Particle Engineering via Supramolecular Assembly of Macroscopic Hydrophobic Building Blocks.

Tailoring the hydrophobicity of supramolecular assembly building blocks enables the fabrication of well-defined functional materials. However, the selection of building blocks used in the assembly of metal-phenolic networks (MPNs), an emerging supramolecular assembly platform for particle engineering, has been essentially limited to hydrophilic molecules. Herein, we synthesized and applied biscatechol-functionalized hydrophobic polymers (poly(methyl acrylate) (PMA) and poly(butyl acrylate) (PBA)) as building blocks to engineer MPN particle systems (particles and capsules). Our method allowed control over the shell thickness (e.g., between 10 and 21 nm), stiffness (e.g., from 10 to 126 mN m-1 ), and permeability (e.g., 28-72 % capsules were permeable to 500 kDa fluorescein isothiocyanate-dextran) of the MPN capsules by selection of the hydrophobic polymer building blocks (PMA or PBA) and by controlling the polymer concentration in the MPN assembly solution (0.25-2.0 mM) without additional/engineered assembly processes. Molecular dynamics simulations provided insights into the structural states of the hydrophobic building blocks during assembly and mechanism of film formation. Furthermore, the hydrophobic MPNs facilitated the preparation of fluorescent-labeled and bioactive capsules through postfunctionalization and also particle-cell association engineering by controlling the hydrophobicity of the building blocks. Engineering MPN particle systems via building block hydrophobicity is expected to expand their use.

Synthesis of Thermoresponsive, Catechol-Rich Poly(ethylene glycol) Brush Polymers for Attenuating Cellular Oxidative Stress.

Herein, we report a platform to integrate customizable quantities of catechol units into polymers by reacting caffeic acid carbonic anhydride with polymers having pendant amine groups. Brush poly(ethylene glycol)-caffeamide (PEG-CAF) copolymers based on oligo(ethylene glycol)methyl ether methacrylate (OEGMA500) were obtained with a catechol content of approximately 30, 40, and 50 mol % (vs OEGMA content). Owing to the hydrophobicity of the introduced CAF groups, the catechol copolymers exhibited cloud points in the range of 23-46 °C and were used to fabricate thermoresponsive FeIII metal-phenolic network capsules. Polymers with the highest CAF content (50 mol %) proved most effective for attenuating reactive oxygen species levels in vitro, in co-cultured fibroblasts, and breast cancer cells, even in the presence of an exogenous oxidant source. The reported approach to synthesize customizable catechol materials could be generalized to other amine-functional polymers, with potential biomedical applications such as adhesives or stimuli-responsive drug delivery systems.

Macromolecular Engineering of Thermoresponsive Metal-Phenolic Networks.

Dynamic nanostructured materials that can react to physical and chemical stimuli have attracted interest in the biomedical and materials science fields. Metal-phenolic networks (MPNs) represent a modular class of such materials: these networks form via coordination of phenolic molecules with metal ions and can be used for surface and particle engineering. To broaden the range of accessible MPN properties, we report the fabrication of thermoresponsive MPN capsules using FeIII ions and the thermoresponsive phenolic building block biscatechol-functionalized poly(N-isopropylacrylamide) (biscatechol-PNIPAM). The MPN capsules exhibited reversible changes in capsule size and shell thickness in response to temperature changes. The temperature-induced capsule size changes were influenced by the chain length of biscatechol-PNIPAM and catechol-to-FeIII ion molar ratio. The metal ion type also influenced the capsule size changes, allowing tuning of the MPN capsule mechanical properties. AlIII-based capsules, having a lower stiffness value (10.7 mN m-1), showed a larger temperature-induced size contraction (∼63%) than TbIII-based capsules, which exhibit a higher stiffness value (52.6 mN m-1) and minimal size reduction (<1%). The permeability of the MPN capsules was controlled by changing the temperature (25-50 °C)─a reduced permeability was obtained as the temperature was increased above the lower critical solution temperature of biscatechol-PNIPAM. This temperature-dependent permeability behavior was exploited to encapsulate and release model cargo (500 kDa fluorescein isothiocyanate-tagged dextran) from the capsules; approximately 70% was released over 90 min at 25 °C. This approach provides a synthetic strategy for developing dynamic and thermoresponsive-tunable MPN systems for potential applications in biological science and biotechnology.

