Engineering of tetanus toxoid-loaded polymeric microneedle patches.

This study is aimed to fabricate tetanus toxoid laden microneedle patches by using a polymeric blend comprising of polyvinyl pyrrolidone and sodium carboxymethyl cellulose as base materials and sorbitol as a plasticizer. The tetanus toxoid was mixed with polymeric blend and patches were prepared by using vacuum micromolding technique. Microneedle patches were evaluated for physical attributes such as uniformity of thickness, folding endurance, and swelling profile. Morphological features were assessed by optical and scanning electron microscopy. In vitro performance of fabricated patches was studied by using bicinchoninic acid assay (BCA). Insertion ability of microstructures was studied in vitro on model skin parafilm and in vivo in albino rat. In vivo immunogenic activity of the formulation was assessed by recording immunoglobulin G (IgG) levels, interferon gamma (IFN-γ) levels, and T-cell (CD4+ and CD8+) count following the application of dosage forms. Prepared patches, displaying sharp-tipped and smooth-surfaced microstructures, remained intact after 350 ± 36 foldings. Optimized microneedle patch formulation showed ~ 74% swelling and ~ 85.6% vaccine release within an hour. The microneedles successfully pierced parafilm. Histological examination of microneedle-treated rat skin confirmed disruption of epidermis without damaging the underneath vasculature. A significant increase in IgG levels (~ 21%), IFN-γ levels (~ 30%), CD4+ (~ 41.5%), and CD8+ (~ 48.5%) cell count was observed in tetanus vaccine-loaded microneedle patches treated albino rats with respect to control (untreated) group at 42nd day of immunization. In conclusion, tetanus toxoid-loaded microneedle patches can be considered as an efficient choice for transdermal delivery of vaccine without inducing pain commonly experienced with hypodermic needles.

Evaluation of sustained-release in-situ injectable gels, containing naproxen sodium, using in vitro, in silico and in vivo analysis.

The study aimed to fabricate naproxen sodium loaded in-situ gels of sodium alginate. Different in-situ gel forming solutions of naproxen sodium and sodium alginate were prepared and gel formation was studied in different physiological ions i.e., CaCl2 and Ca-gluconate. The prepared gel formulations were evaluated for different physical attributes such as gelation time, sol-gel fraction, ATR-FTIR spectroscopy and in silico molecular dynamics (MD) simulations. Drug release studies were carried out in a dialysis membrane using USP dissolution basket apparatus-I. In vivo anti-inflammatory studies were performed in Sprague-Dawley rats having carrageenan-induced hind paw inflammation. Higher polymer concentration in formulations resulted in decreased gelation time and an increased gel fraction. The ATR-FTIR and MD simulation revealed H-bonding between the alginate and naproxen sodium at 3500-3200 cm-1 with a RMSD of ∼2.8 Å and binding free energy ΔGpred (GB) = -10.93 kcal/mol. In vitro drug release studies from F8CAG suggested a sustained release of naproxen sodium. In vivo studies revealed a continuous decrease in swelling degree (≈-5.28 ± 0.210 mm) in inflamed hind paw of Sprague-Dawley rats over 96 h. The in-situ gel forming injectable preparation (F8CAG) offers a sustained release of naproxen sodium in the articular cavity which promises the treatment of chronic inflammatory conditions such as arthritis.

Electrohydrodynamic atomisation driven design and engineering of opportunistic particulate systems for applications in drug delivery, therapeutics and pharmaceutics.

