In situ forming acyl-capped PCLA-PEG-PCLA triblock copolymer based hydrogels

<p>Sustained intra-articular drug delivery opens up new opportunities for targeted treatment of osteoarthritis. In this study, we investigated the in vitro and in vivo properties and performance of a newly developed hydrogel based on acyl-capped PCLA-PEG-PCLA specifically designed for intra-articular use. The hydrogel formulation consisted of a blend of polymers either capped with acetyl, or with 2-(2',3',5',-triiodobenzoyl, TIB) moieties. TIB was added to visualize the gel using mu CT, enabling longitudinal quantification of its degradation. Blends containing TIB-capped polymer degraded in vitro (37 degrees C; pH 7.4 buffer) through dissolution over a period of similar to 20 weeks, and degraded slightly faster (similar to 12 weeks) after subcutaneous injection in rats. This in vivo acceleration was likely due to active (enzymatic) degradation, shown by changes in polymer composition and molecular weight as well as the presence of macrophages. After intra-articular administration in rats, the visualized gel gradually lost signal intensity over the course of 4 weeks. Good cytocompatibility of acetyl-capped polymer based hydrogel was proven in vitro on erythrocytes and chondrocytes. Moreover, intra-articular biocompatibility was demonstrated using mu CT-imaging and histology, since both techniques showed no changes in cartilage quality and/or quantity. (C) 2013 Elsevier Ltd. All rights reserved.</p>

Degradation, Intra-Articular Biocompatibility, Drug Release, and Bioactivity of Tacrolimus-Loaded Poly(d - L -lactide-PEG)- b-poly(l -lactide) Multiblock Copolymer-Based Monospheres

The aim of this study was to develop a formulation with a sustained intra-articular release of the anti-inflammatory drug tacrolimus. Drug release kinetics from the prepared tacrolimus loaded monodisperse biodegradable microspheres based on poly(d-l-lactide-PEG)-b-poly(l-lactide) multiblock copolymers were tunable by changing polymer composition, particularly hydrophobic-hydrophilic block ratio. The monospheres were 30 μm and released the drug, depending on the formulation, in 7 to >42 days. The formulation exhibiting sustained release for 1 month was selected for further in vivo evaluation. Rat knees were injected with three different doses of tacrolimus (10 wt %) loaded monospheres (2.5, 5.0, and 10 mg), contralateral control knees with saline. Micro-CT and histology showed no negative changes on cartilage, indicating good biocompatibility. Minor osteophyte formation was seen in a dose dependent fashion, suggesting local drug release and therapeutic action thereof. To investigate in vivo drug release, tacrolimus monospheres were injected into horse joints, after which multiple blood and synovial fluid samples were taken. Sustained intra-articular release was seen during the entire four-week follow-up, with negligible systemic drug concentrations (<1 ng/mL), confirming the feasibility of local intra-articular drug delivery without provoking systemic effects. Intra-articular injection of unloaded monospheres led to a transient inflammatory reaction, measured by total synovial leucocyte count (72 h). This reaction was significantly lower in joints injected with tacrolimus loaded monospheres, showing not only the successful local tacrolimus delivery but also local anti-inflammatory action. This local anti-inflammatory potential without systemic side-effects can be beneficial in the treatment of inflammatory joint diseases, among which is osteoarthritis

Degradation, Intra-Articular Biocompatibility, Drug Release, and Bioactivity of Tacrolimus-Loaded Poly(d - L -lactide-PEG)- b-poly(l -lactide) Multiblock Copolymer-Based Monospheres

