Synthesis and characterization of acetalated dextran polymer and microparticles with ethanol as a degradation product

Multi-COBRA hemagglutinin formulated with cGAMP microparticles elicits protective immune responses against influenza viruses

In humans, seasonal influenza viruses cause epidemics. Avian influenza viruses are of particular concern because they can infect multiple species and lead to unpredictable and severe disease. Therefore, there is an urgent need for a universal influenza vaccine that provides protection against all influenza strains. The cyclic GMP-AMP (cGAMP) is a promising adjuvant for subunit vaccines, which promotes type I interferons' production through the stimulator of interferon genes (STING) pathway. The encapsulation of cGAMP in acetalated dextran (Ace-DEX) microparticles (MPs) enhances its intracellular delivery. In this study, the Computationally Optimized Broadly Reactive Antigen (COBRA) methodology was used to generate H1, H3, and H5 vaccine candidates. Monovalent and multivalent COBRA HA vaccines formulated with cGAMP Ace-DEX MPs were evaluated in mice for protective antibody responses. cGAMP MPs adjuvanted COBRA HA vaccines elicited robust antigen-specific antibodies following vaccination. Compared with COBRA HA vaccine groups with no adjuvant or blank MPs, the cGAMP MPs enhanced HAI activity elicited by COBRA HA vaccines. The HAI activity was not significantly different between cGAMP MPs adjuvanted monovalent or multivalent COBRA HA vaccines. The cGAMP MPs adjuvanted COBRA vaccine groups had higher antigen-specific IgG2a-binding titers than the COBRA vaccine groups with no adjuvant or blank MPs. The COBRA vaccines formulated with cGAMP MPs mitigated diseases caused by influenza viral challenge and decreased pulmonary viral titers in mice. Therefore, the formulation of COBRA vaccines plus cGAMP MPs is a promising universal influenza vaccine that elicits protective immune responses against human seasonal and pre-pandemic strains.

IMPORTANCE

Influenza viruses cause severe respiratory disease, particularly in the very young and the elderly. Next-generation influenza vaccines are needed to protect against new influenza variants. This report used a promising adjuvant, cyclic GMP-AMP (cGAMP), to enhance the elicited antibodies by an improved influenza hemagglutinin candidate and protect against influenza virus infection. Overall, adding adjuvants to influenza vaccines is an effective method to improve vaccines.

Polymeric cGAMP microparticles affect the immunogenicity of a broadly active influenza mRNA lipid nanoparticle vaccine

Influenza outbreaks are a major burden worldwide annually. While seasonal vaccines do provide protection against infection, they are limited in that they need to be updated every year to account for the constantly mutating virus. Recently, lipid nanoparticles (LNPs) encapsulating mRNA have seen major success as a vaccine platform for SARS-CoV-2. Herein, we applied LNPs to deliver an mRNA encoding a computationally optimized broadly active (COBRA) influenza immunogen. These COBRA mRNA LNPs induced a broadly active neutralizing antibody response and protection after lethal influenza challenge. To further increase the immunogenicity of the COBRA mRNA LNPs, we combined them with acetalated dextran microparticles encapsulating a STING agonist. Contrary to recent findings, the STING agonist decreased the immunogenicity of the COBRA mRNA LNPs which was likely due to a decrease in mRNA translation as shown in vitro. Overall, this work aids in future selection of adjuvants to use with mRNA LNP vaccines.

Comparative study of acetalated-dextran microparticle fabrication methods for a clinically translatable subunit-based influenza vaccine

The most common influenza vaccines are inactivated viruses produced in chicken eggs, which is a time-consuming production method with variable efficacy due to mismatches of the vaccine strains to the dominant circulating strains. Subunit-based vaccines provide faster production times in comparison to the traditional egg-produced vaccines but often require the use of an adjuvant to elicit a highly protective immune response. However, the current FDA approved adjuvant for influenza vaccines (MF59) elicits a primarily helper T-cell type 2 (Th2)-biased humoral immune response. Adjuvants that can stimulate a Th1 cellular response are correlated to have more robust protection against influenza. The cyclic dinucleotide cGAMP has been shown to provide a potent Th1 response but requires the use of a delivery vehicle to best initiate its signalling pathway in the cytosol. Herein, acetalated dextran (Ace-DEX) was used as the polymer to fabricate microparticles (MPs) via double-emulsion, electrospray, and spray drying methods to encapsulate cGAMP. This study compared each fabrication method's ability to encapsulate and retain the hydrophilic adjuvant cGAMP. We compared their therapeutic efficacy to Addavax, an MF59-like adjuvant, and cGAMP Ace-DEX MPs provided a stronger Th1 response in vaccinated BALB/c mice. Furthermore, we compared Ace-DEX MPs to spray dried MPs composed from a commonly used polymer for drug delivery, poly(lactic-co-glycolic acid) (PLGA). We observed that all Ace-DEX MPs elicited similar humoral and cellular responses to the PLGA MPs. Overall, the results shown here indicate Ace-DEX can perform similarly to PLGA as a polymer for drug delivery and that spray drying can provide an efficient way to produce MPs to encapsulate cGAMP and stimulate the immune system.

Immunogenicity of an adjuvanted broadly active influenza vaccine in immunocompromised and diverse populations

Influenza virus outbreaks are a major burden worldwide each year. Current vaccination strategies are inadequate due to antigenic drift/shift of the virus and the elicitation of low immune responses. The use of computationally optimized broadly reactive antigen (COBRA) hemagglutinin (HA) immunogens subvert the constantly mutating viruses; however, they are poorly immunogenic on their own. To increase the immunogenicity of subunit vaccines such as this, adjuvants can be delivered with the vaccine. For example, agonists of the stimulator of interferon genes (STING) have proven efficacy as vaccine adjuvants. However, their use in high-risk populations most vulnerable to influenza virus infection has not been closely examined. Here, we utilize a vaccine platform consisting of acetalated dextran microparticles loaded with COBRA HA and the STING agonist cyclic GMP-AMP. We examine the immunogenicity of this platform in mouse models of obesity, aging, and chemotherapy-induced immunosuppression. Further, we examine vaccine efficacy in collaborative cross mice, a genetically diverse population that mimics human genetic heterogeneity. Overall, this vaccine platform had variable efficacy in these populations supporting work to better tailor adjuvants to specific populations.

Multi-COBRA hemagglutinin formulated with cGAMP microparticles elicit protective immune responses against influenza viruses

Influenza viruses cause a common respiratory disease known as influenza. In humans, seasonal influenza viruses can lead to epidemics, with avian influenza viruses of particular concern because they can infect multiple species and lead to unpredictable and severe disease. Therefore, there is an urgent need for a universal influenza vaccine that provides protection against seasonal and pre-pandemic influenza virus strains. The cyclic GMP-AMP (cGAMP) is a promising adjuvant for subunit vaccines that promotes type I interferons production through the stimulator of interferon genes (STING) pathway. The encapsulation of cGAMP in acetalated dextran (Ace-DEX) microparticles (MPs) enhances its intracellular delivery. In this study, the Computationally Optimized Broadly Reactive Antigen (COBRA) methodology was used to generate H1, H3, and H5 vaccine candidates. Monovalent and multivalent COBRA HA vaccines formulated with cGAMP Ace-DEX MPs were evaluated in a mouse model for antibody responses and protection against viral challenge. Serological analysis showed that cGAMP MPs adjuvanted monovalent and multivalent COBRA vaccines elicited robust antigen-specific antibody responses after a prime-boost vaccination and antibody titers were further enhanced after second boost. Compared to COBRA vaccine groups with no adjuvant or blank MPs, the cGAMP MPs enhanced HAI antibody responses against COBRA vaccination. The HAI antibody titers were not significantly different between cGAMP MPs adjuvanted monovalent and multivalent COBRA vaccine groups for most of the viruses tested in panels. The cGAMP MPs adjuvanted COBRA vaccines groups had higher antigen-specific IgG2a binding titers than the COBRA vaccine groups with no adjuvant or blank MPs. The COBRA vaccines formulated with cGAMP MPs mitigated disease caused by influenza viral challenge and decreased pulmonary viral titers in mice. Therefore, the formulation of COBRA vaccines plus cGAMP MPs is a promising universal influenza vaccine that elicits protective immune responses against human seasonal and pre-pandemic strains.