Electrohydrodynamic atomisation (EHDA) technologies have evolved significantly over the past decade; branching into several established and emerging healthcare remits through timely advances in the engineering sciences and tailored conceptual process designs. More specifically for pharmaceutical and drug delivery spheres, electrospraying (ES) has presented itself as a high value technique enabling a plethora of different particulate structures. However, when coupled with novel formulations (e.g. co-flows) and innovative device aspects (e.g., materials and dimensions), core characteristics of particulates are manipulated and engineered specifically to deliver an application driven need, which is currently lacking, ranging from imaging and targeted delivery to controlled release and sensing. This demonstrates the holistic nature of these emerging technologies; which is often overlooked. Parametric driven control during particle engineering via the ES method yields opportunistic properties when compared to conventional methods, albeit at ambient conditions (e.g., temperature and pressure), making this extremely valuable for sensitive biologics and molecules of interest. Furthermore, several processing (e.g., flow rate, applied voltage and working distance) and solution (e.g., polymer concentration, electrical conductivity and surface tension) parameters impact ES modes and greatly influence the production of resulting particles. The formation of a steady cone-jet and subsequent atomisation during ES fabricates particles demonstrating monodispersity (or near monodispersed), narrow particle size distributions and smooth or textured morphologies; all of which are successfully incorporated in a one-step process. By following a controlled ES regime, tailored particles with various intricate structures (hollow microspheres, nanocups, Janus and cell-mimicking nanoparticles) can also be engineered through process head modifications central to the ES technique (single-needle spraying, coaxial, multi-needle and needleless approaches). Thus, intricate formulation design, set-up and combinatorial engineering of the EHDA process delivers particulate structures with a multitude of applications in tissue engineering, theranostics, bioresponsive systems as well as drug dosage forms for specific delivery to diseased or target tissues. This advanced technology has great potential to be implemented commercially, particularly on the industrial scale for several unmet pharmaceutical and medical challenges and needs. This review focuses on key seminal developments, ending with future perspectives addressing obstacles that need to be addressed for future advancement.

Fibroblast growth factor 7 releasing particles enhance islet engraftment and improve metabolic control following islet transplantation in mice with diabetes.

Transplantation of islets in type 1 diabetes (T1D) is limited by poor islet engraftment into the liver, with two to three donor pancreases required per recipient. We aimed to condition the liver to enhance islet engraftment to improve long-term graft function. Diabetic mice received a non-curative islet transplant (n = 400 islets) via the hepatic portal vein (HPV) with fibroblast growth factor 7-loaded galactosylated poly(DL-lactide-co-glycolic acid) (FGF7-GAL-PLGA) particles; 26-µm diameter particles specifically targeted the liver, promoting hepatocyte proliferation in short-term experiments: in mice receiving 0.1-mg FGF7-GAL-PLGA particles (60-ng FGF7) vs vehicle, cell proliferation was induced specifically in the liver with greater efficacy and specificity than subcutaneous FGF7 (1.25 mg/kg ×2 doses; ~75-µg FGF7). Numbers of engrafted islets and vascularization were greater in liver sections of mice receiving islets and FGF7-GAL-PLGA particles vs mice receiving islets alone, 72 h posttransplant. More mice (six of eight) that received islets and FGF7-GAL-PLGA particles normalized blood glucose concentrations by 30-days posttransplant, versus zero of eight mice receiving islets alone with no evidence of increased proliferation of cells within the liver at this stage and normal liver function tests. This work shows that liver-targeted FGF7-GAL-PLGA particles achieve selective FGF7 delivery to the liver-promoting islet engraftment to help normalize blood glucose levels with a good safety profile.

Electrospinning/electrospraying coatings for metal microneedles: A design of experiments (DOE) and quality by design (QbD) approach.

The research presented here shows QbD implementation for the optimisation of the key process parameters in electrohydrodynamic atomisation (EHDA). Here, the electrosprayed nanoparticles and electrospun fibers consisting of a polymeric matrix and dye. Eight formulations were assessed consisting of 5% w/v of polycaprolactone (PCL) in dichloromethane (DCM) and 5% w/v polyvinylpyrrolidone (PVP) in ethanol. A full factorial DOE was used to assess the various parameters (applied voltage, deposition distance, flow rate). Further particle and fiber analysis using Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), particle/fiber size distribution. In addition to this in vitro release studied were carried out using fluorescein and Rhodamine B as model dyes and in vitro permeation studies were applied. The results show a significant difference in the morphology of resultant structures as well as a more rapid release profile for the PVP particles and fibers in comparison to the sustained release profiles found with PCL. In vitro drug release studies showed 100% drug release after 7 days for PCL particles and showed 100% drug release within 120 min for PVP particles. The release kinetics and the permeation study showed that the MN successfully pierced the membrane and the electrospun MN coating released a large amount of the loaded drug within 6 h. This study has demonstrated the capability of these robust MNs to encapsulate a diverse range drugs within a polymeric matrix giving rise to the potential of developed personalised medical devices.