The aim of this study was to develop a formulation with a sustained intra-articular release of the anti-inflammatory drug tacrolimus. Drug release kinetics from the prepared tacrolimus loaded monodisperse biodegradable microspheres based on poly(d-l-lactide-PEG)-b-poly(l-lactide) multiblock copolymers were tunable by changing polymer composition, particularly hydrophobic-hydrophilic block ratio. The monospheres were 30 μm and released the drug, depending on the formulation, in 7 to >42 days. The formulation exhibiting sustained release for 1 month was selected for further in vivo evaluation. Rat knees were injected with three different doses of tacrolimus (10 wt %) loaded monospheres (2.5, 5.0, and 10 mg), contralateral control knees with saline. Micro-CT and histology showed no negative changes on cartilage, indicating good biocompatibility. Minor osteophyte formation was seen in a dose dependent fashion, suggesting local drug release and therapeutic action thereof. To investigate in vivo drug release, tacrolimus monospheres were injected into horse joints, after which multiple blood and synovial fluid samples were taken. Sustained intra-articular release was seen during the entire four-week follow-up, with negligible systemic drug concentrations (<1 ng/mL), confirming the feasibility of local intra-articular drug delivery without provoking systemic effects. Intra-articular injection of unloaded monospheres led to a transient inflammatory reaction, measured by total synovial leucocyte count (72 h). This reaction was significantly lower in joints injected with tacrolimus loaded monospheres, showing not only the successful local tacrolimus delivery but also local anti-inflammatory action. This local anti-inflammatory potential without systemic side-effects can be beneficial in the treatment of inflammatory joint diseases, among which is osteoarthritis

Degradation, Intra-Articular Biocompatibility, Drug Release, and Bioactivity of Tacrolimus-Loaded Poly(d - L -lactide-PEG)- b-poly(l -lactide) Multiblock Copolymer-Based Monospheres

The aim of this study was to develop a formulation with a sustained intra-articular release of the anti-inflammatory drug tacrolimus. Drug release kinetics from the prepared tacrolimus loaded monodisperse biodegradable microspheres based on poly(d-l-lactide-PEG)-b-poly(l-lactide) multiblock copolymers were tunable by changing polymer composition, particularly hydrophobic-hydrophilic block ratio. The monospheres were 30 μm and released the drug, depending on the formulation, in 7 to >42 days. The formulation exhibiting sustained release for 1 month was selected for further in vivo evaluation. Rat knees were injected with three different doses of tacrolimus (10 wt %) loaded monospheres (2.5, 5.0, and 10 mg), contralateral control knees with saline. Micro-CT and histology showed no negative changes on cartilage, indicating good biocompatibility. Minor osteophyte formation was seen in a dose dependent fashion, suggesting local drug release and therapeutic action thereof. To investigate in vivo drug release, tacrolimus monospheres were injected into horse joints, after which multiple blood and synovial fluid samples were taken. Sustained intra-articular release was seen during the entire four-week follow-up, with negligible systemic drug concentrations (<1 ng/mL), confirming the feasibility of local intra-articular drug delivery without provoking systemic effects. Intra-articular injection of unloaded monospheres led to a transient inflammatory reaction, measured by total synovial leucocyte count (72 h). This reaction was significantly lower in joints injected with tacrolimus loaded monospheres, showing not only the successful local tacrolimus delivery but also local anti-inflammatory action. This local anti-inflammatory potential without systemic side-effects can be beneficial in the treatment of inflammatory joint diseases, among which is osteoarthritis

Degradation, Intra-Articular Biocompatibility, Drug Release, and Bioactivity of Tacrolimus-Loaded Poly(d - L -lactide-PEG)- b-poly(l -lactide) Multiblock Copolymer-Based Monospheres

The aim of this study was to develop a formulation with a sustained intra-articular release of the anti-inflammatory drug tacrolimus. Drug release kinetics from the prepared tacrolimus loaded monodisperse biodegradable microspheres based on poly(d-l-lactide-PEG)-b-poly(l-lactide) multiblock copolymers were tunable by changing polymer composition, particularly hydrophobic-hydrophilic block ratio. The monospheres were 30 μm and released the drug, depending on the formulation, in 7 to >42 days. The formulation exhibiting sustained release for 1 month was selected for further in vivo evaluation. Rat knees were injected with three different doses of tacrolimus (10 wt %) loaded monospheres (2.5, 5.0, and 10 mg), contralateral control knees with saline. Micro-CT and histology showed no negative changes on cartilage, indicating good biocompatibility. Minor osteophyte formation was seen in a dose dependent fashion, suggesting local drug release and therapeutic action thereof. To investigate in vivo drug release, tacrolimus monospheres were injected into horse joints, after which multiple blood and synovial fluid samples were taken. Sustained intra-articular release was seen during the entire four-week follow-up, with negligible systemic drug concentrations (<1 ng/mL), confirming the feasibility of local intra-articular drug delivery without provoking systemic effects. Intra-articular injection of unloaded monospheres led to a transient inflammatory reaction, measured by total synovial leucocyte count (72 h). This reaction was significantly lower in joints injected with tacrolimus loaded monospheres, showing not only the successful local tacrolimus delivery but also local anti-inflammatory action. This local anti-inflammatory potential without systemic side-effects can be beneficial in the treatment of inflammatory joint diseases, among which is osteoarthritis

