A sustained release cysteamine microsphere/thermoresponsive gel eyedrop for corneal cystinosis improves drug stability

Cystinosis is a rare, metabolic, recessive genetic disease in which the intralysosomal accumulation of cystine leads to system wide organ and tissue damage. In the eye, cystine accumulates in the cornea as corneal cystine crystals and severely impacts vision. Corneal cystine crystals are treated with cysteamine eyedrops when administrated 6 to 12 times day and used within 1 week. The strict dosing regimen and poor stability are inconvenient and add to the burden of therapy. To reduce the dosing frequency and improve the stability, we present reformulation of cysteamine into a novel controlled release eyedrop. In this work, we characterize and evaluate a topical drug delivery system comprised of encapsulated cysteamine in polymer microspheres with a thermoresponsive gel carrier. Spray-dried encapsulation of cysteamine was performed. In vitro cysteamine release, stability, and ocular irritation and corneal permeation were evaluated. The data suggest that encapsulated cysteamine improves the stability to 7 weeks when compared with 1-week aqueous cysteamine eyedrops. Release studies from one drop of our system show that cysteamine release was present for 24 h and above the minimum cysteamine eyedrop amount (6 drops). Cysteamine from our system also resulted in negligible irritation and enhanced permeation when compared with traditional cysteamine eyedrops. In vivo studies were implemented to support ease of administration, tolerability, and retention for 24 h. These studies suggest that our controlled release delivery system may provide stable cysteamine from a safe, once daily gel eyedrop.

Controlled release of ciprofloxacin and ceftriaxone from a single ototopical administration of antibiotic-loaded polymer microspheres and thermoresponsive gel

Acute otitis media (AOM) is the main indication for pediatric antibiotic prescriptions, accounting for 25% of prescriptions. While the use of topical drops can minimize the administered dose of antibiotic and adverse systemic effects compared to oral antibiotics, their use has limitations, partially due to low patient compliance, high dosing frequency, and difficulty of administration. Lack of proper treatment can lead to development of chronic OM, which may require invasive interventions. Previous studies have shown that gel-based drug delivery to the ear is possible with intratympanic injection or chemical permeation enhancers (CPEs). However, many patients are reluctant to accept invasive treatments and CPEs have demonstrated toxicity to the tympanic membrane (TM). We developed a novel method of delivering therapeutics to the TM and middle ear using a topical, thermoresponsive gel depot containing antibiotic-loaded poly(lactic-co-glycolic acid) microspheres. Our in vitro and ex vivo results suggest that the sustained presentation can safely allow therapeutically relevant drug concentrations to penetrate the TM to the middle ear for up to 14 days. Animal results indicate sufficient antibiotic released for treatment from topical administration 24h after bacterial inoculation. However, animals treated 72h after inoculation, a more clinically relevant treatment practice, displayed spontaneous clearance of infection as is also often observed in the clinic. Despite this variability in the disease model, data suggest the system can safely treat bacterial infection, with future studies necessary to optimize microsphere formulations for scaled up dosage of antibiotic as well as further investigation of the influence of spontaneous bacterial clearance and of biofilm formation on effectiveness of treatment. To our knowledge, this study represents the first truly topical drug delivery system to the middle ear without the use of CPEs.

Drug delivery systems and novel formulations to improve treatment of rare corneal disease

As the field of ocular drug delivery grows so does the potential for novel drug discovery or reformulation in lesser-known diseases of the eye. In particular, rare corneal diseases are an interesting area of research because drug delivery is limited to the outermost tissue of the eye. This review will highlight the opportunities and challenges of drug reformulation and alternative treatment approaches for rare corneal diseases. The barriers to effective drug delivery and proposed solutions in development will be discussed along with an overview of corneal rare disease resources, their current treatments and ophthalmic drug delivery systems that could benefit such cases. The regulatory considerations for effective translation of orphan-designated products will also be discussed.

Tuning of thermoresponsive pNIPAAm hydrogels for the topical retention of controlled release ocular therapeutics

Low patient compliance and poor bioavailability of ophthalmic medications are the main limitations of topical eye drops. A potential solution to these disadvantages could be provided by thermoresponsive hydrogels, which could be used as the basis for a gelling eye drop for long-term release of therapeutics. We previously reported such a system capable of being retained in the lower fornix of rabbits, continuously releasing an anti-glaucoma drug for one month. Here, we sought to improve the properties of the existing gels as most relevant to patient use without altering the drug release profile. Specifically, we optimized the sol-to-gel transition temperature and de-swelling kinetics of pNIPAAm gels to avoid risk of the gelled drop reverting to liquid during cold or windy weather, and ensure quick gelation upon administration. A reduction of the gel LCST, faster gelation kinetics, and suitable viscosity for the administration as an eye drop were successfully achieved through modification of the poly(ethylene glycol) content in the water phase and its molecular weight. Our data suggest that drug release is not affected by these changes, with representative drug concentration profiles of the previous and new formulations demonstrating comparable anti-glaucoma release kinetics.

