Zeolitic imidazolate frameworks activate endosomal Toll-like receptors and potentiate immunogenicity of SARS-CoV-2 spike protein trimer

Nanomaterials offer unique opportunities to engineer immunomodulatory activity. In this work, we report the Toll-like receptor agonist activity of a nanoscale adjuvant zeolitic imidazolate framework-8 (ZIF-8). The accumulation of ZIF-8 in endosomes and the pH-responsive release of its subunits enable selective engagement with endosomal Toll-like receptors, minimizing the risk of off-target activation. The intrinsic adjuvant properties of ZIF-8, along with the efficient delivery and biomimetic presentation of a severe acute respiratory syndrome coronavirus 2 spike protein receptor-binding domain trimer, primed rapid humoral and cell-mediated immunity in a dose-sparing manner. Our study offers insights for next-generation adjuvants that can potentially impact future vaccine development.

A microneedle vaccine printer for thermostable COVID-19 mRNA vaccines

Decentralized manufacture of thermostable mRNA vaccines in a microneedle patch (MNP) format could enhance vaccine access in low-resource communities by eliminating the need for a cold chain and trained healthcare personnel. Here we describe an automated process for printing MNP Coronavirus Disease 2019 (COVID-19) mRNA vaccines in a standalone device. The vaccine ink is composed of lipid nanoparticles loaded with mRNA and a dissolvable polymer blend that was optimized for high bioactivity by screening formulations in vitro. We demonstrate that the resulting MNPs are shelf stable for at least 6 months at room temperature when assessed using a model mRNA construct. Vaccine loading efficiency and microneedle dissolution suggest that efficacious, microgram-scale doses of mRNA encapsulated in lipid nanoparticles could be delivered with a single patch. Immunizations in mice using manually produced MNPs with mRNA encoding severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein receptor-binding domain stimulate long-term immune responses similar to those of intramuscular administration.

Recent advances in nano- and micro-scale carrier systems for controlled delivery of vaccines

Vaccines provide substantial safety against infectious diseases, saving millions of lives each year. The recent COVID-19 pandemic highlighted the importance of vaccination in providing mass-scale immunization against outbreaks. However, the delivery of vaccines imposes a unique set of challenges due to their large molecular size and low room temperature stability. Advanced biomaterials and delivery systems such as nano- and mciro-scale carriers are becoming critical components for successful vaccine development. In this review, we provide an updated overview of recent advances in the development of nano- and micro-scale carriers for controlled delivery of vaccines, focusing on carriers compatible with nucleic acid-based vaccines and therapeutics that emerged amid the recent pandemic. We start by detailing nano-scale delivery systems, focusing on nanoparticles, then move on to microscale systems including hydrogels, microparticles, and 3D printed microneedle patches. Additionally, we delve into emerging methods that move beyond traditional needle-based applications utilizing innovative delivery systems. Future challenges for clinical translation and manufacturing in this rapidly advancing field are also discussed.

Topical application of Lactobacilli successfully eradicates Pseudomonas aeruginosa biofilms and promotes wound healing in chronic wounds

Chronic wounds are difficult to treat due to the presence of biofilm which prevents wound healing. Pseudomonas aeruginosa is one of the most common pathogens found in chronic wounds and conventional treatment strategies have been ineffective in the eradication of its biofilm, without harming the surrounding healthy tissue at the same time. Here, we introduced an innovative approach applying the probiotic product Bio-K+ (containing three lactobacilli) topically as an antimicrobial and antibiofilm agent. We identified lactic acid as the main active component. While antibiotics and antiseptics such as silver-ions only demonstrated limited efficacy, Bio-K+ was able to completely eradicate mature P. aeruginosa biofilms established in an in-vitro and ex-vivo human skin model. Furthermore, it demonstrated biocompatibility in the co-culture with human dermal fibroblasts and accelerated the migration of fibroblasts in a cell migration assay promoting wound healing. To enhance clinical practicability, we introduced Bio-K+ into the hydrocolloid dressing Aquacel, achieving sustained release of lactic acid and biofilm eradication. This new treatment approach applying probiotics could represent a major improvement in the management of chronic wounds and can be extended in treating other biofilm-associated infections.

A Machine Learning-optimized system for on demand, pulsatile, photo- and chemo-therapeutic treatment using near-infrared responsive MoS 2 -based microparticles in a breast cancer model

Cancer therapy research is of high interest because of the persistence and mortality of the disease and the side effects of traditional therapeutic methods, while often multimodal treatments are necessary based on the patient's needs. The development of less invasive modalities for recurring treatment cycles is thus of critical significance. Herein, a light-activatable microparticle system was developed for localized, pulsatile delivery of anticancer drugs with simultaneous thermal ablation, by applying controlled ON-OFF thermal cycles using near-infrared laser irradiation. The system is composed of poly(caprolactone) microparticles of 200 μm size with incorporated molybdenum disulfide (MoS ₂ ) nanosheets as the photothermal agent and hydrophilic doxorubicin or hydrophobic violacein, as model drugs. Upon irradiation the nanosheets heat up to ≥50 °C leading to polymer matrix melting and release of the drug. MoS ₂ nanosheets exhibit high photothermal conversion efficiency and allow for application of low power laser irradiation for the system activation. A Machine Learning algorithm was applied to acquire optimal laser operation conditions; 0.4 W/cm ² laser power at 808 nm, 3-cycle irradiation, for 3 cumulative minutes. In a mouse subcutaneous model of 4T1 triple-negative breast cancer, 25 microparticles were intratumorally administered and after 3-cycle laser treatment the system conferred synergistic phototherapeutic and chemotherapeutic effect. Our on-demand, pulsatile synergistic treatment resulted in increased median survival up to 40 days post start of treatment compared to untreated mice, with complete eradication of the tumors at the primary site. Such a system could have potential for patients in need of recurring cycles of treatment on subcutaneous tumors.

