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Contains fulltext : 306762.pdf (Publisher’s version ) (Open Access), Radboud University, 13 juni 2024, Promotores : Leeuwenburgh, S.C.G., Flik, G. Co-promotores : Hoff, J.W. Von den, Wagener, F.A.D.T.G., Metz, J.R., 193 p.

Contains fulltext : 306388.pdf (Publisher’s version ) (Open Access), Despite the immense need for effective treatment of spinal cord injury (SCI), no successful repair strategy has yet been clinically implemented. Multifunctional biomaterials, based on porcine adipose tissue-derived extracellular matrix (adECM) and reduced graphene oxide (rGO), were recently shown to stimulate in vitro neural stem cell growth and differentiation. Nevertheless, their functional performance in clinically more relevant in vivo conditions remains largely unknown. Before clinical application of these adECM-rGO nanocomposites can be considered, a rigorous assessment of the cytotoxicity and biocompatibility of these biomaterials is required. For instance, xenogeneic adECM scaffolds could still harbour potential immunogenicity following decellularization. In addition, the toxicity of rGO has been studied before, yet often in experimental settings that do not bear relevance to regenerative medicine. Therefore, the present study aimed to assess both the in vitro as well as in vivo safety of adECM and adECM-rGO scaffolds. First, pulmonary, renal and hepato-cytotoxicity as well as macrophage polarization studies showed that scaffolds were benign invitro. Then, a laminectomy was performed at the 10th thoracic vertebra, and scaffolds were implanted directly contacting the spinal cord. For a total duration of 6 weeks, animal welfare was not negatively affected. Histological analysis demonstrated the degradation of adECM scaffolds and subsequent tissue remodeling. Graphene-based scaffolds showed a very limited fibrous encapsulation, while rGO sheets were engulfed by foreign body giant cells. Furthermore, all scaffolds were infiltrated by macrophages, which were largely polarized towards a pro-regenerative phenotype. Lastly, organ-specific histopathology and biochemical analysis of blood did not reveal any adverse effects. In summary, both adECM and adECM-rGO implants were biocompatible upon laminectomy while establishing a pro-regenerative microenvironment, which ju, 01 juni 2024

Item does not contain fulltext, Biomaterials with the ability to self-heal and recover their structural integrity offer many advantages for applications in biomedicine. The past decade has witnessed the rapid emergence of a new class of self-healing biomaterials commonly termed injectable, or printable in the context of 3D printing. These self-healing injectable biomaterials, mostly hydrogels and other soft condensed matter based on reversible chemistry, are able to temporarily fluidize under shear stress and subsequently recover their original mechanical properties. Self-healing injectable hydrogels offer distinct advantages compared to traditional biomaterials. Most notably, they can be administered in a locally targeted and minimally invasive manner through a narrow syringe without the need for invasive surgery. Their moldability allows for a patient-specific intervention and shows great prospects for personalized medicine. Injected hydrogels can facilitate tissue regeneration in multiple ways owing to their viscoelastic and diffusive nature, ranging from simple mechanical support, spatiotemporally controlled delivery of cells or therapeutics, to local recruitment and modulation of host cells to promote tissue regeneration. Consequently, self-healing injectable hydrogels have been at the forefront of many cutting-edge tissue regeneration strategies. This study provides a critical review of the current state of self-healing injectable hydrogels for tissue regeneration. As key challenges toward further maturation of this exciting research field, we identify (i) the trade-off between the self-healing and injectability of hydrogels vs their physical stability, (ii) the lack of consensus on rheological characterization and quantitative benchmarks for self-healing injectable hydrogels, particularly regarding the capillary flow in syringes, and (iii) practical limitations regarding translation toward therapeutically effective formulations for regeneration of specific tissues. Hence, here we (i) review

Item does not contain fulltext, Stromal vascular fraction (SVF) is the primary isolate obtained after enzymatic digestion of adipose tissue that contains various cell types. Its successful application for cell-based construct preparation in an intra-operative setting for clinical bone augmentation and regeneration has been previously reported. However, the performance of SVF-based constructs compared with traditional ex vivo expanded adipose tissue-derived mesenchymal stromal cells (ATMSCs) remains unclear and direct comparative analyses are scarce. Consequently, we here aimed at comparing the in vitro osteogenic differentiation capacity of donor-matched SVF versus ATMSCs as well as their osteoinductive capacity. Human adipose tissue from nine different donors was used to isolate SVF, which was further purified via plastic-adherence to obtain donor-matched ATMSCs. Both cell populations were immunophenotypically characterized for mesenchymal stromal cell, endothelial, and hematopoietic markers after isolation and immunocytochemical staining was used to identify different cell types during prolonged cell culture. Based on normalization using plastic-adherence fraction determination, SVF and ATMSCs were seeded and cultured in osteogenic differentiation medium for 28 days. Further, SVF and ATMSCs were seeded onto devitalized bovine bone granules and subcutaneously implanted into nude mice. After 42 days of implantation, granules were retrieved, histologically processed, and stained with hematoxylin and eosin (HE) to assess ectopic bone formation. The ATMSCs were shown to be a homogenous cell population during cell culture, whereas SVF cultures consisted of multiple cell types. All donor-matched comparisons showed either accelerated or stronger mineralization for SVF cultures in vitro. However, neither SVF nor ATMSCs loaded on devitalized bone granules induced ectopic bone formation on subcutaneous implantation, as opposed to control granules loaded with bone morphogenetic protein-2 (BMP-2), which trig

