Vascular Response Toward an Absorbable Sirolimus-eluting Polymeric Scaffold for Vascular Application in a Model of Normal Porcine Carotid Arteries.

BACKGROUND: Fully absorbable polymeric scaffolds, as a potential alternative to permanent metallic stents, are entering the clinical field. The aim of this study is to assess the in vivo biocompatibility of a novel Sirolimus-eluting (SIR) absorbable scaffold based on poly(L-lactide) (PLLA) and poly(4-hydroxybutyrate) (P4HB) for interventional application. METHODS: Absorbable PLLA/P4HB scaffolds either loaded with SIR coating or unloaded scaffolds were implanted interventionally into common carotid arteries of 14 female. Bare metal stents (BMS) served as control. Peroral dual anti-platelet therapy was administered throughout the study. Stented common carotid arteries segments were explanted after 4 weeks, and assessed histomorphometrically. RESULTS: The absorbable scaffolds showed a decreased residual lumen area and higher stenosis after 4 weeks (PLLA/P4HB: 6.56 ± 0.41 mm² and 37.56 ± 4.67%; SIR-PLLA/P4HB: 6.90 ± 0.58 mm² and 35.60 ± 3.15%) as compared to BMS (15.29 ± 1.86 mm² and 7.65 ± 2.27%). Incorporation of SIR reduced the significantly higher inflammation of unloaded scaffolds however not to a level compared to bare metal stent (PLLA/P4HB: 1.20 ± 0.19; SIR-PLLA/P4HB: 0.96 ± 0.24; BMS: 0.54 ± 0.12). In contrast, the BMS showed a slightly elevated vascular injury score (0.74 ± 0.15), as compared to the PLLA/P4HB (0.54 ± 0.20) and the SIR-PLLA/P4HB (0.48 ± 0.15) groups. CONCLUSION: In this preclinical model, the new absorbable polymeric (SIR-) scaffolds showed similar technical feasability and safety for vascular application as the permanent metal stents. The higher inflammatory propensity of the polymeric scaffolds was slightly reduced by SIR-coating. A smaller strut thickness of the polymeric scaffolds might have been a positive effect on tissue ingrowth between the struts and needs to be addressed in future work on the stent design.

Influence of Drug Incorporation on the Physico-Chemical Properties of Poly(l-Lactide) Implant Coating Matrices-A Systematic Study.

Local drug delivery has become indispensable in biomedical engineering with stents being ideal carrier platforms. While local drug release is superior to systemic administration in many fields, the incorporation of drugs into polymers may influence the physico-chemical properties of said matrix. This is of particular relevance as minimally invasive implantation is frequently accompanied by mechanical stresses on the implant and coating. Thus, drug incorporation into polymers may result in a susceptibility to potentially life-threatening implant failure. We investigated spray-coated poly-l-lactide (PLLA)/drug blends using thermal measurements (DSC) and tensile tests to determine the influence of selected drugs, namely sirolimus, paclitaxel, dexamethasone, and cyclosporine A, on the physico-chemical properties of the polymer. For all drugs and PLLA/drug ratios, an increase in tensile strength was observed. As for sirolimus and dexamethasone, PLLA/drug mixed phase systems were identified by shifted drug melting peaks at 200 °C and 240 °C, respectively, whereas paclitaxel and dexamethasone led to cold crystallization. Cyclosporine A did not affect matrix thermal properties. Altogether, our data provide a contribution towards an understanding of the complex interaction between PLLA and different drugs. Our results hold implications regarding the necessity of target-oriented thermal treatment to ensure the shelf life and performance of stent coatings.

Development of a biodegradable antifibrotic local drug delivery system for glaucoma microstents.

