29. Jahrestagung der Deutschen Gesellschaft für Biomaterialien

Chair

Prof. Dr.

Surface functionalization of calcium phosphate nanoparticles via click chemistry

Surface modification technologies

Biofabrication

Abstract text (incl. figure legends and references) I: Calcium phosphate nanoparticles (CaP-NPs) are of great interest in modern biomedicine because of their biocompatibility, biodegradability and possibility to target different cells. Their surface functionalization opens new pathways for a biomedical application, for imaging or enhanced targeting. CaP-NPs are easily taken up by cells and represent efficient carriers for biomolecules. O: Elucidate the applicability of click chemistry by attaching fluorescently labelled model proteins, i.e. bovine serum albumin (BSA) and hemoglobin, as well as ultrasmall gold nanoparticles to the surface of CaP-NPs, to investigate their performance in cell uptake. M&amp;M: For colloidal stabilization, CaP-NPs were coated with polyethyleneimine (PEI) and a silica shell. To functionalize the surface of CaP-NPs with fluorescent proteins and gold nanoparticles, either azide groups or alkyne groups were covalently attached to the particle surface. This is a prerequisite for copper-catalyzed azide-alkyne cycloaddition (CuAAC; click chemistry) with alkyne-functionalized proteins or azide-functionalized gold nanoparticles. The characterization of CaP-NPs was performed by scanning electron microscopy (SEM) for the particle diameter and dynamic light scattering (DLS) to analyze the dispersibility. UV-Vis spectroscopy and atomic absorption spectrometry (AAS) were used to determine the number of attached ligands. The uptake by cells was studied by confocal laser scanning microscopy (CLSM). R: Proteins were successfully clicked to the surface of CaP-NPs with a stable bond during and after cellular uptake. Furthermore, gold nanoparticles can be covalently attached to CaP-NPs, creating a multifunctional system to transport more than one agent into cells. All nanoparticles were successfully taken up by HeLa cells and were colloidally stable. C: CaP-NPs can be covalently functionalized with model proteins and ultrasmall gold nanoparticles. The functionalized nanoparticles can act as efficient transporters into cells.

Short Talk

Professor

Creation of a growth factor-based inner ear drug delivery system

Implant associated

Abstract text (incl. figure legends and references) Introduction The effects of hearing loss are restricting for the sufferers. Inserting a cochlear implant, which stimulates the remaining spiral ganglion neurons (SGNs), is the most common treatment for hearing loss caused by hair cell loss. The relatively large gap between the cochlear electrode and these neurons is a crucial problem. Quality of signal transmission is lost as a consequence. An improvement in electrode-nerve contact is required for a better auditory experience. Objectives To reduce the distance between the electrode and the SGNs a composite material is synthesised. Brain-derived neurotrophic factor (BDNF) and neurotrophic factor 3 (NT-3)-containing nanoporous silica nanoparticles (NPSNPs) will be attached to the silicone surface. To overcome the silicone&quot;s inertness, a polymer coating should be created first. Materials &amp; methods Different silanes were used to modify the synthesised NPSNPs. For immobilisation in a growth factor solution combining BDNF and NT-3, amino-modified particles were utilised. An UV-initiated radical reaction in an aqueous acrylate solution was used to create the polymer coating. As a radical initiator, benzophenone was used. Particles that have been allyl-modified were added to the monomer solution for particle integration into the coating. Results The particles were successfully modified which can be drawn from nitrogen physisorption, zeta potential and thermogravimetric measurements. Release experiments proved that BDNF and NT-3 were immobilised reversibly at the particles. Moreover, the successful polymer coating was confirmed by FTIR, XPS and water contact angle measurements. The particle integration was determined by SEM investigation. Conclusion As a result, it has been proven that NPSNPs can release BDNF and NT-3. Additionally, the polymer coating can be used to adhere NPSNPs to the silicone surface. These two findings will be combined to create a potential composite material for a local cochlea drug delivery system.