Cell and biomaterial delivery strategies to induce immune tolerance

The prevalence of immune-mediated disorders, including autoimmune conditions and allergies, is steadily increasing. However, current therapeutic approaches are often non-specific and do not address the underlying pathogenic condition, often resulting in impaired immunity and a state of generalized immunosuppression. The emergence of technologies capable of selectively inhibiting aberrant immune activation in a targeted, antigen (Ag)-specific manner by exploiting the body's intrinsic tolerance pathways, all without inducing adverse side effects, holds significant promise to enhance patient outcomes. In this review, we will describe the body's natural mechanisms of central and peripheral tolerance as well as innovative delivery strategies using cells and biomaterials targeting innate and adaptive immune cells to promote Ag-specific immune tolerance. Additionally, we will discuss the challenges and future opportunities that warrant consideration as we navigate the path toward clinical implementation of tolerogenic strategies to treat immune-mediated diseases.

Ethoxy acetalated dextran nanoparticles for drug delivery: A comparative study of formulation methods

Dextran-based polymers, such as ethoxy acetalated dextran (Ace-DEX), are increasingly becoming the focus of research as they offer great potential for the development of polymer-based nanoparticles as drug delivery vehicles. Their major advantages are the facile synthesis, straightforward particle preparation and the pH-dependent degradation of the particles that can be fine-tuned by the degree of acetalation of the polymer. In this study we have shown that Ace-DEX can not only compete against the commonly used and FDA-approved polymer poly(lactic-co-glycolic acid) (PLGA), but even has the potential to outperform it in its encapsulation properties, e.g., for the herein used anti-inflammatory leukotriene biosynthesis inhibitor BRP-187. We used three different methods (microfluidics, batch nanoprecipitation and emulsion solvent evaporation) for the preparation of BRP-187-loaded Ace-DEX nanoparticles to investigate the influence of the formulation technique on the physicochemical properties of the particles. Finally, we evaluated which production method offers the greatest potential for achieving the demands for a successful translation from research into pharmaceutical production by fulfilling the basic requirements, such as reaching a high loading capacity of the particles and excellent reproducibility while being simple and affordable.

Humoral Response to the Acetalated Dextran M2e Vaccine is Enhanced by Antigen Surface Conjugation

The influenza A virus causes substantial morbidity and mortality worldwide every year and poses a constant threat of an emergent pandemic. Seasonal influenza vaccination strategies fail to provide complete protection against infection due to antigenic drift and shift. A universal vaccine targeting a conserved influenza epitope could substantially improve current vaccination strategies. The ectodomain of the matrix 2 protein (M2e) of influenza is a highly conserved epitope between virus strains but is also poorly immunogenic. Administration of M2e and the immunostimulatory stimulator of interferon genes (STING) agonist 3'3'-cyclic guanosine-adenosine monophosphate (cGAMP) encapsulated in microparticles made of acetalated dextran (Ace-DEX) has previously been shown to be effective for increasing the immunogenicity of M2e, primarily through T-cell-mediated responses. Here, the immunogenicity of Ace-DEX MPs delivering M2e was further improved by conjugating the M2e peptide to the particle surface in an effort to affect B-cell responses more directly. Conjugated or encapsulated M2e co-administered with Ace-DEX MPs containing cGAMP were used to vaccinate mice, and it was shown that two or three vaccinations could fully protect against a lethal influenza challenge, while only the surface-conjugated antigen constructs could provide some protection against lethal challenge with only one vaccination. Additionally, the use of a reducible linker augmented the T-cell response to the antigen. These results show the utility of conjugating M2e to the surface of a particle carrier to increase its immunogenicity for use as the antigen in a universal influenza vaccine.

Acetalized starch-based nanoparticles stabilized acid-sensitive Pickering emulsion as a potential antitumor drug carrier

Pickering emulsions are attracting increased attention owing to their therapeutic applications. However, the slow-release property of Pickering emulsions and the in vivo solid particle accumulation caused by the solid particle stabilizer film limit their applications in therapeutic delivery. In this study, drug-loaded, acid-sensitive Pickering emulsions were prepared using acetal-modified starch-based nanoparticles as stabilizers. The acetalized starch-based nanoparticles (Ace-SNPs) not only act as a solid-particle emulsifier to stabilize Pickering emulsions but also exhibit acid sensitivity and degradability, conducive to the destabilization of Pickering emulsions to release the drug and reduce the effect of particle accumulation in an acidic therapeutic environment. In vitro drug release profiles show that 50 % of curcumin was released in 12 h in an acidic medium (pH 5.4), whereas only 14 % of curcumin was released in 12 h at higher pH (7.4), indicating that the Ace-SNP stabilized Pickering emulsion possess good acid-responsive release characteristics in acidic environments. Moreover, acetalized starch-based nanoparticles and their degradation products showed good biocompatibility, and the resulting curcumin-loaded Pickering emulsions exhibited significant anticancer activity. These features suggest that the acetalized starch-based nanoparticle-stabilized Pickering emulsion has the potential for application as an antitumor drug carrier to enhance therapeutic effects.

In Vitro Study of the Anti-inflammatory and Antifibrotic Activity of Tannic Acid-Coated Curcumin-Loaded Nanoparticles in Human Tenocytes

Tendinitis is a tendon disorder related to inflammation and pain, due to an injury or overuse of the tissue, which is hypocellular and hypovascular, leading to limited repair which occurs in a disorganized deposition of extracellular matrix that leads to scar formation and fibrosis, ultimately resulting in impaired tendon integrity. Current conventional treatments are limited and often ineffective, highlighting the need for new therapeutic strategies. In this work, acetalated-dextran nanoparticles (AcDEX NPs) loaded with curcumin and coated with tannic acid (TA) are developed to exploit the anti-inflammatory and anti-fibrotic properties of the two compounds. For this purpose, a microfluidic technique was used in order to obtain particles with a precise size distribution, aiming to decrease the batch-to-batch variability for possible future clinical translation. Coating with TA increased not only the stability of the nanosystem in different media but also enhanced the interaction and the cell-uptake in primary human tenocytes and KG-1 macrophages. The nanosystem exhibited good biocompatibility toward these cell types and a good release profile in an inflammatory environment. The efficacy was demonstrated by real-time quantitative polymerase chain reaction, in which the curcumin loaded in the particles showed good anti-inflammatory properties by decreasing the expression of NF-κb and TA-coated NPs showing anti-fibrotic effect, decreasing the gene expression of TGF-β. Overall, due to the loading of curcumin and TA in the AcDEX NPs, and their synergistic activity, this nanosystem has promising properties for future application in tendinitis.

Delivery of small molecule mast cell activators for West Nile Virus vaccination using acetalated dextran microparticles

Recently, there has been increasing interest in the activation of mast cells to promote vaccine efficacy. Several mast cell activating (MCA) compounds have been reported such as M7 and Compound 48/80 (C48/80). While these MCAs have been proven to be efficacious vaccine adjuvants, their translatability is limited by batch-to-batch variability, challenging large-scale manufacturing, and poor in vivo stability for the M7 peptide. Due to this, high throughput screening was performed to identify small molecule MCAs. Several potent MCAs were identified via this screening, but the in vivo translatability of the compounds was limited due to their poor aqueous solubility. To enhance the delivery of these MCAs we encapsulated them in acetalated dextran (Ace-DEX) microparticles (MPs). We have previously utilized Ace-DEX MPs for vaccine delivery due to their passive targeting to phagocytic cells, acid sensitivity, and tunable degradation. Four different MCA loaded MPs were combined with West Nile Virus Envelope III protein (EDIII) and their vaccine adjuvant activities were compared in vivo. MPs containing the small molecule MCA ST101036 produced the highest anti-EDIII IgG titers of all the MCAs tested. Further, ST101036 MPs produced higher titers than ST101036 formulated with PEG as a cosolvent which highlights the benefit of Ace-DEX MPs over a conventional formulation technique. Finally, in a mouse model of West Nile Virus infection ST101036 MPs produced similar survival to soluble M7 (80-90%). Overall, these data show that ST101036 MPs produce a robust antibody response against EDIII and survival emphasizing the benefits of using Ace-DEX as a delivery platform for the poorly soluble ST101036.

