Lipid nanoparticle structure and delivery route during pregnancy dictate mRNA potency, immunogenicity, and maternal and fetal outcomes.

Treating pregnancy-related disorders is exceptionally challenging because the threat of maternal and/or fetal toxicity discourages the use of existing medications and hinders new drug development. One potential solution is the use of lipid nanoparticle (LNP) RNA therapies, given their proven efficacy, tolerability, and lack of fetal accumulation. Here, we describe LNPs for efficacious mRNA delivery to maternal organs in pregnant mice via several routes of administration. In the placenta, our lead LNP transfected trophoblasts, endothelial cells, and immune cells, with efficacy being structurally dependent on the ionizable lipid polyamine headgroup. Next, we show that LNP-induced maternal inflammatory responses affect mRNA expression in the maternal compartment and hinder neonatal development. Specifically, pro-inflammatory LNP structures and routes of administration curtailed efficacy in maternal lymphoid organs in an IL-1ß-dependent manner. Further, immunogenic LNPs provoked the infiltration of adaptive immune cells into the placenta and restricted pup growth after birth. Together, our results provide mechanism-based structural guidance on the design of potent LNPs for safe use during pregnancy.

The strawberry-derived permeation enhancer pelargonidin enables oral protein delivery.

Although patients generally prefer oral drug delivery to injections, low permeability of the gastrointestinal tract makes this method impossible for most biomacromolecules. One potential solution is codelivery of macromolecules, including therapeutic proteins or nucleic acids, with intestinal permeation enhancers; however, enhancer use has been limited clinically by modest efficacy and toxicity concerns surrounding long-term administration. Here, we hypothesized that plant-based foods, which are well tolerated by the gastrointestinal tract, may contain compounds that enable oral macromolecular absorption without causing adverse effects. Upon testing more than 100 fruits, vegetables, and herbs, we identified strawberry and its red pigment, pelargonidin, as potent, well-tolerated enhancers of intestinal permeability. In mice, an oral capsule formulation comprising pelargonidin and a 1 U/kg dose of insulin reduced blood glucose levels for over 4 h, with bioactivity exceeding 100% relative to subcutaneous injection. Effects were reversible within 2 h and associated with actin and tight junction rearrangement. Furthermore, daily dosing of mice with pelargonidin for 1 mo resulted in no detectable side effects, including weight loss, tissue damage, or inflammatory responses. These data suggest that pelargonidin is an exceptionally effective enhancer of oral protein uptake that may be safe for routine pharmaceutical use.

Non-Viral RNA Delivery During Pregnancy: Opportunities and Challenges.

During pregnancy, the risk of maternal and fetal adversities increases due to physiological changes, genetic predispositions, environmental factors, and infections. Unfortunately, treatment options are severely limited because many essential interventions are unsafe, inaccessible, or lacking in sufficient scientific data to support their use. One potential solution to this challenge may lie in emerging RNA therapeutics for gene therapy, protein replacement, maternal vaccination, fetal gene editing, and other prenatal treatment applications. In this review, the current landscape of RNA platforms and non-viral RNA delivery technologies that are under active development for administration during pregnancy is explored. Advancements of pregnancy-specific RNA drugs against SARS-CoV-2, Zika, influenza, preeclampsia, and for in-utero gene editing are discussed. Finally, this study highlights bottlenecks that are impeding translation efforts of RNA therapies, including the lack of accurate cell-based and animal models of human pregnancy and concerns related to toxicity and immunogenicity during pregnancy. Overcoming these challenges will facilitate the rapid development of this new class of pregnancy-safe drugs.

Lateral force removal of fungal spores to demonstrate how surface properties affect fungal spore retention.

Microbial biofouling on polymer surfaces can lead to their biodeterioration. This may result in deterioration of the surface, leading to cracking and fracturing. Fungal spores from Aspergillus niger 1957, Aspergillus niger 1988 and Aureobasidium pullulans were tested to determine their strength of attachment on three surfaces, p(γ-MPS-co-MMA), p(γ-MPS-co-LMA) and spin-coated poly(methyl methacrylate) (PMMAsc), using lateral force measurements. The results demonstrate that A. niger 1957 and A. niger 1988 spores were most easily removed from the p(γ-MPS-co-MMA) surface, which was the surface with the highest Ra value. The A. niger 1957 and A. pullulans spores were most difficult to remove from the PMMAsc surface, which was the hardest surface. A. niger 1988 spores were the most difficult to remove from p(γ-MPS-co-LMA), the most hydrophobic surface. The results with A. pullulans were difficult to elucidate since the spores bound to all three surfaces and were removed with similar rates of force. The lateral force results demonstrate that spore attachment to a surface is a multi-factorial process, and independent surface and microbial factors influence spore binding. Thus, each environmental scenario needs to be considered on an individual basis, since a solution to one biofouling issue will probably not translate across to other systems. This article is part of the theme issue 'Nanocracks in nature and industry'.

