The Association Between Short-Acting ß2-Agonist Over-Prescription, and Patient-Reported Acquisition and Use on Asthma Control and Exacerbations: Data from Australia.

INTRODUCTION: In Australia, short-acting ß2-agonists (SABA) are available both over the counter (OTC) and on prescription. This ease of access may impact SABA use in the Australian population. Our aim was to assess patterns and outcome associations of prescribed, acquired OTC and reported use of SABA by Australians with asthma. METHODS: This was a cross-sectional study, using data derived from primary care electronic medical records (EMRs) and patient completed questionnaires within Optimum Patient Care Research Database Australia (OPCRDA). A total of 720 individuals aged ≥ 12 years with an asthma diagnosis in their EMRs and receiving asthma therapy were included. The annual number of SABA inhalers authorised on prescription, acquired OTC and reported, and the association with self-reported exacerbations and asthma control were investigated. RESULTS: 92.9% (n = 380/409) of individuals issued with SABA prescription were authorised ≥ 3 inhalers annually, although this differed from self-reported usage. Of individuals reporting SABA use (n = 546) in the last 12 months, 37.0% reported using ≥ 3 inhalers. These patients who reported SABA overuse experienced 2.52 (95% confidence interval [CI] 1.73-3.70) times more severe exacerbations and were 4.51 times (95% CI 3.13-6.55) more likely to have poor asthma control than those who reported using 1-2 SABA inhalers. Patients who did not receive SABA on prescription (43.2%; n = 311/720) also experienced 2.71 (95% CI 1.07-7.26) times more severe exacerbations than those prescribed 1-2 inhalers. Of these patients, 38.9% reported using OTC SABA and other prescription medications, 26.4% reported using SABA OTC as their only asthma medication, 13.2% were prescribed other therapies but not SABA OTC and 14.5% were not using any medication. CONCLUSION: Both self-reported SABA overuse and zero SABA prescriptions were associated with poor asthma outcomes. The disconnect between prescribing authorisation, OTC availability and actual use, make it difficult for clinicians to quantify SABA use.

Vaccine delivery by zwitterionic polysaccharide-based hydrogel microparticles showing enhanced immunogenicity and suppressed foreign body responses.

The controlled release of antigens from injectable depots has been actively pursued to achieve long-lasting immune responses in vaccine development. Nonetheless, subcutaneous depots are often susceptible to foreign body responses (FBRs) dominated by macrophage clearance and fibrotic encapsulation, resulting in limited antigen delivery to target dendritic cells (DCs) that bridge innate and adaptive immunity. Here, we aim to develop a long-term antigen depot that can bypass FBR and engage DCs to mature and migrate to lymph nodes to activate antigen-specific T-cells. Leveraging the immunomodulatory properties of exogenous polysaccharides and the anti-fouling characteristics of zwitterionic phosphorylcholine (PC) polymers, we developed a PC functionalized dextran (PCDX) hydrogel for long-term antigen delivery. We observed that PCDX in both injectable scaffold and microparticle (MP) forms could effectively evade FBR as the anionic carboxymethyl DX (CMDX) in vitro and in vivo. Meanwhile, PCDX provided slower and longer release of antigens than CMDX, resulting in local enrichment of CD11c+ DCs at the MP injection sites. DC cultured on PCDX exhibited stronger immunogenic activation with higher CD86, CD40, and MHC-I/peptide complex than CMDX. PCDX also generated DC with greater propensity in migration to lymph nodes, as well as antigen presentations to trigger both CD4+ and CD8+ arms of T-cell responses, as compared to other charge derivatives of DX. Besides cellular responses, PCDX could also induce more durable and potent humoral responses, with higher levels of antigen specific IgG1 and IgG2a by day 28, as compared to other treatment groups. In conclusion, PCDX can incorporate the benefits of both immunogenic DX and anti-fouling properties of zwitterionic PC and thus, shows great promise in providing long-term delivery of antigens for vaccine development.

Stochastic Lattice-Based Modeling of Macromolecule Release from Degradable Hydrogel.

A three-dimensional lattice-based model has been developed to describe the release of a macromolecular drug encapsulated in a degradable hydrogel. The degradation-induced network heterogeneity is considered by assigning varying diffusion coefficients to the lattice sites based on the fitted exponential node-diffusivity relationship. As time passes, due to the degradation of crosslink nodes, diffusivity values in lattice sites progress to higher values. To overcome the size limitation of the computational model and to compare it with experimental data, a scaling ratio based on the random walk equation is developed. The model was able to describe the experimental release data from chemically crosslinked dextran hydrogels. The results showed that the effect of the initial network and the chemistry of crosslink nodes (hydrolysis rate) on the drug release profile cannot be decoupled.

The effect of polysaccharide-based hydrogels on the response of antigen-presenting cell lines to immunomodulators.