Trisulfide-Bearing PEG Brush Polymers Donate Hydrogen Sulfide and Ameliorate Cellular Oxidative Stress.

A potential approach to combat cellular dysfunction is to manipulate cell communication and signaling pathways to restore physiological functions while protecting unaffected cells. For instance, delivering the signaling molecule H2S to certain cells has been shown to restore cell viability and re-normalize cell behavior. We have previously demonstrated the ability to incorporate a trisulfide-based H2S-donating moiety into linear polymers with good in vitro releasing profiles and demonstrated their potential for ameliorating oxidative stress. Herein, we report two novel series of brush polymers decorated with higher numbers of H2S-releasing segments. These materials contain two trisulfide-based monomers co-polymerized with oligo(ethylene glycol methyl ether methacrylate) via reversible addition-fragmentation chain-transfer polymerization. The macromolecules were characterized to have a range of trisulfide densities with similar, well-defined molecular weight distribution, good H2S-releasing profiles, and high cellular tolerance. Using an amperometric technique, the H2S liberated and total sulfide release were found to depend on concentrations and chemical nature of triggering molecules (glutathione and cysteine) and, importantly, the position of reactive groups within the brush structure. Notably, when introduced to cells at well-tolerated doses, two macromolecular donors which have the same proportion as of the H2S-donating monomer (30%) but differ in releasing moiety location show similar cellular H2S-releasing kinetics. These donors can restore reactive oxygen species levels to baseline values, when polymer pretreated cells are exposed to exogenous oxidants (H2O2). Our work opens up a new aspect in preparing H2S macromolecule donors and their application to arresting cellular oxidative cascades.

pH-Responsive Polymers for Improving the Signal-to-Noise Ratio of Hypoxia PET Imaging with [18 F]Fluoromisonidazole.

To improve the signal-to-noise ratio of hypoxia positron emission tomography (PET) imaging, stimuli-responsive polymers are designed for the delivery of the hypoxia PET tracer fluorine-18 labeled fluoromisonidazole ([18 F]FMISO). Linear poly(N-(2-(hydroxypropyl)methacrylamide)) polymers are functionalized with hydrazide linkers that form pH-sensitive acyl hydrazone bonds after their conjugation to an [18 F]FMISO ketone analogue. The release of the [18 F]FMISO ketone analogue from the polymers is considerably faster at a lower pH and its uptake is significantly higher in cancer cells growing under acidic conditions. Additionally, the retention of the PET tracer is significantly higher in hypoxic cells compared to normoxic cells. The delivery of a PET tracer using stimuli-responsive polymers may be an attractive strategy to improve signal-to-noise ratios in PET imaging.

Controlling Nanomaterial Size and Shape for Biomedical Applications via Polymerization-Induced Self-Assembly.

Rapid developments in the polymerization-induced self-assembly (PISA) technique have paved the way for the environmentally friendly production of nanoparticles with tunable size and shape for a diverse range of applications. In this feature article, the biomedical applications of PISA nanoparticles and the substantial progress made in controlling their size and shape are highlighted. In addition to early investigations into drug delivery, applications such as medical imaging, tissue culture, and blood cryopreservation are also described. Various parameters for controlling the morphology of PISA nanoparticles are discussed, including the degree of polymerization of the macro-CTA and core-forming polymers, the concentration of macro-CTA and core-forming monomers, the solid content of the final products, the solution pH, the thermoresponsitivity of the macro-CTA, the macro-CTA end group, and the initiator concentration. Finally, several limitations and challenges for the PISA technique that have been recently addressed, along with those that will require further efforts into the future, will be highlighted.

Elucidating the Influences of Size, Surface Chemistry, and Dynamic Flow on Cellular Association of Nanoparticles Made by Polymerization-Induced Self-Assembly.