GRAPHICAL ABSTRACT

Abstract 820: Photo-activatable ON-OFF microparticles for on-demand pulsatile drug delivery in a breast cancer model

The ability to treat tumors with high efficacy in a local microenvironment, while mitigating the side effects of systemic toxicity is an area of active investigation. Towards this goal, designing a minimally-invasive local therapeutic modality, with a controlled, pulsatile drug release mechanism is an attractive proposition.

In this study, a near-infrared (NIR) photo-activatable microparticle was developed for localized, pulsatile delivery of encapsulated anticancer drugs into the tumor with simultaneous thermal ablation, with controlled ON-OFF thermal cycles using NIR laser irradiation. The microparticles were fabricated using a poly(caprolactone) (PCL) matrix, containing 2D molybdenum disulfide (MoS2) nanosheets as the NIR-responsive photothermal agent, and doxorubicin or violacein, as hydrophilic and hydrophobic model anticancer drugs, respectively. Cubic microparticles of 200 µm size were fabricated by casting a polymer-MoS2-drug film on PDMS mold with loading efficiency of 2 μg MoS2 per particle, and 0.2-8 μg of drug per particle. A cytotoxicity assay was performed to test the efficacy of the loaded microparticles in reducing the viability of 4T1 murine-derived cell culture, using the ON-OFF laser switch mechanism. In order to select a suitable laser power and duration of treatment for in vivo studies, a Machine Learning algorithm based on a Random Forest classifier was trained, to arrive at the optimal treatment conditions: 0.4-0.5 W/cm2 of laser power at 808 nm, for 3 cumulative minutes of laser irradiation, to reach the target temperature of 50 °C, which activates PCL melting and subsequent drug release.

The effect of pulsatile treatment was studied in vivo in a murine-derived 4T1 subcutaneous mouse model of breast cancer, using this photo-activatable ON-OFF switch mechanism, for up to 3 cycles of laser irradiation. As control groups, tumor only (no treatment), laser only (no drug or microparticle), drug only (no laser or microparticle), microparticles only (no drug or laser), and microparticles with laser (no drug) were studied. The cohorts receiving the photo-activated 3-cyclic treatment for both drugs showed increased median survival up to 40 days post tumor induction, compared to a median survival of 16 days for the control groups. Although one laser cycle was enough to trigger drug release, there was a significant shrinkage in the tumor volume noticed with 3 cycles, with eventual scarring and shedding of the tissue with no evidence of residual tumor at the primary site.

While this cyclic drug release modality is very effective at treating the primary site, subsequent histopathology revealed that the aggressive tumor in some animals had metastasized to the liver and other organs. More work is ongoing to design better targeted approaches to deliver the drug-loaded microparticles to the site of metastatic tumors, to increase the survival prospects of this disease.

Citation Format: Maria Kanelli, Neelkanth M. Bardhan, Morteza Sarmadi, Shahad Alsaiari, William Rothwell, Apurva Pardeshi, Angela M. Belcher, Ana Jaklenec, Robert S. Langer. Photo-activatable ON-OFF microparticles for on-demand pulsatile drug delivery in a breast cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 820.

Enhanced stability and clinical absorption of a form of encapsulated vitamin A for food fortification

Food fortification is an effective strategy to address vitamin A (VitA) deficiency, which is the leading cause of childhood blindness and drastically increases mortality from severe infections. However, VitA food fortification remains challenging due to significant degradation during storage and cooking. We utilized an FDA-approved, thermostable, and pH-responsive basic methacrylate copolymer (BMC) to encapsulate and stabilize VitA in microparticles (MPs). Encapsulation of VitA in VitA-BMC MPs greatly improved stability during simulated cooking conditions and long-term storage. VitA absorption was nine times greater from cooked MPs than from cooked free VitA in rats. In a randomized controlled cross-over study in healthy premenopausal women, VitA was readily released from MPs after consumption and had a similar absorption profile to free VitA. This VitA encapsulation technology will enable global food fortification strategies toward eliminating VitA deficiency.

Micromolding of Thermoplastic Polymers for Direct Fabrication of Discrete, Multilayered Microparticles

Soft lithography provides a convenient and effective method for the fabrication of microdevices with uniform size and shape. However, formation of an embossed, connective film as opposed to discrete features has been an enduring shortcoming associated with soft lithography. Removing this residual layer requires additional postprocessing steps that are often incompatible with organic materials. This limits adaptation and widespread realization of soft lithography for broader applications particularly in drug discovery and drug delivery fields. A novel and versatile approach is demonstrated that enables fabrication of discrete, multilayered, fillable, and harvestable microparticles directly from any thermoplastic polymer, even at very high molecular weights. The approach, isolated microparticle replication via surface-segregating polymer blend mold, utilizes a random copolymer additive, designed with a highly fluorinated segment that, when blended with the mold's matrix, spontaneously orients to the surface conferring an extremely low surface energy and nonwetting properties to the template. The extremely nonwetting properties of the mold are further utilized to load soluble biologics directly into the built-in microwells in a rapid and efficient manner using an innovative screen-printing approach. It is believed that this approach holds promise for fabrication of large-array, 3D, complex microstructures, and is a significant step toward clinical translation of microfabrication technologies.