Long Term Glaucoma Drug Delivery Using a Topically Retained Gel/Microsphere Eye Drop

The purpose of this study was to characterize and determine the efficacy of a long-term, non-invasive gel/microsphere (GMS) eye drop for glaucoma. This novel drug delivery system is comprised of a thermoresponsive hydrogel carrier and drug-loaded polymer microspheres. In vitro release of brimonidine from the GMS drops and gel properties were quantified. A single brimonidine-loaded GMS drop was administered to 5 normotensive rabbits and intraocular pressure (IOP) was monitored for 28 days. Here we report that IOP reduction in rabbits receiving a single brimonidine GMS drop was comparable to that of rabbits receiving twice daily, standard brimonidine drops. GMS drops were retained in the inferior fornix in all animals for the length of the study. Our results suggest in vivo efficacy over 28 days from a single GMS drop and a potential decrease in systemic absorption, based on a lack of substantial IOP effects on the fellow untreated eye, compared to brimonidine twice-daily eye drops. To our knowledge, this represents the first long-term, drug-releasing depot that can be administered as a traditional eye drop.

Treg-recruiting microspheres prevent inflammation in a murine model of dry eye disease

Dry eye disease (DED) is a common ocular disorder affecting millions of individuals worldwide. The pathology of DED involves the infiltration of CD4+ lymphocytes, leading to tear film instability and destructive inflammation. In the healthy steady state, a population of immunosuppressive T-cells called regulatory T-cells (Treg) regulates proliferation of immune cells that would otherwise lead to a disruption of immunological homeostasis. For this reason, it has been suggested that Tregs could restore the immunological imbalance in DED. To this end, one possible approach would be to recruit the body's own, endogenous Tregs in order to enrich them at the site of inflammation and tissue destruction. Previously, we have demonstrated a reduction of inflammation and disease symptoms in models of periodontitis corresponding to recruitment of endogenous Tregs, which was accomplished by local placement of controlled release systems that sustain a gradient of the chemokine CCL22, referred to here as Treg-recruiting microspheres. Given that DED is characterized by a pro-inflammatory environment resulting in local tissue destruction, we hypothesized that the controlled release of CCL22 could also recruit Tregs to the ocular surface potentially mediating inflammation and symptoms of DED. Indeed, data suggest that Treg-recruiting microspheres are capable of overcoming the immunological imbalance of Tregs and CD4+ IFN-γ+ cells in the lacrimal gland. Administration of Treg-recruiting microspheres effectively mitigated the symptoms of DED as measured through a number of outcomes such as tear clearance, goblet cells density and corneal epithelial integrity, suggesting that recruitment of endogenous Treg can mitigate inflammation associated with DED.

* Programmed Platelet-Derived Growth Factor-BB and Bone Morphogenetic Protein-2 Delivery from a Hybrid Calcium Phosphate/Alginate Scaffold

Bone tissue engineering requires the upregulation of several regenerative stages, including a critical early phase of angiogenesis. Previous studies have suggested that a sequential delivery of platelet-derived growth factor (PDGF) to bone morphogenetic protein-2 (BMP-2) could promote angiogenic tubule formation when delivered to in vitro cocultures of human umbilical vein endothelial cells (HUVECs) and human mesenchymal stem cells (hMSCs). However, it was previously unclear that this PDGF to BMP-2 delivery schedule will result in cell migration into the scaffolding system and affect the later expression of bone markers. Additionally, a controlled delivery system had not yet been engineered for programmed sequential presentation of this particular growth factor. By combining alginate matrices with calcium phosphate scaffolding, a programmed growth factor delivery schedule was achieved. Specifically, a combination of alginate microspheres, alginate hydrogels, and a novel blend of resorbable calcium phosphate-based cement (ReCaPP) was used. PDGF and BMP-2 were sequentially released from this hybrid calcium phosphate/alginate scaffold with the desired 3-day overlap in PDGF to BMP-2 delivery. Using a three-dimensional coculture model, we observed that this sequence of PDGF to BMP-2 delivery influenced both cellular infiltration and alkaline phosphatase (ALP) expression. It was found that the presence of early PDGF delivery increased the distance of cell infiltration into the calcium phosphate/alginate scaffolding in comparison to early BMP-2 delivery and simultaneous PDGF+BMP-2 delivery. It was also observed that hMSCs expressed a greater amount of ALP+ staining in response to scaffolds delivering the sequential PDGF to BMP-2 schedule, when compared with scaffolds delivering no growth factor, or PDGF alone. Importantly, hMSCs cultured with scaffolds releasing the PDGF to BMP-2 schedule showed similar amounts of ALP staining to hMSCs cultured with BMP-2 alone, suggesting that the sequential schedule of PDGF to BMP-2 presentation promotes differentiation of hMSCs toward an osteoblast phenotype while also increasing cellular infiltration of the scaffold.