The size and surface chemistry of nanoparticles dictate their interactions with biological systems. However, it remains unclear how these key physicochemical properties affect the cellular association of nanoparticles under dynamic flow conditions encountered in human vascular networks. Here, the facile synthesis of novel fluorescent nanoparticles with tunable sizes and surface chemistries and their association with primary human umbilical vein endothelial cells (HUVECs) is reported. First, a one-pot polymerization-induced self-assembly (PISA) methodology is developed to covalently incorporate a commercially available fluorescent dye into the nanoparticle core and tune nanoparticle size and surface chemistry. To characterize cellular association under flow, HUVECs are cultured onto the surface of a synthetic microvascular network embedded in a microfluidic device (SynVivo, INC). Interestingly, increasing the size of carboxylic acid-functionalized nanoparticles leads to higher cellular association under static conditions but lower cellular association under flow conditions, whereas increasing the size of tertiary amine-decorated nanoparticles results in a higher level of cellular association, under both static and flow conditions. These findings provide new insights into the interactions between polymeric nanomaterials and endothelial cells. Altogether, this work establishes innovative methods for the facile synthesis and biological characterization of polymeric nanomaterials for various potential applications.

Bioconjugation and Fluorescence Labeling of Iron Oxide Nanoparticles Grafted with Bromomaleimide-Terminal Polymers.

Iron oxide nanoparticles have been widely applied in biomedical applications for their unique physical properties. Despite the relatively mature synthetic approaches for iron oxide nanoparticles, surface modification strategies for obtaining particles with satisfactory biofunctionality are still urgently needed to meet the challenge of nanomedicine. Herein, we report a surface modification and biofunctionalization strategy for iron oxide-based magnetic nanoparticles based on a dibromomaleimide (DBM)-terminated polymer with brushed polyethylene glycol (PEG) chains. PEG acrylate and phosphonate monomers, serving as antibiofouling and surface anchoring compartments for iron oxide nanoparticles, were incorporated utilizing a novel DBM containing reversible addition-fragmentation chain transfer (RAFT) agent. The particles prepared through this new surface architecture possessed high colloidal stability in a physiological buffer and the capacity of covalent conjugation with biomolecules for targeting. Cell tracking of the molecular probes was achieved concomitantly by exploiting DBM conjugation-induced fluorescence of the nanoparticles.

Exploiting Macromolecular Design To Optimize the Antibacterial Activity of Alkylated Cationic Oligomers.

There is growing interest in synthetic polymers which co-opt the structural features of naturally occurring antimicrobial peptides. However, our understanding of how macromolecular architecture affects antibacterial activity remains limited. To address this, we investigated whether varying architectures of a series of block and statistical co-oligomers influenced antibacterial and hemolytic activity. Cu(0)-mediated polymerization was used to synthesize oligomers constituting 2-(Boc-amino)ethyl acrylate units and either diethylene glycol ethyl ether acrylate (DEGEEA) or poly(ethylene glycol) methyl ether acrylate units with varying macromolecular architecture; subsequent deprotection produced primary amine functional oligomers. Further guanylation provided an additional series of antimicrobial candidates. Both chemical composition and macromolecular architecture were shown to affect antimicrobial activity. A broad spectrum antibacterial oligomer (containing guanidine moieties and DEGEEA units) was identified that possessed promising activity (MIC = 2 µg mL-1) toward both Gram-negative and Gram-positive bacteria. Bacterial membrane permeabilization was identified as an important contributor to the mechanism of action.

Influence of Size and Shape on the Biodistribution of Nanoparticles Prepared by Polymerization-Induced Self-Assembly.

Polymerization-induced self-assembly (PISA) is a facile one-pot synthetic technique for preparing polymeric nanoparticles with different sizes and shapes for application in a variety of fields including nanomedicine. However, the in vivo biodistribution of nanoparticles obtained by PISA still remains unclear. To address this knowledge gap, we report the synthesis, cytotoxicity, and biodistribution in an in vivo tumor-bearing mouse model of polystyrene micelles with various sizes and polystyrene filomicelles with different lengths prepared by PISA. First, a library of nanoparticles was prepared comprised of poly(glycidyl methacrylate)-b-poly(oligo(ethylene glycol) methyl ether methacrylate)-b-polystyrene polymers, and their size and morphology were tuned by varying the polystyrene block length without affecting the surface chemistry. The 3H) ethanolamine, and a biodistribution study was carried out in nude mice bearing HT1080 tumor xenografts 48 h after intravenous delivery. In this model, we found that small spherical polystyrene core nanoparticles with a PEG corona (diameter 21 nm) have the highest tumor accumulation when compared to the larger spherical nanoparticles (diameter 33 nm) or rodlike (diameter 37 nm, contour length 350-500 nm) or wormlike counterparts (diameter 45 nm, contour length 1-2 µm). This finding has provided critical information on the biodistribution of polystyrene core nanoparticles with a PEG corona of different sizes and shapes prepared by the PISA technique and will inform their use in medical applications.