Quality by Design Micro-Engineering Optimisation of NSAID-Loaded Electrospun Fibrous Patches.

The purpose of this study was to apply the Quality by Design (QbD) approach to the electrospinning of fibres loaded with the nonsteroidal anti-inflammatory drugs (NSAIDs) indomethacin (INDO) and diclofenac sodium (DICLO). A Quality Target Product Profile (QTPP) was made, and risk assessments (preliminary hazard analysis) were conducted to identify the impact of material attributes and process parameters on the critical quality attributes (CQAs) of the fibres. A full factorial design of experiments (DoE) of 20 runs was built, which was used to carry out experiments. The following factors were assessed: Drugs, voltage, flow rate, and the distance between the processing needle and collector. Release studies exhibited INDO fibres had greater total release of active drug compared to DICLO fibres. Voltage and distance were found to be the most significant factors of the experiment. Multivariate statistical analytical software helped to build six feasible design spaces and two flexible, universal design spaces for both drugs, at distances of 5 cm and 12.5 cm, along with a flexible control strategy. The current findings and their analysis confirm that QbD is a viable and invaluable tool to enhance product and process understanding of electrospinning for the assurance of high-quality fibres.

Targeted protein delivery: carbodiimide crosslinking influences protein release from microparticles incorporated within collagen scaffolds.

Tissue engineering response may be tailored via controlled, sustained release of active agents from protein-loaded degradable microparticles incorporated directly within three-dimensional (3D) ice-templated collagen scaffolds. However, the effects of covalent crosslinking during scaffold preparation on the availability and release of protein from the incorporated microparticles have not been explored. Here, we load 3D ice-templated collagen scaffolds with controlled additions of poly-(DL-lactide-co-glycolide) microparticles. We probe the effects of subsequent N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride crosslinking on protein release, using microparticles with different internal protein distributions. Fluorescein isothiocyanate labelled bovine serum albumin is used as a model protein drug. The scaffolds display a homogeneous microparticle distribution, and a reduction in pore size and percolation diameter with increased microparticle addition, although these values did not fall below those reported as necessary for cell invasion. The protein distribution within the microparticles, near the surface or more deeply located within the microparticles, was important in determining the release profile and effect of crosslinking, as the surface was affected by the carbodiimide crosslinking reaction applied to the scaffold. Crosslinking of microparticles with a high proportion of protein at the surface caused both a reduction and delay in protein release. Protein located within the bulk of the microparticles, was protected from the crosslinking reaction and no delay in the overall release profile was seen.

Spatiotemporal release of VEGF from biodegradable polylactic-co-glycolic acid microspheres induces angiogenesis in chick chorionic allantoic membrane assay.

While vascular endothelial growth factor (VEGF) is an acknowledged potent pro-angiogenic agent there is a need to deliver it at an appropriate concentration for several days to achieve angiogenesis. The aim of this study was to produce microspheres of biodegradable polylactic-co-glycolic acid (PLGA) tailored to achieve sustained release of VEGF at an appropriate concentration over seven days, avoiding excessive unregulated release of VEGF that has been associated with the formation of leaky blood vessels. Several formulations were examined to produce microspheres loaded with both human serum albumin (HSA) and VEGF to achieve release of VEGF between 3 and 10 ng per ml for seven days to match the therapeutic window desired for angiogenesis. In vitro experiments showed an increase in endothelial cell proliferation in response to microspheres bearing VEGF. Similarly, when microspheres containing VEGF were added to the chorionic membrane of fertilised chicken eggs, there was an increase in the development of blood vessels over seven days in response, which was significant for microspheres bearing VEGF and HSA, but not VEGF alone. There was an increase in both blood vessel density and branching - both signs of proangiogenic activity. Further, there was clearly migration of cells to the VEGF loaded microspheres. In summary, we describe the development of an injectable delivery vehicle to achieve spatiotemporal release of physiologically relevant levels of VEGF for several days and demonstrate the angiogenic response to this. We propose that such a treatment vehicle would be suitable for the treatment of ischemic tissue or wounds.

Improved delivery of PLGA microparticles and microparticle-cell scaffolds in clinical needle gauges using modified viscosity formulations.

