population was designed. To determine NP physiochemical properties that promote APC delivery, we developed a library of NP surface chemistries formed by electrostatic adsorption of polyanion coatings onto liposomes using layer-by-layer (LbL) assembly and screened the particles on APCs and off-target cells. Dextran sulfate was identified as a promising coating to enhance specific APC delivery. We applied these design parameters to develop a poly(I:C)-loaded NP for an APC-targeted immunotherapy. In a model of metastatic ovarian cancer, the LbL NP prolonged poly(I:C) retention in the peritoneal space--with 2-fold remaining 24-48hr after administration compared to free poly(I:C)--ultimately reducing systemic accumulation and associated toxicities. Compared to free drug, the NP reduced the increase in serum levels of TNF, IL-6, and CXCL10 by 9-, 4-, and 31-fold respectively. NP-treated mice experienced lower weight loss and recovered more quickly at a higher poly(I:C) dose, indicating a widening of the therapeutic window. The NP formulation enhanced accumulation of poly(I:C) in the tumor 2-fold and activation of the target APC population compared to free drug, and ultimately slowed tumor growth and extended survival in combination with doxorubicin chemotherapy. Overall, this work demonstrates a modular NP delivery strategy to improve the delivery, safety, and therapeutic window of a TLR3 agonist.