Contains fulltext : 293647.pdf (Publisher’s version ) (Open Access)

Item does not contain fulltext, We establish a versatile hydrogel platform based on modular building blocks that allows the design of hydrogels with tailored physical architecture and mechanical properties. We demonstrate its versatility by assembling (i) a fully monolithic gelatin methacryloyl (Gel-MA) hydrogel, (ii) a hybrid hydrogel composed of 1:1 Gel-MA and gelatin nanoparticles, and (iii) a fully particulate hydrogel based on methacryloyl-modified gelatin nanoparticles. The hydrogels were formulated to exhibit the same solid content and comparable storage modulus but different stiffness and viscoelastic stress relaxation. The incorporation of particles resulted in softer hydrogels with enhanced stress relaxation. Murine osteoblastic cells cultured in two-dimensional (2D) on hydrogels showed proliferation and metabolic activity comparable to established collagen hydrogels. Furthermore, the osteoblastic cells showed a trend of increased cell numbers, cell expansion, and more defined protrusions on stiffer hydrogels. Hence, modular assembly allows the design of hydrogels with tailored mechanical properties and the potential to alter cell behavior.

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Item does not contain fulltext, INTRODUCTION: There has recently been a surge of interest in mesoporous bioactive glass nanoparticles (MBGNs) as multi-functional nanocarriers for application in bone-reconstructive and -regenerative surgery. Their excellent control over their structural and physicochemical properties renders these nanoparticles suitable for the intracellular delivery of therapeutic agents to combat degenerative bone diseases, such as bone infection, or bone cancer. Generally, the therapeutic efficacy of nanocarriers strongly depends on the efficacy of their cellular uptake, which is determined by numerous factors including cellular features and the physicochemical characteristics of nanocarriers, particularly surface charge. In this study, we have systematically investigated the effect of the surface charge of MBGNs doped with copper as a model therapeutic agent on cellular uptake by both macrophages and pre-osteoblast cells involved in bone healing and bone infections to guide the future design of MBGN-based nanocarriers. METHODS: Cu-MBGNs with negative, neutral, and positive surface charges were synthesized and their cellular uptake efficiency was assessed. Additionally, the intracellular fate of internalized nanoparticles along with their ability to deliver therapeutic cargo was studied in detail. RESULTS: The results showed that both cell types internalized Cu-MBGNs regardless of their surface charge, indicating that cellular uptake of nanoparticles is a complex process influenced by multiple factors. This similarity in cellular uptake was attributed to the formation of a protein corona surrounding the nanoparticles when exposed to protein-rich biological media, which masks the original nanoparticle surface. Once internalized, the nanoparticles were found to mainly colocalize with lysosomes, exposing them to a more compartmentalized and acidic environment. Furthermore, we verified that Cu-MBGNs released their ionic components (Si, Ca, and Cu ions) in both acidic and neutral env

Radboud University, 30 augustus 2023, Promotores : Goor, H. van, Leeuwenburgh, S.C.G. Co-promotor : Felix Lanao, R.P., Contains fulltext : 294846.pdf (Publisher’s version ) (Closed access)

Contains fulltext : 296918.pdf (Publisher’s version ) (Open Access), OBJECTIVE: Novel self-healing resin-based composites containing microcapsules have been developed to improve the mechanical performance of dental restorations. However, the long-term fatigue behaviour of these self-healing composites has still been hardly investigated. Therefore, this manuscript studied the fatigue behaviour of self-healing composites containing microcapsules by subjecting the specimens to traditional staircase tests and ageing in a custom-designed chewing simulator (Rub&Roll) to simulate oral ageing physiologically relevant conditions. METHODS: To prepare self-healing composite, poly(urea-formaldehyde) microcapsules containing acrylic self-healing liquids were synthesized. Subsequently, these microcapsules (10 wt%) and initiator (benzoyl peroxide, BPO, 2 wt%) were incorporated into a commercial flowable resin-based composite. Microcapsule-free resin-based composites with and without BPO were also prepared as control specimens. A three-point flexural test was used to measure the initial flexural strength (S(initial)). Subsequently, half of the specimens were used for fatigue testing using a common staircase approach to measure the fatigue strengths (FS). In addition, the other specimens were aged in the Rub&Roll machine for four weeks where after the final flexural strength (S(final)) was measured. RESULTS: Compared to S(initial), FS of all tested specimens significantly decreased as measured through staircase testing. After 4 weeks of ageing in the Rub&Roll machine, S(final) was significantly reduced compared to S(initial) for microcapsule-free resin-based composites, but not for the self-healing composites (p = 0.3658). However, the self-healing composites are still in the experimental phase characterized by a low mechanical strength, which still impedes further clinical translation. SIGNIFICANCE: Self-healing composites containing microcapsules exhibit improved fatigue resistance compared to microcapsule-free non-self-healing composites.

