Delivery Of Small Molecule Drugs Research Articles

Extracellular Vesicles as Drug Delivery Vehicles to the Central Nervous System.

Effective drug delivery to the CNS to achieve the desired therapeutic response is a significant challenge in the field of drug delivery. In central nervous system (CNS), blood brain barrier (BBB) restricts the desired therapeutic responses due to inefficient targeting, release kinetics, and failure to reach therapeutic concentrations in the brain. Therefore, most potentially beneficial diagnostic and therapeutic agents are not able to reach to the brain upon systemic administration. Despite the existence of many invasive techniques to promote drug deliveries across BBB, novel strategies of drug delivery system which can cross BBB effectively are required, otherwise translation of novel neurotherapeutics from bench to bedside will be difficult to achieve. In this review, we briefly outline the existing and emerging strategies for CNS drug deliveries with a focus on potential and challenges of using extracellular vesicles (EVs) in CNS drug delivery system. EVs are emerging as a promising tool for therapeutic delivery owing to its favorable intrinsic features of biocompatibility, stability, stealth capacity, ability to overcome natural barriers and inherent homing capability. EVs are nanovesicles that allow cell-cell communication. The EVs-cargo reflects the physiological as well as the pathophysiological state of a cell. EVs are shown to play a role in human immunodeficiency virus (HIV) infection and dissemination, which contributes to acquired immune deficiency syndrome (AIDS). In the context of HIV-1 infection, this review also outlines the role of EVs in dissemination, challenges faced in EVs research in HIV-1 co-morbid conditions and potential of nanotechnologies, especially EVs in Neuro-AIDS. Graphical Abstract EVs are used for the delivery of small molecule drugs, protein, and nucleic acid to the CNS as well as imaging molecules for in vivo tracking. For the purpose of delivery, EVs may or may not be subjected to membrane modification. The advantages of EVs, including its biocompatibility, low immunogenicity, and low toxicity profiles, can be exploited to potentially devise novel therapeutic delivery system for CNS drug targeting. This article outlines the challenges in potential EV-based therapeutic delivery.

Abstract 2175: Synthetic antigen receptor mesenchymal stem cells (SAR-MSCs) targeting perlecan for drug delivery to ovarian cancer

Abstract Mesenchymal stem cells (MSCs) can be engineered with polymeric nanoparticles for tumor-targeted delivery of small molecule drugs. Such nano-engineered MSCs have demonstrated exciting anticancer activity in multiple ovarian cancer models. Despite significantly improved delivery of chemotherapeutics to tumor tissues, non-specific accumulation of MSCs in clearance organs remains a concern. Paralleling the concept of CAR-T cells, we advance here a strategy for synthetic modification of MSCs with antibodies targeting specific antigens overexpressed on cancer cells. Our approach consists of stably incorporating recombinant protein G (PG) on the surface of MSCs, followed by binding of a full-length IgG to the PG handle. Because protein G binds to the Fc region of IgG, antigen-binding affinity of the antibody is conserved. We have previously shown the overexpression of perlecan (HSPG2) on ovarian cancer cells and its correlation to poor patient survival. In the current study, we investigated the incorporation of anti-perlecan antibody on the surface of nano-engineered MSCs. The anti-perlecan IgG antibody was first derivatized with palmitic acid (PA), which was then used to insert PG on MSCs cell membrane. We characterized the PAPG derivative by LC/Q-TOF/MS. Flow cytometry and confocal microscopy were used to confirm the incorporation of fluorescently labeled PAPG handle on MSC surface. Similarly, the binding of fluorescently labeled anti-perlecan IgG to PAPG-functionalized MSCs was confirmed by flow cytometry. We are currently investigating the anticancer efficacy of paclitaxel-loaded, anti-perlecan SAR-MSCs using in vitro and mouse models of ovarian cancer. Citation Format: Susheel Kumar Nethi, Dristhi Sehgal, Shen Cheng, Jayanth Panyam, Swayam Prabha. Synthetic antigen receptor mesenchymal stem cells (SAR-MSCs) targeting perlecan for drug delivery to ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2175.