Vinyl Sulfone-functionalized Acetalated Dextran Microparticles as a Subunit Broadly Acting Influenza Vaccine

Influenza is a global health concern with millions of infections occurring yearly. Seasonal flu vaccines are one way to combat this virus; however, they are poorly protective against influenza as the virus is constantly mutating, particularly at the immunodominant hemagglutinin (HA) head group. A more broadly acting approach involves Computationally Optimized Broadly Reactive Antigen (COBRA). COBRA HA generates a broad immune response that is capable of protecting against mutating strains. Unfortunately, protein-based vaccines are often weekly immunogenic, so to help boost the immune response, we employed the use of acetalated dextran (Ace-DEX) microparticles (MPs) two ways: one to conjugate COBRA HA to the surface and a second to encapsulate cGAMP. To conjugate the COBRA HA to the surface of the Ace-DEX MPs, a poly(L-lactide)-polyethylene glycol co-polymer with a vinyl sulfone terminal group (PLLA-PEG-VS) was used. MPs encapsulating the STING agonist cGAMP were co-delivered with the antigen to form a broadly active influenza vaccine. This vaccine approach was evaluated in vivo with a prime-boost-boost vaccination schedule and illustrated generation of a humoral and cellular response that could protect against a lethal challenge of A/California/07/2009 in BALB/c mice.

Particle-Based therapies for antigen specific treatment of type 1 diabetes

Type 1 diabetes mellitus (T1D) is the leading metabolic disorder in children worldwide. Over time, incidence rates have continued to rise with 20 million individuals affected globally by the autoimmune disease. The current standard of care is costly and time-consuming requiring daily injections of exogenous insulin. T1D is mediated by autoimmune effector responses targeting autoantigens expressed on pancreatic islet β-cells. One approach to treat T1D is to skew the immune system away from an effector response by taking an antigen-specific approach to heighten a regulatory response through a therapeutic vaccine. An antigen-specific approach has been shown with soluble agents, but the effects have been limited. Micro or nanoparticles have been used to deliver a variety of therapeutic agents including peptides and immunomodulatory therapies to immune cells. Particle-based systems can be used to deliver cargo into the cell and microparticles can passively target phagocytic cells. Further, surface modification and controlled release of encapsulated cargo can enhance delivery over soluble agents. The induction of antigen-specific immune tolerance is imperative for the treatment of autoimmune diseases such as T1D. This review highlights studies that utilize particle-based platforms for the treatment of T1D.

Dextran Formulations as Effective Delivery Systems of Therapeutic Agents

Dextran is by far one of the most interesting non-toxic, bio-compatible macromolecules, an exopolysaccharide biosynthesized by lactic acid bacteria. It has been extensively used as a major component in many types of drug-delivery systems (DDS), which can be submitted to the next in-vivo testing stages, and may be proposed for clinical trials or pharmaceutical use approval. An important aspect to consider in order to maintain high DDS' biocompatibility is the use of dextran obtained by fermentation processes and with a minimum chemical modification degree. By performing chemical modifications, artefacts can appear in the dextran spatial structure that can lead to decreased biocompatibility or even cytotoxicity. The present review aims to systematize DDS depending on the dextran type used and the biologically active compounds transported, in order to obtain desired therapeutic effects. So far, pure dextran and modified dextran such as acetalated, oxidised, carboxymethyl, diethylaminoethyl-dextran and dextran sulphate sodium, were used to develop several DDSs: microspheres, microparticles, nanoparticles, nanodroplets, liposomes, micelles and nanomicelles, hydrogels, films, nanowires, bio-conjugates, medical adhesives and others. The DDS are critically presented by structures, biocompatibility, drugs loaded and therapeutic points of view in order to highlight future therapeutic perspectives.

Sustained delivery of CpG oligodeoxynucleotide by acetalated dextran microparticles augments effector response to Computationally Optimized Broadly Reactive Antigen (COBRA) influenza hemagglutinin

A subunit or protein-based influenza vaccine can be a safer alternative to live attenuated vaccine (Flumist) and require fewer boosts than an inactivated vaccine (e.g. Fluzone). However, to form an effective subunit vaccine, an adjuvant is often needed. In this work we used electrospray to encapsulate the hydrophilic adjuvant CpG into microparticles made from the hydrophobic biodegradable polymer acetalated dextran. To understand the rate of particle degradation on CpG release, polymer that was slow (21 h at phagosomal pH 5) and fast (0.25 h at pH 5) degrading was used to encapsulate the adjuvant. The slow-degrading particles exhibited the greatest degree of innate immune stimulation of antigen-presenting cells in vitro. In mice, the broadly acting Computationally Optimized Broadly Reactive Antigen (COBRA) Y2 influenza hemagglutinin (HA) antigen was used with CpG particles, soluble CpG, or MF-59 like adjuvant Addavax. Particles and soluble CpG elicited similar induction of anti-HA antibodies and protection against lethal influenza challenge, but the sustained release particles elicited the highest levels antibody effector functions. These results demonstrate a suitable method for encapsulation of CpG oligonucleotide in a hydrophobic particle matrix, and suggest that sustained release of CpG from Ace-DEX microparticles could potentially be used to induce potent antibody effector functions.

Developing Next-Generation Protein-Based Vaccines Using High-Affinity Glycan Ligand-Decorated Glyconanoparticles

Major diseases, such as cancer and COVID-19, are frightening global health problems, and sustained action is necessary to develop vaccines. Here, for the first time, ethoxy acetalated dextran nanoparticles (Ace-Dex-NPs) are functionalized with 9-N-(4H-thieno[3,2-c]chromene-2-carbamoyl)-Siaα2-3Galβ1-4GlcNAc (TCC Sia-LacNAc) targeting macrophages as a universal vaccine design platform. First, azide-containing oxidized Ace-Dex-NPs are synthesized. After the NPs are conjugated with ovalbumin (OVA) and resiquimod (Rd), they are coupled to TCC Sia-LacNAc-DBCO to produce TCC Sia-Ace-Dex-OVA-Rd, which induce a potent, long-lasting OVA-specific cytotoxic T-lymphocyte (CTL) response and high anti-OVA IgG, providing mice with superior protection against tumors. Next, this strategy is exploited to develop vaccines against infection by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). The receptor-binding domain (RBD) of the SARS-CoV-2 spike protein is the main target for neutralizing antibodies. The TCC Sia-Ace-Dex platform is preferentially used for designing an RBD-based vaccine. Strikingly, the synthetic TCC Sia-Ace-Dex-RBD-Rd elicited potent RBD-neutralizing antibodies against live SARS-CoV-2 infected Vero E6 cells. To develop a universal SARS-CoV-2 vaccine, the TCC Sia-Ace-Dex-N-Rd vaccine carrying SARS-CoV-2 nucleocapsid protein (N) is also prepared, which is highly conserved among SARS-CoV-2 and its variants of concern (VOCs), including Omicron (BA.1 to BA.5); this vaccine can trigger strong N-specific CTL responses against target cells infected with SARS-CoV-2 and its VOCs.

