The composition of the stent microbiome is associated with morbidity and adverse events during endoscopic drainage therapy of pancreatic necroses and pseudocysts.

Background: Development of pancreatic necroses or pseudocysts are typical complications of pancreatitis and may require endoscopic drainage therapy using metal or plastic stents. Microbial infection of these lesions poses a major challenge. So far, the composition and significance of the microbial colonization on drainage stents are largely unknown although it may impact outcomes during endoscopic drainage therapy. Methods: A total of 26 stents used for drainage of pancreatic lesions were retrieved and the stent microbiome was determined by 16S rRNA gene sequencing. Additional analysis included comparison of the stent microbiome to the intracavitary necrosis microbiome as well as scanning electron microscopy (SEM) and micro-computed tomography (µCT) imaging of selected metal or plastic stents. Results: The stent microbiome comprises a large proportion of opportunistic enteric pathogens such as Enterococcus (14.4%) or Escherichia (6.1%) as well as oral bacteria like Streptococcus (13.1%). Increased levels of opportunistic enteric pathogens were associated with a prolonged hospital stay (r = 0.77, p = 3e-06) and the occurrence of adverse events during drainage therapy (p = 0.011). Higher levels of oral bacteria were associated (r = -0.62, p = 8e-04) with shorter durations of inpatient treatment. SEM and µCT investigations revealed complex biofilm networks on the stent surface. Conclusion: The composition of the stent microbiome is associated with prolonged hospital stays and adverse events during endoscopic drainage therapy, highlighting the need for effective infection control to improve patient outcomes. In addition to systemic antibiotic therapy, antimicrobial stent coatings could be a conceivable option to influence the stent microbiome and possibly enhance control of the necrotic microflora.

3-Sulfopropyl acrylate potassium-based polyelectrolyte hydrogels: sterilizable synthetic material for biomedical application.

Hydrogels are extensively used in the biomedical field due to their highly valued properties, biocompatibility and antimicrobial activity and resistance to rheological stress. However, determining an efficient sterilization protocol that does not compromise the functional properties of hydrogels is one of the challenges researchers face when developing a material for a medical application. In this work, conventional sterilization methods (steam-, radiation- and gas sterilization) were investigated regarding the influence on the degree of swelling, mechanical performance and chemical effects on the poly 3-sulfopropyl acrylate potassium (pAESO3) hydrogel, which is a promising representative for biomedical engineering applications. In summary, no significant changes in the gel properties were observed after sterilization, showing the potential of the selected hydrogel for biomedical applications.

In Vitro Corrosion of Polyester-Coated Magnesium Alloy under pH-Static Conditions.

The resorption rate of bioresorbable implants requires tuning to match the desired field of application. The use of Mg as implant material is highly advantageous, as it provides sufficient mechanical strength combined with its biodegradability. Consequently, the implant vanishes after it has served its intended purpose, allowing the complete restoration of natural tissue and organ function. However, a biodegradable Mg implant requires a biodegradable coating to slow the rate of Mg corrosion, as a permanent coating would negate the benefits of using Mg as an implant material. Therefore, degradable polymers are the materials of choice, especially polyester-based coatings, such as PLLA, as they have been proven in clinical practice over the long term. Within this work, the degradation retarding effect of a physical barrier in form of four clinically relevant polyester-based coatings, poly-l-lactide (PLLA), poly-l-lactide-co-glycolide (PLGA), poly(l-lactide-co-PEG) triblock copolymer (PLLA-co-PEG), and polydioxanone (PDO), is investigated in vitro under pH-static conditions using CO2 gas to compensate pH changes due to Mg corrosion. Coating thicknesses of 7.5 to 8.3 µm were comparable to commercially available stent systems. Quantitative analysis of magnesium concentration in buffered test medium by a photometric assay allows real-time monitoring. Shielding effect of different polyesters through polymer coating and formation of a protective passivation layer beneath the polymer coating was observed and characterized using SEM and EDX techniques. Our finding was that even imperfect polymer layers provide a considerable protective effect, and the used in vitro setup matches reported in vivo observations regarding elemental composition of corrosion products.