Ionic gold demonstrates antimicrobial activity against Pseudomonas aeruginosa strains due to cellular ultrastructure damage.

Due to the ever-increasing rise of antimicrobial resistant (AMR) bacteria, the development of alternative antimicrobial agents is a global priority. The antimicrobial activity of ionic gold was explored against four Pseudomonas aeruginosa strains with different AMR profiles in order to determine the antimicrobial activity of ionic gold and elucidate the mechanisms of action. Disc diffusion assays (zone of inhibition: ZoI) coupled with minimum inhibitory/bactericidal concentrations (MIC/MBC) were conducted to determine the antimicrobial efficacy of ionic gold. Scanning electron microscopy (SEM) was used to visualise morphological changes to the bacterial cell ultrastructure. Strains with increased AMR were slower to grow which is likely a fitness cost due to the enhanced AMR activity. Although greater concentrations of ionic gold were required to promote antimicrobial activity, ionic gold demonstrated similar antimicrobial values against all strains tested. Lowry assay results indicated that protein leakage was apparent following incubation with ionic gold, whilst SEM revealed cellular ultrastructure damage. This study suggests that the application of ionic gold as an alternative antimicrobial is promising, particularly against AMR P. aeruginosa. The antimicrobial activity of ionic gold against P. aeruginosa could potentially be utilised as an alternative therapeutic option in wound management, an approach that could benefit healthcare systems worldwide.

Principal Component Analysis to Determine the Surface Properties That Influence the Self-Cleaning Action of Hydrophobic Plant Leaves.

It is well established that many leaf surfaces display self-cleaning properties. However, an understanding of how the surface properties interact is still not achieved. Consequently, 12 different leaf types were selected for analysis due to their water repellency and self-cleaning properties. The most hydrophobic surfaces demonstrated splitting of the νs CH2 and ν CH2 bands, ordered platelet-like structures, crystalline waxes, high-surface-roughness values, high-total-surface-free energy and apolar components of surface energy, and low polar and Lewis base components of surface energy. The surfaces that exhibited the least roughness and high polar and Lewis base components of surface energy had intracuticular waxes, yet they still demonstrated the self-cleaning action. Principal component analysis demonstrated that the most hydrophobic species shared common surface chemistry traits with low intra-class variability, while the less hydrophobic leaves had highly variable surface-chemistry characteristics. Despite this, we have shown through partial least squares regression that the leaf water contact angle (i.e., hydrophobicity) can be predicted using attenuated total reflectance Fourier transform infrared spectroscopy surface chemistry data with excellent ability. This is the first time that such a statistical analysis has been performed on a complex biological system. This model could be utilized to investigate and predict the water contact angles of a range of biological surfaces. An understanding of the interplay of properties is extremely important to produce optimized biomimetic surfaces.

Polyamine biomarkers as indicators of human disease.

The significant increase of periodontitis, chronic kidney disease (CKD), Alzheimer's disease and cancer can be attributed to an ageing population. Each disease produces a range of biomarkers that can be indicative of disease onset and progression. Biomarkers are defined as cellular (intra/extracellular components and whole cells), biochemical (metabolites, ions and toxins) or molecular (nucleic acids, proteins and lipids) alterations which are measurable in biological media such as human tissues, cells or fluids. An interesting group of biomarkers that merit further investigation are the polyamines. Polyamines are a group of molecules consisting of cadaverine, putrescine, spermine and spermidine and have been implicated in the development of a range of systemic diseases, in part due to their production in periodontitis. Cadaverine and putrescine within the periodontal environment have demonstrated cell signalling interfering abilities, by way of leukocyte migration disruption. The polyamines spermine and spermidine in tumour cells have been shown to inhibit cellular apoptosis, effectively prolonging tumorigenesis and continuation of cancer within the host. Polyamine degradation products such as acrolein have been shown to exacerbate renal damage in CKD patients. Thus, the use of such molecules has merit to be utilized in the early indication of such diseases in patients.

A Potent Branched-Tail Lipid Nanoparticle Enables Multiplexed mRNA Delivery and Gene Editing In Vivo.