Mild Acidosis-Directed Signal Amplification in Tumor Microenvironment via Spatioselective Recruitment of DNA Amplifiers

DNA biotechnology offers intriguing opportunities for amplification-based sensitive detection. However, spatiotemporally-controlled manipulation of signal amplification for in situ imaging of the tumor microenvironment remains an outstanding challenge. Here, we demonstrate a DNA-based strategy that can spatial-selectively amplify the acidic signal in the extracellular milieu of the tumor to achieve specific imaging with improved sensitivity. The strategy, termed mild acidosis-targeted amplification (MAT-amp), leverages the specific acidic microenvironment to engineer tumor cells with artificial DNA receptors through a pH (low) insertion peptide, which permits controlled recruitment of fluorescent amplifiers via a hybridization chain reaction. The acidosis-responsive amplification cascade enables significant fluorescence enhancement in tumors with a reduced background signal in normal tissues, leading to improved signal-to-background ratio. These results highlight the utility of MAT-amp for in situ imaging of the microenvironment characterized by pH disequilibrium.

Experimental and computational understanding of pulsatile release mechanism from biodegradable core-shell microparticles

Next-generation therapeutics require advanced drug delivery platforms with precise control over morphology and release kinetics. A recently developed microfabrication technique enables fabrication of a new class of injectable microparticles with a hollow core-shell structure that displays pulsatile release kinetics, providing such capabilities. Here, we study this technology and the resulting core-shell microstructures. We demonstrated that pulsatile release is governed by a sudden increase in porosity of the polymeric matrix, leading to the formation of a porous path connecting the core to the environment. Moreover, the release kinetics within the range studied remained primarily independent of the particle geometry but highly dependent on its composition. A qualitative technique was developed to study the pattern of pH evolution in the particles. A computational model successfully modeled deformations, indicating sudden expansion of the particle before onset of release. Results of this study contribute to the understanding and design of advanced drug delivery systems.

Parenteral vaccination strategies target protective immunity to the small and large intestine mucosa

Prophylactic vaccines are most commonly given by a parenteral route. However, this strategy often confers poor protection against GI pathogens because antigens are primarily presented in peripheral lymph nodes, which do not provide the prerequisite ‘tissue imprinting signals’ to target memory T and B cells to the gut. Here, we describe a platform that enables parenteral vaccines to target protection to the GI tract. This was achieved by subcutaneous (s.c.) delivery of compounds known to imprint gut tropism onto lymphocytes. Am80, a retinoic acid receptor agonist, targeted immunity to the small intestine through up-regulation of gut-homing receptors α4β7 and CCR9, and promotion of IgA class-switching. S.c. injection of OVA + CpG combined with repeated injections of Am80 generated significantly higher and durable fecal anti-OVA IgA titers, compared to OVA + CpG without Am80. Vaccination with Am80 also increased antigen-specific CD4 and CD8 T cell trafficking to the small intestine and generated tissue resident memory T (Trm) cells. To overcome the need for multiple doses of Am80, which can cause tissue toxicity at the injection site and hinder clinical translation, we developed a polymeric nanocarrier that showed equivalent imprinting efficacy upon a single injection, lowering the cumulative dose to one-third. Furthermore, we also developed a modified vaccination strategy that could augment effector and memory T cell responses not only in the small intestine, but also in the cecum, colon and rectum, conferring protection to the entire intestinal tract. We conclude that supplementation with mucosal imprinting signals is a promising approach to enhance parenteral vaccines by generating mucosal protection against GI infections.

Supported by the Bill & Melinda Gates Foundation

Vaccine delivery systems toward lymph nodes

Strategies of improving vaccine targeting ability toward lymph nodes have been attracting considerable interest in recent years, though there are remaining delivery barriers based on the inherent properties of lymphatic systems and limited administration routes of vaccination. Recently, emerging vaccine delivery systems using various materials as carriers are widely developed to achieve efficient lymph node targeting and improve vaccine-triggered adaptive immune response. In this review, to further optimize the vaccine targeting ability for future research, the design principles of lymph node targeting vaccine delivery based on the anatomy of lymph nodes and vaccine administration routes are first summarized. Then different designs of lymph node targeting vaccine delivery systems, including vaccine delivery systems in clinical applications, are carefully surveyed. Also, the challenges and opportunities of current delivery systems for vaccines are concluded in the end.

Stimuli-responsive transdermal microneedle patches

Microneedle (MN) patches consisting of miniature needles have emerged as a promising tool to perforate the stratum corneum and translocate biomolecules into the dermis in a minimally invasive manner. Stimuli-responsive MN patches represent emerging drug delivery systems that release cargos on-demand as a response to internal or external triggers. In this review, a variety of stimuli-responsive MN patches for controlled drug release are introduced, covering the mechanisms of action toward different indications. Future opportunities and challenges with respect to clinical translation are also discussed.