Peritumoral scaffold neutralizes tumor pH for chemotherapy sensitization and metastasis inhibition

The abnormal metabolism of rapidly growing tumors can create an acidic tumor microenvironment (TME) that renders cancer cells resistant to chemotherapy and further facilitates endothelial-to-mesenchymal transition (EMT) progress to promote metastasis. Here, we developed a combination strategy consisting of (1) peritumorally injected scaffold that alleviates TME acidosis, and (2) intravenously injected nanoparticles that delivers anti-cancer agents to tumor. Concurrent treatment with these two drug delivery systems profoundly delayed the growth of primary tumor and reduced the spontaneous metastasis to lung in an orthotopic breast cancer mouse model. Mechanism studies both in vitro and in vivo further revealed that neutralization of TME pH by the hydrogel scaffold sensitized cancer cells to nanoparticle-based chemotherapy, thereby strengthening the cytotoxicity against tumor growth; In parallel, reversal of tumor acidity downregulated various pro-metastatic proteins intratumorally to block the EMT progress, thereby reducing the metastatic potential of cancer cells. This work provided proof-of-concept demonstration that chemotherapy sensitization and EMT suppression could be synchronized by the modulation of TME pH, which may be potentially beneficial for simultaneous inhibition of tumor growth and cancer metastasis.

A predictive mechanistic model of drug release from surface eroding polymeric nanoparticles

Effective drug delivery requires ample dosing at the target tissue while minimizing negative side effects. Drug delivery vehicles such as polymeric nanoparticles (NPs) are often employed to accomplish this challenge. In this work, drug release of numerous drugs from surface eroding polymeric NPs was evaluated in vitro in physiologically relevant pH 5 and neutral buffers. NPs were loaded with paclitaxel, rapamycin, resiquimod, or doxorubicin and made from an FDA approved polyanhydride or from acetalated dextran (Ace-DEX), which has tunable degradation rates based on cyclic acetal coverage (CAC). By varying encapsulate, pH condition, and polymer, a range of distinct drug release profiles were achieved. To model the obtained drug release curves, a mechanistic mathematical model was constructed based on drug diffusion and polymer degradation. The resulting diffusion-erosion model accurately described drug release from the variety of surface eroding NPs. For drug release from varied CAC Ace-DEX NPs, the goodness of fit of the developed diffusion-erosion model was compared to several conventional drug release models. The diffusion-erosion model maintained optimal fit compared to conventional models across a range of conditions. Machine learning was then employed to estimate effective diffusion coefficients for the diffusion-erosion model, resulting in accurate prediction of in vitro release of dexamethasone and 3'3'-cyclic guanosine monophosphate-adenosine monophosphate from Ace-DEX NPs. This predictive modeling has potential to aid in the design of future Ace-DEX formulations where optimized drug release kinetics can lead to a desired therapeutic effect.

Microparticle Delivery of a STING Agonist Enables Indirect Activation of NK Cells by Antigen-Presenting Cells

Natural killer (NK) cells are an important member of the innate immune system and can participate in direct tumor cell killing in response to immunotherapies. One class of immunotherapy is stimulator of interferon gene (STING) agonists, which result in a robust type I interferon (IFN-I) response. Most mechanistic studies involving STING have focused on macrophages and T cells. Nevertheless, NK cells are also activated by IFN-I, but the effect of STING activation on NK cells remains to be adequately investigated. We show that both direct treatment with soluble STING agonist cyclic di-guanosine monophosphate-adenosine monophosphate (cGAMP) and indirect treatment with cGAMP encapsulated in microparticles (MPs) result in NK cell activation in vitro, although the former requires 100× more cGAMP than the latter. Additionally, direct activation with cGAMP leads to NK cell death. Indirect activation with cGAMP MPs does not result in NK cell death but rather cell activation and cell killing in vitro. In vivo, treatment with soluble cGAMP and cGAMP MPs both cause short-term activation, whereas only cGAMP MP treatment produces long-term changes in NK cell activation markers. Thus, this work indicates that treatment with an encapsulated STING agonist activates NK cells more efficiently than that with soluble cGAMP. In both the in vitro and in vivo systems, the MP delivery system results in more robust effects at a greatly reduced dosage. These results have potential applications in aiding the improvement of cancer immunotherapies.

Multiplexed electrospray enables high throughput production of cGAMP microparticles to serve as an adjuvant for a broadly acting influenza vaccine

Subunit vaccines employing designer antigens such as Computationally Optimized Broadly Reactive Antigen (COBRA) hemagglutinin (HA) hold the potential to direct the immune response toward more effective and broadly-neutralizing targets on the Influenza virus. However, subunit vaccines generally require coadministration with an adjuvant to elicit a robust immune response. One such adjuvant is the stimulator of interferon genes (STING) agonist cyclic dinucleotide 3'3'-cyclic guanosine monophosphate-adenosine monophosphate (cGAMP). We have shown that encapsulation of cGAMP in acetalated dextran (Ace-DEX) microparticles through electrospray results in significantly greater biological activity. Electrospray is a continuous manufacturing process which achieves excellent encapsulation efficiency. However, the throughput of electrospray with a single spray head is limited. Here we report the development of a multiplexed electrospray apparatus with an order of magnitude greater throughput than a single-head apparatus. Physicochemical characterization and evaluation of adjuvant activity in vitro and in vivo indicated that microparticles produced with the higher throughput process are equally suited for use as a potent vaccine adjuvant to induce a balanced immune response to COBRA HA antigens.

Drug delivery across the blood-brain barrier for the treatment of pediatric brain tumors - An update

Even though the last decade has seen a surge in the identification of molecular targets and targeted therapies in pediatric brain tumors, the blood brain barrier (BBB) remains a significant challenge in systemic drug delivery. This continues to undermine therapeutic efficacy. Recent efforts have identified several strategies that can facilitate enhanced drug delivery into pediatric brain tumors. These include invasive methods such as intra-arterial, intrathecal, and convection enhanced delivery and non-invasive technologies that allow for transient access across the BBB, including focused ultrasound and nanotechnology. This review discusses current strategies that are being used to enhance delivery of different therapies across the BBB to the tumor site - a major unmet need in pediatric neuro-oncology.

STING agonist-containing microparticles improve seasonal influenza vaccine efficacy and durability in ferrets over standard adjuvant

The current pandemic highlights the need for effective vaccines against respiratory viruses. An ideal vaccine should induce robust and long-lasting responses with high manufacturing scalability. We use an adjuvant comprised of a Stimulator of Interferon Genes (STING) agonist incorporated in a scalable microparticle platform to achieve durable protection against the influenza virus. This formulation overcomes the challenges presented by the cytosolic localization of STING and the hydrophilicity of its agonists. We evaluated a monoaxial formulation of polymeric acetalated dextran microparticles (MPs) to deliver the STING agonist cyclic GMP-AMP (cGAMP) which achieved >10× dose-sparing effects compared to other published work. Efficacy was evaluated in ferrets, a larger animal model of choice for influenza vaccines. cGAMP MPs with recombinant hemagglutinin reduced viral shedding and improved vaccine outcomes compared to a seasonal influenza vaccine. Importantly, sustained protection against a lethal influenza infection was detected a year after a single dose of the vaccine-adjuvant.

Glucose and H2O2 Dual-Responsive Nanocomplex Grafted with Insulin Prodrug for Blood Glucose Regulation

Although "closed-loop" smart insulin delivery systems have been extensively investigated, the majority of them suffer from low insulin loading efficiency and slow glucose response. Here, we constructed a novel nanocomplex (NC), which was prepared by electrostatic interaction between negatively charged insulin prodrug nanoparticles (NPs) and positively charged polycaprolactone-polyethylenimine (PCL-PEI) micelles. The insulin prodrug was linked to acetalated dextran (AD) via borate ester bonds to form IAD NPs, and glucose oxidase (GOx) was encapsulated in PCL-PEI micelles. The NC was negatively charged with a high insulin grafting rate (0.473 mg/mg), and in vitro experiments revealed that IAD was sensitive to hyperglycemia and H₂O₂, whereas GOx significantly improved the response to glucose by altering the microenvironment to promote sustained insulin release. Furthermore, compared with free insulin and IAD NPs, subcutaneously injected NCs in diabetic rats had long-term hypoglycemic effects, showing excellent biocompatibility in vitro and in vivo, which had good potential in insulin self-regulation delivery.