Endophthalmitis Prophylaxis Using a Single Drop of Thermoresponsive Controlled-Release Microspheres Loaded with Moxifloxacin in a Rabbit Model

Purpose

Postsurgical endophthalmitis is a sight-threatening problem. We introduce a simple approach by using a single application of thermoresponsive controlled-release microspheres, loaded with moxifloxacin, to prevent bacterial endophthalmitis in a rabbit endophthalmitis prevention model.

Methods

We separated 24 rabbits into 3 treatment groups in which topical drop treatment was placed onto the conjunctival cul-de-sac: (1) a single drop of controlled-release microspheres containing moxifloxacin, (2) a single drop of controlled-release microspheres without moxifloxacin, and (3) multiple topical treatment with moxifloxacin alone every 15 minutes for 1 hour. All rabbits were challenged, 1 hour after microspheres drop placement and immediately after the fifth topical dose of moxifloxacin, with anterior chamber injections of Staphylococcus aureus. Rabbits in the topical moxifloxacin group also were treated after challenge and four additional times over the next 24 hours. After 24 hours, the rabbits were clinically evaluated for endophthalmitis and the animals were euthanized to culture for intraocular S. aureus. The treatment groups were compared statistically for bacterial endophthalmitis.

Results

No eyes had endophthalmitis, based on clinical presentation and/or positive culture, in the groups with controlled-release microspheres loaded with moxifloxacin (0/8, 0%) or multiple drops of topical moxifloxacin (0/8, 0%). In contrast, 8 of 8 eyes (100%; P = 0.0001), had endophthalmitis among eyes treated with controlled-release microspheres drops without moxifloxacin.

Conclusion

A single drop of controlled-release microspheres loaded with moxifloxacin was successful in preventing endophthalmitis. Further clinical studies will be required to confirm the full potential of controlled-release anti-infective loaded microspheres to prevent endophthalmitis.

Translational Relevance

This study presents a simple method of prophylaxis to prevent postsurgical endophthalmitis.

The impact of monomer sequence and stereochemistry on the swelling and erosion of biodegradable poly(lactic-co-glycolic acid) matrices

Monomer sequence is demonstrated to be a primary factor in determining the hydrolytic degradation profile of poly(lactic-co-glycolic acid)s (PLGAs). Although many approaches have been used to tune the degradation of PLGAs, little effort has been expended in exploring the sequence-control strategy exploited by nature in biopolymers. Cylindrical matrices and films prepared from a series of sequenced and random PLGAs were subjected to hydrolysis in a pH 7.4 buffer at 37 °C. Swelling ranged from 107% for the random racemic PLGA with a 50:50 ratio of lactic (L) to glycolic (G) units to 6% for the sequenced alternating copolymer poly LG. Erosion followed an inverse trend with the random 50:50 PLGA showing an erosion half-life of 3-4 weeks while poly LG required ca. >10 weeks. Stereosequence was found to play a large role in determining swelling and erosion; stereopure analogs swelled less and were slower to lose mass. Molecular weight loss followed similar trends and increases in dispersity correlated with the onset of significant swelling. The relative proportion of rapidly cleavable G-G linkages relative to G-L/L-G (moderate) and L-L (slow) correlates strongly with the degree of swelling observed and the rate of erosion. The dramatic sequence-dependent variation in swelling, in the absence of a parallel hydrophilicity trend, suggest that osmotic pressure, driven by the differential accumulation of degradation products, plays an important role.

