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Filter membranes (pore size 0.2 μm) are frequently used to perform a sterile filtration. To characterize the pore size of filter membranes, a method to determine the particle retention of nanoparticles was defined. The Dynamic Light Scattering method was first analysed and calibrated to correlate the particle concentration with absolute intensity of scattered light. Afterwards, standard particle suspensions with particle sizes of 0.150 μm and 0.239 μm were lead through an infusion filter and the particle retention of the filter was evaluated by the determination of the original and the filtrated particle concentration. The test filter retained 91% of the smaller and 98% of the larger particles. Evaluating the particle retention with Dynamic Light Scattering could be a time saving method with lesser effort compared to existing methods.

Electrospun fibers based on synthetic and natural polymers represent a promising approach in order to mimic the mechanical stability and the required cell-polymer interaction of the natural extracellular matrix (ECM), . In this biomedical context, the biodegradable medical grade poly-llactide (PLLA) and the natural gelatin are already well established. However, to obtain a stabilized structured PLLA/gelatin blend, crosslinking of gelatin is required. In this study, the influence of the post processed crosslinking via Glutaraldehyde (GTA) vapor and GTA solution on the morphological and physicochemical properties of the blend, as well as on the in vitrorelease of previously incorporated dexamethasone (DMS), was investigated. The addition of gelatin decreased the fiber diameter and increased the surface hydrophilicity, which is furthermore unaffected by the crosslinking process. The in vitrorelease of DMS was decisively changed by both, the addition of gelatin and the subsequent crosslinking processes. For all modified samples, a very rapid burst release of DMS was detected within the first 24 h, which is crucial for biomedical applications such as tumor therapy.

Polycarbonate-urethane-co-silicone (PCU-Sil) are gaining increasing interest in biomedical application, such as drug delivery systems, coatings and combination products, due to their adjustable mechanical properties. They can be easily processed using a wide range of methods. Biocompatibility can be improved by surface modifications, such as coupling drugs, proteins, antibodies or polymer layers, which extends the range of biomedical applications. To generate additional coupling, the first step would be the generation of functional groups on the polymer surface using surface activations, such as plasma activation. In this context, the assignment of the functional groups is important, which can be done by XPS measurements. Within this study the analysis of the generated functional groups after oxygen (O2) plasma activation of two PCU-Sils was performed. In addition, the stability of the generated surface modification was evaluated after 24 hours. It was surprising that the generated groups were differently stable and also different groups were generated or rearranged over time, which would not have been recognizable if only contact angle measurements were used.

Poly(N-isopropylacrylamide) (PNIPAM) hydrogels are one of the most commonly studied thermoresponsive biomaterials. In this work, we investigate ball milling as a method of producing PNIPAM nanogels and confirm that the temperature responsiveness is maintained in the nanogel form based on hydrodynamic diameter and zeta potential measurements.

For the use of polymers as biomaterials in the production of implants, several processing methods are needed. Besides injection molding or Fused Deposition Modeling as temperature based processes, also solvent based processes were performed such as solvent-casting and electrospinning. As fabrication of medical devices makes use of potentially hazardous or toxic solvents, they have to be extracted from the final medical device. For analyses of residual solvents different methods can be used e.g. gas chromatography (GC), coulometric elemental analysis or thermogravimetrical analyses (TGA). Here we present first results for the use of X-ray photoelectron spectroscopy (XPS) to yield elemental as well as spatial information on residual solvents in polymeric materials. Therefore we analysed PLLA as biodegradable electrospun polymer, TPC-ET as biostable polymer and a PLLA-iron composite as example of a polymer metal composite via XPS and etching processes. It was possible to determine residual halogen containing solvents in all tested polymers processed from polymeric solution. As discrimination between polymer and solvent was made possible by specific elements, XPS measurements may be a suitable tool to identify even small amounts of solvent. Thus XPS analyses will help to optimize polymer processing in order to remove residual solvents.