Sustained intra-articular release of celecoxib from in situ forming gels made of acetyl-capped PCLA-PEG-PCLA triblock copolymers in horses

In this study, the intra-articular tolerability and suitability for local and sustained release of an in situ forming gel composed of an acetyl-capped poly(ε-caprolactone-co-lactide)-b-poly(ethylene glycol)-b-poly(ε-caprolactone-co-lactide) (PCLA-PEG-PCLA) copolymer loaded with celecoxib was investigated in horse joints. The systems were loaded with two dosages of celecoxib, 50 mg/g ('low CLB gel') and 260 mg/g ('high CLB gel'). Subsequently, they were injected into the joints of five healthy horses. For 72 h after intra-articular injection, they induced a transient inflammatory response, which was also observed after application of Hyonate(®), a commercial formulation containing hyaluronic acid for the intra-articular treatment of synovitis in horses. However, only after administration of the 'high CLB gel' the horses showed signs of discomfort (lameness score: 1.6 ± 1.3 on a 5-point scale) 1 day after injection, which completely disappeared 3 days after injection. Importantly, there was no indication of cartilage damage. Celecoxib Cmax in the joints was reached at 8 h and 24 h after administration of the 'low CLB gel' and 'high CLB gel', respectively. In the joints, concentrations of celecoxib were detected 4 weeks post administration. Celecoxib was also detected in plasma at concentrations of 150 ng/ml at day 3 post administration and thereafter its concentration dropped below the detection limit. These results show that the systems were well tolerated after intra-articular administration and showed local and sustained release of celecoxib for 4 weeks with low and short systemic exposure to the drug, demonstrating that these injectable in situ forming hydrogels are promising vehicles for intra-articular drug delivery

Degradation, intra-articular retention and biocompatibility of monospheres composed of [PDLLA-PEG-PDLLA]-b-PLLA multi-block copolymers

In this study, we investigated the use of microspheres with a narrow particle size distribution (‘monospheres’) composed of biodegradable poly(DL-lactide)-PEG-poly(DL-lactide)-b-poly(L-lactide) multiblock copolymers that are potentially suitable for local sustained drug release in articular joints. Monospheres with sizes of 5, 15 and 30 μm and a narrow particle size distribution were prepared by a micro-sieve membrane emulsification process. During in vitro degradation, less crystallinity, higher swelling and accelerated mass loss during was observed with increasing the PEG content of the polymer. The monospheres were tested in both a small (mice/rat) and large animal model (horse). In vivo imaging after injection with fluorescent dye loaded microspheres in mice knees showed that monospheres of all sizes retained within the joint for at least 90 days, while the same dose of free dye redistributed to the whole body within the first day after intra-articular injection. Administration of monospheres in equine carpal joints caused a mild transient inflammatory response without any clinical signs and without degradation of the cartilage, as evidenced by the absence of degradation products of sulfated glycosaminoglycans or collagen type 2 in the synovial fluid. The excellent intra-articular biocompatibility was confirmed in rat knees, where μCT-imaging and histology showed neither changes in cartilage quality nor quantity. Given the good intra-articular retention and the excellent biocompatibility, these novel poly(DL-lactide)-PEG-poly(DL-lactide)-b-poly(L-lactide)-based monospheres can be considered a suitable platform for intra-articular drug delivery. Statement of Significance This paper demonstrates the great potential in intra-articular drug delivery of monodisperse biodegradable microspheres which were prepared using a new class of biodegradable multi-block copolymers and a unique membrane emulsification process allowing the preparation of microspheres with a narrow particle size distribution (monospheres) leading to multiple advantages like better injectability, enhanced reproducibility and predictability of the in vivo release kinetics. We report not only on the synthesis and preparation, but also in vitro characterization, followed by in vivo testing of intra-articular biocompatibility of the monospheres in both a small and a large animal model. The favourable intra-articular biocompatibility combined with the prolonged intra-articular retention (>90 days) makes these monospheres an interesting drug delivery platform. What should also be highlighted is the use of horses; a very accurate translational model for the human situation, making the results not only relevant for equine healthcare, but also for the development of novel human OA therapies