To prevent implant failure due to fibrosis is a major objective in glaucoma research. The present study investigated the antifibrotic effects of paclitaxel (PTX), caffeic acid phenethyl ester (CAPE), and pirfenidone (PFD) coated microstent test specimens in a rat model. Test specimens based on a biodegradable blend of poly(4-hydroxybutyrate) biopolymer and atactic poly(3-hydroxybutyrate) (at.P(3HB)) were manufactured, equipped with local drug delivery (LDD) coatings, and implanted in the subcutaneous white fat depot. Postoperatively, test specimens were explanted and analyzed for residual drug content. Fat depots including the test specimens were histologically analyzed. In vitro drug release studies revealed an initial burst for LDD devices. In vivo, slow drug release of PTX was found, whereas it already completed 1 week postoperatively for CAPE and PFD LDD devices. Histological examinations revealed a massive cell infiltration in the periphery of the test specimens. Compact fibrotic capsules around the LDD devices were detectable at 4-36 weeks and least pronounced around PFD-coated specimens. Capsules stained positive for extracellular matrix (ECM) components. The presented model offers possibilities to investigate release kinetics and the antifibrotic potential of drugs in vivo as well as the identification of more effective agents for a novel generation of drug-eluting glaucoma microstents.

In vitro chlorhexidine release from alginate based microbeads for periodontal therapy.

Periodontitis is one of the most common infectious diseases globally that, if untreated, leads to destruction of the tooth supporting tissues and finally results in tooth loss. Evidence shows that standard procedures as mechanical root cleaning could be supported by further treatment options such as locally applied substances. Due to gingival crevicular fluid flow, substances are commonly washed out off the periodontal pockets. The evaluation of administration techniques and the development of local drug releasing devices is thus an important aspect in periodontal research. This study describes the development and examination of a new alginate based, biodegradable and easily applicable drug delivery system for chlorhexidine (CHX). Different micro beads were produced and loaded with CHX and the release profiles were investigated by high performance liquid chromatography (HPLC). The in vitro-demonstrated release of CHX from alginate based beads shows comparable releasing characteristics as clinically approved systems. Yet many characteristics of this new delivery system show to be favourable for periodontal therapy. Easy application by injection, low production costs and multifunctional adaptions to patient related specifics may improve the usage in routine care.

Development of a biodegradable flow resisting polymer membrane for a novel glaucoma microstent.

Within this paper we analyzed the technical feasibility of a novel microstent for glaucoma therapy. For lowering of intraocular pressure, the flexible polyurethane (PUR) implant is designed to drain aqueous humour from the anterior chamber of the eye into subconjunctival, or alternatively suprachoroidal, space. The microstent includes a biodegradable, flow resisting polymer membrane serving as temporary flow resistance for the prevention of early postoperative hypotony. A biodegradable local drug delivery (LDD)-device was designed to prevent fibrous encapsulation. Biodegradable components were made of flexible, nonwoven membranes of Poly(4-hydroxybutyrate) (P(4HB)). Polymer samples and microstent prototypes were manufactured by means of dip coating, electrospinning and femtosecond-laser micromachining and characterized in vitro with regard to structural and fluid mechanical properties, degradation behavior and drug release. Bending stiffness of PUR-tubing (62.53 ± 7.57 mN mm2) is comparable to conventional glaucoma drainage devices in a tube-plate design. Microstent prototypes yield a flow resistance of 2.4 ± 0.6 mmHg/µl min-1 which is close to the aspired value corresponding to physiological pressure (15 mmHg) and aqueous humour flow (2 µl min-1) conditions inside the eye. Degradation of electrospun P(4HB) specimens was found to be almost completely finished after six months in vitro. Within this time frame, flow capacity of the microstent increases, which is beneficial to compensate potentially increasing flow resistance of fibrous tissue in vivo. Fast drug release of the LDD-device was found. One microstent prototype was implanted into a porcine eye ex vivo. Future preclinical studies will allow further information about Microstent performance.

Biosimilars and cancer treatment of older patients.

Biosimilar monoclonal antibodies are being developed globally to meet clinical demand in oncology and potentially provide greater access to biologic therapies for patients with cancer, including older patients. In this supplement, we present an overview of the development, approval requirements, and characteristics of biosimilar monoclonal antibodies that may help practicing oncologists and other healthcare providers to acquire familiarity with this new group of therapeutic biologic agents. Furthermore, we review and discuss some of the challenges and potential strategies for the management of older patients with cancer, who represent an increasing population in many countries.

Osteoporosis Diagnosis and Management in Long-Term Care Facility.