Biocompatible near-infrared quantum dots delivered to the skin by microneedle patches record vaccination

Accurate medical recordkeeping is a major challenge in many low-resource settings where well-maintained centralized databases do not exist, contributing to 1.5 million vaccine-preventable deaths annually. Here, we present an approach to encode medical history on a patient using the spatial distribution of biocompatible, near-infrared quantum dots (NIR QDs) in the dermis. QDs are invisible to the naked eye yet detectable when exposed to NIR light. QDs with a copper indium selenide core and aluminum-doped zinc sulfide shell were tuned to emit in the NIR spectrum by controlling stoichiometry and shelling time. The formulation showing the greatest resistance to photobleaching after simulated sunlight exposure (5-year equivalence) through pigmented human skin was encapsulated in microparticles for use in vivo. In parallel, microneedle geometry was optimized in silico and validated ex vivo using porcine and synthetic human skin. QD-containing microparticles were then embedded in dissolvable microneedles and administered to rats with or without a vaccine. Longitudinal in vivo imaging using a smartphone adapted to detect NIR light demonstrated that microneedle-delivered QD patterns remained bright and could be accurately identified using a machine learning algorithm 9 months after application. In addition, codelivery with inactivated poliovirus vaccine produced neutralizing antibody titers above the threshold considered protective. These findings suggest that intradermal QDs can be used to reliably encode information and can be delivered with a vaccine, which may be particularly valuable in the developing world and open up new avenues for decentralized data storage and biosensing.

Engineered PLGA microparticles for long-term, pulsatile release of STING agonist for cancer immunotherapy

Activation of the stimulator of interferon gene (STING) pathway within the tumor microenvironment has been shown to generate a strong antitumor response. Although local administration of STING agonists has promise for cancer immunotherapy, the dosing regimen needed to achieve efficacy requires frequent intratumoral injections over months. Frequent dosing for cancer treatment is associated with poor patient adherence, with as high as 48% of patients failing to comply. Multiple intratumoral injections also disrupt the tumor microenvironment and vascular networks and therefore increase the risk of metastasis. Here, we developed microfabricated polylactic-co-glycolic acid (PLGA) particles that remain at the site of injection and release encapsulated STING agonist as a programmable sequence of pulses at predetermined time points that mimic multiple injections over days to weeks. A single intratumoral injection of STING agonist-loaded microparticles triggered potent local and systemic antitumor immune responses, inhibited tumor growth, and prolonged survival as effectively as multiple soluble doses, but with reduced metastasis in several mouse tumor models. STING agonist-loaded microparticles improved the response to immune checkpoint blockade therapy and substantially decreased the tumor recurrence rate from 100 to 25% in mouse models of melanoma when administered during surgical resection. In addition, we demonstrated the therapeutic efficacy of STING microparticles on an orthotopic pancreatic cancer model in mice that does not allow multiple intratumoral injections. These findings could directly benefit current STING agonist therapy by decreasing the number of injections, reducing risk of metastasis, and expanding its applicability to hard-to-reach cancers.

Modeling, design, and machine learning-based framework for optimal injectability of microparticle-based drug formulations

Inefficient injection of microparticles through conventional hypodermic needles can impose serious challenges on clinical translation of biopharmaceutical drugs and microparticle-based drug formulations. This study aims to determine the important factors affecting microparticle injectability and establish a predictive framework using computational fluid dynamics, design of experiments, and machine learning. A numerical multiphysics model was developed to examine microparticle flow and needle blockage in a syringe-needle system. Using experimental data, a simple empirical mathematical model was introduced. Results from injection experiments were subsequently incorporated into an artificial neural network to establish a predictive framework for injectability. Last, simulations and experimental results contributed to the design of a syringe that maximizes injectability in vitro and in vivo. The custom injection system enabled a sixfold increase in injectability of large microparticles compared to a commercial syringe. This study highlights the importance of the proposed framework for optimal injection of microparticle-based drugs by parenteral routes.

Chiral Supraparticles for Controllable Nanomedicine

Chirality is ubiquitous in nature and hard-wired into every biological system. Despite the prevalence of chirality in biological systems, controlling biomaterial chirality to influence interactions with cells has only recently been explored. Chiral-engineered supraparticles (SPs) that interact differentially with cells and proteins depending on their handedness are presented. SPs coordinated with d-chirality demonstrate greater than threefold enhanced cell membrane penetration in breast, cervical, and multiple myeloma cancer cells. Quartz crystal microbalance with dissipation and isothermal titration calorimetry measurements reveal the mechanism of these chiral-specific interactions. Thermodynamically, d-SPs show more stable adhesion to lipid layers composed of phospholipids and cholesterol compared to l-SPs. In vivo, d-SPs exhibit superior stability and longer biological half-lives likely due to opposite chirality and thus protection from endogenous proteins including proteases. This work shows that incorporating d-chirality into nanosystems enhances uptake by cancer cells and prolonged in vivo stability in circulation, providing support for the importance of chirality in biomaterials. Thus, chiral nanosystems may have the potential to provide a new level of control for drug delivery systems, tumor detection markers, biosensors, and other biomaterial-based devices.

