A Biodegradable, Sustained-Released, Tacrolimus Microfilm Drug Delivery System for the Management of Allergic Conjunctivitis in a Mouse Model.

Purpose: To investigate the drug release profiles of a tacrolimus-loaded poly(D,L-lactide-co-ε-caprolactone) (PLC) microfilm, and to evaluate its efficacy on the treatment of allergic conjunctivitis using a mouse model. Methods: The in vitro and in vivo drug release profiles were first characterized. Balb/c mice were immunized with short ragweed (SRW) injection followed by re-challenges with topical SRW solution. The mice were divided into six groups (n = 12 in each): negative control (NC); positive control (PC); tacrolimus eye drops (Te); subconjunctival tacrolimus microfilm (Tm); dexamethasone eye drops (De); and tacrolimus + dexamethasone eye drops (Te+De). The mice were evaluated for 28 days by a scoring system for allergic conjunctivitis. Histopathologic and immunohistochemical staining with CD11c, CD4, and IL-4 were performed. Results: The microfilms were biocompatible and delivered clinically sufficient dose in a sustained manner, with a steady rate of 0.212 to 0.243 µg/day in vivo. Compared to the PC groups, the Te, Tm, De, and Te+De groups significantly reduced the allergic clinical scores throughout the study period (all P < 0.01; 0.0 ± 0.0, 5.6 ± 0.9, 3.3 ± 0.9, 3.2 ± 0.9, 1.9 ± 0.4 and 1.7 ± 0.8 for the NC, PC, Tm, Te, De, and Te+De groups, respectively, at 4 weeks after treatment). The suppressed eosinophils, CD11c, CD4, and IL-4 expression were also observed in all treatment groups, with more reduction in the Te+De group. Conclusions: Tacrolimus-loaded microfilms display good biocompatibility and desirable sustained drug release. It was as effective as conventional tacrolimus eye drops on the treatment of allergic conjunctivitis, providing a promising clinically applicable alternative for controlling allergic disease activity, or other immune-mediated ocular diseases.

Evaluation of a Sustained-Release Prednisolone Acetate Biodegradable Subconjunctival Implant in a Non-Human Primate Model.

PURPOSE: We evaluate the toxicity and plasma toxicokinetic (TK) profile of a biodegradable subconjunctival microrod for sustained prednisolone acetate (PA) release over 12 weeks in a non-human primate model. METHODS: The biodegradable copolymer poly(l-lactide-co-ε-caprolactone) (PLC) and 40-wt% PA microrods were used and fashioned into 8 and 16 mm lengths. Twelve monkeys were divided into two treatment groups of PA-loaded and blank microrods, with six monkeys each receiving either 8- or 16-mm microrods subconjunctively implanted into both eyes. TK and hematology parameters were analyzed. Ophthalmic clinical evaluation, including slit-lamp and ophthalmoscopy examinations, was performed. RESULTS: Over the study period of 12 weeks, the mean area under the plasma concentration-time curve was 45.7% higher, and the maximum plasma concentration was 17.2% lower for the animals treated with 40-wt% PA 16-mm microrods compared to 8-mm microrods (251.44 versus 172.54 hours × nanograms per milliliter and 8.53 versus 10.30 ng/mL, respectively). The PA release was significantly below the levels of assumed toxicity. There was no significant difference in the time to reach maximum concentration between the 8- and 16-mm microrod groups (7.33 and 8 hours; P = 0.421). Findings from clinical evaluation, hematology, and histopathology showed no ocular side effects and no significant adverse systemic effects. CONCLUSION: The PA biodegradable microrods demonstrated safe toxicokinetics even with the larger size implant containing a higher amount of drug. The PA implant may be considered as a safe alternative to the application of topical PA eyedrops. TRANSLATIONAL RELEVANCE: The results provide the evidence of the safety of implanting a steroid delivery system subconjunctively, offering an alternative to topical PA eyedrops.

In vivo Evaluation of Cenderitide-Eluting Stent (CES) II.