BACKGROUND: Contemporary estimates of the prevalence of diagnosed osteoporosis among long-term care facility residents are limited. METHODS: This chart review collected data between April 1, 2012 and August 31, 2013 for adult (age ≥ 30 years) residents of 11 long-term care facilities affiliated with the Louisiana State University Health Sciences Center in the New Orleans metropolitan area. Data (demographics; comorbidities; osteoporosis diagnosis, risk factors, diagnostic assessments, treatments; fracture history; fall risk; activities of daily living) were summarized. Data for residents with and without diagnosed osteoporosis were compared using χ tests and t tests. RESULTS: The study included 746 residents (69% women, mean [SD] age: 76.3 [13.9] years, median length of stay approximately 18.5 months). An osteoporosis diagnosis was recorded for 132 residents (18%), 30% of whom received a pharmacologic osteoporosis therapy. Fewer than 2% of residents had bone mineral density assessments; 10% had previous fracture. Calcium and vitamin D use was more prevalent in residents with diagnosed osteoporosis compared with other residents (calcium: 49% versus 12%, vitamin D: 52% versus 28%; both P < 0.001). Over half (304/545) of assessed residents had a high fall risk. Activities of daily living were similarly limited regardless of osteoporosis status. CONCLUSIONS: The prevalence of diagnosed osteoporosis was higher than previously reported for long-term care residents, but lower than epidemiologic estimates of osteoporosis prevalence for the noninstitutional U.S. POPULATION: In our sample, osteoporosis diagnostic testing was rare and treatment rates were low. Our results suggest that osteoporosis may be underdiagnosed and undertreated in long-term care settings.

In vitro evaluation of paclitaxel coatings for delivery via drug-coated balloons.

Lately, drug-coated balloons have been introduced in interventional cardiology as an approach to treat occluded blood vessel. They were developed for the rapid transfer of antiproliferative drugs during the angioplasty procedure in stenosed vessels with the intent to reduce the risk of restenosis. In this study five different paclitaxel (PTX) balloon coatings were tested in vitro in order to examine how solvents and additives influence coating stability and drug transfer rates. PTX-coated balloons were advanced through a guiding catheter and a simulated coronary artery pathway under perfusion and were then inflated in a hydrogel acceptor compartment. The fractions transferred to the gel, remaining on the balloon and the PTX lost in the simulated coronary pathway were then analysed. The results obtained suggest that the solvent used for the coating process strongly influences the surface structure and the stability of the coating. Ethanol/water and acetone based PTX coatings showed the lowest drug transfer rates to the simulated vessel wall (both <1%) due to their high drug losses during the prior passage through the coronary artery model (more than 95%). Balloons coated with PTX from ethyl acetate-solutions showed smaller drug loss (83%±9%), but most of the remaining PTX was not transferred (mean balloon residue approximately 15%). Beside the solvent, the use of additives seemed to have a great impact on transfer properties. The balloon pre-treatment with a crosslinked polyvinylpyrrolidone (PVP) film was able to increase the PTX transfer rate from less than 1% (without PVP) to approximately 6%. The best results in this study were obtained for balloon coatings with commercially available SeQuent© Please balloons containing the contrast agent iopromide. For this formulation drug transfer rates of approximately 17% were determined. Fluorescence microscopic imaging could visualize the particulate transfer of labelled PTX from the balloon surface during dilatation. The findings of this study underline the importance of drug adhesion and coating stability for the efficiency of PTX transfer.

Development of an Experimental Drug Eluting Suprachoroidal Microstent as Glaucoma Drainage Device.