A heat-stable microparticle platform for oral micronutrient delivery

Micronutrient deficiencies affect up to 2 billion people and are the leading cause of cognitive and physical disorders in the developing world. Food fortification is effective in treating micronutrient deficiencies; however, its global implementation has been limited by technical challenges in maintaining micronutrient stability during cooking and storage. We hypothesized that polymer-based encapsulation could address this and facilitate micronutrient absorption. We identified poly(butylmethacrylate-co-(2-dimethylaminoethyl)methacrylate-co-methylmethacrylate) (1:2:1) (BMC) as a material with proven safety, offering stability in boiling water, rapid dissolution in gastric acid, and the ability to encapsulate distinct micronutrients. We encapsulated 11 micronutrients (iron; iodine; zinc; and vitamins A, B2, niacin, biotin, folic acid, B12, C, and D) and co-encapsulated up to 4 micronutrients. Encapsulation improved micronutrient stability against heat, light, moisture, and oxidation. Rodent studies confirmed rapid micronutrient release in the stomach and intestinal absorption. Bioavailability of iron from microparticles, compared to free iron, was lower in an initial human study. An organotypic human intestinal model revealed that increased iron loading and decreased polymer content would improve absorption. Using process development approaches capable of kilogram-scale synthesis, we increased iron loading more than 30-fold. Scaled batches tested in a follow-up human study exhibited up to 89% relative iron bioavailability compared to free iron. Collectively, these studies describe a broad approach for clinical translation of a heat-stable ingestible micronutrient delivery platform with the potential to improve micronutrient deficiency in the developing world. These approaches could potentially be applied toward clinical translation of other materials, such as natural polymers, for encapsulation and oral delivery of micronutrients.

Biofilm-Inspired Encapsulation of Probiotics for the Treatment of Complex Infections

The emergence of antimicrobial resistance poses a major challenge to healthcare. Probiotics offer a potential alternative treatment method but are often incompatible with antibiotics themselves, diminishing their overall therapeutic utility. This work uses biofilm-inspired encapsulation of probiotics to confer temporary antibiotic protection and to enable the coadministration of probiotics and antibiotics. Probiotics are encapsulated within alginate, a crucial component of pseudomonas biofilms, based on a simple two-step alginate cross-linking procedure. Following exposure to the antibiotic tobramycin, the growth and metabolic activity of encapsulated probiotics are unaffected by tobramycin, and they show a four-log survival advantage over free probiotics. This results from tobramycin sequestration on the periphery of alginate beads which prevents its diffusion into the core but yet allows probiotic byproducts to diffuse outward. It is demonstrated that this approach using tobramycin combined with encapsulated probiotic has the ability to completely eradicate methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa in coculture, the two most widely implicated bacteria in chronic wounds.

Evaporative Cooling Hydrogel Packaging for Storing Biologics Outside of the Cold Chain

Stabilizing thermolabile pharmaceuticals outside of the cold chain has the potential to alleviate some of the logistical and monetary burden of providing health care access in the developing world. Evaporative cooling hydrogel packaging is designed to extend the storage stability of existing pharmaceutical products without the need for reformulation. Hydrogels with high water content and reversible hydrophilicity offer a promising platform for reducing storage temperatures without refrigeration. As a model, poly(N-isopropylacrylamide) is selected as a basis for creating a potentially low cost and easy-to-fabricate hydrogels.

Stabilized single-injection inactivated polio vaccine elicits a strong neutralizing immune response

Vaccination in the developing world is hampered by limited patient access, which prevents individuals from receiving the multiple injections necessary for protective immunity. Here, we developed an injectable microparticle formulation of the inactivated polio vaccine (IPV) that releases multiple pulses of stable antigen over time. To accomplish this, we established an IPV stabilization strategy using cationic polymers for pH modulation to enhance traditional small-molecule-based stabilization methods. We investigated the mechanism of this strategy and showed that it was broadly applicable to all three antigens in IPV. Our lead formulations released two bursts of IPV 1 month apart, mimicking a typical vaccination schedule in the developing world. One injection of the controlled-release formulations elicited a similar or better neutralizing response in rats, considered the correlate of protection in humans, than multiple injections of liquid vaccine. This single-administration vaccine strategy has the potential to improve vaccine coverage in the developing world.

Controlling the Growth of Staphylococcus epidermidis by Layer-By-Layer Encapsulation

Commensal skin bacteria such as Staphylococcus epidermidis are currently being considered as possible components in skin-care and skin-health products. However, considering the potentially adverse effects of commensal skin bacteria if left free to proliferate, it is crucial to develop methodologies that are capable of maintaining bacteria viability while controlling their proliferation. Here, we encapsulate S. epidermidis in shells of increasing thickness using layer-by-layer assembly, with either a pair of synthetic polyelectrolytes or a pair of oppositely charged polysaccharides. We study the viability of the cells and their delay of growth depending on the composition of the shell, its thickness, the charge of the last deposited layer, and the degree of aggregation of the bacteria which is varied using different coating procedures-among which is a new scalable process that easily leads to large amounts of nonaggregated bacteria. We demonstrate that the growth of bacteria is not controlled by the mechanical properties of the shell but by the bacteriostatic effect of the polyelectrolyte complex, which depends on the shell thickness and charge of its outmost layer, and involves the diffusion of unpaired amine sites through the shell. The lag times of growth are sufficient to prevent proliferation for daily topical applications.