Star Polymers Reduce Islet Amyloid Polypeptide Toxicity via Accelerated Amyloid Aggregation.

Protein aggregation into amyloid fibrils is a ubiquitous phenomenon across the spectrum of neurodegenerative disorders and type 2 diabetes. A common strategy against amyloidogenesis is to minimize the populations of toxic oligomers and protofibrils by inhibiting protein aggregation with small molecules or nanoparticles. However, melanin synthesis in nature is realized by accelerated protein fibrillation to circumvent accumulation of toxic intermediates. Accordingly, we designed and demonstrated the use of star-shaped poly(2-hydroxyethyl acrylate) (PHEA) nanostructures for promoting aggregation while ameliorating the toxicity of human islet amyloid polypeptide (IAPP), the peptide involved in glycemic control and the pathology of type 2 diabetes. The binding of PHEA elevated the ß-sheet content in IAPP aggregates while rendering a new morphology of "stelliform" amyloids originating from the polymers. Atomistic molecular dynamics simulations revealed that the PHEA arms served as rodlike scaffolds for IAPP binding and subsequently accelerated IAPP aggregation by increased local peptide concentration. The tertiary structure of the star nanoparticles was found to be essential for driving the specific interactions required to impel the accelerated IAPP aggregation. This study sheds new light on the structure-toxicity relationship of IAPP and points to the potential of exploiting star polymers as a new class of therapeutic agents against amyloidogenesis.

Macromolecular Hydrogen Sulfide Donors Trigger Spatiotemporally Confined Changes in Cell Signaling.

Hydrogen sulfide (H2S) is involved in a myriad of cell signaling processes that trigger physiological events ranging from vasodilation to cell proliferation. Moreover, disturbances to H2S signaling have been associated with numerous pathologies. As such, the ability to release H2S in a cellular environment and stimulate signaling events is of considerable interest. Herein we report the synthesis of macromolecular H2S donors capable of stimulating cell signaling pathways in both the cytosol and at the cell membrane. Specifically, copolymers having pendent oligo(ethylene glycol) and benzonitrile groups were synthesized, and the benzonitrile groups were subsequently transformed into primary aryl thioamide groups via thionation using sodium hydrosulfide. These thioamide moieties could be incorporated into a hydrophilic copolymer or a block copolymer (i.e., into either the hydrophilic or hydrophobic domain). An electrochemical sensor was used to demonstrate release of H2S under simulated physiological conditions. Subsequent treatment of HEK293 cells with a macromolecular H2S donor elicited a slow and sustained increase in cytosolic ERK signaling, as monitored using a FRET-based biosensor. The macromolecular donor was also shown to induce a small, fast and sustained increase in plasma membrane-localized PKC activity immediately following addition to cells. Studies using an H2S-selective fluorescent probe in live cells confirmed release of H2S from the macromolecular donor over physiologically relevant time scales consistent with the signaling observations. Taken together, these results demonstrate that by using macromolecular H2S donors it is possible to trigger spatiotemporally confined cell signaling events. Moreover, the localized nature of the observed signaling suggests that macromolecular donor design may provide an approach for selectively stimulating certain cellular biochemical pathways.

Organic arsenicals as efficient and highly specific linkers for protein/peptide-polymer conjugation.