The clinical translation of messengerRNA (mRNA) drugs has been slowed by a shortage of delivery vehicles that potently and safely shuttle mRNA into target cells. Here, we describe the properties of a particularly potent branched-tail lipid nanoparticle that delivers mRNA to >80% of three major liver cell types. We characterize mRNA delivery spatially, temporally, and as a function of injection type. Following intravenous delivery, our lipid nanoparticle induced greater protein expression than two benchmark lipids, C12-200 and DLin-MC3-DMA, at an mRNA dose of 0.5 mg/kg. Lipid nanoparticles were sufficiently potent to codeliver three distinct mRNAs (firefly luciferase, mCherry, and erythropoietin) and, separately, Cas9 mRNA and single guide RNA (sgRNA) for proof-of-concept nonviral gene editing in mice. Furthermore, our branched-tail lipid nanoparticle was neither immunogenic nor toxic to the liver. Together, these results demonstrate the unique potential of this lipid material to improve the management of diseases rooted in liver dysfunction.

Exploring the putative interactions between chronic kidney disease and chronic periodontitis.

Chronic kidney disease (CKD) and chronic periodontitis (CP) are both common diseases, which are found disproportionately comorbid with each other and have been reported to have a detrimental effect on the progression of each respective disease. They have an overlap in risk factors and both are a source of systemic inflammation along with a wide selection of immunological and non-specific effects that can affect the body over the lifespan of the conditions. Previous studies have investigated the directionality of the relationship between these two diseases; however, there is a lack of literature that has examined how these diseases may be interacting at the localized and systemic level. This review discusses how oral microorganisms have the ability to translocate and have distal effects and provides evidence for microbial involvement in a systemic disease. Furthermore, it summarizes the reported local and systemic effects of CKD and CP and discusses how the interaction of these effects may be responsible for directionality associations reported.

Metal ions and graphene-based compounds as alternative treatment options for burn wounds infected by antibiotic-resistant Pseudomonas aeruginosa.

Burn infections caused by Pseudomonas aeruginosa pose a major complication in wound healing. This study aimed to determine the antimicrobial effect of metal ions, graphene (Gr), and graphene oxide (GO), individually and in combination, against the planktonic and biofilm states of two antimicrobially resistant clinical strains of P. aeruginosa each with different antibiotic resistance profiles. Minimum inhibitory, minimum bactericidal, and fractional inhibitory concentrations were performed to determine the efficacy of the metal ions and graphene composites individually and their synergy in combination. Crystal violet biofilm and XTT assays measured the biofilm inhibition and metabolic activity, respectively. Molybdenum, platinum, tin, gold, and palladium ions exhibited the greatest antimicrobial activity (MIC = 7.8-26.0 mg/L), whilst GO and Gr demonstrated moderate-to-no effect against the planktonic bacterial cells, irrespective of their antibiograms. Biofilms were inhibited by zinc, palladium, silver, and graphene. In combination, silver-graphene and molybdenum-graphene inhibited both the planktonic and biofilm forms of the bacteria making them potential candidates for development into topical antimicrobials for burns patients infected with antibiotic-resistant P. aeruginosa.

Branched-Tail Lipid Nanoparticles Potently Deliver mRNA In Vivo due to Enhanced Ionization at Endosomal pH.

The potential of mRNA therapeutics will be realized only once safe and effective delivery systems are established. Unfortunately, delivery vehicle development is stymied by an inadequate understanding of how the molecular properties of a vehicle confer efficacy. Here, a small library of lipidoid materials is used to elucidate structure-function relationships and identify a previously unappreciated parameter-lipid nanoparticle surface ionization-that correlates with mRNA delivery efficacy. The two most potent materials of the library, 306O10 and 306Oi10 , induce substantial luciferase expression in mice following a single 0.75 mg kg-1 mRNA dose. These lipidoids, which have ten-carbon tails and identical molecular weights, vary only in that the 306O10 tail is straight and the 306Oi10 tail has a one-carbon branch. Remarkably, this small difference in structure conferred a tenfold improvement in 306Oi10 efficacy. The enhanced potency of this branched-tail lipidoid is attributed to its strong surface ionization at the late endosomal pH of 5.0. A secondary lipidoid library confirms that Oi10 materials ionize more strongly and deliver mRNA more potently than lipidoids containing linear tails. Together, these data highlight the exquisite control that lipid chemistry exerts on the mRNA delivery process and show that branched-tail lipids facilitate protein expression in animals.