Mitochondria-Targeting, Intracellular Delivery of Native Proteins Using Biodegradable Silica Nanoparticles.

Mitochondria are key organelles in mammalian cells whose dysfunction is linked to various diseases. Drugs targeting mitochondrial proteins provide a highly promising strategy for potential therapeutics. Methods for the delivery of small-molecule drugs to the mitochondria are available, but these are not suitable for macromolecules, such as proteins. Herein, we report the delivery of native proteins and antibodies to the mitochondria using biodegradable silica nanoparticles (BS-NPs). The modification of the nanoparticle surface with triphenylphosphonium (TPP) and cell-penetrating poly(disulfide)s (CPD) facilitated their rapid intracellular uptake with minimal endolysosomal trapping, providing sufficient time for effective mitochondrial localization followed by glutathione-triggered biodegradation and of native, functional proteins into the mitochondria.

Improving Payload Capacity and Anti-Tumor Efficacy of Mesenchymal Stem Cells Using TAT Peptide Functionalized Polymeric Nanoparticles.

Mesenchymal stem cells (MSCs) accumulate specifically in both primary tumors and metastases following systemic administration. However, the poor payload capacity of MSCs limits their use in small molecule drug delivery. To improve drug payload in MSCs, we explored polymeric nanoparticles that were functionalized with transactivator of transcription (TAT) peptide. Paclitaxel loaded poly(DL-lactide-co-glycolide) (PLGA) nanoparticles (15–16% w/w paclitaxel; diameter of 225 ± 7 nm; and zeta potential of −15 ± 4 mV) were fabricated by emulsion-solvent evaporation method, followed by TAT-conjugation to the surface of nanoparticles via maleimide-thiol chemistry. Our studies demonstrated that TAT functionalization improved the intracellular accumulation and retention of nanoparticles in MSCs. Further, nano-engineering of MSCs did not alter the migration and differentiation potential of MSCs. Treatment with nano-engineered MSCs resulted in significant (p < 0.05) inhibition of tumor growth and improved survival (p < 0.0001) in a mouse orthotopic model of lung cancer compared to that with free or nanoparticle encapsulated drug. In summary, our results demonstrated that MSCs engineered using TAT functionalized nanoparticles serve as an efficient carrier for tumor specific delivery of anticancer drugs, resulting in greatly improved therapeutic efficacy.

Correction: In-silico dynamic analysis of cytotoxic drug administration to solid tumours: Effect of binding affinity and vessel permeability.

[This corrects the article DOI: 10.1371/journal.pcbi.1006460.].

Role of Endocytosis in Nanoparticle Penetration of 3D Pancreatic Cancer Spheroids.

Robust deposition of extracellular matrix is a significant barrier for delivery of nanotherapeutics and small-molecule anticancer drugs to different tumors including pancreatic ductal adenocarcinoma. Here, we investigated permeation and total uptake of polystyrene nanoparticles of different diameters in 3D multicellular spheroid models of pancreatic tumors. Special attention was given to analysis of the impact of endocytic processes on nanoparticle accumulation and distribution in spheroids. We generated spheroids of BxPC3 or PANC-1 cells that were able to internalize 20, 100, and 500 nm fluorescent polystyrene beads with different efficacies, resulting in 20 ≫100 > 500 nm and 100 > 500 > 20 nm trends, respectively. It was found that endocytosis and transcytosis increased overall nanoparticle uptake and facilitated permeation of 20 nm beads in BxPC3 spheroids, whereas 100 and 500 nm particles did not penetrate. In PANC-1 spheroids, penetration of nanoparticles also decreased with the increase of size but was not significantly affected by endocytic processes. Thus, our study showed that passive diffusion and endocytic processes may have a different contribution to nanoparticle accumulation and distribution in spheroid models of pancreatic cancer.