Experimental glaucoma microstent implantation in two animal models and human donor eyes-an ex vivo micro-computed tomography-based evaluation of applicability.

Background: Minimally invasive glaucoma surgery (MIGS) has become an important treatment approach for primary open angle glaucoma. Restoration of aqueous humour drainage by means of alloplastic implants represents a promising treatment option and is itself subject of methodological development. An adequate positioning in the targeted tissue regions is essential is important for the performance of our in-house developed Rostock glaucoma microstent (RGM). The aim of this study was to evaluate the applicability of two animal models and human donor eyes regarding RGM placement. Methods: Eyes were obtained from rabbits, pigs, and human body donations. After orbital exenterations, RGMs were placed in the anterior chamber draining in the subconjunctival space. X-ray contrast was increased by incubation in aqueous iodine solution for subsequent detailed micro-computed tomography (micro-CT)-based visualization and analysis. Results: In contrast to the human and porcine eyes, the stent extended far to the posterior pole with a more pronounced curvature along the globe in the rabbit eyes due to their smaller size. However, dysfunctional deformations were not depicted. Adequate positioning of the stent's inflow area in the anterior chamber and the outflow area in the Tenon space was achieved in both the animal models and the human eye. Conclusions: Micro-CT has proven to be a valuable tool for postoperative ex vivo evaluation of glaucoma drainage devices in its entire complexity. With regard to morphology, the porcine eye is the ideal animal model to test implantation procedures of the RGM. Nevertheless, rabbit eye morphology facilitates successful implantation results and provides all prerequisites for preclinical animal studies.

γ-Cyclodextrin hydrogel for the sustained release of josamycin for potential ocular application.

Glaucoma is the leading cause of blindness worldwide. However, its surgical treatment, in particular via trabeculectomy, can be complicated by fibrosis. In current clinical practice, application of the drug, Mitomycin C, prevents or delays fibrosis, but can lead to additional side effects, such as bleb leakage and hypotony. Previous in silico drug screening and in vitro testing has identified the known antibiotic, josamycin, as a possible alternative antifibrotic medication with potentially fewer side effects. However, a suitable ocular delivery mechanism for the hydrophobic drug to the surgical site does not yet exist. Therefore, the focus of this paper is the development of an implantable drug delivery system for sustained delivery of josamycin after glaucoma surgery based on crosslinked γ-cyclodextrin. γ-Cyclodextrin is a commonly used solubilizer which was shown to complex with josamycin, drastically increasing the drug's solubility in aqueous solutions. A simple γ-cyclodextrin crosslinking method produced biocompatible hydrogels well-suited for implantation. The crosslinked γ - cyclodextrin retained the ability to form complexes with josamycin, resulting in a 4-fold higher drug loading efficiency when compared to linear dextran hydrogels, and prolonged drug release over 4 days.

Utilization of a highly adaptable murine air pouch model for minimally invasive testing of the inflammatory potential of biomaterials.

Introduction: The biocompatibility of an implanted material strongly determines the subsequent host immune response. After insertion into the body, each medical device causes tissue reactions. How intense and long-lasting these are is defined by the material properties. The so-called foreign body reaction is a reaction leading to the inflammation and wound healing process after implantation. The constantly expanding field of implant technology and the growing areas of application make optimization and adaptation of the materials used inevitable. Methods: In this study, modified liquid silicone rubber (LSR) and two of the most commonly used thermoplastic polyurethanes (TPU) were compared in terms of induced inflammatory response in the body. We evaluated the production of inflammatory cytokines, infiltration of inflammatory cells and encapsulation of foreign bodies in a subcutaneous air-pouch model in mice. In this model, the material is applied in a minimally invasive procedure via a cannula and in one piece, which allows material testing without destroying or crushing the material and thus studying an intact implant surface. The study design includes short-term (6 h) and long-term (10 days) analysis of the host response to the implanted materials. Air-pouch-infiltrating cells were determined by flow cytometry after 6 h and 10 days. Inflammation, fibrosis and angiogenesis markers were analyzed in the capsular tissue by qPCR after 10 days. Results: The foreign body reaction was investigated by macroscopic evaluation and scanning electron microscopy (SEM). Increased leukocyte infiltration was observed in the air-pouch after 6 h, but it markedly diminished after 10 days. After 10 days, capsule formations were observed around the materials without visible inflammatory cells. Discussion: For biocompatibility testing materials are often implanted in muscle tissue. These test methods are not sufficiently conclusive, especially for materials that are intended to come into contact with blood. Our study primarily shows that the presented model is a highly adaptable and minimally invasive test system to test the inflammatory potential of and foreign body reaction to candidate materials and offers more precise analysis options by means of flow cytometry.