Nano/microparticle Formulations for Universal Influenza Vaccines

Influenza affects millions of people worldwide and can result in severe sickness and even death. The best method of prevention is vaccination; however, the seasonal influenza vaccine often suffers from low efficacy and requires yearly vaccination due to changes in strain and viral mutations. More conserved universal influenza antigens like M2 ectodomain (M2e) and the stalk region of hemagglutinin (HA stalk) have been used clinically but often suffer from low antigenicity. To increase antigenicity, universal antigens have been formulated using nano/microparticles as vaccine carriers against influenza. Utilizing polymers, liposomes, metal, and protein-based particles, indicators of immunity and protection in mouse, pig, ferrets, and chicken models of influenza have been shown. In this review, seasonal and universal influenza vaccine formulations comprised of these materials including their physiochemical properties, fabrication, characterization, and biologic responses in vivo are highlighted. The review is concluded with future perspectives for nano/microparticles as carrier systems and other considerations within the universal influenza vaccine delivery landscape.

Ethoxy acetalated dextran-based nanocarriers accomplish efficient inhibition of leukotriene formation by a novel FLAP antagonist in human leukocytes and blood

Leukotrienes are pro-inflammatory lipid mediators generated by 5-lipoxygenase aided by the 5-lipoxygenase-activating protein (FLAP). BRP-201, a novel benzimidazole-based FLAP antagonist, inhibits leukotriene biosynthesis in isolated leukocytes. However, like other FLAP antagonists, BRP-201 fails to effectively suppress leukotriene formation in blood, which limits its therapeutic value. Here, we describe the encapsulation of BRP-201 into poly(lactide-co-glycolide) (PLGA) and ethoxy acetalated dextran (Ace-DEX) nanoparticles (NPs), aiming to overcome these detrimental pharmacokinetic limitations and to enhance the bioactivity of BRP-201. NPs loaded with BRP-201 were produced via nanoprecipitation and the physicochemical properties of the NPs were analyzed in-depth using dynamic light scattering (size, dispersity, degradation), electrophoretic light scattering (effective charge), NP tracking analysis (size, dispersity), scanning electron microscopy (size and morphology), UV-VIS spectroscopy (drug loading), an analytical ultracentrifuge (drug release, degradation kinetics), and Raman spectroscopy (chemical attributes). Biological assays were performed to study cytotoxicity, cellular uptake, and efficiency of BRP-201-loaded NPs versus free BRP-201 to suppress leukotriene formation in primary human leukocytes and whole blood. Both PLGA- and Ace-DEX-based NPs were significantly more efficient to inhibit leukotriene formation in neutrophils versus free drug. Whole blood experiments revealed that encapsulation of BRP-201 into Ace-DEX NPs strongly increases its potency, especially upon pro-longed (≥ 5 h) incubations and upon lipopolysaccharide-challenge of blood. Finally, intravenous injection of BRP-201-loaded NPs significantly suppressed leukotriene levels in blood of mice in vivo. These results reveal the feasibility of our pharmacological approach using a novel FLAP antagonist encapsulated into Ace-DEX-based NPs with improved efficiency in blood to suppress leukotriene biosynthesis.

Design of Biopolymer-Based Interstitial Therapies for the Treatment of Glioblastoma

Glioblastoma multiforme (GBM) is the most common form of primary brain cancer and has the highest morbidity rate and current treatments result in a bleak 5-year survival rate of 5.6%. Interstitial therapy is one option to increase survival. Drug delivery by interstitial therapy most commonly makes use of a polymer implant encapsulating a drug which releases as the polymer degrades. Interstitial therapy has been extensively studied as a treatment option for GBM as it provides several advantages over systemic administration of chemotherapeutics. Primarily, it can be applied behind the blood–brain barrier, increasing the number of possible chemotherapeutic candidates that can be used and reducing systemic levels of the therapy while concentrating it near the cancer source. With interstitial therapy, multiple drugs can be released locally into the brain at the site of resection as the polymer of the implant degrades, and the release profile of these drugs can be tailored to optimize combination therapy or maintain synergistic ratios. This can bypass the blood–brain barrier, alleviate systemic toxicity, and resolve drug resistance in the tumor. However, tailoring drug release requires appropriate consideration of the complex relationship between the drug, polymer, and formulation method. Drug physicochemical properties can result in intermolecular bonding with the polymeric matrix and affect drug distribution in the implant depending on the formulation method used. This review is focused on current works that have applied interstitial therapy towards GBM, discusses polymer and formulation methods, and provides design considerations for future implantable biodegradable materials.

Collagenase-loaded pH-sensitive nanocarriers efficiently remodeled tumor stroma matrixes and improved the enrichment of nanomedicines

The dense extracellular matrix (ECM) in tumor tissue severely hinders the penetration and enrichment of antitumor nanomedicines, which could significantly affect their efficiency. In this study, we used pH-sensitive nanocarriers loaded with collagenase (Col) to remold the tumor microenvironment (TME). Furthermore, we combined the collagenase delivery system with a nanomedicine to improve its penetration and enrichment in the tumor, thereby improving efficacy. We synthesized acetalated dextran (Ace-DEX) with an ideal pH-sensitivity as the carrier material of collagenase. Under mild preparation conditions, collagenase was loaded into Ace-DEX nanoparticles (NPs) with a high loading capacity (>4%) and remained highly active (>90%). Col-carrying NPs (Col-NPs) significantly reduced the tumor collagen content by 15.1%. Pretreatment with Col-NPs increased the accumulation of doxorubicin (DOX)-loaded liposome (DOX-Lipo) in the tumor by 2.8-fold. There were no safety concerns as the Col-NP showed no significant toxicity and reduced Col-induced damage to healthy tissues. Additionally, the number of circulating tumor cells remained unchanged after Col-NP treatment, suggesting no increased risk of tumor metastasis. Because the Col-NP acts essentially independent of the subsequent treatment, it has considerable potential for enhancing many existing delivery systems and drugs for cancer treatment. It may also be used for treating other collagen-related diseases.

Acetalated dextran based nano- and microparticles: synthesis, fabrication, and therapeutic applications

Acetalated dextran (Ac-DEX) is a pH-responsive dextran derivative polymer. Prepared by a simple acetalation reaction, Ac-DEX has tunable acid-triggered release profile. Despite its relatively short research history, Ac-DEX has shown great potential in various therapeutic applications. Furthermore, the recent functionalization of Ac-DEX makes versatile derivatives with additional properties. Herein, we summarize the cutting-edge development of Ac-DEX and related polymers. Specifically, we focus on the chemical synthesis, nano- and micro-particle fabrication techniques, the controlled-release mechanisms, and the rational design Ac-DEX-based of drug delivery systems in various biomedical applications. Finally, we briefly discuss the challenges and future perspectives in the field.

Merozoite surface protein 2 adsorbed onto acetalated dextran microparticles for malaria vaccination

Malaria remains a global health threat, with significant morbidity and mortality worldwide despite current interventions. The human disease is caused by five different parasitic species, with Plasmodium falciparum being the deadliest. As a result, vaccine research against P. falciparum is a global priority. Merozoite surface protein 2 (MSP2) is a promising vaccine antigen as MSP2-specific antibodies have been shown previously to be protective against malaria infection. In this study, the formulation of an MSP2 vaccine was explored to enhance antigen uptake and achieve both an antibody and Th1 immune response by adsorbing MSP2 antigen onto a biomaterial carrier system. Specifically, MSP2 antigen was adsorbed onto acetalated dextran (Ace-DEX) microparticles (MPs). IgG and IgG2a titers elicited by the Ace-DEX MP platform were compared to titer levels elicited by MSP2 adsorbed to an FDA-approved alum adjuvant, MSP2 alone, and PBS alone. Both adsorption of MSP2 to Ace-DEX MPs and to alum elicited antibody responses in vivo, but only the formulation containing Ace-DEX MPs was able to elicit a significant Th1-biased response needed to combat the intracellular pathogen. As such, MSP2 adsorbed to Ace-DEX MPs demonstrates promise as a malaria vaccine.