Aligned microchannel polymer-nanotube composites for peripheral nerve regeneration: Small molecule drug delivery

Peripheral nerve injury accounts for roughly 2.8% of all trauma patients with an annual cost of 7 billion USD in the U.S. alone. Current treatment options rely on surgical intervention with the use of an autograft, despite associated shortcomings. Engineered nerve guidance conduits, stem cell therapies, and transient electrical stimulation have reported to increase speeds of functional recovery. As an alternative to the conduction effects of electrical stimulation, we have designed and optimized a nerve guidance conduit with aligned microchannels for the sustained release of a small molecule drug that promotes nerve impulse conduction. A biodegradable chitosan structure reinforced with drug-loaded halloysite nanotubes (HNT) was formed into a foam-like conduit with interconnected, longitudinally-aligned pores with an average pore size of 59.3 ± 14.2 μm. The aligned composite with HNTs produced anisotropic mechanical behavior with a Young's modulus of 0.33 ± 0.1 MPa, very similar to that of native peripheral nerve. This manuscript reports on the sustained delivery of 4-Aminopyridine (4AP, molecular weight 94.1146 g/mol), a potassium-channel blocker as a growth factor alternative to enhance the rate of nerve regeneration. The conduit formulation released a total of 30 ± 2% of the encapsulated 4AP in the first 7 days. Human Schwann cells showed elevated expression of key proteins such as nerve growth factor, myelin protein zero, and brain derived neurotrophic factor in a 4AP dose dependent manner. Preliminary in vivo studies in a critical-sized sciatic nerve defect in Wistar rats confirmed conduit suturability and strength to withstand ambulatory forces over 4 weeks of their implantation. Histological evaluations suggest conduit biocompatibility and Schwann cell infiltration and organization within the conduit and lumen. These nerve guidance conduits and 4AP sustained delivery may serve as an attractive strategy for nerve repair and regeneration.

Macromolecular Drug Carriers for Targeted Glioblastoma Therapy: Preclinical Studies, Challenges, and Future Perspectives.

Glioblastoma, the most common, aggressive brain tumor, ranks among the least curable cancers—owing to its strong tendency for intracranial dissemination, high proliferation potential, and inherent tumor resistance to radiation and chemotherapy. Current glioblastoma treatment strategies are further hampered by a critical challenge: adverse, non-specific treatment effects in normal tissue combined with the inability of drugs to penetrate the blood brain barrier and reach the tumor microenvironment. Thus, the creation of effective therapies for glioblastoma requires development of targeted drug-delivery systems that increase accumulation of the drug in the tumor tissue while minimizing systemic toxicity in healthy tissues. As demonstrated in various preclinical glioblastoma models, macromolecular drug carriers have the potential to improve delivery of small molecule drugs, therapeutic peptides, proteins, and genes to brain tumors. Currently used macromolecular drug delivery systems, such as liposomes and polymers, passively target solid tumors, including glioblastoma, by capitalizing on abnormalities of the tumor vasculature, its lack of lymphatic drainage, and the enhanced permeation and retention (EPR) effect. In addition to passive targeting, active targeting approaches include the incorporation of various ligands on the surface of macromolecules that bind to cell surface receptors expressed on specific cancer cells. Active targeting approaches also utilize stimulus responsive macromolecules which further improve tumor accumulation by triggering changes in the physical properties of the macromolecular carrier. The stimulus can be an intrinsic property of the tumor tissue, such as low pH, or extrinsic, such as local application of ultrasound or heat. This review article explores current preclinical studies and future perspectives of targeted drug delivery to glioblastoma by macromolecular carrier systems, including polymeric micelles, nanoparticles, and biopolymers. We highlight key aspects of the design of diverse macromolecular drug delivery systems through a review of their preclinical applications in various glioblastoma animal models. We also review the principles and advantages of passive and active targeting based on various macromolecular carriers. Additionally, we discuss the potential disadvantages that may prevent clinical application of these carriers in targeting glioblastoma, as well as approaches to overcoming these obstacles.