The use of drug-eluting coronary stents has led to significant reduction in in-stent restenosis (ISR), but led to delayed endothelialization, necessitating the prolonged use of expensive anti-thrombotic drugs with their side-effects. Cenderitide (CD-NP) is a novel anti-proliferative chimeric peptide of semi-endothelial origin. Our previous work in vitro has demonstrated; that the smooth muscle cells were inhibited significantly more than endothelial cells which is the desirable feature of an anti-restenosis drug. This work reports the effects of implantation of a centeritide-eluting stent (CES) on ISR and endothelialization in an in vivo model. CESs were produced by coating bare metallic stents with CD-NP entrapped in biodegradable poly(ε-caprolactone) using an ultrasonic spray coater. A total of 32 stents were successfully implanted into 16 pigs, and all animal survived for 28 days. The plasma levels of CD-NP were significantly higher in the CES group than in the control group (bare metal stents and polymer-coated stent) at post-stenting, indicating the successful release of CD-NP from the stent in vivo. Furthermore, SEM analysis results showed the greater endothelial coverage of the stent struts, as well as between the struts in CES group. Moreover, histological results showed mild inflammation, and low fibrin score at 28 days. However, plasma cGMP (second messenger, cyclic 3',5' guanosine monophosphate) does not show a significant difference, and the CES is also unable to show significant difference in terms on neointimal area and stenosis, in comparison to BMS at 28 days.

A biodegradable ocular implant for long-term suppression of intraocular pressure.

Timolol maleate (TM) has been used for many years for the reduction of intraocular pressure (IOP) in glaucoma patients. However, the topical mode of administration (eyedrops) is far from optimal because of the issues of low bioavailability, high drug wastage, and lack of patient compliance. Suboptimal control of the IOP leads to disease progression and eventually to blindness. Ideally, TM is delivered to the patient so that its action is both localized and sustained for 3 months or more. In this work, we developed a subconjunctival TM microfilm for sustained, long-term delivery of TM to the eyes, using the biodegradable elastomer poly(lactide-co-caprolactone) (PLC). The copolymer is biocompatible and has flexibility and mechanical characteristics suitable for a patient-acceptable implant. Controlling the release of TM for 3 months is challenging, and this work describes how, by using a combination of multilayering and blending with poly(ethylene glycol) (PEG) copolymers, we were able to develop a TM-incorporated biodegradable film that can deliver TM at a therapeutic dose for 90 days in vitro. The data was further confirmed in a diseased primate model, with sustained IOP-lowering effects for 5 months with a single implant, with acceptable biocompatibility and partial degradation.

In vitro evaluation of cenderitide-eluting stent I -an antirestenosis and proendothelization approach.

Despite the success that drug-eluting stents (DESs) have achieved for minimizing in-stent restenosis (ISR), the antirestenotic agents used in DES have been implicated in delayed endothelial healing and impairment of endothelial functions. Cenderitide (CD-NP) is a novel antiproliferation chimeric peptide of semiendothelial origin; thus, this paper aims to demonstrate the selectivity aspect of this new peptide via in vitro evaluation on key players in ISR-smooth muscle cells (SMCs) and endothelial cells. The microbicinchoninic acid protein assay was used to investigate the CD-NP release from films and stents. Cenderitide-containing films blended with poly(ethylene glycol) and its copolymer exhibited higher release kinetics compared with neat poly(ε-caprolactone) (PCL) formulation. Cenderitide-eluting stents (CES) was produced by coating bare metallic stents with CD-NP entrapped PCL using an ultrasonic spray coater. The investigation of CD-NP on in vitro cells revealed that CD-NP inhibits human coronary smooth muscle cells (HCaSMCs) proliferation but exhibits no effects on human umbilical vein endothelial cells (HUVECs) proliferation. Moreover, CD-NP released up to 7 days displayed inhibitory effects on SMCs proliferation. The CES produced in this work shows that the released CD-NP inhibits HCaSMCs proliferation but did not hamper HUVECs proliferation in vitro, suggesting that it has potential to reduce ISR without retarding the endothelialization healing in vivo.

Drug-eluting biostable and erodible stents.

This paper reviews the latest research and development of drug-eluting stents. The emphasis is on coronary stenting, and both biostable and bioerodible stents are covered in this review. The advantages and shortcomings of the bioactive molecules used in these stents are analyzed, along with the rationale for using bioerodible coatings. The overall emphasis is on the performance of these stents in the clinic. Based on the evaluation of the different stent types, we conclude that fully-erodible stents with a coating of antiproliferative drug will slowly gain market share in the near future, and that the search for a more selective anti-proliferative compound will continue. Dual-drug eluting stents (DDESs) will have their market share but possibly a much smaller one than that for single-drug eluting stents due to the complexities and costs of DDES unless significantly superior performance is demonstrated in the clinic.

Sustained-release from nanocarriers: a review.

