11:40am - 12:00pm
Triaxial electrospun fibers for prolonged drug release
Institute of Fundamental Technological Research, Polish Academy of Sciences, Poland
Electrospun nanofibers are a challenging system for effective and targeted drug delivery in tissue engineering applications. The triaxial technique is a fairly new method under investigation. The fibers obtained by this method consist of three layers: a core and two layers surrounding the core. Triaxial electrospinning is a competitive method to solve the critical limitations in other techniques, i.e. uniaxial, and coaxial, such as lack of sustained and controlled drug release, poor solubility of drugs, problems with loading multiple drugs, and biodegradation, not adequate biocompatibility.
The first objective of the research is to optimize the manufacturing process using triaxial electrospinning to get homogenous-free beads fibers and beneficial effects on drug release.
For the development of the fibers, a combination of biodegradable synthetic and natural polymers were used: polycaprolactone (PCL) (core layer), poly(lactic-co-glycolide) (PLGA) (shell layer), and gelatin (intermediate layer). Natural polymer improves biocompatibility, while the combination of PCL and PLGA is expected to maintain preferred structural properties e.g. hydrophilicity and morphology. As a model of the drug, Rhodamin B (Rh B) was loaded for the optimization process.
Preliminary investigations including optimization of manufacturing triaxial fibers are discussed. Microscopic images demonstrated homogenous free-beads fibers were developed as a result of many trials. Furthermore, it was observed fibers are covered with an outer layer according to the expectancy. Under the shell layer, there is a middle surrounding the core layer indicating that the proposed process with parameters selected in this way allows producing of core-shell fiber structure. Preliminary in-vitro studies were performed with Rh B to investigate release profiles from triaxial fibers compared to coaxial fibers. The results showed triaxial fibers decreased initial burst release significantly over the coaxial fibers.
The research reported here shows triaxial fibers as promising biomaterials that can be used as novel drug delivery systems in biomedical applications.
12:00pm - 12:20pm
Synthesis and characterization of drug loaded hybrid mesoporous silica particles for biomedical applications
1Institute of Fundamental Technological Research, Polish Academy of Sciences, Poland; 2Institut Charles Gerhardt, University of Montpellier, France
Mesoporous silica materials are promising candidates for drug delivery systems, due to their high specific surface area, large pore volume, ordered network and narrow pore size distribution.
Traditionally, non-ionic or ionic surfactant micelles were used as a structure directing agent of silica. However, a polyion complex (PIC) assembly, which is based on interactions between a pH stimuli-responsive double-hydrophilic block copolymer (DHBC) with a weak polyamine, benefits from functional hybrid silica mesoporous shell and a tuneable stimuli responsive copolymeric core. This gives them specific functionalities, such as the ability of drug encapsulation and release in a specific pH.
In this study, silica particles were prepared by (i) micellization of cationic surfactant cetylpyridinium chloride (CPC), (ii) PIC assembly of neutral-ionizable poly(ethylene oxide)-block-poly(acrylic acid) copolymer (PEO-b-PAA)/CPC and silica condensation. CPC it’s an oral antiseptic and it was used both as an active component of PIC assembly, due to electrostatic complexation with CPC/-PAA at pH > 4.5 and antibacterial drug which can be released from pores below pH 4.5.
FTIR and ICP confirm presence of CPC or CPC/DHBC components in obtained silica powders. DHBC has a positive impact on decreasing size of particles, improving their homogeneity and imputes mesoporosity depending on synthesis conditions: DHBC concentration, complexation between the carboxylate (AA) and amine (N) groups, ratio between the Si species/EO units. In the CPC-based system, particles are in the size range of 46-535 nm with majority ~150 nm, while in the DHBC/CPC system particles are below 50 nm. BET surface area increases from 129.4 m2/g for CPC-based silica to up to 1045 m2/g for CPC/DHBC-based silica. TEM confirms mesoporous structure for CPC/DHBC particles. Kinetics of the CPC uptake was evaluated by UV-Vis at pH of 1, 3 and 7.4 and confirms a pH stimuli-responsive release at pH 1 and 3.
12:20pm - 12:40pm
Development and characterization of zein-based coatings incorporating fluoride- and copper-doped bioactive glass on titanium for biomedical applications
1Institute of Biomaterials, Department of Materials Science and Engineering, University of Erlangen-Nuremberg, Germany; 2Faculty of Materials Science and Ceramics, AGH University of Science and Technology, Poland; 3Faculty of Metals Engineering and Industrial Computer Science, AGH University of Science and Technology, Poland; 4Institute of Physics of Materials, Czech Academy of Sciences, Brno, Czech Republic
The long-term application of metallic implants is limited due to their poor osseointegration capability and proneness to bacterial infections. In order to tackle these issues, the surface of the metallic implant can be coated with bioactive and antibacterial organic-inorganic composite coatings, e.g., by using electrophoretic deposition (EPD) [1,2]. Thus, the present work aims to develop coatings based the natural polymer zein and SiO2-CaO-P2O5 bioactive glass particles (BG) doped with fluoride (BG-F) and copper (BG-F-Cu) on titanium by EPD. Morphological observations demonstrated that the glass particles were homogeneously embedded in the polymeric coating matrix, while pull-off and tape tests indicated that the addition of BG particles improved the coating adhesion to the substrate. Nanoindentation measurements and scratch tests showed that zein/BG coatings possessed higher hardness and improved scratch resistance in comparison to zein/BG-F and zein/BG-F-Cu coatings. The ion substitution in the BG structure did not affect the bioactivity of the coatings as apatite formations could be detected on all composite coatings after 3 days of immersion in simulated body fluid (SBF), according to FTIR, XRD, SEM and EDX analyses. All composite coatings showed decreased wettability, higher susceptibility to collagenase degradation and lower swelling capability than pure zein coatings. Both direct and indirect cytocompatibility assays revealed significantly improved viability of osteoblast-like MG-63 cells on all composite coatings after 1 and 3 days of incubation. Moreover, the presence of ion-doped bioactive glass endowed antibacterial activity of the coatings against Gram-positive S. aureus and Gram-negative E. coli as confirmed by Alamar blue assay and SEM observations. The obtained results prove that the prepared coatings can be promising candidates to facilitate bone tissue integration and to prevent infections around orthopaedic and dental implants.