Polymer microparticles are widely used as acellular drug delivery platforms in regenerative medicine, and have emerging potential as cellular scaffolds for therapeutic cell delivery. In the clinic, PLGA microparticles are typically administered intramuscularly or subcutaneously, with the clinician and clinical application site determining the precise needle gauge used for delivery. Here, we explored the role of needle diameter in microparticle delivery yield, and develop a modified viscosity formulation to improve microparticle delivery across a range of clinically relevant needle diameters. We have identified an optimal biocompatible formulation containing 0.25% pluronic F127 and 0.25% carboxymethyl cellulose, which can increase delivery payload to 520% across needle gauges 21-30G, and note that needle diameter impacts delivery efficacy. We use this formulation to increase the delivery yield of PLGA microparticles, and separately, PLGA-cell scaffolds supporting viable mesenchymal stem cells (MSCs), demonstrating the first in vitro delivery of this cell scaffold system. Together, these results highlight an optimal formulation for the delivery of microparticle and microparticle-cell scaffolds, and illustrate how careful choice of delivery formulation and needle size can dramatically impact delivery payload.

Remote regulation of magnetic particle targeted Wnt signaling for bone tissue engineering.

Wnt signaling is critically involved in the differentiation of human Mesenchymal Stem Cells (hMSC). Wnt proteins therefore have considerable therapeutic value, but are expensive and difficult to produce. UM206 is a synthetic peptide and ligand for the Wnt receptor Frizzled. Attachment of UM206 to magnetic nanoparticles (MNP) enables the ligand-MNP complex to be manipulated using magnetic fields, allowing control of Frizzled stimulation. Using this approach, Wnt signaling was activated in hMSC which resulted in Frizzled clustering, ß-catenin translocalization and activation of TCF/LEF responsive transcription. During osteogenesis, UM206-MNP initiated localized mineralized matrix formation. Injection and magnetic stimulation of UM206-MNP-labeled MSC in ex vivo chick femurs resulted in increased mineralization which acted synergistically with addition of bone morphogenic protein 2 (BMP2) releasing micro-particles. As this facilitates external control over signal transduction, conjugated MNP technology has applications both as a research tool and for regulating tissue formation in clinical cell therapies.

A dual-application poly (dl-lactic-co-glycolic) acid (PLGA)-chitosan composite scaffold for potential use in bone tissue engineering.

The development of patient-friendly alternatives to bone-graft procedures is the driving force for new frontiers in bone tissue engineering. Poly (dl-lactic-co-glycolic acid) (PLGA) and chitosan are well-studied and easy-to-process polymers from which scaffolds can be fabricated. In this study, a novel dual-application scaffold system was formulated from porous PLGA and protein-loaded PLGA/chitosan microspheres. Physicochemical and in vitro protein release attributes were established. The therapeutic relevance, cytocompatibility with primary human mesenchymal stem cells (hMSCs) and osteogenic properties were tested. There was a significant reduction in burst release from the composite PLGA/chitosan microspheres compared with PLGA alone. Scaffolds sintered from porous microspheres at 37 °C were significantly stronger than the PLGA control, with compressive strengths of 0.846 ± 0.272 MPa and 0.406 ± 0.265 MPa, respectively (p < 0.05). The formulation also sintered at 37 °C following injection through a needle, demonstrating its injectable potential. The scaffolds demonstrated cytocompatibility, with increased cell numbers observed over an 8-day study period. Von Kossa and immunostaining of the hMSC-scaffolds confirmed their osteogenic potential with the ability to sinter at 37 °C in situ.

Surface modification of PdlLGA microspheres with gelatine methacrylate: Evaluation of adsorption, entrapment, and oxygen plasma treatment approaches.