Melt blending of poly(lactic acid) with biomedically relevant polyurethanes to improve mechanical performance.

Minimally invasive surgery procedures are of utmost relevance in clinical practice. However, the associated mechanical stress on the material poses a challenge for new implant developments. In particular PLLA, one of the most widely used polymeric biomaterials, is limited in its application due to its high brittleness and low elasticity. In this context, blending is a conventional method of improving the performance of polymer materials. However, in implant applications and development, material selection is usually limited to the use of medical grade polymers. The focus of this work was to investigate the extent to which blending poly-l-lactide (PLLA) with low contents of a selection of five commercially available medical grade polyurethanes leads to enhanced material properties. The materials obtained by melt blending were characterized in terms of their morphology and thermal properties, and the mechanical performance of the blends was evaluated taking into account physiological conditions. From these data, we found that mixing PLLA with Pellethane 80A is a promising approach to improve the material's performance, particularly for stent applications. It was found that PLLA/Pellethane blend with 10% polyurethane exhibits considerable plastic deformation before fracture, while pure PLLA fractures with almost no deformation. Furthermore, the addition of Pellethane only leads to a moderate reduction in elongation at yield and yield stress. In addition, dynamic mechanical analysis for three different PLLA/Pellethane ratios was performed to investigate thermally induced shape retention and shape recovery of the blends.

Micro Injection Molding of Drug-Loaded Round Window Niche Implants for an Animal Model Using 3D-Printed Molds.

A novel approach for the long-term medical treatment of the inner ear is the diffusion of drugs through the round window membrane from a patient-individualized, drug-eluting implant, which is inserted in the middle ear. In this study, drug-loaded (10 wt% Dexamethasone) guinea pig round window niche implants (GP-RNIs, ~1.30 mm × 0.95 mm × 0.60 mm) were manufactured with high precision via micro injection molding (µIM, Tmold = 160 °C, crosslinking time of 120 s). Each implant has a handle (~3.00 mm × 1.00 mm × 0.30 mm) that can be used to hold the implant. A medical-grade silicone elastomer was used as implant material. Molds for µIM were 3D printed from a commercially available resin (TG = 84 °C) via a high-resolution DLP process (xy resolution of 32 µm, z resolution of 10 µm, 3D printing time of about 6 h). Drug release, biocompatibility, and bioefficacy of the GP-RNIs were investigated in vitro. GP-RNIs could be successfully produced. The wear of the molds due to thermal stress was observed. However, the molds are suitable for single use in the µIM process. About 10% of the drug load (8.2 ± 0.6 µg) was released after 6 weeks (medium: isotonic saline). The implants showed high biocompatibility over 28 days (lowest cell viability ~80%). Moreover, we found anti-inflammatory effects over 28 days in a TNF-α-reduction test. These results are promising for the development of long-term drug-releasing implants for human inner ear therapy.

Investigation of Stent Prototypes for the Eustachian Tube in Human Donor Bodies.