Injectable, Ribbon-Like Microconfetti Biopolymer Platform for Vaccine Applications

Previously, high-aspect- ratio ribbon-like microconfetti (MC) composed of acetalated dextran (Ace-DEX) have been shown to form a subcutaneous depot for sustained drug release. In this study, MC were explored as an injectable vaccine platform. Production of MC by electrospinning followed by high-shear homogenization allowed for precise control over MC fabrication. Three distinct sizes of MC, small (0.67 × 10.2 μm²), medium (1.28 × 20.7 μm²), and large (5.67 × 90.2 μm²), were fabricated and loaded with the adjuvant, resiquimod. Steady release rates of resiquimod were observed from MC, indicating their ability to create an immunostimulatory depot in vivo. Resiquimod-loaded MC stimulated inflammatory cytokine production in bone marrow-derived dendritic cells without incurring additional cytotoxicity in vitro. Interestingly, even medium and large MC were able to be internalized by antigen-presenting cells and facilitate antigen presentation when ovalbumin was adsorbed onto their surface. After subcutaneous injection in vivo with adsorbed ovalbumin, blank MC of all sizes were found to stimulate a humoral response. Adjuvant activity of resiquimod was enhanced by loading it into MC and small- and medium-sized MC effectively induced a Th1-skewed immune response. Antigen co-delivered with adjuvant-loaded MC of various sizes illustrates a new potential vaccine platform.

Tumor Responsive and Tunable Polymeric Platform for Optimized Delivery of Paclitaxel to Treat Glioblastoma

Current interstitial therapies for glioblastoma can overcome the blood-brain barrier but fail to optimally release therapy at a rate that stalls cancer reoccurrence. To address this lapse, acetalated dextran (Ace-DEX) nanofibrous scaffolds were used for their unique degradation rates that translate to a broad range of drug release kinetics. A distinctive range of drug release rates was illustrated via electrospun Ace-DEX or poly(lactic acid) (PLA) scaffolds. Scaffolds composed of fast, medium, and slow degrading Ace-DEX resulted in 14.1%, 2.9%, and 1.3% paclitaxel released per day. To better understand the impact of paclitaxel release rate on interstitial therapy, two clinically relevant orthotopic glioblastoma mouse models were explored: (1) a surgical model of resection and recurrence (resection model) and (2) a distant metastasis model. The effect of unique drug release was illustrated in the resection model when a 78% long-term survival was observed with combined fast and slow release scaffolds, in comparison to a survival of 20% when the same dose is delivered at a medium release rate. In contrast, only the fast release rate scaffold displayed treatment efficacy in the distant metastasis model. Additionally, the acid-sensitive Ace-DEX scaffolds were shown to respond to the lower pH conditions associated with GBM tumors, releasing more paclitaxel in vivo when a tumor was present in contrast to nonacid sensitive PLA scaffolds. The unique range of tunable degradation and stimuli-responsive nature makes Ace-DEX a promising drug delivery platform to improve interstitial therapy for glioblastoma.

Synergistic drug combinations for a precision medicine approach to interstitial glioblastoma therapy

Glioblastoma (GBM) is a highly aggressive and heterogeneous form of brain cancer. Genotypic and phenotypic heterogeneity drives drug resistance and tumor recurrence. Combination chemotherapy could overcome drug resistance; however, GBM's location behind the blood-brain barrier severely limits chemotherapeutic options. Interstitial therapy, delivery of chemotherapy locally to the tumor site, via a biodegradable polymer implant can overcome the blood-brain barrier and increase the range of drugs available for therapy. Ideal drug candidates for interstitial therapy are those that are potent against GBM and work in combination with both standard-of-care therapy and new precision medicine targets. Herein we evaluated paclitaxel for interstitial therapy, investigating the effect of combination with both temozolomide, a clinical standard-of-care chemotherapy for GBM, and everolimus, a mammalian target of rapamycin (mTOR) inhibitor that modulates aberrant signaling present in >80% of GBM patients. Tested against a panel of GBM cell lines in vitro, paclitaxel was found to be effective at nanomolar concentrations, complement therapy with temozolomide, and synergize strongly with everolimus. The strong synergism seen with paclitaxel and everolimus was then explored in vivo. Paclitaxel and everolimus were separately formulated into fibrous scaffolds composed of acetalated dextran, a biodegradable polymer with tunable degradation rates, for implantation in the brain. Acetalated dextran degradation rates were tailored to attain matching release kinetics (~3% per day) of both paclitaxel and everolimus to maintain a fixed combination ratio of the two drugs. Combination interstitial therapy of both paclitaxel and everolimus significantly reduced GBM growth and improved progression free survival in two clinically relevant orthotopic models of GBM resection and recurrence. This work illustrates the advantages of synchronized interstitial therapy of paclitaxel and everolimus for post-surgical tumor control of GBM.

Carbohydrate Conjugates in Vaccine Developments

Vaccines are powerful tools that can activate the immune system for protection against various diseases. As carbohydrates can play important roles in immune recognition, they have been widely applied in vaccine development. Carbohydrate antigens have been investigated in vaccines against various pathogenic microbes and cancer. Polysaccharides such as dextran and β-glucan can serve as smart vaccine carriers for efficient antigen delivery to immune cells. Some glycolipids, such as galactosylceramide and monophosphoryl lipid A, are strong immune stimulators, which have been studied as vaccine adjuvants. In this review, we focus on the current advances in applying carbohydrates as vaccine delivery carriers and adjuvants. We will discuss the examples that involve chemical modifications of the carbohydrates for effective antigen delivery, as well as covalent antigen-carbohydrate conjugates for enhanced immune responses.

Impact of composite scaffold degradation rate on neural stem cell persistence in the glioblastoma surgical resection cavity

Tumoricidal neural stem cells (NSCs) are an emerging therapy to combat glioblastoma (GBM). This therapy employs genetically engineered NSCs that secrete tumoricidal agents to seek out and kill tumor foci remaining after GBM surgical resection. Biomaterial scaffolds have previously been utilized to deliver NSCs to the resection cavity. Here, we investigated the impact of scaffold degradation rate on NSC persistence in the brain resection cavity. Composite acetalated dextran (Ace-DEX) gelatin electrospun scaffolds were fabricated with two distinct degradation profiles created by changing the ratio of cyclic to acyclic acetal coverage of Ace-DEX. In vitro, fast degrading scaffolds were fully degraded by one week, whereas slow degrading scaffolds had a half-life of >56 days. The scaffolds also retained distinct degradation profiles in vivo. Two different NSC lines readily adhered to and remained viable on Ace-DEX gelatin scaffolds, in vitro. Therapeutic NSCs secreting tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) had the same TRAIL output as tissue culture treated polystyrene (TCPS) when seeded on both scaffolds. Furthermore, secreted TRAIL was found to be highly potent against the human derived GBM cell line, GBM8, in vitro. Firefly luciferase expressing NSCs were seeded on scaffolds, implanted in a surgical resection cavity and their persistence in the brain was monitored by bioluminescent imaging (BLI). NSC loaded scaffolds were compared to a direct injection (DI) of NSCs in suspension, which is the current clinical approach to NSC therapy for GBM. Fast and slow degrading scaffolds enhanced NSC implantation efficiency 2.87 and 3.08-fold over DI, respectively. Interestingly, scaffold degradation profile did not significantly impact NSC persistence. However, persistence and long-term survival of NSCs was significantly greater for both scaffolds compared to DI, with scaffold implanted NSCs still detected by BLI at day 120 in most mice. Overall, these results highlight the benefit of utilizing a scaffold for application of tumoricidal NSC therapy for GBM.