Sterilization processes ensure sterility of drug delivery systems, but may negatively affect the properties of biomaterials and incorporated drugs by changing their physical, chemical, mechanical properties and drug release behaviour. Therefore, it is important to investigate their influence. In this study, the influence of ethylene oxide (EtO) sterilization on the drug loading and release behaviour of incorporated Diclofenac (DCF) in a Poly-L-lactide (PLLA) coating and Dexamethasone (DMS) in the silicone carrier is presented. Silicone samples containing DMS were coated with PLLA containing DCF varying in layer thickness (5, 10, and 20 μm). Half of the samples underwent EtO sterilization, the other half was not sterilized. All un-/sterilized sample surfaces were in view of the morphology and hydrophilicity examined. Furthermore, in vitro release studies of DMS and DCF were conducted. The sterilized sample surfaces showed no morphological and hydrophilicity changes. The DCF and DMS loadings were similar for the sterile and untreated samples. This also applied to the in vitro DMS release profiles apart from the end of the studies where slight differences were evident. The results indicate that both drugs loaded in the polymer coating and the silicone were not impaired by the sterilization process. Thus, EtO sterilization appears suitable for DMS containing silicone and DCF incorporated PLLA coatings as a dual drug delivery system.

For the development of combination products, the determination of the release kinetics of polymer-based drug delivery systems (DDS) is a central and often timeconsuming investigation. Classical methods are often unsuitable for large-scale screening of potential polymers for combination products. We present a rapid method based on surface plasmon resonance spectroscopy (SPR), using PEGDA700 (Poly(ethylene glycol) diacrylate, average molecular weight (Mn) 700) as an example. This method is capable of determinating the kinetics of drug association and subsequent release within minutes. The proportion of desorption and diffusion can be determined separately. Surface plasmon resonance spectroscopy (SPR) is a label-free and very sensitive optical technique, which allows for real-time observation of surface interactions. The prepared SPR chips were spin-coated with PEGDA700 and crosslinked via photoinduced polymerization. The association and dissociation kinetics of dexamethasone phosphate in swollen PEGDA700 have been studied at different concentrations. The maximum loading of the surface was also obtained by this method. The study of PEGDA presented here identified the wellestablished SPR-based spectroscopy as a potential tool in the development of combination products.

Analysis of the active ingredient distribution of medical devices is typically performed using Raman spectroscopy, a method that is fast and inexpensive [1]. In addition, it offers the advantage of non-destructive analysis without the need for special sample preparation. Assuming that all components are Raman-active and present in sufficient quantities, their distribution can be well represented. The drug distribution in dexamethasone-loaded polymer nonwovens was investigated in order to draw conclusions on the quality of the fleece batches and to make predictions for the release behavior. In the present study, dexamethasone (DMS), a glucocorticoid was used as the active ingredient. Qualitative and quantitative studies of the content of DMS in polymer films by means of Raman spectroscopy have already been carried out in the working group [2]. A representative square section was examined to describe the distribution of active ingredients. The required number of measurement points (spectra) was determined earlier [2].

The use of biomaterials in medicine is becoming increasingly important. One of the main concerns is the foreign body associated infection caused by direct microbial contamination or clinical infections. The bacterial biofilm formation on biomaterials depends on their surface properties. Therefore, several anti-adhesive surface modifications were developed. Nevertheless, the demand for antimicrobial agents that prevent bacterial colonisation is still largely unmet. The immobilization of active antimicrobial agents, such as antibacterial peptides or enzymes, offers a potential approach to achieve long-lasting effectiveness. In this investigation, the hydrolytic enzyme papain with its published antibacterial activity was covalently immobilized on the well-established biodegradable biomaterial poly-L-lactic acid (PLLA). For the characterization of the enzymes on the PLLA surfaces, the protein content and enzyme activity were determined. A biofilm assay was performed to test the effect of the papain-modified PLLA samples on the biofilm-forming bacterial strain Clostridioides difficile, one of the most frequently occurring human nosocomial pathogens. The investigated hydrolytic enzyme papain could be immobilized by coupling via the crosslinker EDC to the PLLA surface. Detection was performed by determination of the amount of protein and the reduced biofilm growth after 24 h and 72 h compared to the reference.