Chronic otitis media is often connected to Eustachian tube dysfunction. As successful treatment cannot be guaranteed with the currently available options, the aim is to develop a stent for the Eustachian tube (ET). Over the course of this development, different prototypes were generated and tested in ex vivo experiments. Four different prototypes of an ET stent and one commercially available coronary stent were implanted in the ET of seven human donor bodies. The position of the stents was verified by cone beam CT. The implanted ETs were harvested, embedded in resin and ground at 200 µm steps. Resulting images of the single steps were used to generate 3D models. The 3D models were then evaluated regarding position of the stent in the ET, its diameters, amount of squeezing, orientation of the axes and other parameters. Virtual reconstruction of the implanted ET was successful in all cases and revealed one incorrect stent placement. The cross-section increased for all metal stents in direction from the isthmus towards the pharyngeal orifice of the ET. Depending on the individual design of the metal stents (open or closed design), the shape varied also between different positions along a single stent. In contrast, the cross-section area and shape remained constant along the polymeric prototype. With the current investigation, insight into the behavior of different prototypes of ET stents was gained, which can help in defining the specifications for the intended ET stent.

Fetuin A functionalisation of biodegradable PLLA-co-PEG nonwovens towards enhanced biomineralisation and osteoblastic growth behaviour.

Therapy for large-scale bone defects remains a major challenge in regenerative medicine. In this context, biodegradable electrospun nonwovens are a promising material to be applied as a temporary implantable scaffold as their fibre diameters are in the micro- and nanometre range and possess a high surface-to-volume ratio paired with high porosity. In this work, in vitro assessment of biodegradable PLLA-co-PEG nonwovens with fetuin A covalently anchored to the surface has been performed in terms of biomineralisation and the influence on MG-63 osteoblast cell metabolic activity, biosynthesis of type I collagen propeptide and inflammatory potential. Our finding was that covalent fetuin A funtionalisation of the nonwoven material leads to a distinct increase in calcium affinity, thus enhancing biomineralisation while maintaining the distinct fibre morphology of the nonwoven. The cell seeding experiments showed that the fetuin A functionalised and subsequently in vitro biomineralised PLLA-co-PEG nonwovens did not show negative effects on MG-63 growth. Fetuin A funtionalisation and enhanced biomineralisation supported cell attachment, leading to improved cell morphology, spreading and infiltration into the material. Furthermore, no signs of increase in the inflammatory potential of the material have been detected by flow cytometry experiments. Overall, this study provides a contribution towards the development of artificial scaffolds for guided bone regeneration with the potential to enhance osteoinduction and osteogenesis.

Revisiting SFA stent technology: an updated overview on mechanical stent performance.

OBJECTIVES: The study investigated mechanical parameters of stent systems indicated for treatment of femoropopliteal (FP) arterial disease to support interpretation of clinical results and the related causalities. METHODS: Eight stent system types of same dimensions were investigated (n=2). Parameters were the profile of stent delivery system (SDS), radiopacity, trackability and pushability, bending stiffness (flexibility) and axial stiffness of expanded stents, length change during expansion, radial force, crush resistance, strut thickness and general surface condition. RESULTS: The trackability ranged from 0.237 to 0.920 N and the pushability was 47.9-67.6 %. The bending stiffness of SDS was between 108.42 and 412.68 N mm2. The length change during stent release to 5 mm was low, with one exception. The bending stiffness of the expanded stents was 2.73-41.67 N mm2. The normalized radial forces at 5 mm diameter ranged from 0.133 N/mm to 0.503 N/mm. During non-radial compression by 50 %, the forces were 3.07-8.42 N, with one exception (58.7 N). The strut thickness was 153-231 µm. CONCLUSIONS: Large differences occurred for flexibility, radial force and length change during expansion. The data should be used when choosing the proper device for restoring vascular function.

Influence of PEGDA Molecular Weight and Concentration on the In Vitro Release of the Model Protein BSA-FITC from Photo Crosslinked Systems.