Electrospray for generation of drug delivery and vaccine particles applied in vitro and in vivo

Also known as electrospray, electrohydrodynamic atomization has been used extensively in the last 15 years to develop polymer-based particles for drug delivery in cell and animal models. More recently, novel core-shell, multi-axial, and other electrospray particles have been developed from an array of polymers for a variety of biomedical applications. This review focuses on electrospray as a novel method of particle fabrication for drug delivery, specifically highlighting the applications of these particle systems in cell culture and animal models while also discussing polymers used for particle fabrication. Applications of electrospray particles to treat glioma, ovarian cancer, and breast cancer are reviewed. Additionally, delivery of antibiotics, gene therapy, and bacterial cells formulated in electrospray particles is discussed. Finally, vaccines as well as drug eluting particles for differentiation of stem cells and tissue engineering are highlighted. The article concludes with a discussion of where the future of electrospray technology can go to strengthen its foothold in the biomedical field.

Tailored Design of an ROS-Responsive Drug Release Platform for Enhanced Tumor Therapy via "Sequential Induced Activation Processes"

The reactive oxygen species (ROS)-responsive intelligent drug delivery system has developed rapidly in recent years. However, because of the low concentration of ROS in most types of tumor cells, it is not possible to rapidly and effectively stimulate the drug delivery system to release the active drug. Here, we introduced "sequential induced activation processes" for efficient tumor therapy by designing a new ROS-responsive drug release platform. β-Lapachone, a positively charged nitrogen mustard (NM) prodrug, and two diblock molecules (mPEG-AcMH and PAsp-AcMH) are self-assembled to form prodrug primary micelles, which are further aggregated into nanoparticles that facilitate drug codelivery. When administered by intravenous injection, the nanoparticles reach the tumor site and enter the tumor cells by endocytosis. The β-lapachone released in the tumor cells induces a large amount of H₂O₂, and the ROS-responsive NM prodrug is activated to form activated NM, quinone methide, and boric acid under the induction of H₂O₂. The activated NM leads to tumor cell apoptosis.

A microparticle platform for STING-targeted immunotherapy enhances natural killer cell- and CD8+ T cell-mediated anti-tumor immunity

Immunotherapies have significantly improved cancer patient survival, but response rates are still limited. Thus, novel formulations are needed to expand the breadth of immunotherapies. Pathogen associated molecular patterns (PAMPs) can be used to stimulate an immune response, but several pathogen recognition receptors are located within the cell, making delivery challenging. We have employed the biodegradable polymer acetalated dextran (Ace-DEX) to formulate PAMP microparticles (MPs) in order to enhance intracellular delivery. While treatment with four different PAMP MPs resulted in tumor growth inhibition, cyclic GMP-AMP (cGAMP) MPs were most effective. cGAMP MPs showed anti-tumor efficacy at doses 100-1000 fold lower than published doses of soluble cGAMP in two murine tumor models. Treatment with cGAMP MPs resulted in increased natural killer cell numbers in the tumor environment. Immune cell depletion studies confirmed that NK cells were responsible for the anti-tumor efficacy in an aggressive mouse melanoma model. NK cells and CD8⁺ T cells were both required for early anti-tumor function in a triple negative breast cancer model. In summary, cGAMP MP treatment results in NK and T cell-dependent anti-tumor immune response.

In Vivo and Cellular Trafficking of Acetalated Dextran Microparticles for Delivery of a Host-Directed Therapy for Salmonella enterica Serovar Typhi Infection

Previously we have encapsulated host-directed therapy AR-12 into acetalated dextran (Ace-DEX) microparticles (MPs) to mitigate drug toxicity and passively target phagocytic host cells. Herein, we have improved upon our initial emulsion-based formulation of Ace-DEX MPs encapsulating AR-12 (AR-12/MPs) by improving the drug encapsulation efficiency, evaluating sterilization processes for manufacturing, and understanding cellular and in vivo trafficking of the MPs. By using an alternative solvent system, ethyl acetate, we report an increased encapsulation efficiency of AR-12 while maintaining the pH-responsive degradation kinetics of Ace-DEX MPs. To better manufacture this novel antimicrobial formulation, we sterilized AR-12/MPs by gamma irradiation or ethylene oxide and evaluated their efficacy against intracellular Salmonella enterica serovar Typhi. Sterilized AR-12/MPs resulted in a significant reduction in intracellular bacterial burden compared to Blank/MPs. We also characterized intracellular trafficking of Ace-DEX MPs encapsulating fluorophores, which demonstrated internalization of MPs in endo/lysosomal compartments and time and degradation-rate dependent lysosomal escape into cytosolic compartments. Additionally, in vivo toxicity was mitigated following encapsulation of AR-12, where the maximum tolerated dose of AR-12 was increased compared to soluble treatment via intranasal, intravenous, and intraperitoneal administration routes. Following in vivo trafficking of Ace-DEX MPs via the same routes, intranasal administration demonstrated the highest accumulation in the lungs, liver, and kidneys, which persisted out to 240 h. Overall, we have advanced the formulation of this host-directed therapy and broadened the understanding of Ace-DEX MP delivery.

Acetalated Dextran Microparticles for Codelivery of STING and TLR7/8 Agonists

Vaccines are the most effective tool for preventing infectious diseases; however, subunit vaccines, considered the safest type, suffer from poor immunogenicity and require adjuvants to create a strong and sustained immune response. As adjuvants, pathogen-associated molecular patterns (PAMPs) offer potent immunostimulatory properties and defined mechanisms of action through their cognate pattern recognition receptors (PRRs). Their activity can be further enhanced through combining two or more PAMPs, particularly those that activate multiple immune signaling pathways. However, the cytosolic localization of many PRRs requires intracellular delivery of PAMPs for optimal biological activity, which is particularly true of the stimulator of interferon genes (STING) PRR. Using acetalated dextran (Ace-DEX) microparticles (MPs) encapsulating STING agonist 3'3'-cyclic GMP-AMP (cGAMP) combined with soluble PAMPS, we screened the effect of codelivery of adjuvants using primary mouse bone marrow derived dendritic cells (BMDCs). We identified that codelivery of cGAMP MPs and soluble Toll-like receptor 7/8 (TLR7/8) agonist resiquimod (R848) elicited the broadest cytokine response. cGAMP and R848 were then coencapsulated within Ace-DEX MPs via electrospray. Using the model antigen ovalbumin, we observed that Ace-DEX MPs coencapsulating cGAMP and R848 (cGAMP/R848 Ace-DEX MPs) induced antigen-specific cellular immunity, and a balanced Th1/Th2 humoral response that was greater than cGAMP Ace-DEX MPs alone and PAMPs delivered in separate MPs. These data indicate that polymeric Ace-DEX MPs loaded with STING and TLR7/8 agonists represent a potent cellular and humoral vaccine adjuvant.

Investigation of tunable acetalated dextran microparticle platform to optimize M2e-based influenza vaccine efficacy

Influenza places a significant health and economic burden on society. Efficacy of seasonal influenza vaccines can be suboptimal due to poor matching between vaccine and circulating viral strains. An influenza vaccine that is broadly protective against multiple virus strains would significantly improve vaccine efficacy. The highly conserved ectodomain of matrix protein 2 (M2e) and 3'3' cyclic GMP-AMP (cGAMP) were selected as the antigen and adjuvant, respectively, to develop the basis for a potential universal influenza vaccine. The magnitude and kinetics of adaptive immune responses can have great impact on vaccine efficacy. M2e and cGAMP were therefore formulated within acetalated dextran (Ace-DEX) microparticles (MPs) of varying degradation profiles to examine the effect of differential vaccine delivery on humoral, cellular, and protective immunity. All Ace-DEX MP vaccines containing M2e and cGAMP elicited potent humoral and cellular responses in vivo and offered substantial protection against a lethal influenza challenge, suggesting significant vaccine efficacy. Serum antibodies from Ace-DEX MP vaccinated mice also demonstrated cross reactivity against M2e sequences of various viral strains, which indicates the potential for broadly protective immunity. Of all the formulations tested, the slowest-degrading M2e or cGAMP MPs elicited the greatest antibody production, cellular response, and protection against a viral challenge. This indicated the importance of flexible control over antigen and adjuvant delivery. Overall, robust immune responses, cross reactivity against multiple viral strains, and tunable delivery profiles make the Ace-DEX MP platform a powerful subunit vaccine delivery system.