Nanocarriers have been explored for delivering drugs and other bioactive molecules for well over 35years. Since the introduction of Doxil®, a nanoliposomal delivery system for the cancer drug doxorubicin, several products have been approved worldwide. The majority of these products focus on cancer chemotherapy, and utilize the size advantage of nanocarriers to obtain a favourable distribution of the drug carrier in the human body. In general, such carriers do not sustain drug release over more than a few days at best. In this review, we explore the reasons for this, and present an overview of successful research that is capable of generating sustained-release products in non-cancer applications. A variety of nanocarriers have been studied, and their advantages and shortcomings are highlighted in this review. The achievement of sustained release of bioactive molecules opens new doors in nanotherapeutics.

Investigation of cenderitide controlled release platforms for potential local treatment of cardiovascular pathology.

In this work, we focused on the development and investigation of controlled release matrices for a novel cardiotherapeutic peptide, cenderitide (CD-NP) that has shown to be useful for control of ventricular remodeling. To circumvent the hydrophilicity disparity between CD-NP and hydrophobic polymer matrix, a cosolvent system (water/dichloromethane) was selected for investigation. The effect of emulsification conditions, addition of poly(ethylene glycol) (PEG) and its copolymer on the release mechanism and profile were investigated. To verify the retention of bioactivity of entrapped CD-NP in different formulations, the generation of 3',5' cyclic guanosine monophospate (cGMP) and the inhibition of human cardiac fibroblast (HCF) were evaluated. The results showed that neat poly(ε-caprolactone) matrices carried out via two distinct emulsification conditions had either an unacceptably high burst or incomplete release of CD-NP; and the addition of PEG and its copolymer obtained intermediate profiles. Our confocal laser scanning microscopy and surface morphological investigations showed that the copolymer excipient was superior in playing stabilizer role by colocalizing and redistributing peptide throughout the matrix, making the release less sensitive to emulsification conditions. Furthermore, the released CD-NP is able to generate the cGMP and inhibit the HCF proliferation. Our investigations showed that CD-NP-loaded platforms can be a feasible option to provide sustained antifibrotic moderation of fibrotic scar formation and be potentially used to alleviate the adverse effects of cardiac remodeling.

Cenderitide-eluting film for potential cardiac patch applications.

Cenderitide, also known as CD-NP, is a designer peptide developed by combining native mammalian c-type natriuretic peptide (CNP) and the C-terminus isolated from the dendroapis natriuretic peptide (DNP) of the venom from the green mamba. In early studies, intravenous and subcutaneous infusion of cenderitide was reported to reduce left ventricular (LV) mass and ameliorate cardiac remodelling. In this work, biodegradable polymeric films encapsulating CD-NP were developed and were investigated for their in vitro release and degradation characteristics. Subsequently, the bioactivity of released peptide and its effects on human cardiac fibroblast (HCF) were explored. We achieved sustained release from three films with low, intermediate and high release profiles for 30 days. Moreover, the bioactivity of released peptide was verified from the elevated production of cyclic guanosine monophospate (cGMP). The CD-NP released from films was able to inhibit the proliferation of hypertrophic HCF as well as suppress DNA synthesis in HCF. Furthermore, the sustained delivery from films showed comparable or superior suppressive actions on hypertrophic HCF compared to daily infusion of CD-NP. The results suggest that these films could be used to inhibit fibrosis and reduce cardiac remodelling via local delivery as cardiac patches.

A new insight for an old system: protein-PEG colocalization in relation to protein release from PCL/PEG blends.

Quantification of protein-polymer colocalization in a phase-separated polymer blend gives important insights into the protein release mechanism. Here, we report on the first visualization of protein-poly(ethylene glycol) (protein-PEG) colocalization in poly(ε-caprolactone)/poly(ethylene glycol) (PCL/PEG) blend films using a combined application of confocal Raman mapping and confocal laser scanning microscopy (CLSM) imaging. The degree of protein-PEG colocalization was further quantified via a novel image processing technique. This technique also allowed us to characterize the 3-D protein distribution within the films. Our results showed that the proteins were homogeneously distributed within the film matrix, independent of PEG content. However, the degree of protein-PEG colocalization was inversely proportional to PEG content, ranging from 65 to 94%. This quantitative data on protein-PEG colocalization was used along with in vitro PEG leaching profile to construct a predictive model for overall protein release. Our prediction matched well with the experimental protein release profile, which is characterized by an initial burst release and a subsequent slower diffusional release. More importantly, the success of this predictive model has highlighted the influence of protein-PEG colocalization on the protein release mechanism.