Thrifty, Rapid Intestinal Monolayers (TRIM) Using Caco-2 Epithelial Cells for Oral Drug Delivery Experiments.

PURPOSE: Caco-2 monolayers are the most common model of the intestinal epithelium and are critical to the development of oral drug delivery strategies and gastrointestinal disease treatments. However, current monolayer systems are cost- and/or time-intensive, hampering progress. This study evaluates two separate methods to reduce resource input: FB Essence as a fetal bovine serum (FBS) alternative and a new, 3-day Caco-2 system deemed "thrifty, rapid intestinal monolayers" (TRIM). METHODS: Caco-2 cells were cultured with FB Essence and compared to cells in 10% FBS for proliferation and monolayer formation. TRIM were compared to commonly-used 21-day and Corning® HTS monolayer systems, as well as mouse intestines, for permeability behavior, epithelial gene expression, and tight junction arrangement. RESULTS: No amount of FB Essence maintained Caco-2 cells beyond 10 passages. In contrast, TRIM compared favorably in permeability and gene expression to intestinal tissues. Furthermore, TRIM cost $109 and required 1.3 h of time per 24-well plate, compared to $164 and 3.7 h for 21-day monolayers, and $340 plus 1.0 h for the HTS system. CONCLUSIONS: TRIM offer a new approach to generating Caco-2 monolayers that resemble the intestinal epithelium. They are anticipated to accelerate the pace of in vitro intestinal experiments while easing financial burden.

Lipid Nanoparticle Formulations for Enhanced Co-delivery of siRNA and mRNA.

Although mRNA and siRNA have significant therapeutic potential, their simultaneous delivery has not been previously explored. To facilitate the treatment of diseases associated with aberrant gene upregulation and downregulation, we sought to co-formulate siRNA and mRNA in a single lipidoid nanoparticle (LNP) formulation. We accommodated the distinct molecular characteristics of mRNA and siRNA in a formulation consisting of an ionizable and biodegradable amine-containing lipidoid, cholesterol, DSPC, DOPE, and PEG-lipid. Surprisingly, the co-formulation of siRNA and mRNA in the same LNP enhanced the efficacy of both drugs in vitro and in vivo. Compared to LNPs encapsulating siRNA only, co-formulated LNPs improved Factor VII gene silencing in mice from 44 to 87% at an siRNA dose of 0.03 mg/kg. Co-formulation also improved mRNA delivery, as a 0.5 mg/kg dose of mRNA co-formulated with siRNA induced three times the luciferase protein expression compared to when siRNA was not included. As not all gene therapy applications require both RNA drugs, we sought to extend the benefit of co-formulated LNPs to formulations encapsulating only a single type of RNA. We accomplished this by substituting the "helper" RNA with a negatively charged polymer, polystyrenesulfonate (PSS). LNPs containing PSS mediated the same level of protein silencing or expression as standard LNPs using 2-3-fold less RNA. For example, LNPs formulated with and without PSS induced 50% Factor VII silencing at siRNA doses of 0.01 and 0.03 mg/kg, respectively. Together, these studies demonstrate potent co-delivery of siRNA and mRNA and show that inclusion of a negatively charged "helper polymer" enhances the efficacy of LNP delivery systems.

Exploring the electrochemical performance of graphite and graphene paste electrodes composed of varying lateral flake sizes.

We report the fabrication, characterisation (SEM/EDX, TEM, XRD, XPS and Raman spectroscopy) and electrochemical properties of graphite and graphene paste electrodes with varying lateral flake sizes. The fabricated paste electrodes are electrochemically analysed using both outer-sphere and inner-sphere redox probes, namely; hexaammineruthenium(iii) chloride, N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), potassium ferrocyanide(ii) and ammonium ferrous(ii) sulphate. Upon comparison of different graphite paste electrodes, a clear correlation between the lateral flake sizes (La), ranging from 1.5 mm-0.5 µm, and electrochemical activity (heterogeneous electron transfer (HET) kinetics) is evident, where an improvement in the HET is observed at smaller lateral flake sizes. We infer that the beneficial response evident when employing laterally smaller flakes is due to an increased number of edge plane like-sites/defects available upon the electrode surface, facilitating electron transfer. Interestingly, given that the overall lateral flake sizes of the graphenes utilised (10.0-1.3 µm) were significantly smaller than those studied previously, an improvement in HET kinetics was also evident with the reduction of lateral flake size; the extent to which is redox-probe dependent. Improvements are observed up to a distinct point, termed the 'lateral size threshold' (ca. ≤2 µm) where the electrochemical reversible limit is approached. Further support is provided from density functional theory (DFT), exploring the electronic structure (i.e. HOMO-LUMO) as a function of flake size, which demonstrates that the coverage of edge plane like-sites/defects comprising the geometric structure of the relatively small graphene flakes is such that effectively the entire flake has become electrochemically active. In this study, the importance of lateral flake size with respect to electrochemical reactivity at carbon-based electrodes has been demonstrated alongside a structural relationship upon HET performance, a phenomenon that has not previously been described in the literature. Such work is both highly important and informative for the field of electrochemistry and electrode performance, with potential implications in a plethora of areas, ranging from novel renewable energy sources to electroanalytical sensing platforms.