C-Terminal Residue of Ultrashort Peptides Impacts on Molecular Self-Assembly, Hydrogelation, and Interaction with Small-Molecule Drugs

Single molecular changes on a tripeptide can have dramatic effects on their self-assembly and hydrogelation. Herein, we explore C-terminal residue variation on two consistent ultrashort peptide backbones, i.e. acetylated-Leu-Ile-Val-Ala-Gly-Xaa and acetylated-Ile-Val-Xaa (Xaa = His, Arg, Asn). The objective of this study is to identify candidates that can form hydrogels for small-molecule drug (SMD) delivery. Haemolysis and cytotoxicity (with human adipose-derived mesenchymal stem cells) assays showed that the new soluble peptides (Xaa = His, Arg) are cytocompatible. Gelation studies showed that all but acetylated-Ile-Val-Arg could gel under physiological conditions. Longer peptidic backbones drive self-assembly more effectively as reflected in field emission scanning electron microscopy (FESEM) and circular dichroism spectroscopy studies. Rheological studies revealed that the resultant hydrogels have varying stiffness and yield stress, depending on the backbone and C-terminal residue. Visible spectroscopy-based elution studies with SMDs (naltrexone, methotrexate, doxorubicin) showed that besides the C-terminal residue, the shape of the SMD also determines the rate and extent of SMD elution. Based on the elution assays, infrared spectroscopy, and FESEM, we propose models for the peptide fibril-SMD interaction. Our findings highlight the importance of matching the molecular properties of the self-assembling peptide and SMD in order to achieve the desired SMD release profile.

An overview on oral drug delivery via nano-based formulations

Oral drug administration is used for a large number of medications, intended to create a systemic effect in the body. Over the recent years, an increasing attention has been directed by pharmacists toward the development of successful formulations for oral drug delivery. However, this issue is still controversial in pharmaceutical technology with many limitations due to the numerous barriers against the absorption and permeability in the gastrointestinal tract. On the other hand, drug carriers play an important role in providing prolonged release and delivery and overcome the multiple barriers of maintaining appropriate bioavailability. Nano scaling of the particles, carriers, and polymers has also provided the capability to characterize and control materials in order to produce unique pharmaceutical components and structures. Furthermore, personalized healthcare, rational drug design, and site-specific targeted drug delivery are some of the profits gained from a nano-based formulation approach. This review aimed to evaluate the evidence on some different types of nanoscaled drug delivery systems, which allow for the delivery of smallmolecule drugs and facilitate the merging of larger particles, such as nucleic acids, peptides, and proteins. The delivery of these molecules to the exact target areas inside the body can be accomplished, which would decrease systemic adverse effects and allow for more effective application of the pharmaceutical preparations.

Brief Local Application of Progesterone via a Wearable Bioreactor Induces Long-Term Regenerative Response in Adult Xenopus Hindlimb

SUMMARYThe induction of limb repair in adult vertebrates is a pressing, unsolved problem. Here, we characterize the effects of an integrated device that delivers drugs to severed hindlimbs of adult Xenopus laevis, which normally regenerate cartilaginous spikes after amputation. A wearable bioreactor containing a silk protein-based hydrogel that delivered progesterone to the wound site immediately after hindlimb amputation for only 24 hr induced the regeneration of paddle-like structures in adult frogs. Molecular markers, morphometric analysis, X-ray imaging, immunofluorescence, and behavioral assays were used to characterize the differences between the paddle-like structures of successful regenerates and hypomorphic spikes that grew in untreated animals. Our experiments establish a model for testing therapeutic cocktails in vertebrate hindlimb regeneration, identify pro-regenerative activities of progesterone-containing bioreactors, and provide proof of principle of brief use of integrated device-based delivery of small-molecule drugs as a viable strategy to induce and maintain a long-term regenerative response.