PURPOSE: A novel glaucoma drainage device (GDD) with local drug delivery (LDD) system was created and characterized for safety and effectiveness after implantation into the suprachoroidal space (SCS) of rabbit eyes. METHODS: Thin films of two different polymers, Poly(3-hydroxybutyrate) (P(3HB)) and Poly(4-hydroxybutyrate) (P(4HB)), containing the drugs mitomycin C (MitC) or paclitaxel (PTX) were attached to silicone-tubes to create LDD devices. The release kinetics of these drugs were explored in vitro using high performance liquid chromatography (HPLC). Twenty-four New Zealand white rabbits, randomly divided into eight groups, were implanted with different kinds of microstents into SCS. The intraocular pressure (IOP) was monitored noninvasively. After 6 weeks, rabbits were sacrificed and enucleated eyes were used for anterior segment optical coherence tomography (OCT), micro magnetic resonance imaging (MRI), and histology. RESULTS: In vitro, faster drug release from both polymers was observed for MitC compared to PTX. Comparing polymers, the release from P(3HB) matrix was slower for both drugs. MRI and OCT showed all implants maintained a proper location. An effective IOP reduction was observed for up to 6 weeks in eyes with microstents combined with a drug-releasing LDD system. Overall, the surrounding tissue revealed mild-to-moderate inflammation. No pronounced fibrosis was observed in any of the groups. However, both drugs caused damage to the neighboring retina. CONCLUSIONS: The suprachoroidal microstent reduced IOP with mild inflammation in rabbit eyes. To avoid negative effects on the retina, it is necessary to identify novel drugs with less cytotoxicity. Future studies are needed to explore the fibrotic process over the long-term. TRANSLATIONAL RELEVANCE: The presented data serve as a proof of principle study for the concept of a suprachoroidal drug eluting microstent. Future device improvements will be focused on the design of LDD systems and the use of specific anti-inflammatory or antifibrotic agents with less cytotoxicity compared to MitC or PTX. Long-term animal studies using a reliable glaucoma model will be a further step towards clinical application and improvement of surgical glaucoma therapy.

In vitro study of sirolimus release from a drug-eluting stent: Comparison of the release profiles obtained using different test setups.

In this study drug release from the CYPHER™ stent, the gold standard in drug-eluting stent therapy until the end of its marketing in 2011/2012, was systematically evaluated using different in vitro release tests. The test systems included incubations setups, the reciprocating holder apparatus (USP7), the flow-through cell apparatus (USP4) and the vessel-simulating flow-through cell (vFTC) specifically designed for stent testing. The results obtained show a large variability regarding the fractions released into the media after 7d ranging from 38.6% ± 4.5% to 74.6% ± 1.2%. The lowest fraction released was observed in the vFTC and the highest in an incubation setup with frequently changed media of a volume of 2 mL. Differences were even observed when using fairly similar and simple incubations setups with mere changes of the media volume, under maintenance of sink conditions, and of the vessel geometry. From these data it can be concluded, that in vitro release even from a slow releasing drug-eluting stent is greatly influenced by the experimental conditions and care must be taken when choosing a suitable setup. Comparison of the obtained in vitro release profiles to published in vivo data did not result in a distinct superiority of any of the tested methods regarding the predictability for the situation in vivo due to large differences in the reported in vivo data. However, this comparison yielded that the release observed in vitro using the 2 mL incubation setup and the reciprocating holder apparatus may be faster than the reported in vivo release. The results of this study also emphasize the necessity to use highly standardized release tests when comparisons between results from different experiments or even different labs are to be performed. In this context, the compendial methods are most likely offering the highest degree of standardization.

An analysis of chronic kidney disease risk factors in a Louisiana nursing home population: a cross-sectional study.

BACKGROUND: Chronic Kidney Disease (CKD) and its progression are associated with multiple risk factors. CKD is prevalent in nursing homes residents, but factors related to CKD in this setting have not been defined. METHODS: A cross-sectional study was conducted (n=103). Data was abstracted using standardized forms and analyzed (SAS 9.2). Chi square and t-test statistics were used to compare proportions and means; correlation coefficients were used to describe associations. Logistic models were fit to the data to determine multivariate associations. Modification of Diet in Renal Disease (MDRD) formula was used to estimate GFR. CKD was defined according to established standards. A cutoff point of 60 was chosen for further analysis. RESULTS: Twenty-three percent of subjects had CKD. Mean age for eGFR <60 was 70.8 +/- 13 and for eGFR >60 was 61.7 +/-14. Frequent co-morbidities were hypertension (75%), GERD (40%), obesity (39%), dyslipidemia (35%), depression (34%), anemia (32%), and diabetes (32%). CONCLUSIONS: Our population is unique in terms of its age and reasons for nursing home admission. Factors associated with CKD in our study include age >65 years old, being male, having a positive history of cardiovascular disease (including congestive heart failure and coronary artery disease,) anemia, polypharmacy, and being obese (BMI >30). Further analysis showed that age and anemia are the strongest factors associated with CKD in our population. Management targeted at CKD risk factor reduction may play a vital role in controlling the magnitude of this disease. Prospective studies to investigate the relationship between gender, a BMI greater than 30, cardiovascular disease, and CKD and its complications are warranted.