The Influence of Platelet-Derived Growth Factor and Bone Morphogenetic Protein Presentation on Tubule Organization by Human Umbilical Vascular Endothelial Cells and Human Mesenchymal Stem Cells in Coculture

A three-dimensional in vitro Matrigel plug was used as a model to explore delivery patterns of platelet-derived growth factor (PDGF) and bone morphogenetic protein-2 (BMP-2) to a coculture of human mesenchymal and endothelial cells. While BMP-2 is well recognized for its role in promoting fracture healing through proliferation and differentiation of osteoclast precursors, it is not a growth factor known to promote the process of angiogenesis, which is also critical for complete bone tissue repair. PDGF, in contrast, is a known regulator of angiogenesis, and also a powerful chemoattractant for osteoblast precursor cells. It has been suggested that presentation of PDGF followed by BMP may better promote vascularized bone tissue formation. Yet, it is unclear as to how cells would respond to various durations of delivery of each growth factor as well as to various amounts of overlap in presentation in terms of angiogenesis. Using a three-dimensional in vitro Matrigel plug model, we observed how various presentation schedules of PDGF and BMP-2 influenced tubule formation by human mesenchymal stem cells and human umbilical vascular endothelial cells. We observed that sequential presentation of PDGF to BMP-2 led to increased tubule formation over simultaneous delivery of these growth factors. Importantly, a 2-4 day overlap in the sequential presentation of PDGF and BMP-2 increased tubule formation as compared with groups with zero or complete growth factor overlap, suggesting that a moderate amount of angiogenic and osteogenic growth factor overlap may be beneficial for processes associated with angiogenesis.

Modeling and Hemofiltration Treatment of Acute Inflammation

The body responds to endotoxins by triggering the acute inflammatory response system to eliminate the threat posed by gram-negative bacteria (endotoxin) and restore health. However, an uncontrolled inflammatory response can lead to tissue damage, organ failure, and ultimately death; this is clinically known as sepsis. Mathematical models of acute inflammatory disease have the potential to guide treatment decisions in critically ill patients. In this work, an 8-state (8-D) differential equation model of the acute inflammatory response system to endotoxin challenge was developed. Endotoxin challenges at 3 and 12 mg/kg were administered to rats, and dynamic cytokine data for interleukin (IL)-6, tumor necrosis factor (TNF), and IL-10 were obtained and used to calibrate the model. Evaluation of competing model structures was performed by analyzing model predictions at 3, 6, and 12 mg/kg endotoxin challenges with respect to experimental data from rats. Subsequently, a model predictive control (MPC) algorithm was synthesized to control a hemoadsorption (HA) device, a blood purification treatment for acute inflammation. A particle filter (PF) algorithm was implemented to estimate the full state vector of the endotoxemic rat based on time series cytokine measurements. Treatment simulations show that: (i) the apparent primary mechanism of HA efficacy is white blood cell (WBC) capture, with cytokine capture a secondary benefit; and (ii) differential filtering of cytokines and WBC does not provide substantial improvement in treatment outcomes vs. existing HA devices.

One-step synthesis of fluorescently labelled, single-walled carbon nanotubes

Single-walled carbon nanotubes (SWNTs) can be labelled with functional moieties that endow them with a number of unique characteristics, which can be applicable to biomedical applications such as imaging. Herein we describe a facile, one-step esterification process to functionalize SWNT with fluorescein.

The scope and sequence of growth factor delivery for vascularized bone tissue regeneration

Bone regeneration is a complex process, that in vivo, requires the highly coordinated presentation of biochemical cues to promote the various stages of angiogenesis and osteogenesis. Taking inspiration from the natural healing process, a wide variety of growth factors are currently being released within next generation tissue engineered scaffolds (in a variety of ways) in order to heal non-union fractures and bone defects. This review will focus on the delivery of multiple growth factors to the bone regeneration niche, specifically 1) dual growth factor delivery signaling and crosstalk, 2) the importance of growth factor timing and temporal separation, and 3) the engineering of delivery systems that allow for temporal control over presentation of soluble growth factors. Alternative methods for growth factor presentation, including the use of gene therapy and platelet-rich plasma scaffolds, are also discussed.

Scaling up self-assembly: bottom-up approaches to macroscopic particle organization

This review presents an overview of recent work in the field of non-Brownian particle self-assembly. Compared to nanoparticles that naturally self-assemble due to Brownian motion, larger, non-Brownian particles (d > 6 μm) are less prone to autonomously organize into crystalline arrays. The tendency for particle systems to experience immobilization and kinetic arrest grows with particle radius. In order to overcome this kinetic limitation, some type of external driver must be applied to act as an artificial "thermalizing force" upon non-Brownian particles, inducing particle motion and subsequent crystallization. Many groups have explored the use of various agitation methods to overcome the natural barriers preventing self-assembly to which non-Brownian particles are susceptible. The ability to create materials from a bottom-up approach with these characteristics would allow for precise control over their pore structure (size and distribution) and surface properties (topography, functionalization and area), resulting in improved regulation of key characteristics such as mechanical strength, diffusive properties, and possibly even photonic properties. This review will highlight these approaches, as well as discuss the potential impact of bottom-up macroscale particle assembly. The applications of such technology range from customizable and autonomously self-assembled niche microenvironments for drug delivery and tissue engineering to new acoustic dampening, battery, and filtration materials, among others. Additionally, crystals made from non-Brownian particles resemble naturally derived materials such as opals, zeolites, and biological tissue (i.e. bone, cartilage and lung), due to their high surface area, pore distribution, and tunable (multilevel) hierarchy.