Prevention of Type 1 Diabetes with Acetalated Dextran Microparticles Containing Rapamycin and Pancreatic Peptide P31

Type 1 diabetes (T1D) is a common autoimmune disease with no cure. T1D subjects are dependent on daily exogenous insulin administration, due to the loss of functional insulin-producing β cells. Needed are immunotherapies that prevent and/or treat T1D. One approach of immunotherapy is to administer an autoantigen to selectively tolerize diabetogenic effector T cells without global immunosuppression. To date, however, strategies of antigen-specific immunotherapy are largely ineffective in the clinic. Using an antigen-specific approach, a biodegradable polymeric delivery vehicle, acetalated dextran microparticles (Ace-DEX MPs), is applied and T1D development is prevented through coadministration of the immunosuppressant rapamycin and the diabetogenic peptide P31 (Rapa/P31/MPs), via alterations of both innate and adaptive immunity. Ex vivo, adoptively transferred CD4⁺ T cells exhibit reduced proliferation and an increased ratio of FoxP3⁺ to IFNγ⁺ T cells. In vitro analysis indicates dendritic cells exhibit a less mature phenotype following coculture with Rapa/P31/MPs, which results in reduced CD4⁺ T cell proliferation and proinflammatory cytokine production (IFNγ and IL-2), but promotes PD-1 expression. Together these results demonstrate Ace-DEX MP-based antigen-specific therapy effectively tolerizes diabetogenic CD4⁺ T cells to prevent T1D, thereby demonstrating one of the first successful attempts of T1D prevention using a single-formulation particulate delivery platform.

Delivery of Cargo with a Bioelectronic Trigger

Biological systems exchange information often with chemical signals. Here, we demonstrate the chemical delivery of a fluorescent label using a bioelectronic trigger. Acid-sensitive microparticles release fluorescin diacetate upon low pH induced by a bioelectronic device. Cardiac fibroblast cells (CFs) uptake fluorescin diacetate, which transforms into fluorescein and emits a fluorescent signal. This proof-of-concept bioelectronic triggered delivery may be used in the future for real-time programming and control of cells and cell systems.

Tunable degradation of acetalated dextran microparticles enables controlled vaccine adjuvant and antigen delivery to modulate adaptive immune responses

Subunit vaccines are often poorly immunogenic, and adjuvants and/or delivery vehicles, such as polymeric microparticles (MPs), can be used to enhance immune responses. MPs can also be used to understand cell activation kinetics and the significant impact antigen and adjuvant release has on adaptive immune responses. By controlling antigen and adjuvant release, we can determine if it is important to have precise temporal control over release of these elements to optimize the peak and duration of protective immunity and improve vaccine safety profiles. In order to study the effect of tunable adjuvant or antigen delivery on generation of adaptive immunity, we used acetalated dextran (Ace-DEX) MPs. Ace-DEX MPs were used because their tunable degradation can be controlled based on polymer cyclic acetal coverage (CAC). Ace-DEX MPs of varying degradation profiles were used to deliver murabutide or ovalbumin (OVA) as a model adjuvant or antigen, respectively. When murabutide was encapsulated within Ace-DEX MPs to test for controlled adjuvant delivery, fast-degrading MPs exhibited higher humoral and cellular responses in vivo at earlier time points, while slow-degrading MPs resulted in stronger responses at later time points. When OVA was encapsulated within Ace-DEX MPs to test for controlled antigen delivery, fast-degrading MPs induced greater antibody and cytokine production throughout the length of the experiment. This differential response suggests the need for distinct, flexible control over adjuvant or antigen delivery and its impact on immune response modulation.

Sustained Delivery of Doxorubicin via Acetalated Dextran Scaffold Prevents Glioblastoma Recurrence after Surgical Resection

The primary cause of mortality for glioblastoma (GBM) is local tumor recurrence following standard-of-care therapies, including surgical resection. With most tumors recurring near the site of surgical resection, local delivery of chemotherapy at the time of surgery is a promising strategy. Herein drug-loaded polymer scaffolds with two distinct degradation profiles were fabricated to investigate the effect of local drug delivery rate on GBM recurrence following surgical resection. The novel biopolymer, acetalated dextran (Ace-DEX), was compared with commercially available polyester, poly(l-lactide) (PLA). Steady-state doxorubicin (DXR) release from Ace-DEX scaffolds was found to be faster when compared with scaffolds composed of PLA, in vitro. This increased drug release rate translated to improved therapeutic outcomes in a novel surgical model of orthotopic glioblastoma resection and recurrence. Mice treated with DXR-loaded Ace-DEX scaffolds (Ace-DEX/10DXR) resulted in 57% long-term survival out to study completion at 120 days compared with 20% survival following treatment with DXR-loaded PLA scaffolds (PLA/10DXR). Additionally, all mice treated with PLA/10DXR scaffolds exhibited disease progression by day 38, as defined by a 5-fold growth in tumor bioluminescent signal. In contrast, 57% of mice treated with Ace-DEX/10DXR scaffolds displayed a reduction in tumor burden, with 43% exhibiting complete remission. These results underscore the importance of polymer choice and drug release rate when evaluating local drug delivery strategies to improve prognosis for GBM patients undergoing tumor resection.

A robust microparticle platform for a STING-targeted adjuvant that enhances both humoral and cellular immunity during vaccination

Most FDA-approved adjuvants for infectious agents boost humoral but not cellular immunity, and have poorly-understood mechanisms. Stimulator of interferon genes (STING, also known as MITA, MPYS, or ERIS) is an exciting adjuvant target due to its role in cyclic dinucleotide (CDN)-driven anti-viral immunity; however, a major hindrance is STING's cytosolic localization which requires intracellular delivery of its agonists. As a result, STING agonists administered in a soluble form have elicited suboptimal immune responses. Delivery of STING agonists via particle platforms has proven a more successful strategy, but the opportunity for improved formulations and bioactivity remains. In this study we evaluated the adjuvant activity of the potent STING agonist, CDN 3'3'-cGAMP (cGAMP), encapsulated in acid-sensitive acetalated dextran (Ace-DEX) polymeric microparticles (MPs) which passively target antigen-presenting cells for intracellular release. This formulation was superior to all particle delivery systems evaluated and maintained its bioactivity following a sterilizing dose of gamma irradiation. Compared to soluble cGAMP, the Ace-DEX cGAMP MPs enhanced type-I interferon responses nearly 1000-fold in vitro and 50-fold in vivo, caused up to a 104-fold boost in antibody titers, increased Th1-associated responses, and expanded germinal center B cells and memory T cells. Furthermore, the encapsulated cGAMP elicited no observable toxicity in animals and achieved protective immunity against a lethal influenza challenge seven months post-immunization when using CDN adjuvant doses up to 100-fold lower than previous reports. For these reasons, Ace-DEX MP-encapsulated cGAMP represents a potent vaccine adjuvant of humoral and cellular immunity.

Diblock copolymer glyco-nanomicelles constructed by a maltoheptaose-based amphiphile for reduction- and pH-mediated intracellular drug delivery

A new type of reduction- and pH-mediated glyco-polymeric micelles was synthesized for the antitumor drug doxorubicin (DOX) delivery in this study.