Injectable poly (dl-lactic-co-glycolic acid) (PdlLGA) microspheres are promising candidates as biodegradable controlled release carriers for drug and cell delivery applications; however, they have limited functional groups on the surface to enable dense grafting of tissue specific biocompatible molecules. In this study we have evaluated surface adsorption, entrapment and oxygen plasma treatment as three approaches to modify the surfaces of PdlLGA microspheres with gelatine methacrylate (gel-MA) as a biocompatible and photo cross-linkable macromolecule. Time of flight secondary ion mass spectroscopy (TOF SIMS) and X-ray photoelectron spectroscopy (XPS) were used to detect and quantify gel-MA on the surfaces. Fluorescent and scanning electron microscopies (SEM) were used to image the topographical changes. Human mesenchymal stem cells (hMSCs) of immortalised cell line were cultured on the surface of gel-MA modified PdlLGA microspheres and Presto-Blue assay was used to study the effect of different surface modifications on cell proliferation. Data analysis showed that the oxygen plasma treatment approach resulted in the highest density of gel-MA deposition. This study supports oxygen plasma treatment as a facile approach to modify the surface of injectable PdlLGA microspheres with macromolecules such as gel-MA to enhance proliferation rate of injected cells and potentially enable further grafting of tissue specific molecules. STATEMENT OF SIGNIFICANCE: Poly (dl lactic-co-glycolic) acid (PdlLGA) microspheres offer limited functional groups on their surface to enable proper grafting of tissue specific bioactive molecules. To overcome this limitation, previous approaches have suggested using alkaline solutions to introduce active groups to the surface; however, they may compromise surface topography and lose any potential surface patterns. Plasma polymerisation of bioactive monomers has been suggested to enhance surface biocompatibility; however, it is not applicable on low vapour pressure macromolecules such as most extracellular matrix (ECM) proteins and growth factors. This study aims to evaluate three different approaches to modify the surface of PdlLGA microspheres with gelatine-methacrylate (gel-MA) to enable further grafting of cross-linkable biomolecules without compromising the surface topography or the biocompatibility of the system.

Microparticles for Sustained Growth Factor Delivery in the Regeneration of Critically-Sized Segmental Tibial Bone Defects.

This study trialled the controlled delivery of growth factors within a biodegradable scaffold in a large segmental bone defect model. We hypothesised that co-delivery of vascular endothelial growth factor (VEGF) and platelet derived growth factor (PDGF) followed by bone morphogenetic protein-2 (BMP-2) could be more effective in stimulating bone repair than the delivery of BMP-2 alone. Poly(lactic-co-glycolic acid) (PLGA ) based microparticles were used as a delivery system to achieve a controlled release of growth factors within a medical-grade Polycaprolactone (PCL) scaffold. The scaffolds were assessed in a well-established preclinical ovine tibial segmental defect measuring 3 cm. After six months, mechanical properties and bone tissue regeneration were assessed. Mineralised bone bridging of the defect was enhanced in growth factor treated groups. The inclusion of VEGF and PDGF (with BMP-2) had no significant effect on the amount of bone regeneration at the six-month time point in comparison to BMP-2 alone. However, regions treated with VEGF and PDGF showed increased vascularity. This study demonstrates an effective method for the controlled delivery of therapeutic growth factors in vivo, using microparticles.

In Vivo Assessment of Bone Regeneration in Alginate/Bone ECM Hydrogels with Incorporated Skeletal Stem Cells and Single Growth Factors.

The current study has investigated the use of decellularised, demineralised bone extracellular matrix (ECM) hydrogel constructs for in vivo tissue mineralisation and bone formation. Stro-1-enriched human bone marrow stromal cells were incorporated together with select growth factors including VEGF, TGF-ß3, BMP-2, PTHrP and VitD3, to augment bone formation, and mixed with alginate for structural support. Growth factors were delivered through fast (non-osteogenic factors) and slow (osteogenic factors) release PLGA microparticles. Constructs of 5 mm length were implanted in vivo for 28 days within mice. Dense tissue assessed by micro-CT correlated with histologically assessed mineralised bone formation in all constructs. Exogenous growth factor addition did not enhance bone formation further compared to alginate/bone ECM (ALG/ECM) hydrogels alone. UV irradiation reduced bone formation through degradation of intrinsic growth factors within the bone ECM component and possibly also ECM cross-linking. BMP-2 and VitD3 rescued osteogenic induction. ALG/ECM hydrogels appeared highly osteoinductive and delivery of angiogenic or chondrogenic growth factors led to altered bone formation. All constructs demonstrated extensive host tissue invasion and vascularisation aiding integration and implant longevity. The proposed hydrogel system functioned without the need for growth factor incorporation or an exogenous inducible cell source. Optimal growth factor concentrations and spatiotemporal release profiles require further assessment, as the bone ECM component may suffer batch variability between donor materials. In summary, ALG/ECM hydrogels provide a versatile biomaterial scaffold for utilisation within regenerative medicine which may be tailored, ultimately, to form the tissue of choice through incorporation of select growth factors.