 Maciag et al., Materials, 14, 2021, 312.
 Meyer et al., Coatings, 8, 2018, 27.
12:40pm - 1:00pm
Alteration of vimentin cytoskeleton in senescent cells
Ludwig Boltzmann Institue for Traumatology, Austria
Cellular senescence occurs in response to various triggers, including DNA damage, telomere dysfunction, oncogene activation, and organelle stress. It has been linked to tumor suppression, tissue repair, embryogenesis, and organismal aging. It is known that senescent human fibroblasts show an increase in an intermediate cytoskeletal protein, vimentin, yet the senescence-associated alteration of the function of vimentin in senescent cells is largely unexplored.
Here, we present unpublished results showing that vimentin accumulates in senescent cells and forms a highly compacted, juxtanuclear, and monopolar structure. Vimentin accumulates in close proximity to the nucleus, and our findings indicate an association between the accumulation of vimentin and the deformation of the nucleus in senescence. We demonstrate that nuclei of senescent cells showing deposition of vimentin have further increased number of DNA damage foci and display chromatin structure changes. Finally, accumulation of vimentin in senescent cells is also associated with changes in microtubular but not actin cytoskeleton and re-positioning of cytoplasmic organelles. Experiments in vimentin knock-out (KO) fibroblasts provide further evidence on the relationship between nucleus structure and vimentin, as senescent cells deprived of vimentin show reduced DNA damage and lack of nuclear distortions and structure of chromatin resembling that in young cells. Overall, our findings indicate that induction of senescence causes immense changes in the vimentin cytoskeleton in a process that has consequences on the re-arrangement and damage response of cellular structures such as the nucleus and cytoskeleton and cytoplasmic organelles.
1:00pm - 1:20pm
Auricular cartilage scaffolds: an innovative tool to study cellular infiltration by glycosaminoglycans removal and altered stiffness
1Department of Orthopedics and Trauma-Surgery, Division of Trauma-Surgery, Medical University of Vienna.; 2Ludwig Boltzmann Institute for Traumatology. The Research Center in Cooperation with AUVA. Austrian Cluster for Tissue Regeneration, Vienna, Austria; 3Department of Life Science Engineering, University of Applied Sciences Technikum Wien, Vienna, Austria; 4Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria; 5University Clinic of Dentistry, Medical University of Vienna, Vienna, Austria
Decellularized materials are an ideal candidate for articular cartilage regeneration due to the similarity of its structure and composition with the native tissue. However, the modulation of the materials properties, such as topography or porosity remain as a challenge. Our group previously developed a biomaterial based on auricular cartilage by removal of the elastic fibers and glycosaminoglycans (GAGs) with tunable mechanical stiffness. Hence, we aim to investigate cellular ingrowth into the matrix according to different stiffnesses.
Auricular cartilage discs were harvested from bovine ears and enzymatically treated with pepsin and elastase. A pepsin concentration series was used to gradually remove the GAGs from the matrix. First, GAG content was quantified by histology and Dimethylmethylene Blue assay. Second, a stepwise compressive test using a Zwick uniaxial testing machine was performed to characterize the mechanical properties (i.e: viscosity and elasticity), which were computed using a mathematical model. Last, cell infiltration was monitored by confocal microscopy and immunohistochemistry using fluorescently labelled adipose derived stromal cells and human articular chondrocytes.
GAG concentration and mechanical properties varied according to the concentration of pepsin used. Residual GAG content differed significantly between the highest and lowest concentration (1 mg/mL: 0.058 0.014 mg/µg vs. 0.2 mg/mL: 0.15 0.042 mg/µg; p = 0.0022). Similarly, native scaffolds and those treated with 0.2 mg/mL pepsin showed a viscoelastic behavior and higher stiffness, while concentrations above 0.4 mg/mL led to a more viscoplastic and fluid-like behavior. Cellular migration into the scaffolds followed the inverse trend, higher concentrations of pepsin (i.e.: fewer GAGs and stiffness) increased cellular infiltration. Nevertheless, cells were still able to migrate into the matrix with the lowest pepsin concentration. Interestingly, without pepsin cells could not penetrate the open channels.
By diminishing the GAG content, the stiffness of auricular cartilage scaffolds is reduced, translating into differences in cellular infiltration.