The entropy-driven affinity of trivalent (in)organic arsenicals for closely spaced dithiols has been exploited to develop a novel route to peptide/protein-polymer conjugation. A trivalent arsenous acid (As(III)) derivative (1) obtained from p-arsanilic acid (As(V)) was shown to readily undergo conjugation to the therapeutic peptide salmon calcitonin (sCT) via bridging of the Cys(1)-Cys(7) disulfide, which was verified by RP-HPLC and MALDI-ToF-MS. Conjugation was shown to proceed rapidly (t < 2 min) in situ and stoichiometrically through sequential reduction-conjugation protocols, therefore exhibiting conjugation efficiencies equivalent to those reported for the current leading disulfide-bond targeting strategies. Furthermore, using bovine serum albumin as a model protein, the trivalent organic arsenical 1 was found to demonstrate enhanced specificity for disulfide-bond bridging in the presence of free cysteine residues relative to established maleimide functional reagents. This specificity represents a shift toward potential orthogonality, by clearly distinguishing between the reactivity of mono- and disulfide-derived (vicinal or neighbors-through-space) dithiols. Finally, p-arsanilic acid was transformed into an initiator for aqueous single electron-transfer living radical polymerization, allowing the synthesis of hydrophilic arsenic-functional polymers which were shown to exhibit negligible cytotoxicity relative to a small molecule organic arsenical, and an unfunctionalized polymer control. Poly(poly[ethylene glycol] methyl ether acrylate) (PPEGA480, DPn = 10, Mn,NMR = 4900 g·mol(-1), D = 1.07) possessing a pentavalent arsenic acid (As(V)) α-chain end was transformed into trivalent As(III) post-polymerization via initial reduction by biological reducing agent glutathione (GSH), followed by binding of GSH. Conjugation of the resulting As(III)-functional polymer to sCT was realized within 35 min as indicated by RP-HPLC and verified later by thermodynamically driven release of sCT, from the conjugate, in the presence of strong chelating reagent ethanedithiol.

Cholesterol Modified Self-Assemblies and Their Application to Nanomedicine.

Cholesterol is a ubiquitous molecule in biological systems, and in particular plays various important roles in mammalian cellular processes. The presence of cholesterol is integral to the structure and behavior of biological membranes, and profoundly influences membrane involvement in cellular mechanisms. This review focuses on the incorporation of cholesterol into synthetic nanomaterials and assemblies, focusing on LC phase behavior, morphology/self-organization and hydrophobic interactions, all important factors in the design of nanomedicines. We highlight cholesteryl conjugates, liposomes and polymeric micelles, focusing on self-assembly capabilities, drug encapsulation and intracellular delivery. An area of considerable interest identified in this review is the use of cholesteryl-functional vectors to deliver drugs or nucleic acids. Such applications depend on the ability of the nanoparticle carrier to associate with both the cellular and endosomal membrane.

Discovery of a new chemical series of BRD4(1) inhibitors using protein-ligand docking and structure-guided design.

Bromodomains are key transcriptional regulators that are thought to be druggable epigenetic targets for cancer, inflammation, diabetes and cardiovascular therapeutics. Of particular importance is the first of two bromodomains in bromodomain containing 4 protein (BRD4(1)). Protein-ligand docking in BRD4(1) was used to purchase a small, focused screening set of compounds possessing a large variety of core structures. Within this set, a small number of weak hits each contained a dihydroquinoxalinone ring system. We purchased other analogs with this ring system and further validated the new hit series and obtained improvement in binding inhibition. Limited exploration by new analog synthesis showed that the binding inhibition in a FRET assay could be improved to the low µM level making this new core a potential hit-to-lead series. Additionally, the predicted geometries of the initial hit and an improved analog were confirmed by X-ray co-crystallography with BRD4(1).

Molecular weight (hydrodynamic volume) dictates the systemic pharmacokinetics and tumour disposition of PolyPEG star polymers.

Herein we report for the first time the biological fate of poly[(oligoethylene glycol) acrylate] (POEGA) star polymers synthesised via a versatile arm-first reversible addition-fragmentation chain transfer (RAFT) polymerisation approach. The biopharmaceutical behaviour of three different molecular weight (49, 64 and 94kDa) POEGA stars was evaluated in rats and nude mice bearing human MDA MB-231 tumours after intravenous administration. The 94kDa star polymer exhibited a longer plasma exposure time than the 49kDa or 64kDa star polymer; an observation attributable to differences in the rates of both polymer biodegradation and urinary excretion. Tumour biodistribution also correlated with molecular weight and was greatest for the longest circulating 94kDa star. Different patterns of liver and spleen biodistribution were observed between mice and rats for the different sized polymers. The polymers were also well-tolerated in vivo and in vitro at therapeutic concentrations. FROM THE CLINICAL EDITOR: Advances in nanotechnology has enabled scientists to produce nanoparticle as drug carriers in cancer therapeutics. In this article, the authors studied the biological fate of poly[(oligoethylene glycol) acrylate] (POEGA) star polymers of different size, after intravenous injections. This would allow the subsequent comparison to other drug delivery systems for better drug delivery.