Positive Charge of "Sticky" Peptides and Proteins Impedes Release From Negatively Charged PLGA Matrices

The influence of electrostatic interactions and/or acylation on release of charged ("sticky") agents from biodegradable polymer matrices was systematically characterized. We hypothesized that release of peptides with positive charge would be hindered from negatively charged poly(lactic-co-glycolic acid) (PLGA) microparticles. Thus, we investigated release of peptides with different degrees of positive charge from several PLGA microparticle formulations, with different molecular weights and/or end groups (acid- or ester-terminated). Indeed, release studies revealed distinct inverse correlations between the amount of positive charge on peptides and their release rates from each PLGA microparticle formulation. Furthermore, we examined the case of peptides with net charge that changes from negative to positive within the pH range observed in degrading microparticles. These charge changing peptides displayed counterintuitive release kinetics, initially releasing faster from slower degrading (less acidic) microparticles, and releasing slower from the faster degrading (more acidic) microparticles. Importantly, trends between agent charge and release rates for model peptides also translated to larger, therapeutically relevant proteins and oligonucleotides. The results of these studies may improve future design of controlled release systems for numerous therapeutic biomolecules exhibiting positive charge, ultimately reducing time-consuming and costly trial and error iterations of such formulations.

Fabrication and characterization of non-Brownian particle-based crystals

Particle-based crystals have been explored in the literature for applications in molecular electronics, photonics, sensors, and drug delivery. However, much of the research on these crystals has been focused on particles of nano- and submicrometer dimensions (so-called colloidal crystals) with limited attention directed toward building blocks with dimensions ranging from tens to hundreds of micrometers. This can be attributed, in part, to the fact that the underlying thermal effects in these larger systems typically cannot naturally overcome kinetic barriers at the meso- and macroscales so that many of the methods used for nanoscale particle assembly cannot be directly applied to larger components, as they become kinetically arrested in nonequilibrium states. In this work, ultrasonic agitation is being explored as a means of allowing large, non-Brownian microparticles (18-750 μm) to overcome the kinetic barriers to packing in the creation of close-packed, highly ordered, crystalline structures. In addition, we study how the energy input affects bulk particle behavior and describe several new ways to characterize particle-based crystals made from microparticles.

Hemoadsorption reprograms inflammation in experimental gram-negative septic peritonitis: insights from in vivo and in silico studies

Improper compartmentalization of the inflammatory response leads to systemic inflammation in sepsis. Hemoadsorption (HA) is an emerging approach to modulate sepsis-induced inflammation. We sought to define the effects of HA on inflammatory compartmentalization in Escherichia coli-induced fibrin peritonitis in rats.

HYPOTHESIS

HA both reprograms and recompartmentalizes inflammation in sepsis. Sprague Dawley male rats were subjected to E. coli peritonitis and, after 24 h, were randomized to HA or sham treatment (sepsis alone). Venous blood samples collected at 0, 1, 3 and 6 h (that is, 24-30 h of total experimental sepsis), and peritoneal samples collected at 0 and 6 h, were assayed for 14 cytokines along with NO(2)(-/)NO(3)(-). Bacterial counts were assessed in the peritoneal fluid at 0 and 6 h. Plasma tumor necrosis factor (TNF)-α, interleukin (IL)-6, CXCL-1, and CCL2 were significantly reduced in HA versus sham. Principal component analysis (PCA) suggested that inflammation in sham was driven by IL-6 and TNF-α, whereas HA-associated inflammation was driven primarily by TNF-α, CXCL-1, IL-10 and CCL2. Whereas -peritoneal bacterial counts, plasma aspartate transaminase levels and peritoneal IL-5, IL-6, IL-18, interferon (IFN)-γ and NO(2)(-)/NO(3)(-) were significantly lower, both CXCL-1 and CCL2 as well as the peritoneal-to-plasma ratios of TNF-α, CXCL-1 and CCL2 were significantly higher in HA versus sham, suggesting that HA-induced inflammatory recompartmentalization leads to the different inflammatory drivers discerned in part by PCA. In conclusion, this study demonstrates the utility of combined in vivo/in silico methods and suggests that HA exerts differential effects on mediator gradients between local and systemic compartments that ultimately benefit the host.