Electrospun fiber nonwoven materials of different polymer classes provide promising perspectives in almost all fields of application, including medical science. In this paper we present the fiber generation of selected biostable polymers (PBT, TPC-ET, PA 6.12 and PVDF) by direct electrospinning, as an extremely powerful tool for manufacturing of new superfiber implant materials. This initial study includes the variation of some relevant process parameters, such as polymer concentrations or electrode spacing. The influence on fiber morphology, tensile strength and biocompatibility is shown. The results presented indicate that the choice and combination of materials is crucial for the application on load-bearing implants, independent of the processing technology and thus of the fiber bonding, delamination or fiber strength.

In recent years, nanofiber based materials have emerged as especially interesting for several biomedical applications, regarding their high surface to volume ratio. Due to the superficial nano- and microstructuring and the different wettability compared to nonstructured surfaces, the water absorption is an important parameter with respect to the degradation stability, thermomechanic properties and drug release properties, depending on the type of polymer [1]. In this investigation, the water absorption of different non- and plasma modified biostable nanofiber nonwovens based on polyurethane, polyester and polyamide were analysed and compared. Also, the water absorption by specified water wetting, the contact angle and morphology changes were examined. The results show that the water uptake is highly dependent on the surface modification and the polymer composition itself and can therefore be partially changed.

Glaucoma represents the leading cause of irreversible blindness worldwide. Therapeutic approaches are based on the lowering of intraocular pressure (IOP). Micro-invasive glaucoma surgery (MIGS) offers perspectives for implant based IOP-reduction with reduced complication rates compared to conventional surgical approaches. Nevertheless, available devices suffer from complications like hypotony and fibrotic encapsulation. The current work focuses on the development of a minimally invasive implantable drugeluting microstent for the drainage of aqueous humour into suprachoroidal or subconjunctival space. Technical feasibility of a micro-scale resorbable nonwoven for the prevention of hypotony and of a drug-eluting coating for the prevention of fibrosis is assessed. Microstent base bodies with a length of 10 mm and an inner/outer diameter of 0.20 mm / 0.35 mm were manufactured. For the prevention of hypotony, resorbable nonwovens with an adequate flow resistance of 1.543 mmHg/μl min-1 were manufactured in the inflow area of microstents. A drug-eluting coating in the outflow area of microstents was developed based on the model drug fluorescein diacetate. Micro-invasive ab interno implantation of a microstent prototype into suprachoroidal space of a porcine eye post mortem was successfully performed, using an injector device. Future studies will focus on the development of an antifibrotic drug-eluting coating and further in vitro, ex vivo and in vivo testing of the devices.

Insertion of a cochlear implant (CI) into the scala tympani evokes electrode insertion trauma that can result in mechanical damage of the lateral and medial wall and causes ingrowth of fibrous tissue on the implant surface. In consequence, it is of great clinical interest to modify the silicone surface of CI electrodes in order to inhibit and minimize the overgrowth by connective tissue. In this case, the covalent coupling of bifunctional polymers on common CI silicone surfaces is a versatile method to influence the implant cell interaction, but is still a challenge due to the chemically unreactive properties of silicone. We present a sophisticated method to apply a biodegradable polymer coating, such as polylactide or polyhydroxybutyrate, on silicone surfaces to generate a drug delivery system using a covalently bound intermediate layer. The adhesive coatings were applied via spincoating processes with different adherence to the intermediate layer. Changes in surface morphology were investigated by comparison of pure silicone and coated silicone. Specific polymer bands of the infrared spectra were detected by IR spectroscopy. Results indicate a complete coating with polylactide or polyhydroxybutyrate. The presented method is a versatile tool for the coating of silicone CI electrodes with degradable polymer layers.