Biocompatible Semiconductor Quantum Dots as Cancer Imaging Agents

Approximately 1.7 million new cases of cancer will be diagnosed this year in the United States leading to 600 000 deaths. Patient survival rates are highly correlated with the stage of cancer diagnosis, with localized and regional remission rates that are much higher than for metastatic cancer. The current standard of care for many solid tumors includes imaging and biopsy with histological assessment. In many cases, after tomographical imaging modalities have identified abnormal morphology consistent with cancer, surgery is performed to remove the primary tumor and evaluate the surrounding lymph nodes. Accurate identification of tumor margins and staging are critical for selecting optimal treatments to minimize recurrence. Visible, fluorescent, and radiolabeled small molecules have been used as contrast agents to improve detection during real-time intraoperative imaging. Unfortunately, current dyes lack the tissue specificity, stability, and signal penetration needed for optimal performance. Quantum dots (QDs) represent an exciting class of fluorescent probes for optical imaging with tunable optical properties, high stability, and the ability to target tumors or lymph nodes based on surface functionalization. Here, state-of-the-art biocompatible QDs are compared with current Food and Drug Administration approved fluorophores used in cancer imaging and a perspective on the pathway to clinical translation is provided.

Fabrication of fillable microparticles and other complex 3D microstructures

Three-dimensional (3D) microstructures created by microfabrication and additive manufacturing have demonstrated value across a number of fields, ranging from biomedicine to microelectronics. However, the techniques used to create these devices each have their own characteristic set of advantages and limitations with regards to resolution, material compatibility, and geometrical constraints that determine the types ofmicrostructures that can be formed.We describe a microfabrication method, termed StampEd Assembly of polymer Layers (SEAL), and create injectable pulsatile drug-delivery microparticles, pH sensors, and 3D microfluidic devices that we could not produce using traditional 3D printing. SEAL allows us to generate microstructures with complex geometry at high resolution, produce fully enclosed internal cavities containing a solid or liquid, and use potentially any thermoplastic material without processing additives.

Rapid, Single-Cell Analysis and Discovery of Vectored mRNA Transfection In Vivo with a loxP-Flanked tdTomato Reporter Mouse

mRNA therapeutics hold promise for the treatment of diseases requiring intracellular protein expression and for use in genome editing systems, but mRNA must transfect the desired tissue and cell type to be efficacious. Nanoparticle vectors that deliver the mRNA are often evaluated using mRNA encoding for reporter genes such as firefly luciferase (FLuc); however, single-cell resolution of mRNA expression cannot generally be achieved with FLuc, and, thus, the transfected cell populations cannot be determined without additional steps or experiments. To more rapidly identify which types of cells an mRNA formulation transfects in vivo, we describe a Cre recombinase (Cre)-based system that permanently expresses fluorescent tdTomato protein in transfected cells of genetically modified mice. Following in vivo application of vectored Cre mRNA, it is possible to visualize successfully transfected cells via Cre-mediated tdTomato expression in bulk tissues and with single-cell resolution. Using this system, we identify previously unknown transfected cell types of an existing mRNA delivery vehicle in vivo and also develop a new mRNA formulation capable of transfecting lung endothelial cells. Importantly, the same formulations with mRNA encoding for fluorescent protein delivered to wild-type mice did not produce sufficient signal for any visualization in vivo, demonstrating the significantly improved sensitivity of our Cre-based system. We believe that the system described here may facilitate the identification and characterization of mRNA delivery vectors to new tissues and cell types.

Immunogenicity of pulsatile-release PLGA microspheres for single-injection vaccination

The World Health Organization's Expanded Programme on Immunization has led to a dramatic rise in worldwide vaccination rates over the past 40 years, yet 19.4 million infants remain underimmunized each year. Many of these infants have received at least one vaccine dose but may remain unprotected because they did not receive subsequent booster doses due to logistical challenges. This study aimed to develop injectable controlled release microparticles with kinetics that mimic common vaccine dosing regimens consisting of large antigen doses administered periodically over the course of months in order to eliminate the need for boosters. Sixteen poly(lactic-co-glycolic acid) (PLGA) microsphere formulations containing bovine serum albumin (BSA) as a model vaccine antigen were screened in vitro to determine their respective release kinetics. Three formulations that exhibited desirable pulsatile release profiles were then selected for studying immunogenicity in mice. Two low-dose microsphere formulations induced peak anti-BSA IgG antibody titers of 13.9 ± 1.3 and 13.7 ± 2.2 log₂ compared to 15.5 ± 1.5 log₂ for a series of three bolus injections delivered at 0, 4, and 8 weeks with an equivalent cumulative dose. Similarly, high-dose formulations induced peak antibody titers that were 16.1 ± 2.1 log₂ compared to 17.7 ± 2.2 log₂ for controls. All three microparticle formulations studied in vivo induced peak antibody titers that were statistically similar to bolus controls. These results suggest that pulsatile antigen release from polymeric microparticles is a promising approach for single-injection vaccination, which could potentially reduce the logistical burden associated with immunization in the developing world.

Ultrasound-Mediated Delivery of RNA to Colonic Mucosa of Live Mice

BACKGROUND & AIMS

It is a challenge to deliver nucleic acids to gastrointestinal (GI) tissues due to their size and need for intracellular delivery. They are also extremely susceptible to degradation by nucleases, which are ubiquitous in the GI tract. We investigated whether ultrasound, which can permeabilize tissue through a phenomenon known as transient cavitation, can be used to deliver RNA to the colonic mucosa of living mice.