Development of a sirolimus-eluting poly (L-lactide)/poly(4-hydroxybutyrate) absorbable stent for peripheral vascular intervention.

Fully absorbable drug-eluting stent platforms are currently entering the clinical arena for the interventional treatment of coronary artery disease. This new technology also holds potential for application in peripheral vascular settings. Our study reports on the development of a sirolimus- (SIR) eluting absorbable polymer stent made from a blend of poly(l-lactide) and poly(4-hydroxybutyrate) (PLLA/P4HB) for peripheral vascular intervention. Stent prototypes were laser-cut from PLLA/P4HB tubes (I.D.=2.2 mm, t=250 µm), spray-coated with different PLLA/P4HB/SIR solutions, and bench-tested to determine expansion properties, fatigue, trackability and in vitro drug release kinetics. The stent prototypes were expanded with a 5.0 × 20 mm balloon catheter, and exhibited a recoil of 3.6% upon balloon deflation. Stent collapse pressure of 0.4 bar (300 mm Hg) was measured under external pressure load. Sustained scaffolding properties were observed in vitro over 14 weeks of radial fatigue loading (50 ± 25 mm Hg at 1.2 Hz). Trackability was demonstrated in bench tests with an 8 French contralateral introducer sheath. SIR release kinetics were adjusted over a broad range by varying the PLLA/P4HB ratio of the coating matrix. The newly developed absorbable SIR-eluting PLLA/P4HB stent successfully fulfilled the requirements for peripheral vascular intervention under in vitro conditions.

Permeability of the anterior lens capsule for large molecules and small drugs.

PURPOSE: For developing injectable lenses the retention properties of the capsular bag are important. Therefore the apparent permeability coefficients of sodium fluorescein and fluorescent dextrans of different sizes were determined for the human anterior lens capsule to calculate a molecular weight cutoff from these data. In addition, permeability coefficients of drugs helpful for the suppression of secondary cataract were determined. MATERIALS AND METHODS: Capsulorhexis specimens were fixed in a specially designed two compartment diffusion chamber to investigate the permeation of sodium fluorescein and fluorescent dextrans of different sizes (10, 40, 70 and 150 kDa) for 24 h (n ≥ 3) and of the antiproliferative drugs actinomycin D and methotrexate for 0.5, 24, 48 and 72 h (n ≥ 3). RESULTS: The molecular weight cutoff of the anterior lens capsule was found to be 166 ± 82 kDa. After 0.5 h, no passage of actinomycin D and methotrexate was detectable through the lens capsule. The apparent permeability coefficients for actinomycin D and methotrexate were calculated to 0.71 ± 0.02 µm/s and to 0.80 ± 0.13 µm/s, respectively. CONCLUSIONS: The capsular bag retains fluorescent dextrans with a molecular weight of >166 kDa. Hence, prepolymers are required to polymerize rapidly to be retained inside of the capsular bag. In addition, low-molecular substances intended as antiproliferative drugs for secondary cataract prevention should be applied within a time frame of five minutes in such a way that cells adjacent to the capsular bag will not be damaged.

In vitro study of dual drug-eluting stents with locally focused sirolimus and atorvastatin release.

Within the context of novel stent designs we developed a dual drug-eluting stent (DDES) with an abluminally focussed release of the potent anti-proliferative drug sirolimus and a luminally focussed release of atorvastatin with stabilizing effect on atherosclerotic deposits and stimulating impact on endothelial function, both from biodegradable poly(L-lactide)-based stent coatings. With this concept we aim at simultaneous inhibition of in-stent restenosis as a result of disproportionally increased smooth muscle cell proliferation and migration as well as thrombosis due to failed or incomplete endothelialisation. The especially adapted spray-coating processes allowed the formation of smooth form-fit polymer coatings at the abluminal and luminal side with 70% respectively 90% of the drug/polymer solution being deposited at the intended stent surface. The impacts of tempering, sterilization, and layer composition on drug release are thoroughly discussed making use of a semi-empirical model. While tempering at 80 °C seems to be necessary for the achievement of adequate and sustained drug release, the coating sequence for DDES should be rather abluminal-luminal than luminal-abluminal, as reduction of the amount of sirolimus eluted luminally could then potentially minimize the provocation of endothelial dysfunction. In vitro proliferation and viability assays with smooth muscle and endothelial cells underline the high potential of the developed DDES.