Hydrogel presents as foreign material to the host and participates in immune responses, which skew the biofunctions of immunologic loads (antigen and adjuvants) during in situ DC priming. This study aims to investigate the effect of the hydrogel made from different polysaccharides on macrophage (RAW264.7) activation and DC (JAWSII) modulation. We adopted polysaccharides of different sugar chemistry to fabricate hydrogels. Hyaluronate (HA), glycol chitosan (GC) and dextran (DX) were functionalized with vinyl sulfone and chemically cross-linked with dithiothreitol via thiol-click chemistry. We found that HA reduced macrophage adhesion and activation on the hydrogel surface. GC and DX promoted M1 polarization in terms of higher CCR7 expression and TNF-α, IL-6 production. In terms of DC engagement, GC promoted antigen uptake by JAWSII and all hydrogels promoted antigen presentation on MHC-I molecules. GC and DX favoured the generation of immunogenic DC while accommodating immunostimulatory functions of IFN-γ and polyI:C or LPS during co-incubation. Particularly, the co-incubation of IP with GC promoted CCR7 expression on JAWSII. Conversely, HA was more appropriate for the construction of a tolerogenic DC priming platform. We observed that HA did not induce co-stimulatory markers expression on DC but suppressed the action of LPS in inducing TNF-α generation. Moreover, when immunosuppressive cytokines, IL-10 and TGF-ß were added, cytokines' immunosuppressive action was amplified by hydrogel bedding, HA, GC and to a less extent DX in suppressing LPS-induced IL-6 generation from JAWSII. We concluded that HA is preferable for tolerogenic DC development while minimizing the macrophage response in conferring foreign body response, whereas DX and GC are more appropriate for immunogenic DC development. This study demonstrates the potential of polysaccharides in conferring in situ DC priming together with antigen and adjuvant loads while addressing the tradeoff between the foreign body responses and DC engagement by selecting appropriate polysaccharides for the hydrogel platform construction.

A bioinspired synthetic soft hydrogel for the treatment of dry eye.

Natural soft hydrogels are unique elastic soft materials utilized by living organisms for protecting delicate tissues. Under a theoretical framework derived from the Blob model, we chemically crosslinked high molecular weight hyaluronic acid at a concentration close to its overlap concentration (c*), and created synthetic soft hydrogels that exhibited unique rheological properties similar to a natural soft hydrogel: being dominantly elastic under low shear stress while being viscous when the stress is above a small threshold. We explored a potential application of the hyaluronic acid-based soft hydrogel as a long-acting ocular surface lubricant and evaluated its therapeutic effects for dry eye. The soft hydrogel was found to be biocompatible after topical instillation on experimental animals' and companion dogs' eyes. In a canine clinical study, twice-a-day ocular instillation of the soft hydrogel in combination with cyclosporine for 1 month improved the clinical signs in more than 65% of dog patients previously unresponsive to cyclosporine treatment.

Controllable multi-phase protein release from in-situ hydrolyzable hydrogel.

Using hydrogels to control the long-term release of protein remains challenging, especially for in-situ forming formulations. The uncontrollable burst release in the initial phase, the halted release in the subsequent phase, and the undesired drug dumping at the late stage are some obstacles hydrogel-based depots commonly encounter. In this study, we report hydrolyzable dextran-based hydrogels crosslinked by Michael addition to demonstrate a systematic solution to solve these problems. First, the polymer concentration was used as the critical parameter to control the proportion of releasable versus physically trapped protein molecules in the initial hydrogel meshwork. Subsequently, the dynamic change of the hydrogel meshwork was modulated by the crosslinking density and the cleavage rate of ester linkers. To this end, we designed and synthesized a series of ester linkers with hydrolytic half-life ranging from 4 h to 4 months and incorporate them into the hydrogel. Controlled release was demonstrated for model proteins varied in size, including lysozyme (14 kDa), bovine serum albumin (66 kDa), immunoglobulin G (150 kDa), and bevacizumab (149 kDa). In particular, sustained release of IgG ranging from 10 days to 8 months was achieved. Lastly, a tunable multi-phase release profile was made feasible by incorporating multiple ester linkers into one hydrogel formulation. The linker's half-life determined each phase's release duration, and the linkers' mixing ratio determined the corresponding release fraction. The reported hydrogel design engenders a versatile platform to address the needs for long-term and readily adjustable protein release for biomedical applications.

Droplet-Based Microfluidic Synthesis of Hydrogel Microparticles via Click Chemistry-Based Cross-Linking for the Controlled Release of Proteins.