Microbubble-Mediated Delivery for Cancer Therapy

Despite an overall improvement in survival rates for cancer, certain resistant forms of the disease still impose a significant burden on patients and healthcare systems. Standard chemotherapy in these cases is often ineffective and/or gives rise to severe side effects. Targeted delivery of chemotherapeutics could improve both tumour response and patient experience. Hence, there is an urgent need to develop effective methods for this. Ultrasound is an established technique in both diagnosis and therapy. Its use in conjunction with microbubbles is being actively researched for the targeted delivery of small-molecule drugs. In this review, we cover the methods by which ultrasound and microbubbles can be used to overcome tumour barriers to cancer therapy.

In-silico dynamic analysis of cytotoxic drug administration to solid tumours: Effect of binding affinity and vessel permeability.

The delivery of blood-borne therapeutic agents to solid tumours depends on a broad range of biophysical factors. We present a novel multiscale, multiphysics, in-silico modelling framework that encompasses dynamic tumour growth, angiogenesis and drug delivery, and use this model to simulate the intravenous delivery of cytotoxic drugs. The model accounts for chemo-, hapto- and mechanotactic vessel sprouting, extracellular matrix remodelling, mechano-sensitive vascular remodelling and collapse, intra- and extravascular drug transport, and tumour regression as an effect of a cytotoxic cancer drug. The modelling framework is flexible, allowing the drug properties to be specified, which provides realistic predictions of in-vivo vascular development and structure at different tumour stages. The model also enables the effects of neoadjuvant vascular normalisation to be implicitly tested by decreasing vessel wall pore size. We use the model to test the interplay between time of treatment, drug affinity rate and the size of the vessels’ endothelium pores on the delivery and subsequent tumour regression and vessel remodelling. Model predictions confirm that small-molecule drug delivery is dominated by diffusive transport and further predict that the time of treatment is important for low affinity but not high affinity cytotoxic drugs, the size of the vessel wall pores plays an important role in the effect of low affinity but not high affinity drugs, that high affinity cytotoxic drugs remodel the tumour vasculature providing a large window for the normalisation of the vascular architecture, and that the combination of large pores and high affinity enhances cytotoxic drug delivery efficiency. These results have implications for treatment planning and methods to enhance drug delivery, and highlight the importance of in-silico modelling in investigating the optimisation of cancer therapy on a personalised setting.

Macroporous silica nanoparticles for delivering Bcl2-function converting peptide to treat multidrug resistant-cancer cells

The abundance of B cell lymphoma gene 2 (Bcl-2) is closely correlated with the resistance of cancer cells to chemotherapeutic agents, and a peptide derived from orphan nuclear receptor Nur77 can convert Bcl-2 from a protector to a killer of cancer cells. However, successful application of the Bcl-2-converting peptide to treat drug-resistant cancer cells depends on an efficient delivery carrier. Mesoporous silica nanoparticles (MSNs) have been extensively studied as promising candidates for small molecule drug delivery. However, the effective encapsulation and intracellular delivery of peptides using small pore-sized MSNs still remain a great technical challenge. In this paper, an effective delivery platform for Bcl-2-converting peptide was fabricated by us to treat multidrug resistant-cancer cells via tuning the surface functionality of macroporous silica nanoparticles. The resulting large-sized pore silica nanoparticles, especially those modified with thiol group, exhibited the high Bcl-2-converting peptide-loading efficiency of over 40%. Moreover, the peptide induced MCF7/DOX cells into apoptotic status by penetrating cytomembrane into mitochondria and being bound with Bcl-2 to expose the BH3 domain with the aid of various surface functionalities-decorated MSNs. In particular, amine-modified surface of MSNs caused the greater influence on the cell apoptosis-inducing effects of peptide in comparison with other functionalities-modified ones. Taken together, our study, for the first time, demonstrates a special approach towards pore size and surface functionality-collectively modulated silica-based nanostructural material for effective delivery of bio-macromolecules (e.g., Bcl-2-converting peptide) to treat the multidrug resistant-cancer cells with elevated Bcl-2 levels.