Plasma enhanced chemical vapor deposition is a promising process for the generation of tailor-made polymer coatings on medical devices in order to improve their implant/ host interaction. The ultra-thin coatings can fulfil a variety of purposes, depending on the monomers used, the process conditions and the location of the coated implants in the human body. In addition, even complex geometries can be coated easily and without the application of solvents. Particularly hydrophilic and hydrophobic plasma polymer coatings can improve biocompatibility, especially in blood contact. Furthermore, the selection of the monomers used enables the generation of specific functional groups for further surface immobilization of drugs, such as proteins, by chemical crosslinking. The release of toxic residues from polymeric implants, such as monomers, additives or degraded components, can also be avoided. The aim of our investigation was the generation of plasma polymer films, their characterization and application as coatings for biodegradable metallic biomaterials in order to retard the degradation process. Metallic biomaterials, in various forms are frequently used in orthopaedics, dentistry, cardiovascular and neurosurgical equipment, because of their tensile strength, fracture toughness, fatigue strength and electrical conductivity. Plasma polymerization was performed using the monomers hexamethyldisiloxane and allylamine. The resulting plasma polymers were analysed in an accelerated degradation test. Both plasma polymers appear to be promising, while polyHMDSO appears to degrade over time and polyallylamine indicates to be stable.

Medical device-related infections are becoming a steadily increasing challenge for the health care system regarding the difficulties in the clinical treatment. In particular, cardiovascular implant infections, catheter-related infections, as well as infective endocarditis are associated with high morbidity and mortality risks for the patients. Antimicrobial materials may help to prevent medical device-associated infections and supplement the currently available therapies. In this study, we present an easy-to-handle and simplified in vivo model to test antimicrobial materials in the bloodstream of mice. The model system is composed of the implantation of a bacteria-laden micro-stent scaffold into the murine tail vein. Our model enables the simulation of catheter-related infections as well as the development of infective endocarditis specific pathologies in combination with material testing. Furthermore, this in vivo model can cover two phases of the biofilm formation, including both the local tissue response to the bacterial biofilm and the systemic inflammatory response against circulating bacteria in the bloodstream that detached from a mature biofilm.

In the last decades PLLA-based copolymers have been among the most attractive polymeric candidates used to fabricate devices for drug delivery and stent applications in the cardiovascular system. PLLA is biocompatible and biodegradable, exhibits a wide range of erosion times and has tunable mechanical properties. Therefore, the influence of drug incorporation on the physicochemical properties of biodegradable PLLA copolymers were examined in this study using Fluorescein diacetate (FDAc) and Paclitaxel (PTX). A percental amount of these drugs (17.5 %) were incorporated into poly(L-lactide-co-glycolide) (P(LLA-co-GA)) and poly(L-lactide-co-ε-caprolactone) (P(LLA-co-CL)) made via spray coating. The polymer surface properties, such as surface morphology and hydrophilicity were also examined and remained rather unchanged for both polymers after drug loadings. Furthermore, also the contact angle changed rather marginally. However, both polymers have already different thermal properties without the drug embedded, especially the glass transition temperature (TG) is for P(LLA-co-CL) under 37°C and for P(LLA-co-GA) considerable above with around 66°C. An rather high increase in TG achieved by addition of FDAc or PTX, crucial influences the drug release profiles for P(LLA-co-CL) in contrast to P(LLA-co-GA). Besides these results preliminarily experiments of additional coupling of other drugs on the polymer surface were performed and we obtained an influence of FDAc or PTX. The drug incorporation and physicochemical characterization data obtained in this study is relevant in optimizing the incorporation or coupling of further drugs on the polymer surface and delivery properties of these potential multi drug delivery coatings.

For a long-term efficient drug-eluting stent for vascular applications, the development of drug-loaded coating, combining the effective inhibition of smooth muscle cell proliferation while promoting the re-endothelialization, is a promising concept. However the mostly required simultaneous incorporation of drugs can influence decisively the stability, efficacy and release of the respective drug. Therefore, the mutual influence of a dual local drug delivery coatings based on poly(L-lactide-co-ε-caprolactone) (PLLA-co-CL) containing vascular endothelial growth factor (VEGF165) coupled to the surface and an embedded drug, such as fluorescein diacetate (FDAc) instead of Paclitaxel (PTX) on the in vitro drug release was investigated. Surprisingly, for the investigated coating the immobilized VEGF loading was enhanced and the release profile was accelerated by FDAc incorporation. Even a manifold increase for the in vitro released amounts of VEGF was detected. In contrast, the immobilization of VEGF seems to have a negligible influence on the in vitro FDAc release profiles.