In vitro determination of drug transfer from drug-coated balloons.

Drug-coated balloons are medical devices designed to locally deliver drug to diseased segments of the vessel wall. For these dosage forms, drug transfer to the vessel wall needs to be examined in detail, since drug released into the blood is cleared from the site. In order to examine drug transfer, a new in vitro setup was developed combining the estimation of drug loss during advancement to the site of application in a model coronary artery pathway with a hydrogel compartment representing, as a very simplified model, the vessel wall. The transfer of fluorescent model substances as well as the drug paclitaxel from coated balloons to the simulated vessel wall was evaluated using this method. The model was suitable to quantify the fractions transferred to the hydrogel and also to qualitatively assess distribution patterns in the hydrogel film. In the case of fluorescein sodium, rhodamin b and paclitaxel, vast amounts of the coated substance were lost during the simulated passage and only very small fractions of about 1% of the total load were transferred to the gel. This must be attributed to good water solubility of the fluorescent substances and the mechanical instability of the paclitaxel coating. Transfer of the hydrophobic model substance triamterene was however nearly unaffected by the preliminary tracking procedure with transferred fractions ranging from 8% to 14%. Analysis of model substance distribution yielded inhomogeneous distributions indicating that the coating was not evenly distributed on the balloon surface and that a great fraction of the coating liquid did not penetrate the folds of the balloon. This finding is contradictory to the generally accepted assumption of a drug depot inside the folds and emphasizes the necessity to thoroughly characterize in vitro performance of drug-coated balloons to support the very promising clinical data.

Mechanism of action of immunomodulatory agents in multiple myeloma.

Immunomodulatory agents (IMiD's) have become an important drug category in the treatment of multiple myeloma. The agents have a complex mechanism of action that influence the microenvironment in the bone marrow. The microenvironment is an essential promotor of disease progression and therefore important in targeting the disease. The article reviews mechanism of action and essential pathways of IMiD's that are important in disease treatment.

Electrochemical detection of DNA hybridization by means of osmium tetroxide complexes and protective oligonucleotides.

We have utilized protective oligonucleotides to modify DNA fragments with osmium tetroxide complexes without compromising their ability to hybridize with immobilized thiol-linked probe-SAMs on gold electrodes. Due to reversible voltammetric signals of Os(VI/IV), this method allowed sensitive electrochemical hybridization detection of short (25 bases) and long (120 bases) thymine-containing DNA targets. The detection limit was 3.2 nM for the long target. We found an optimum 40 degrees C hybridization temperature for the short target. No interference by noncomplementary DNA was observed. At least 10 repetitive hybridization experiments at the same probe-SAM were possible with thermal denaturation in between. Such use of protective strands could be useful also for other types of DNA recognition and even for other DNA-modifying agents. Moreover, it is possible to produce electrochemically active oligonucleotides (targets and reporter probes) in ones own laboratory in a simple way.

Electrochemical detection of osmium tetroxide-labeled PCR-products by means of protective strands.

This communication reports about how single-stranded 136 base polymerase chain reaction (PCR) products labeled with electrochemically active osmium tetroxide bipyridine can be detected voltammetrically by hybridization with probe strands immobilized on gold electrodes. These electroactive ssDNA targets have been obtained by means of Lambda Exonuclease treatment of the double-stranded PCR products followed by hybridization of the remaining single strands with short protective strands and covalent labeling with osmium tetroxide bipyridine. Square-wave voltammetric signals of these osmium labels have been obtained only upon hybridization with the immobilized probe strands. An optimal 50 degrees C hybridization temperature has been found with a saturation of the probe layer at 30 min hybridization time and 7.5 nmol/l target concentration. The blank capture probe layer alone did not yield any signal. Unprotected strands produced almost no interference. Such double-selective switch-on electrochemical hybridization assays hold great promise for the specific detection of PCR products.