In Vivo Small Molecule Delivery to the Optic Nerve in a Rodent Model

Small molecule delivery to the optic nerve would allow for exploration of molecular and cellular pathways involved in normal physiology and optic neuropathies such as glaucoma, and provide a tool for screening therapeutics in animal models. We report a novel surgical method for small molecule drug delivery to the optic nerve head (ONH) in a rodent model. In proof-of-principle experiments, we delivered cytochalasin D (Cyt D; a filamentous actin inhibitor) to the junction of the superior optic nerve and globe in rats to target the actin-rich astrocytic cytoskeleton of the ONH. Cyt D delivery was quantified by liquid chromatography and mass spectrometry of isolated optic nerve tissue. One day after Cyt D delivery, anterior ONH filamentous actin bundle content was significantly reduced as assessed by fluorescent-tagged phalloidin labeling, relative to sham delivery. Anterior ONH nuclear counts and axon-specific beta-3 tubulin levels, as well as peripapillary retinal ganglion cell layer nuclear counts were not significantly altered after Cyt D delivery relative to sham delivery. Lastly, the surgical delivery technique caused minimal observable axon degeneration up to 10 days post-surgery. This small molecule delivery technique provides a new approach to studying optic neuropathies in in vivo rodent models.

Nanofibrous peptide hydrogel elicits angiogenesis and neurogenesis without drugs, proteins, or cells

The design of materials for regenerative medicine has focused on delivery of small molecule drugs, proteins, and cells to help accelerate healing. Additionally, biomaterials have been designed with covalently attached mimics of growth factors, cytokines, or key extracellular matrix components allowing the biomaterial itself to drive biological response. While the approach may vary, the goal of biomaterial design has often centered on promoting either cellular infiltration, degradation, vascularization, or innervation of the scaffold. Numerous successful studies have utilized this complex, multicomponent approach; however, we demonstrate here that a simple nanofibrous peptide hydrogel unexpectedly and innately promotes all of these regenerative responses when subcutaneously implanted into the dorsal tissue of healthy rats. Despite containing no small molecule drugs, cells, proteins or protein mimics, the innate response to this material results in rapid cellular infiltration, production of a wide range of cytokines and growth factors by the infiltrating cells, and remodeling of the synthetic material to a natural collagen-containing ECM. During the remodeling process, a strong angiogenic response and an unprecedented degree of innervation is observed. Collectively, this simple peptide-based material provides an ideal foundational system for a variety of bioregenerative approaches.

Multi-layered tumor-targeting photothermal-doxorubicin releasing nanotubes eradicate tumors in vivo with negligible systemic toxicity.

Multi-layered single-walled carbon nanotubes, termed SWNT@BSA@Au-S-PEG-FA@DOX, which integrate photothermal therapy with small molecule drug delivery, were prepared using a facile layer-by-layer assembly process. Oxidized and cut single-walled carbon nanotubes (SWNTs) were coated with bovine serum albumin (BSA) to provide abundant active sites for the nucleation of Au seeds, which are subsequently converted into gold nanoparticles (Au NPs) by in situ reduction. The resulting SWNT@BSA@Au material exhibits ideal photothermal properties. Further modification of the nanomaterial with folic acid terminated-polyglycol (FA-PEG-SH) and subsequent loading with doxorubicin (DOX) afford the SWNT@BSA@Au-S-PEG-FA@DOX. The FA terminated PEG endows the material with high water-dispersibility, biocompatibility and cancer cell selectivity. A high drug loading ratio for DOX of up to 590% was achieved, with the drug release being pH and temperature dependent, adding to the selectivity of the system. High efficacy of the SWNT@BSA@Au-S-PEG-FA@DOX material, when combined with photothermal therapy (irradiation of the tumor with an 808 nm laser, 1 W cm-2 for 5 min, 24 h after systemic injection of the nanomedicine), was demonstrated in vivo, resulting in complete tumor eradication. Remarkably, the side effects are negligible with only minor damage to normal tissues including the liver and kidneys being observed.