An ongoing challenge in drug delivery systems for a variety of medical applications, including cardiovascular diseases, is the delivery of multiple drugs to address numerous phases of a treatment or healing process. Therefore, an extended dual drug delivery system (DDDS) based on our previously reported cardiac DDDS was generated. Here we use the polymer poly(L-lactide) (PLLA) as drug carrier with the cytostatic drug Paclitaxel (PTX) and the endothelial cell proliferation enhancing growth factor, human vascular endothelial growth factor (VEGF), to overcome typical in-stent restenosis complications. We succeeded in using one solution to generate two separate DDDS via spray coating (film) and electrospinning (nonwoven) with the same content of PTX and the same post processing for VEGF immobilisation. Both processes are suitable as coating techniques for implants. The contact angle analysis revealed differences between films and nonwovens. Whereas, the morphological analysis demonstrated nearly no changes occurred after immobilisation of both drugs. Glass transition temperatures (Tg ) and degree of crystallinity (χ) show only minor changes. The amount of immobilised VEGF on nonwovens was over 300% higher compared to the films. Also, the nonwovens revealed a much faster and over three times higher PTX release over 70 d compared to the films. The almost equal physical properties of nonwovens and films allow the comparison of both DDDS independently of their fabrication process. Both films and nonwovens have significantly increased in vitro cell viability for human umbilical vein endothelial cells (EA.hy926) with dual loaded PTX and VEGF compared to PTX-only loaded samples.

As it has been demonstrated that bioactive substances can be delivered locally using coated surgical suture materials, the authors developed a vascular endothelial growth factor (VEGF)-releasing suture material that should promote vascularization and potentially wound healing. In this context, the study focused on the characterization of the developed suture material and the verification of its biological activity, as well as establishing a coating process that allows reproducible and stable coating of a commercially available polydioxanone suture material with poly(l-lactide) (PLLA) and 0.1μg and 1.0μg VEGF. The in vitro VEGF release kinetics was studied using a Sandwich ELISA. The biological activity of the released VEGF was investigated in vitro using human umbilical vein endothelial cells. The potential of the VEGF-releasing suture material was also studied in vivo 5days after implantation in the hind limb of Wistar rats, when the histological findings were analyzed. The essential results, enhanced cell viability in vitro as well as significantly increased vascularization in vivo, were achieved using PLLA/1.0μg VEGF-coated suture material. Furthermore, ELISA measurements revealed a high reproducibility of the VEGF release behavior. Based on the results achieved regarding the dose-effect relationship of VEGF, the stability during its processing and the release behavior, it can be predicted that a bioactive suture material would be successful in later in vivo studies. Therefore, this knowledge could be the basis for future studies, where bioactive substances with different modes of action are combined for targeted, overall enhancement of wound healing.

The high degree of clinical routine in percutaneous transluminal coronary angioplasty (PTCA) with and without stenting has not changed the fact that a large number of coronary heart disease patients are still affected by post-operative complications such as restenosis and thrombosis. Because re-endothelialization is the crucial aspect of wound healing after cardiovascular implant surgery, there is a need for modern biomaterials to aid endothelial cells in their adhesion and functional recovery post-stenting. This study systematically examines the potential of numerous chemical polymer modifications with regard to endothelialization. Poly(ε-caprolactone) (PCL) and its chemically activated forms are investigated in detail, as well as the impact of polymer surface morphology and precoating with matrix protein. Human umbilical vein endothelial cells (HUVECs) are used to characterize endothelial cell responses in terms of in vitro viability and adhesion. As a potential component in drug eluting implants, VEGF is applied as stimulus to boost endothelial cell proliferation on the polymer. In conclusion, plasma chemical activation of PCL combined with VEGF stimulation best enhances in vitro endothelialization. Examining the impact of morphological, chemical and biological modifications of PCL, this study makes an important new contribution towards the existing body of work on polymer endothelialization.