Controlling nanoparticle-induced endothelial leakiness with the protein corona.

Understanding nanoparticle-cell interaction is essential for advancing research in nanomedicine and nanotoxicology. Apart from the transcytotic pathway mediated by cellular recognition and energetics, nanoparticles (including nanomedicines) may harness the paracellular route for their transport by inducing endothelial leakiness at cadherin junctions. This phenomenon, termed as NanoEL, is correlated with the physicochemical properties of the nanoparticles in close association with cellular signalling, membrane mechanics, as well as cytoskeletal remodelling. However, nanoparticles in biological systems are transformed by the ubiquitous protein corona and yet the potential effect of the protein corona on NanoEL remains unclear. Using confocal fluorescence microscopy, biolayer interferometry, transwell, toxicity, and molecular inhibition assays, complemented by molecular docking, here we reveal the minimal to significant effects of the anionic human serum albumin and fibrinogen, the charge neutral immunoglobulin G as well as the cationic lysozyme on negating gold nanoparticle-induced endothelial leakiness in vitro and in vivo. This study suggests that nanoparticle-cadherin interaction and hence the extent of NanoEL may be partially controlled by pre-exposing the nanoparticles to plasma proteins of specific charge and topology to facilitate their biomedical applications.

Functionalisation of brush polyethylene glycol polymers with specific lipids extends their elimination half-life through association with natural lipid trafficking pathways.

Polymeric prodrugs have been applied to control the delivery of various types of therapeutics. Similarly, conjugation of peptide therapeutics to lipids has been used to prolong systemic exposure. Here, we extend on these two approaches by conjugating brush polyethylene glycol (PEG) polymers with different lipid components including short-chain (1C2) or medium-chain (1C12) monoalkyl hydrocarbon tails, cholesterol (Cho), and diacylglycerols composed of two medium-chain (2C12) or long-chain (2C18) fatty acids. We uniquely evaluate the integration of these lipid-polymers into endogenous lipid trafficking pathways (albumin and lipoproteins) and the impact of lipid conjugation on plasma pharmacokinetics after intravenous (IV) and subcutaneous (SC) dosing to cannulated rats. The IV and SC elimination half-lives of Cho-PEG (13 and 22 h, respectively), 2C12-PEG (11 and 17 h, respectively) and 2C18-PEG (12 h for both) were prolonged compared to 1C2-PEG (3 h for both) and 1C12-PEG (4 h for both). Interestingly, 1C2-PEG and 1C12-PEG had higher SC bioavailability (40 % and 52 %, respectively) compared to Cho-PEG, 2C12-PEG and 2C18-PEG (25 %, 24 % and 23 %, respectively). These differences in pharmacokinetics may be explained by the different association patterns of the polymers with rat serum albumin (RSA), bovine serum albumin (BSA) and lipoproteins. For example, in pooled plasma (from IV pharmacokinetic studies), 2C18-PEG had the highest recovery in the high-density lipoprotein (HDL) fraction. In conclusion, the pharmacokinetics of brush PEG polymers can be tuned via conjugation with different lipids, which can be utilised to tune the elimination half-life, biodistribution and effect of therapeutics for a range of medical applications. STATEMENT OF SIGNIFICANCE: Lipidation of therapeutics such as peptides has been employed to extend their plasma half-life by promoting binding to serum albumin, providing protection against rapid clearance. Here we design and evaluate innovative biomaterials consisting of brush polyethylene glycol polymers conjugated with different lipids. Importantly, we show for the first time that lipidated polymeric materials associate with endogenous lipoprotein trafficking pathways and this, in addition to albumin binding, controls their plasma pharmacokinetics. We find that conjugation to dialkyl lipids and cholesterol leads to higher association with lipid trafficking pathways, and more sustained plasma exposure, compared to conjugation to short and monoalkyl lipids. Our lipidated polymers can thus be utilised as delivery platforms to tune the plasma half-life of various pharmaceuticals.