Physicomechanical properties of sintered scaffolds formed from porous and protein-loaded poly(DL-lactic-co-glycolic acid) microspheres for potential use in bone tissue engineering.

An injectable poly(DL-lactic-co-glycolic acid) (PLGA) system comprising both porous and protein-loaded microspheres capable of forming porous scaffolds at body temperature was developed for tissue regeneration purposes. Porous and non-porous (lysozyme loaded) PLGA microspheres were formulated to represent 'low molecular weight' 22-34 kDa, 'intermediate molecular weight' (IMW) 53 kDa and 'high molecular weight' 84-109 kDa PLGA microspheres. The respective average size of the microspheres was directly related to the polymer molecular weight. An initial burst release of lysozyme was observed from both microspheres and scaffolds on day 1. In the case of the lysozyme-loaded microspheres, this burst release was inversely related to the polymer molecular weight. Similarly, scaffolds loaded with 1 mg lysozyme/g of scaffold exhibited an inverse release relationship with polymer molecular weight. The burst release was highest amongst IMW scaffolds loaded with 2 and 3 mg/g. Sustained lysozyme release was observed after day 1 over 50 days (microspheres) and 30 days (scaffolds). The compressive strengths of the scaffolds were found to be inversely proportional to PLGA molecular weight at each lysozyme loading. Surface analysis indicated that some of the loaded lysozyme was distributed on the surfaces of the microspheres and thus responsible for the burst release observed. Overall the data demonstrates the potential of the scaffolds for use in tissue regeneration.

Formulations for modulation of protein release from large-size PLGA microparticles for tissue engineering.

In this study we present an approach to pre-program lysozyme release from large size (100-300 µm) poly(DL-lactic acid-co-glycolic acid) (PLGA) microparticles. This approach involved blending in-house synthesized triblock copolymers with a PLGA 85:15. In this work it is demonstrated that the lysozyme release rate and the total release are related to the mass of triblock copolymer present in polymer formulation. Two triblock copolymers (PLGA-PEG1500-PLGA and PLGA-PEG1000-PLGA) were synthesized and used in this study. In a like-for-like comparison, these two triblock copolymers appeared to have similar effects on the release of lysozyme. It was shown that blending resulted in the increase of the total lysozyme release and shortened the release period (70% release within 30 days). These results demonstrated that blending PLGA-PEG-PLGA triblock copolymer with PLGA 85:15 can be used as a method to pre-program protein release from microparticles. These microparticles with modulated protein release properties may be used to create microparticle-based tissue engineering constructs with pre-programmed release properties.

Injectable and porous PLGA microspheres that form highly porous scaffolds at body temperature.

Injectable scaffolds are of interest in the field of regenerative medicine because of their minimally invasive mode of delivery. For tissue repair applications, it is essential that such scaffolds have the mechanical properties, porosity and pore diameter to support the formation of new tissue. In the current study, porous poly(dl-lactic acid-co-glycolic acid) (PLGA) microspheres were fabricated with an average size of 84±24µm for use as injectable cell carriers. Treatment with ethanolic sodium hydroxide for 2min was observed to increase surface porosity without causing the microsphere structure to disintegrate. This surface treatment also enabled the microspheres to fuse together at 37°C to form scaffold structures. The average compressive strength of the scaffolds after 24h at 37°C was 0.9±0.1MPa, and the average Young's modulus was 9.4±1.2MPa. Scaffold porosity levels were 81.6% on average, with a mean pore diameter of 54±38µm. This study demonstrates a method for fabricating porous PLGA microspheres that form solid porous scaffolds at body temperature, creating an injectable system capable of supporting NIH-3T3 cell attachment and proliferation in vitro.

Accelerating protein release from microparticles for regenerative medicine applications.