Modular Synthesis and Biological Investigation of 5-Hydroxymethyl Dibenzyl Butyrolactones and Related Lignans.

Dibenzyl butyrolactone lignans are well known for their excellent biological properties, particularly for their notable anti-proliferative activities. Herein we report a novel, efficient, convergent synthesis of dibenzyl butyrolactone lignans utilizing the acyl-Claisen rearrangement to stereoselectively prepare a key intermediate. The reported synthetic route enables the modification of these lignans to give rise to 5-hydroxymethyl derivatives of these lignans. The biological activities of these analogues were assessed, with derivatives showing an excellent cytotoxic profile which resulted in programmed cell death of Jurkat T-leukemia cells with less than 2% of the incubated cells entering a necrotic cell death pathway.

Structure-Function Analysis of Phenylpiperazine Derivatives as Intestinal Permeation Enhancers.

PURPOSE: A major obstacle preventing oral administration of macromolecular therapeutics is poor absorption across the intestinal epithelium into the bloodstream. One strategy to improve transport across this barrier is the use of chemical permeation enhancers. Several molecular families with permeation enhancing potential have been identified previously, including piperazines. In particular, 1-phenylpiperazine has been shown to enhance transepithelial transport with minimal cytotoxicity compared to similarly effective molecules. To better understand how the chemistry of 1-phenylpiperazine affects its utility as an intestinal permeation enhancer, this study examined a small library of 13 derivatives of 1-phenylpiperazine. METHODS: The efficacy and cytotoxicity of 13 phenylpiperazine compounds were assessed in a Caco-2 model of the intestinal epithelium. Efficacy was measured using the paracellular diffusion marker calcein as well as by immunostaining and confocal imaging of Caco-2 monolayers. RESULTS: Of the 13 derivatives, two enhanced the permeability of the fluorescent marker calcein over 100-fold. It was found that hydroxyl or primary amine substitutions on the phenyl ring significantly increased toxicity, while aliphatic substitutions resulted in efficacy and toxicity profiles comparable to 1-phenylpiperazine. CONCLUSIONS: Several potent derivatives, including 1-methyl-4-phenylpiperazine and 1-(4-methylphenyl)piperazine, displayed lower toxicity than 1-phenylpiperazine, suggesting promise in future applications.

The pH of Piperazine Derivative Solutions Predicts Their Utility as Transepithelial Permeation Enhancers.

The oral delivery of macromolecular drugs, including proteins and nucleic acids, is one of the greatest unmet needs in modern biomedicine. Although engineering solutions have been used to overcome enzymatic degradation and the low pH in the stomach, poor absorption across the intestinal epithelium into the bloodstream continues to pose the most significant challenge to clinical translation. One common approach to increase the flux of macromolecules across the intestinal epithelium is the use of chemical permeation enhancers. Unfortunately, the vast majority of effective enhancers have been thwarted by toxicity, and the structural and molecular parameters that contribute to this behavior are poorly understood. Previous work has shown that select piperazine-derived molecules favorably affect transepithelial and intracellular delivery outcomes, suggesting that piperazine-derived molecules interface uniquely with cellular barriers. To gain a better understanding of piperazine-mediated permeation enhancement, this work examined piperazine and 13 of its simple, hydrocarbon-substituted derivatives using Caco-2 monolayers as a model of the intestinal epithelium. After evaluating each piperazine for permeation enhancement efficacy and cytotoxicity at three concentrations, it became clear that piperazine derivatives consistently enhance permeability with each derivative resulting in noncytotoxic permeation enhancement at one or more concentrations. In attempting to identify structure-function relationships for the piperazine derivatives, it was found that treatment concentration, structural characteristics, and molecular pKa were not reliable indicators of permeation potential. Interestingly, the pH of the enhancer solution was identified as a controlling parameter even when accounting for the effects from pH change alone. Specifically, piperazine treatments with a pH between 9.2 and 9.6 guaranteed noncytotoxic efficacy. Furthermore, all effective treatments resulted in pH values between 8.7 and 9.6, behavior that was not shared by the other small, noncyclic amines studied. These data have important implications in the design of oral biologic delivery systems that employ permeation enhancers and underscore the need to carefully control the final treatment pH of the local intestinal epithelial environment.