Novel 3D printing techniques enable the development of medical devices with drug delivery systems that are tailored to the patient in terms of scaffold shape and the desired pharmaceutically active substance release. Gentle curing methods such as photopolymerization are also relevant for the incorporation of potent and sensitive drugs including proteins. However, retaining the pharmaceutical functions of proteins remains challenging due to the possible crosslinking between the functional groups of proteins, and the used photopolymers such as acrylates. In this work, the in vitro release of the model protein drug, albumin-fluorescein isothiocyanate conjugate (BSA-FITC) from differently composed, photopolymerized poly(ethylene) glycol diacrylate (PEGDA), an often employed, nontoxic, easily curable resin, was investigated. Different PEGDA concentrations in water (20, 30, and 40 wt %) and their different molecular masses (4000, 10,000, and 20,000 g/mol) were used to prepare a protein carrier with photopolymerization and molding. The viscosity measurements of photomonomer solutions revealed exponentially increasing values with increasing PEGDA concentration and molecular mass. Polymerized samples showed increasing medium uptake with an increasing molecular mass and decreasing uptake with increasing PEGDA content. Therefore, the modification of the inner network resulted in the most swollen samples (20 wt %) also releasing the highest amount of incorporated BSA-FITC for all PEGDA molecular masses.

Development of a Novel Valve-Controlled Drug-Elutable Microstent for Microinvasive Glaucoma Surgery: In Vitro and Preclinical In Vivo Studies.

Purpose: Microinvasive glaucoma surgery (MIGS) has become an important treatment approach for primary open-angle glaucoma, although the safe and long-term effective lowering of intraocular pressure with currently available implants for MIGS is not yet achieved to a satisfactory extent. The study focusses on the development and in vitro and in vivo testing of a novel microstent for MIGS. Methods: A silicone elastomer-based microstent was developed. Implants were manufactured using dip coating, fs-laser cutting, and spray coating. Within the current study no antifibrotic drug was loaded into the device. Sterilized microstents were analyzed in vitro regarding pressure-flow characteristics and biocompatibility. Six New Zealand white rabbits were implanted with a microstent draining the aqueous humor from the anterior chamber into the subconjunctival space. Drainage efficacy was evaluated using oculopressure tonometry as a transient glaucoma model. Noninvasive imaging was performed. Results: Microstents were manufactured successfully and characterized in vitro. Implantation in vivo was successful for four animals with additional device fixation. Without additional fixation, dislocation of microstents was found in two animals. Safe and effective intraocular pressure reduction was observed for the four eyes with correctly implanted microstent during the 6-month trial period. Conclusions: The described microstent represents an innovative treatment approach for MIGS. The incorporation of a selectively antifibrotic drug into the microstent drug-elutable coating will be addressed in future investigations. Translational Relevance: The current preclinical study successfully provided proof of concept for our microstent for MIGS which is suitable for safe and effective intraocular pressure reduction and offers promising perspectives for the clinical management of glaucoma.

Detection of acoustic emission from nanofiber nonwovens under tensile strain - An ultrasonic test setup for critical medical device components.

In the biomedical field, nanofiber materials are gaining increasing application. For material characterization of nanofiber fabrics, tensile testing and scanning electron microscopy (SEM) are established standards. However, tensile tests provide information about the entire sample without information about single fibers. Conversely, SEM images examine individual fibers, but cover only a small section near the surface of the sample. To gain information on failure at the fiber level under tensile stress, recording of acoustic emission (AE) is a promising method, but challenging due to weak signal intensity. Using AE recording, beneficial findings can be obtained even on "invisible" material failure without affecting tensile tests. In this work, a technology for recording weak ultrasonic AE of tearing nanofiber nonwovens is presented, which uses a highly sensitive sensor. Functional proof of the method using biodegradable PLLA nonwoven fabrics is provided. The potential benefit is demonstrated by unmasking significant AE intensity in an almost imperceptible bend in the stress-strain curve of a nonwoven fabric. AE recording has not yet been performed on standard tensile tests of unembedded nanofiber material intended for safety-related medical applications. The technology has the potential to enrich the spectrum of testing methods, even those not confined to medical field.