METHODS

We investigated delivery of fluorescently labeled permeants to colon tissues of Yorkshire pigs ex vivo and mice in vivo. Colon tissues were collected and fluorescence was measured by confocal microscopy. We then evaluated whether ultrasound is effective in delivering small interfering (si)RNA to C57BL/6 mice with dextran sodium sulfate-induced colitis. Some mice were given siRNA against tumor necrosis factor (Tnf) mRNA for 6 days; colon tissues were collected and analyzed histologically and TNF protein levels measured by enzyme-linked immunosorbent assay. Feces were collected and assessed for consistency and occult bleeding. We delivered mRNA encoding firefly luciferase to colons of healthy C57BL/6 mice.

RESULTS

Exposure of ex vivo pig colon tissues to 20 kHz ultrasound for 1 minute increased the level of delivery of 3 kDa dextran 7-fold compared with passive diffusion (P = .037); 40 kHz ultrasound application for 0.5 seconds increased the delivery 3.3-fold in living mice (P = .041). Confocal microscopy analyses of colon tissues from pigs revealed regions of punctuated fluorescent dextran signal, indicating intracellular delivery of macromolecules. In mice with colitis, ultrasound delivery of unencapsulated siRNA against Tnf mRNA reduced protein levels of TNF in colon tissues, compared with mice with colitis given siRNA against Tnf mRNA without ultrasound (P ≤ .014), and reduced features of inflammation (P ≤ 4.1 × 10^-5). Separately, colons of mice administered an mRNA encoding firefly luciferase with ultrasound and the D-luciferin substrate had levels of bioluminescence 11-fold greater than colons of mice given the mRNA alone (P = .0025). Ultrasound exposures of 40 kHz ultrasound for 0.5 seconds were well tolerated, even in mice with acute colitis.

CONCLUSIONS

Ultrasound can be used to deliver mRNAs and siRNAs to the colonic mucosa of mice and knock down expression of target mRNAs.

Lipid Nanoparticle Assisted mRNA Delivery for Potent Cancer Immunotherapy

The induction of a strong cytotoxic T cell response is an important prerequisite for successful immunotherapy against many viral diseases and tumors. Nucleotide vaccines, including mRNA vaccines with their intracellular antigen synthesis, have been shown to be potent activators of a cytotoxic immune response. The intracellular delivery of mRNA vaccines to the cytosol of antigen presenting immune cells is still not sufficiently well understood. Here, we report on the development of a lipid nanoparticle formulation for the delivery of mRNA vaccines to induce a cytotoxic CD 8 T cell response. We show transfection of dendritic cells, macrophages, and neutrophils. The efficacy of the vaccine was tested in an aggressive B16F10 melanoma model. We found a strong CD 8 T cell activation after a single immunization. Treatment of B16F10 melanoma tumors with lipid nanoparticles containing mRNA coding for the tumor-associated antigens gp100 and TRP2 resulted in tumor shrinkage and extended the overall survival of the treated mice. The immune response can be further increased by the incorporation of the adjuvant LPS. In conclusion, the lipid nanoparticle formulation presented here is a promising vector for mRNA vaccine delivery, one that is capable of inducing a strong cytotoxic T cell response. Further optimization, including the incorporation of different adjuvants, will likely enhance the potency of the vaccine.

Layer-by-Layer Encapsulation of Probiotics for Delivery to the Microbiome

The gastrointestinal (GI) microbiome is widely investigated for its role in many diseases. However, technologies designed for microbiome delivery are lacking. Here, a layer-by-layer (LbL) approach is reported for probiotic encapsulation to protect probiotics against GI tract insults and improve their adhesion and growth on the intestines. These advantages translate to significantly enhanced survival of LbL-probiotics in vivo.

Magnetic Multivalent Trehalose Glycopolymer Nanoparticles for the Detection of Mycobacteria

A multivalent trehalose-grafted poly(lactic acid) is synthesized and encapsulated with iron oxide magnetic nanoparticles. The magnetic micelles interact with Mycobacterium smegmatis to form orange clusters. Very little particle interaction is found on Staphylococcus epidermidis 35984 or Escherichia coli ORN 208. The presented new approach to the detection of mycobacteria does not require molecular biology reagents or sophisticated instruments.

Thermostabilization of inactivated polio vaccine in PLGA-based microspheres for pulsatile release