There is a need to control the spatio-temporal release kinetics of growth factors in order to mitigate current usage of high doses. A novel delivery system, capable of providing both structural support and controlled release kinetics, has been developed from PLGA microparticles. The inclusion of a hydrophilic PLGA-PEG-PLGA triblock copolymer altered release kinetics such that they were decoupled from polymer degradation. A quasi zero order release profile over four weeks was produced using 10% w/w PLGA-PEG-PLGA with 50:50 PLGA whereas complete and sustained release was achieved over ten days using 30% w/w PLGA-PEG-PLGA with 85:15 PLGA and over four days using 30% w/w PLGA-PEG-PLGA with 50:50 PLGA. These three formulations are promising candidates for delivery of growth factors such as BMP-2, PDGF and VEGF. Release profiles were also modified by mixing microparticles of two different formulations providing another route, not previously reported, for controlling release kinetics. This system provides customisable, localised and controlled delivery with adjustable release profiles, which will improve the efficacy and safety of recombinant growth factor delivery.

Delivery of definable number of drug or growth factor loaded poly(DL-lactic acid-co-glycolic acid) microparticles within human embryonic stem cell derived aggregates.

Embryoid bodies (EBs) generated from embryonic stem cells are used to study processes of differentiation within a three dimensional (3D) cell environment. In many instances however, EBs are dispersed to single cell suspensions with a subsequent monolayer culture. Moreover, where the 3D integrity of an EB is maintained, cytokines or drugs of interest to stimulate differentiation are often added directly to the culture medium at fixed concentrations and effects are usually limited to the outer layers of the EB. The aim of this study was to create an EB model with localised drug and or growth factor delivery directly within the EB. Using poly(DL-lactic acid-co-glycolic acid) microparticles (MPs) with an average diameter of 13µm, we have demonstrated controllable incorporation of defined numbers of MPs within human ES cell derived EBs, down to 1 MP per EB. This was achieved by coating MPs with human ES cell lysate and centrifugation of specific ratios of ES cells and MPs to form 3D aggregates. Using MPs loaded with simvastatin (pro or active drug) or BMP-2, we have demonstrated osteogenic differentiation within the 3D aggregates, maintained in culture for up to 21days, and quantified by real time QPCR for osteocalcin. Immunostaining for RUNX2 and osteocalcin, and also histochemical staining with picrosirius red to demonstrate collage type 1 and Alizarin red to demonstrate calcium/mineralisation further demonstrated osteogenic differentiation and revealed regional staining associated with the locations of MPs within the aggregates. We also demonstrated endothelial differentiation within human ES cell-derived aggregates using VEGF loaded MPs. In conclusion, we demonstrate an effective and reliable approach for engineering stem aggregates with definable number of MPs within the 3D cellular structure. We also achieved localised osteogenic and endothelial differentiation associated with MPs releasing encapsulated drug molecules or cytokines directly within the cell aggregate. This provides a powerful tool for controlling and investigating differentiation within 3D cell cultures and has applications to drug delivery, drug discovery, stem cell biology, tissue engineering and regenerative medicine.

Biofilm eradication with biodegradable modified-release antibiotic pellets: a potential treatment for glue ear.

OBJECTIVE: To develop a biodegradable, modified-release antibiotic pellet capable of eradicating biofilms as a potential novel treatment for biofilm infections. DESIGN: Pellets containing poly(DL-lactic-co-glycolic acid) microparticles, rifampin and clindamycin hydrochloride (3.5%, 7%, or 28% antibiotic by weight), and carrier gel (carboxymethylcellulose or poloxamer 407) were tested in vitro. Drug release was assessed using serial plate transfer testing and high-performance liquid chromatography, and pellets were tested against biofilms in an in vitro model of Staphylococcus aureus biofilm grown on silicone. RESULTS: Serial plate transfer testing demonstrated continuing bacterial inhibition for up to 21 days for all pellets studied. High-performance liquid chromatography showed high levels of drug release for 2 to 4 days, with greatly reduced levels subsequently; continued measurable clindamycin (but not rifampin) release for up to 21 days was achieved. Pellets made with poloxamer released higher drug levels for a longer period. Irrespective of the carrier gel used, pellets containing 7% and 28% (but not 3.5%) antibiotic eradicated biofilms successfully. CONCLUSIONS: Antibiotic pellets can release antibiotics for up to 21 days and are able to eradicate biofilms in an in vitro model. Use of modified-release antibiotic formulations in the middle ear as a treatment for biofilms appears to be a potentially promising new therapy for otitis media with effusion.