Polyelectrolyte multilayer (PEM) films, established by layer-by-layer deposition, are attractive for drug delivery systems as drug delivery can be systematically controlled. However, one limitation of this coating method is the time-consuming character. The adsorption time of one layer typically takes minutes and commonly, investigated multilayers loaded with drugs contain more than 80 layers. Within our study we systematically evaluate parameters allowing the generation of a PEM-based drug delivery system on poly(L-lactide) (PLLA) with a reduced time consuming construction process and a controlled delivery of physiological amounts of active drugs. Therefore, several PEM based on PLLA with only five tetralayers consisting of polycation/polyanion/drug/polyanion are established and investigated regarding the release profiles of avidin fluorescein isothiocyanate as model substance and vascular endothelial growth factor (VEGF). We demonstrate that the polyelectrolyte nature and molecular weight of polyanions (hyaluronic acid, polyacrylic acid) and polycations (poly-L-lysine, chitosan) strongly influence the drug release profiles. Furthermore, in vitro cell culture studies show that the released VEGF amount and the cover layer from the favorite coating systems can beneficially enhance human umbilical vein endothelial cell (HUVEC) proliferation.

Previous studies indicate an important role for the cellular prion protein (PrP(C)) in the development of Alzheimer's disease (AD) pathology. In the present study, we analyzed the involvement of PrP(C) in different pathological mechanisms underlying AD: the processing of the amyloid-β protein precursor (AβPP) and its interaction with AβPP, tau, and different phosphorylated forms of the tau protein (p-tau). The effect of PrP(C) on tau expression was investigated in various cellular compartments using a HEK293 cell model expressing a tau mutant (3PO-tau) or wild type (WT)-tau. We could show that PrP(C) reduces AβPP cleavage, leading to decreased levels of Aβ40 and sAβPP without changing the protein expression of AβPP, β-secretase, or γ-secretase. Tau and its phosphorylated forms were identified as interactions partners for PrP(C), raising the question as to whether PrP(C) might also be involved in tau pathology. Overexpression of PrP(C) in PRNP and 3PO-tau transfected cells resulted in a reduction of 3PO-tau and p-tau as well as a decrease of 3PO-tau-related toxicity. In addition, we used the transgenic PrP(C) knockout (Prnp0/0) mouse line to study the dynamics of tau phosphorylation, an important pathological hallmark in the pathogenesis of AD in vivo. There, an effect of PrP(C) on tau expression could be observed under oxidative stress conditions but not during aging. In summary, we provide further evidence for interactions of PrP(C) with proteins that are known to be the key players in AD pathogenesis. We identified tau and its phosphorylated forms as potential PrP-interactors and report a novel protective function of PrP(C) in AD-like tau pathology. peerReviewed

Based on the theoretical framework and the analysis of the interviews with ethics and compliance officers from different multinational organizations, this part will show how organizations should proceed when developing and implementing an effective ethics and compliance program. Part Three will give organizations a detailed step-by-step manual for building an effective ethics and compliance program. It combines relevant laws and regulations (particularly the 2004 Amendments) as presented in the theoretical framework (Part One) as well as the empirical results from the expert interviews (Part Two). Furthermore, the manual will be extended by the incorporation of relevant literature in the field of ethics and compliance. This part is thus the logical consequence of the theoretical framework and the empirical study of the interviews.

In Part One of this study, I developed a theoretical framework which shows how multinational organizations can develop and implement an effective ethics and compliance program based on the 2004 Amendments to the Federal Sentencing Guidelines. In Part Two, the research process will be substantiated and explained. A thorough description and disclosure of the research process is necessary in order to demonstrate the plausibility and inter-subjective comprehensibility of the methods applied. Revealing the research process – its chronology, choice of methods, etc. – is crucial to making it plausible and understandable to others.