Neuronal guidance scaffold for cochlear implants

Abstract text (incl. figure legends and references) In case of sensorineural hearing loss, a cochlear implant can be implanted to help the patient to hear again. But the problem with this is, that the distance between the implant&quot;s electrode and the spiral ganglion neurons (SGN) is rather large. As a result, there is a loss in signal transmission and poor auditory perception. To solve this problem, an enhanced electrode-nerve contact is needed. A neuronal guidance scaffold based on polymer fibres attached to the cochlear implant is designed to accomplish this. To mimic the extracellular matrix (ECM), heparan sulphate (HS) and laminin are covalently attached to these fibres. Then the growth factors brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) are added. The growth factors are anticipated to be released and ought to benefit the SGN&quot;s survival and neurite outgrowth. The ECM components should encourage the neurites to grow along the fibres once they are in contact with them with the final goal to increase the electrode-nerve contact. First, an aminolysis was performed with the fibres to get amino groups on the surface. Then, HS was covalently attached to unmodified and amino-modified fibres. Following that, the fibres were incubated in a BDNF/NT-3 solution and release experiments were done to evaluate the release behaviours. In addition, cell culture studies with supernatants were carried out to determine the effect of the released growth factor on SGN. In another experiment, laminin was covalently bound to the fibres and SGN explants were put on them. The fibres were successfully modified with amino-groups on the surface. In the release experiments it was shown, that the release of growth factors is more continuous from the amino-modified fibres. And there is an effect on the survival rate of SGN. In the studies with laminin it was shown that explants with SGN can grow on the coated fibres. The fibres show promising results with regard to their use as a neuronal guidance scaffold for SGN neurites.

Control of protein adsorption on biomaterials by thin polyelectrolyte multilayers

Cell-material interactions

Abstract text (incl. figure legends and references) Introduction: Proteins adsorb onto biomaterial surface within seconds of the first material-tissue contact and play a pivotal function as mediators between the biomaterial and tussie. Ruling the adsorption of proteins onto biomaterials allows controlling subsequent cell adhesion and growth, and therefore is critical for the successful implantation and proper functioning of implants. In this work, polyelectrolyte multilayer (PEM) coatings were explored as a strategy for biofunctionalization of biomaterials by controlling the extent of protein adsorption. Materials &amp; methods: Three types of ultratin PEM coatings, composed of pairs of natural and synthetic polyelectrolytes, were build and characterized by ellipsometry, water contact angle, atomic force microscopy and streaming potential. Adsorption of human serum albumin (HSA) on the coatings was quantified by protein-dye binding (Bradford assay). Human umbilical vein endothelial cells (HUVEC) and mouse embryonic fibroblast 3T3 cells were used for cell adhesion and proliferation studies. Results: The extent of HSA adsorption was found to be related to the surface properties of PEM coatings. The major role was played by the surface charge, and for all three PEM types, a greater amount of protein was adsorbed on coatings with a positively charged surface. The number of adhered cells, their proliferation and viability increased in parallel with the amount of the adsorbed HSA. All investigated coating were found to be non-cytotoxic. Conclusion: We demonstrated that application of ultratin PEM coatings is one avenue to regulate the extent of protein adsorption and thereby cell adhesion and growth. The amount of adsorbed proteins correlated to the adhesion and proliferation of cells on the model surfaces. The results of this study may help to improve the biocompatibility of biomaterials. Acknowledgements: The authors gratefully acknowledge the funding by the German Research Foundation (DFG) for the subproject 2 within the Research Unit FOR5250 "Permanent and bioresorbable implants with tailored functionality" (No. 449916462).

Lecture hall 6

Short Talks 1

Surface Modification

Short Talk Session

Short Talks 1
Surface Modification

Appointment

Chair

Topic

Programme

Short Talks 1Surface Modification

Appointment

Chair

Topic

Programme

Short Talks 1
Surface Modification