Vaccines are a critical clinical tool in preventing illness and death due to infectious diseases and are regularly administered to children and adults across the globe. In order to obtain full protection from many vaccines, an individual needs to receive multiple doses over the course of months. However, vaccine administration in developing countries is limited by the difficulty in consistently delivering a second or third dose, and some vaccines, including the inactivated polio vaccine (IPV), must be injected more than once for efficacy. In addition, IPV does not remain stable over time at elevated temperatures, such as those it would encounter over time in the body if it were to be injected as a single-administration vaccine. In this manuscript, we describe microspheres composed of poly(lactic-co-glycolic acid) (PLGA) that can encapsulate IPV along with stabilizing excipients and release immunogenic IPV over the course of several weeks. Additionally, pH-sensitive, cationic dopants such as Eudragit E polymer caused clinically relevant amounts of stable IPV release upon degradation of the PLGA matrix. Specifically, IPV was released in two separate bursts, mimicking the delivery of two boluses approximately one month apart. In one of our top formulations, 1.4, 1.1, and 1.2 doses of the IPV serotype 1, 2, and 3, respectively, were released within the first few days from 50mg of particles. During the delayed, second burst, 0.5, 0.8, and 0.6 doses of each serotype, respectively, were released; thus, 50mg of these particles released approximately two clinical doses spaced a month apart. Immunization of rats with the leading microsphere formulation showed more robust and long-lasting humoral immune response compared to a single bolus injection and was statistically non-inferior from two bolus injections spaced 1 month apart. By minimizing the number of administrations of a vaccine, such as IPV, this technology can serve as a tool to aid in the eradication of polio and other infectious diseases for the improvement of global health.

High Throughput Layer-by-Layer Films for Extracting Film Forming Parameters and Modulating Film Interactions with Cells

A high-throughput approach which automates the synthesis of polyelectrolyte-based layer-by-layer films (HT-LbL) to facilitate rapid film generation, systematic film characterization, and rational investigations into their interactions with cells is described. Key parameters, such as polyelectrolyte adsorption time and polyelectrolyte deposition pH, were used to modulate LbL film growth to create LbL films of distinct thicknesses using the widely utilized polyelectrolytes poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA). We highlight how HT-LbL can be used to rapidly characterize film-forming parameters and robustly create linearly growing films of various molecular architectures. Film thickness and growth rates of HT-LbL films were shown to increase as a function of adsorption time. Subsequently, we investigated the role that polyelectrolyte solution pH (ranging from 2.5 to 9) has in forming molecularly distinct films of weak polyelectrolytes and report the effect this has on modulating cell attachment and spreading. Films synthesized at PAA-pH of 5.5 and PAH-pH 2.5-5.5 exhibited the highest cellular attachment. These results indicate that HT-LbL is a robust method that can shift the paradigm regarding the use of LbL in biomedical applications as it provides a rapid method to synthesize, characterize, and screen the interactions between molecularly distinct LbL films and cells.

Single-injection vaccines: Progress, challenges, and opportunities

Currently, vaccination is the most efficient and cost-effective medical treatment for infectious diseases; however, each year 10 million infants remain underimmunized due to current vaccination schedules that require multiple doses to be administered across months or years. These dosing regimens are especially challenging in the developing world where limited healthcare access poses a major logistical barrier to immunization. Over the past four decades, researchers have attempted to overcome this issue by developing single-administration vaccines based on controlled-release antigen delivery systems. These systems can be administered once, but release antigen over an extended period of time to elicit both primary and secondary immune responses resulting in antigen-specific immunological memory. Unfortunately, unlike controlled release systems for drugs, single-administration vaccines have yet to be commercialized due to poor antigen stability and difficulty in obtaining unconventional release kinetics. This review discusses the current state of single-administration vaccination, challenges delaying the development of these vaccines, and potential strategies for overcoming these challenges.

Progress in the tissue engineering and stem cell industry "are we there yet?"

This report presents a detailed update to our 2008 publication on the tissue engineering (TE) and stem cell industry. Data are reported through mid 2011 showing an almost three-fold growth in commercial sales over the past 4 years. In addition, the number of companies selling products or offering services has increased over two-fold to 106, and they are generating a remarkable $3.5 billion in sales. Overall, the TE and stem cell sector is spending $3.6 billion and employing almost 14,000 employees. These data suggest the TE and stem cell industry has stabilized and is on a path pointing toward continued success.

Encapsulation of BSA using a modified W/O/O emulsion solvent removal method

A systematic investigation of protein encapsulation in polylactic-co-glycolic-acid (PLGA) was carried out using the formation of a w/o/o emulsion followed by solvent removal. Various factors were studied, including composition of the suspension medium and the relative amounts of aqueous phase containing protein to polymer solution. High yields of microsphere fabrication were achieved by using silicon oil containing methylene chloride as a suspension medium instead of pure silicon oil, with minimal loss of polymer and protein drug (<2%). The amount of aqueous phase influenced the process and successful encapsulation was obtained if the volume ratios of aqueous phase to polymer solution were less than 5% (v/v) at a wide range of polymer concentration (2-15% g ml-1). Protein encapsulation by this w/o/o emulsion and solvent removal method has a high yield of microsphere fabrication and protein encapsulation (98%). In addition, it provides an easy way to control the release rate of protein encapsulated in microspheres by modulating their porosity in fabrication process.

A potential approach for decreasing the burst effect of protein from PLGA microspheres

A central issue in controlled delivery of therapeutics from biodegradable microspheres is the immediate burst of drug release upon injection. This burst is often observed with microsphere systems made by the double emulsion (w/o/w) technique, and may be prevented by improving the drug distribution throughout the polymer matrix. To this end, protein and polymer (poly-lactide-co-glycolide or PLGA) were dissolved within the same solvent system, and micron-sized microspheres were created from this solution by spontaneous emulsification. Improved protein loading was achieved by ion-pairing the protein with charged surfactants to increase solubility in the single-phase solvent system. Both in vitro and in vivo results showed a much diminished burst: compared to microspheres made by double emulsion, it was reduced over 10-fold.