Impact of conjugation to different lipids on the lymphatic uptake and biodistribution of brush PEG polymers.

Delivery to peripheral lymphatics can be achieved following interstitial administration of nano-sized delivery systems (nanoparticles, liposomes, dendrimers etc) or molecules that hitchhike on endogenous nano-sized carriers (such as albumin). The published work concerning the hitchhiking approach has mostly focussed on the lymphatic uptake of vaccines conjugated directly to albumin binding moieties (ABMs such as lipids, Evans blue dye derivatives or peptides) and their subsequent trafficking into draining lymph nodes. The mechanisms underpinning access and transport of these constructs into lymph fluid, including potential interaction with other endogenous nanocarriers such as lipoproteins, have largely been ignored. Recently, we described a series of brush polyethylene glycol (PEG) polymers containing end terminal short-chain or medium-chain hydrocarbon tails (1C2 or 1C12, respectively), cholesterol moiety (Cho), or medium-chain or long-chain diacylglycerols (2C12 or 2C18, respectively). We evaluated the association of these materials with albumin and lipoprotein in rat plasma, and their intravenous (IV) and subcutaneous (SC) pharmacokinetic profiles. Here we fully detail the association of this suite of polymers with albumin and lipoproteins in rat lymph, which is expected to facilitate lymph transport of the materials from the SC injection site. Additionally, we characterise the thoracic lymph uptake, tissue and lymph node biodistribution of the lipidated brush PEG polymers following SC administration to thoracic lymph cannulated rats. All polymers had moderate lymphatic uptake in rats following SC dosing with the lymph uptake higher for 1C2-PEG, 2C12-PEG and 2C18-PEG (5.8%, 5.9% and 6.7% dose in lymph, respectively) compared with 1C12-PEG and Cho-PEG (both 1.5% dose in lymph). The enhanced lymph uptake of 1C2-PEG, 2C12-PEG and 2C18-PEG appeared related to their association profile with different lipoproteins. The five polymers displayed different biodistribution patterns in major organs and tissues in mice. All polymers reached immune cells deep within the inguinal lymph nodes of mice following SC dosing. The ability to access these immune cells suggests the potential of the polymers as platforms for the delivery of vaccines and immunotherapies. Future studies will focus on evaluating the lymphatic targeting and therapeutic potential of drug or vaccine-loaded polymers in pre-clinical disease models.

Lipid sulfoxide polymers as potential inhalable drug delivery platforms with differential albumin binding affinity.

Inhalable nanomedicines are increasingly being developed to optimise the pharmaceutical treatment of respiratory diseases. Large lipid-based nanosystems at the forefront of the inhalable nanomedicines development pipeline, though, have a number of limitations. The objective of this study was, therefore, to investigate the utility of novel small lipidated sulfoxide polymers based on poly(2-(methylsulfinyl)ethyl acrylate) (PMSEA) as inhalable drug delivery platforms with tuneable membrane permeability imparted by differential albumin binding kinetics. Linear PMSEA (5 kDa) was used as a hydrophilic polymer backbone with excellent anti-fouling and stealth properties compared to poly(ethylene glycol). Terminal lipids comprising single (1C2, 1C12) or double (2C12) chain diglycerides were installed to provide differing affinities for albumin and, by extension, albumin trafficking pathways in the lungs. Albumin binding kinetics, cytotoxicity, lung mucus penetration and cellular uptake and permeability through key cellular barriers in the lungs were examined in vitro. The polymers showed good mucus penetration and no cytotoxicity over 24 h at up to 1 mg ml-1. While 1C2-showed no interaction with albumin, 1C12-PMSEA and 2C12-PMSEA bound albumin with KD values of approximately 76 and 10 µM, respectively. Despite binding to albumin, 2C12-PMSEA showed reduced cell uptake and membrane permeability compared to the smaller polymers and the presence of albumin had little effect on cell uptake and membrane permeability. While PMSEA strongly shielded these lipids from albumin, the data suggest that there is scope to tune the lipid component of these systems to control membrane permeability and cellular interactions in the lungs to tailor drug disposition in the lungs.