Hydrogel microparticles (HMPs) have been widely applied in biological, pharmacologic, and biomedical industries due to their versatility. Particle size is a paramount factor for controlling drug release profiles from HMPs. Conventional fabrication methods such as bulk emulsion, coacervation, and spray drying do not offer a precise size control and high reproducibility, which may compromise the utility of HMPs for controlled release. Here, we report a droplet-based microfluidic synthesis method for the precise fabrication of HMPs. Functionalized polysaccharides/protein fluid mixtures were emulsified into monodisperse droplets in light mineral oil using a flow-focusing device and well mixed in precursor droplets through a serpentine mixing channel before the solidification of HMPs. The homogenized precursor polymers cross-link in the droplets by catalyst-free Michael addition. As a demonstration of the controlled release of a model drug from the HMPs, fluorescein-labeled immunoglobulin G (F-IgG) and bevacizumab were encapsulated in the HMPs of different diameters for measuring its release dynamics over time. The release kinetics of F-IgG from the HMPs was shown to be controllable by altering the particle size while keeping other parameters unchanged. Around 70% of bevacizumab released from DX HMPs was functional. Both HA and DX HMPs showed no cytotoxicity in the HEK293 cell line. We anticipate that this approach could be used as a general method to fabricate HMPs made of hydrophilic polymers for the controlled release of biotherapeutics.

Dual-Diffusivity Stochastic Model for Macromolecule Release from a Hydrogel.

A three-dimensional model has been developed to describe the multiphase release of macromolecular drugs encapsulated in a hydrogel. The heterogeneity of network mesh size was considered by assigning varying diffusion coefficients to the network lattices randomly. Using a stochastic approach, the random nature of diffusion of drug molecules was captured within the network. The simplest form of distribution containing two diffusion coefficients was tested. To generate the drug release profiles for experimental validation under the limitation of computational cost, a simple scaling relationship was employed. Unlike the single-diffusivity model, the dual-diffusivity model showed good agreement with the experimental data in describing the release profiles of macromolecular drugs of three different sizes from chemically cross-linked dextran hydrogels.

Local environment-dependent kinetics of ester hydrolysis revealed by direct 1H NMR measurement of degrading hydrogels.

We have demonstrated the use of a simple 1H NMR spectrometry-based method to directly measure the pseudo first-order hydrolytic cleavage rate constant (kobs) of methacrylate-derived ester crosslinkers in hydrogels composed of PEG, dextran, carboxymethyl dextran (CM-dextran) and hyaluronic acid (HA). Using this technique, we systematically examined how the local environment in the hydrogel influenced the rate of ester hydrolysis. Within the formulations being studied, the esters in the crosslinked polymer network (gel state) degraded 1.8 times faster than esters of similar chemistry in soluble polymers (solution state). Furthermore, the value of kobs was independent of the polymer concentration or the hydrogel network structure, although these parameters affected the swelling profiles in response to the hydrolytic degradation. On the other hand, the presence of the negatively charged carboxylate groups in the polymer chains decreased kobs in gel state, while only minimally affecting kobs in solution state. Hydrogels composed of negatively charged polymers (HA and CM-dextran) had a kobs about 30% smaller than hydrogels composed of neutral polymers (dextran and PEG). The reported method provides a reliable tool to resolve conflicting views about hydrogel degradation, and to guide the rational design of degradable hydrogel. STATEMENT OF SIGNIFICANCE: Degradable hydrogels are widely used in biological applications. A common degradation mechanism of the crosslinked polymer is by hydrolytic cleavage. However, the hydrogel micro-milieu do affect the behavior of the hydrolysable bonds, for example esters. There have been several conflicting speculations on how hydrogel composition would affect the macroscopic degradation behavior. In this report, we simply, but innovatively applied ordinary 1H NMR spectrometry-based method to probe the rate of ester cleavage in the native hydrogel milieu. We tried to answer whether these parameters will have direct influence on ester cleavage, or have indirect effect on the overall network disintegration behavior. This study provides quantitative evidences to assist theoretical modeling and to guide rational formulation design.

Controlled release technology for anti-angiogenesis treatment of posterior eye diseases: Current status and challenges.

Antiangiogenic therapeutics, such as corticosteroids, VEGF targeting antibodies and aptamers have been demonstrated effective in controlling retinal and choroidal neovascularization related vision loss. However, to manage the chronic conditions, it requires long term and frequent intravitreal injections of these drugs, resulting in poor patient compliance and suboptimal treatment. In addition, emerging drugs such as tyrosine kinase inhibitors and siRNAs received much expectations, but the late stage clinical trials encountered various obstacles. Controlled release technology could improve the existing treatment regimen by extending therapeutic duration, reducing risks and burdens caused by frequent injections, and enabling new drugs to overcome the hurdles of translation. Here, we give qualitative and quantitative discussions about the principle mechanisms of polymeric reservoir, polymeric matrix and hydrogel systems. We also reveal the design rationales of the existing drug delivery and release systems in preclinical and clinical stages. Lastly, the animal models of ocular angiogenesis diseases are critically reviewed, which could help to facilitate the translation of controlled release technologies from bench to bedside.