Evaluation of pharmacokinetic and pharmacodynamic profiles of liposomes for the cell type-specific delivery of small molecule drugs

Liposome-based drug formulations represent an exciting avenue of research as they increase efficacy to toxicity ratios. Current formulations rely on passive accumulation to the disease site where drug is taken up by the cells. Ligand mediated targeting increases the net accumulation of liposomes, however, an unexplored benefit is to potentially refine pharmacodynamics (PD) of a drug specifically to different cell types within diseased tissue. As a model system, we engineered cardiomyocyte- (I-1) and endothelial-targeted (B-40) liposomes to carry a VEGFR2 inhibitor (PTK787), and examined the effect of cell type-specific delivery on both pharmacokinetics (PK) and PD. Neovascularization in post-myocardial infarction was significantly reduced by B-40 liposomes loaded with PTK787 as compared to animals injected with I-1 liposomes, and profoundly more as compared to free PTK787. This study thus shows that the intraorgan targeting of drugs through cell type-specific delivery holds substantial promise towards lowering the minimal efficacious dose administered systemically.

Endocytic Uptake, Transport and Macromolecular Interactions of Anionic PAMAM Dendrimers within Lung Tissue

PurposePolyamidoamine (PAMAM) dendrimers are a promising class of nanocarrier with applications in both small and large molecule drug delivery. Here we report a comprehensive evaluation of the uptake and transport pathways that contribute to the lung disposition of dendrimers.MethodsAnionic PAMAM dendrimers and control dextran probes were applied to an isolated perfused rat lung (IPRL) model and lung epithelial monolayers. Endocytosis pathways were examined in primary alveolar epithelial cultures by confocal microscopy. Molecular interactions of dendrimers with protein and lipid lung fluid components were studied using small angle neutron scattering (SANS).ResultsDendrimers were absorbed across the intact lung via a passive, size-dependent transport pathway at rates slower than dextrans of similar molecular sizes. SANS investigations of concentration-dependent PAMAM transport in the IPRL confirmed no aggregation of PAMAMs with either albumin or dipalmitoylphosphatidylcholine lung lining fluid components. Distinct endocytic compartments were identified within primary alveolar epithelial cells and their functionality in the rapid uptake of fluorescent dendrimers and model macromolecular probes was confirmed by co-localisation studies.ConclusionsPAMAM dendrimers display favourable lung biocompatibility but modest lung to blood absorption kinetics. These data support the investigation of dendrimer-based carriers for controlled-release drug delivery to the deep lung.

Development of DNA Nanostructures for High-Affinity Binding to Human Serum Albumin.

The development of nucleic acid therapeutics has been hampered by issues associated with their stability and in vivo delivery. To address these challenges, we describe a new strategy to engineer DNA structures with strong binding affinity to human serum albumin (HSA). HSA is the most abundant protein in the blood and has a long circulation half-life (19 days). It has been shown to hinder phagocytosis, is retained in tumors, and aids in cellular penetration. Indeed, HSA has already been successfully used for the delivery of small-molecule drugs and nanoparticles. We show that conjugating dendritic alkyl chains to DNA creates amphiphiles that exhibit high-affinity (Kd in low nanomolar range) binding to HSA. Notably, complexation with HSA did not hinder the activity of silencing oligonucleotides inside cells, and the degradation of DNA strands in serum was significantly slowed. We also show that, in a site-specific manner, altering the number and orientation of the amphiphilic ligand on a self-assembled DNA nanocube can modulate the affinity of the DNA cage to HSA. Moreover, the serum half-life of the amphiphile bound to the cage and the protein was shown to reach up to 22 hours, whereas unconjugated single-stranded DNA was degraded within minutes. Therefore, adding protein-specific binding domains to DNA nanostructures can be used to rationally control the interface between synthetic nanostructures and biological systems. A major challenge with nanoparticles delivery is the quick formation of a protein corona (i.e., protein adsorbed on the nanoparticle surface) upon injection to biological media. We foresee such DNA cage-protein complexes as new tools to study the role of this protein adsorption layer with important implications in the efficient delivery of RNAi therapeutics in vitro and in vivo.