Novel dalbavancin-PLLA implant coating prevents hematogenous Staphylococcus aureus infection in a minimally invasive mouse tail vein model.

Infective/bacterial endocarditis is a rare but life-threatening disease with a hospital mortality rate of 22.7% and a 1-year mortality rate of 40%. Therefore, continued research efforts to develop efficient anti-infective implant materials are of the utmost importance. Equally important is the development of test systems that allow the performance of new materials to be comprehensively evaluated. In this study, a novel antibacterial coating based on dalbavancin was tested in comparison to rifampicin/minocycline, and the suitability of a recently developed mouse tail vein model for testing the implant coatings was validated. Small polymeric stent grafts coated with a poly-L-lactic acid (PLLA) layer and incorporated antibiotics were colonized with Staphylococcus (S.) aureus before implantation into the tail vein of mice. The main assessment criteria were the hematogenous spread of the bacteria and the local tissue reaction to the contaminated implant. For this purpose, colony-forming units (CFU) in the blood, spleen and kidneys were determined. Tail cross sections were prepared for histological analysis, and plasma cytokine levels and expression values of inflammation-associated genes were examined. Both antibiotic coatings performed excellently, preventing the onset of infection. The present study expands the range of available methods for testing the anti-infectivity of cardiovascular implants, and the spectrum of agents for effective surface coating.

Mimicking critical environment factors for a static in vitro biofilm formation model on blood-contact implant materials.

The prevention of implant infections is a major challenge for implant developers and clinicians. Understanding biofilm dynamics and favorable implant or environmental characteristics will help to prevent biofilm formation. Blood-contact implants, such as cardiovascular implants, are particularly susceptible to infections as the blood provides a favorable growth environment for bacteria due to its rich supply of micro- and macro substances, such as glucose and plasma proteins. In this context, Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis are the most reported causes accompanying foreign body-associated infections, mainly due to their ability to form an adherent, multilayered bacterial biofilm on a wide variety of surfaces. The present study demonstrates that the provision of glucose and human plasma to the growth medium or coating of the flask with human plasma differentially affects the biofilm formation of these three bacterial species, with human plasma being the most effective regulator. However, glucose supplementation promoted and stabilized biofilm formation of S. aureus and E. faecalis, while an opposite effect was observed for additional plasma. These findings highlight the urgent need to intensify studies on the impact of host soluble factors as risk factors promoting fitness and persistence of bacterial biofilms.

GIFT: An ImageJ macro for automated fiber diameter quantification.

This paper details the development and testing of the GIFT macro, which is a freely available program for ImageJ for the automated measurement of fiber diameters in SEM images of electrospun materials. The GIFT macro applies a validated method which distinguishes fiber diameters based on distance frequencies within an image. In this work, we introduce an applied version of the GIFT method which has been designed to be user-friendly while still allowing complete control over the various parameters involved in the image processing steps. The macro quickly processes large data sets and creates results that are reproducible and accurate. The program outputs both raw data and fiber diameter averages, so that the user can quickly assess the results and has the opportunity for further analysis if desired. The GIFT macro was compared directly to other software designed for fiber diameter measurements and was found to have comparable or lower average error, especially when measuring very small fibers, and reduced processing times per image. The macro, detailed instructions for use, and sample images are freely available online (https://github.com/IBMTRostock/GIFT). We believe that the GIFT macro is a valuable new tool for researchers looking to quickly, easily and reliably assess fiber diameters in electrospun materials.

Bacterial Adhesion and Biofilm Formation of Enterococcus faecalis on Zwitterionic Methylmethacrylat and Polysulfones.