Combinatorial synthesis of chemically diverse core-shell nanoparticles for intracellular delivery.

Analogous to an assembly line, we employed a modular design for the high-throughput study of 1,536 structurally distinct nanoparticles with cationic cores and variable shells. This enabled elucidation of complexation, internalization, and delivery trends that could only be learned through evaluation of a large library. Using robotic automation, epoxide-functionalized block polymers were combinatorially cross-linked with a diverse library of amines, followed by measurement of molecular weight, diameter, RNA complexation, cellular internalization, and in vitro siRNA and pDNA delivery. Analysis revealed structure-function relationships and beneficial design guidelines, including a higher reactive block weight fraction, stoichiometric equivalence between epoxides and amines, and thin hydrophilic shells. Cross-linkers optimally possessed tertiary dimethylamine or piperazine groups and potential buffering capacity. Covalent cholesterol attachment allowed for transfection in vivo to liver hepatocytes in mice. The ability to tune the chemical nature of the core and shell may afford utility of these materials in additional applications.

Multidrug-Resistant Escherichia coli Remains Susceptible to Metal Ions and Graphene-Based Compounds.

Escherichia coli is listed as a priority 1 pathogen on the World Health Organization (WHO) priority pathogen list. For this list of pathogens, new antibiotics are urgently needed to control the emergence and spread of multidrug-resistant strains. This study assessed eighteen metal ions, graphene, and graphene oxide for their antimicrobial efficacy against E. coli in both planktonic and biofilm growth states and the potential synergy between metal ions and graphene-based compounds. Molybdenum and tin ions exhibited the greatest antimicrobial activity against the planktonic states of the isolates with minimal inhibitory concentrations (MIC) ranging between 13 mg/L and 15.6 mg/L. Graphene oxide had no antimicrobial effect against any of the isolates, while graphene showed a moderate effect against E. coli (MIC, 62.5 mg/L). Combinations of metal ions and graphene-based compounds including tin-graphene, tin-graphene oxide, gold-graphene, platinum-graphene, and platinum-graphene oxide exhibited a synergistic antimicrobial effect (FIC ≤ 0.5), inhibiting the planktonic and biofilm formation of the isolates regardless of their antibiotic-resistant profiles. The bactericidal effect of the metal ions and the synergistic effects when combined with graphene/graphene oxide against medically relevant pathogens demonstrated that the antimicrobial efficacy was increased. Hence, such agents may potentially be used in the production of novel antimicrobial/antiseptic agents.

Branched-Tail Lipid Nanoparticles for Intravenous mRNA Delivery to Lung Immune, Endothelial, and Alveolar Cells in Mice.

Lipid nanoparticles (LNPs) are proven safe and effective delivery systems on a global scale. However, their efficacy has been limited primarily to liver and immune cell targets. To extend the applicability of mRNA drugs, 580 ionizable lipidoids are synthesized and tested for delivery to extrahepatocellular targets. Of these, over 40 enabled protein expression in mice, with the majority transfecting the liver. Beyond the liver, several LNPs containing new, branched-tail ionizable lipidoids potently delivered mRNA to the lungs, with cell-level specificity depending on helper lipid chemistry. Incorporation of the neutral helper lipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) at 16 mol% enabled highly specific delivery to natural killer and dendritic cells within the lung. Although inclusion of the cationic lipid 1,2-di-(9Z-octadecenoyl)-3-trimethylammonium-propane (DOTAP) improved lung tropism, it decreased cell specificity, resulting in equal transfection of endothelial and lymphoid cells. DOTAP formulations are also less favorable than DOPE formulations because they elevated liver enzyme and cytokine levels. Together, these data identify a new branched-tailed LNP with a unique ability to selectively transfect lung immune cell populations without the use of toxicity-prone cationic helper lipids. This novel vehicle may unlock RNA therapies for lung diseases associated with immune cell dysregulation, including cancer, viral infections, and autoimmune disorders.