Biofilm-associated implant infections represent a major challenge for healthcare systems around the world due to high patient burden and enormous costs incurred. Enterococcus faecalis (E. faecalis) is the most prevalent enterococcal species identified in biofilm-associated infections. The steadily growing areas of application of implants demand a solution for the control of bacterial infections. Therefore, the development of modified anti-microbial implant materials and the testing of the behavior of different relevant bacterial strains towards them display an indispensable task. Recently, we demonstrated an anti-microbial effect of zwitterionic modified silicone rubber (LSR) against Staphylococcus aureus. The aim of this study was to evaluate bacterial colonization and biofilm formation of another clinically relevant strain, E. faecalis, on this material in comparison to two of the most commonly used thermoplastic polyurethanes (TPUs) and other modified LSR surfaces. By generating growth curves, crystal violet, and fluorescence staining, as well as analyzing the expression of biofilm-associated genes, we demonstrated no anti-microbial activity of the investigated materials against E. faecalis. These results point to the fact that anti-microbial effects of novel implant materials do not always apply across the board to all bacterial strains.

A PLLA Coating Does Not Affect the Insertion Pressure or Frictional Behavior of a CI Electrode Array at Higher Insertion Speeds.

To prevent endocochlear insertion trauma, the development of drug delivery coatings in the field of CI electrodes has become an increasing focus of research. However, so far, the effect of a polymer coating of PLLA on the mechanical properties, such as the insertion pressure and friction of an electrode array, has not been investigated. In this study, the insertion pressure of a PLLA-coated, 31.5-mm long standard electrode array was examined during placement in a linear cochlear model. Additionally, the friction coefficients between a PLLA-coated electrode array and a tissue simulating the endocochlear lining were acquired. All data were obtained at different insertion speeds (0.1, 0.5, 1.0, 1.5, and 2.0 mm/s) and compared with those of an uncoated electrode array. It was shown that both the maximum insertion pressure generated in the linear model and the friction coefficient of the PLLA-coated electrode did not depend on the insertion speed. At higher insertion speeds above 1.0 mm/s, the insertion pressure (1.268 ± 0.032 mmHg) and the friction coefficient (0.40 ± 0.15) of the coated electrode array were similar to those of an uncoated array (1.252 ± 0.034 mmHg and 0.36 ± 0.15). The present study reveals that a PLLA coating on cochlear electrode arrays has a negligible effect on the electrode array insertion pressure and the friction when higher insertion speeds are used compared with an uncoated electrode array. Therefore, PLLA is a suitable material to be used as a coating for CI electrode arrays and can be considered for a potential drug delivery system.

Accelerated Endothelialization of Nanofibrous Scaffolds for Biomimetic Cardiovascular Implants.

Nanofiber nonwovens are highly promising to serve as biomimetic scaffolds for pioneering cardiac implants such as drug-eluting stent systems or heart valve prosthetics. For successful implant integration, rapid and homogeneous endothelialization is of utmost importance as it forms a hemocompatible surface. This study aims at physicochemical and biological evaluation of various electrospun polymer scaffolds, made of FDA approved medical-grade plastics. Human endothelial cells (EA.hy926) were examined for cell attachment, morphology, viability, as well as actin and PECAM 1 expression. The appraisal of the untreated poly-L-lactide (PLLA L210), poly-ε-caprolactone (PCL) and polyamide-6 (PA-6) nonwovens shows that the hydrophilicity (water contact angle > 80°) and surface free energy (<60 mN/m) is mostly insufficient for rapid cell colonization. Therefore, modification of the surface tension of nonpolar polymer scaffolds by plasma energy was initiated, leading to more than 60% increased wettability and improved colonization. Additionally, NH3-plasma surface functionalization resulted in a more physiological localization of cell−cell contact markers, promoting endothelialization on all polymeric surfaces, while fiber diameter remained unaltered. Our data indicates that hydrophobic nonwovens are often insufficient to mimic the native extracellular matrix but also that they can be easily adapted by targeted post-processing steps such as plasma treatment. The results achieved increase the understanding of cell−implant interactions of nanostructured polymer-based biomaterial surfaces in blood contact while also advocating for plasma technology to increase the surface energy of nonpolar biostable, as well as biodegradable polymer scaffolds. Thus, we highlight the potential of plasma-activated electrospun polymer scaffolds for the development of advanced cardiac implants.