Item does not contain fulltext, Viscoelastic properties of hydrogels such as stress relaxation or plasticity have been recognized as important mechanical cues that dictate the migration, proliferation, and differentiation of embedded cells. Stress relaxation rates in conventional hydrogels are usually much slower than cellular processes, which impedes rapid cellularization of these elastic networks. Colloidal hydrogels assembled from nanoscale building blocks may provide increased degrees of freedom in the design of viscoelastic hydrogels with accelerated stress relaxation rates due to their strain-sensitive rheology which can be tuned via interparticle interactions. Here, we investigate the stress relaxation of colloidal hydrogels from gelatin nanoparticles in comparison to physical gelatin hydrogels and explore the particle interactions that govern stress relaxation. Colloidal and physical gelatin hydrogels exhibit comparable rheology at small deformations, but colloidal hydrogels fluidize beyond a critical strain while physical gels remain primarily elastic independent of strain. This fluidization facilitates fast exponential stress relaxation in colloidal gels at strain levels that correspond to strains exerted by cells embedded in physiological extracellular matrices (10-50%). Increased attractive particle interactions result in a higher critical strain and slower stress relaxation in colloidal gels. In physical gels, stress relaxation is slower and mostly independent of strain. Hence, colloidal hydrogels offer the possibility to modulate viscoelasticity via interparticle interactions and obtain fast stress relaxation rates at strains relevant for cell activity. These beneficial features render colloidal hydrogels promising alternatives to conventional monolithic hydrogels for tissue engineering and regenerative medicine. STATEMENT OF SIGNIFICANCE: In the endeavor to design biomaterials that favor cell activity, research has long focused on biochemical cues. Recently, the time-, stress-, and

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Item does not contain fulltext, Currently, steel implants are used for osteosynthesis of (comminuted) fractures and intra-articular bone defects. These osteosyntheses can sometimes be complicated procedures and can have several drawbacks including stress shielding of the bone. A bone glue might be a safe and effective alternative to current materials. Despite numerous animal studies on bone adhesives, no such material is clinically applied yet. We have conducted a systematic review to summarize the evidence in experimental animal models used in research on bone adhesive materials for trauma and orthopedic surgery. Additionally, we analysed the efficacy of the different bone adhesives for different experimental designs. A heterogeneity in experimental parameters including animal species, defect types, and control measurements resulted in a wide variety in experimental models. In addition, no standard outcome measurements could be identified. Meta-analysis on bone regeneration between adhesive treatment and nonadhesive treatment showed a high heterogeneity and no statistically significant overall effect (M: -0.71, 95% confidence interval [CI]: -1.63-0.21, p = 0.13). Besides, currently there is not enough evidence to draw conclusions based on the effectiveness of the individual types of adhesives or experimental models. A positive statistically significant effect was found for the adhesive treatment in comparison with conventional osteosynthesis materials (M: 2.49, 95% CI: 1.20-3.79, p = 0.0002). To enhance progression in bone adhesive research and provide valuable evidence for clinical application, more standard experimental parameters and a higher reporting quality in animal studies are needed. Statement of Clinical Significance: Current materials restoring anatomical alignments of bones have several drawbacks. A (biodegradable) adhesive for fixating bone defects can be a treatment breakthrough. Although numerous bone adhesives have been researched, most seemed to fail at the preclinical stage. An

Item does not contain fulltext, Calcium phosphates (CaPs) and silicate-based bioglasses have been extensively studied since the early 1970s due to their unique capacity to bind to host bone, which led to their clinical translation and commercialization in the 1980s. Since the mid-1990s, researchers have synthesized nanoscale CaP and silicate-based particles of increased specific surface area, chemical reactivity, and solubility, which offer specific advantages compared to their bulk counterparts. This review provides a critical perspective on the history and emerging trends of these two classes of ceramic nanoparticles. Their synthesis and functional properties in terms of particle composition, size, shape, charge, dispersion, and toxicity are discussed as a function of relevant processing parameters. Specifically, emerging trends such as the influence of ion doping and mesoporosity on the biological and pharmaceutical performance of these nanoparticles are reviewed in more detail. Finally, a broad comparative overview is provided on the physicochemical properties and applicability of CaP and silicate-based nanoparticles within the fields of (i) local delivery of therapeutic agents, (ii) functionalization of biomaterial scaffolds or implant coatings, and (iii) bioimaging applications. Impact statement This review provides a critical perspective on the history and emerging trends of the two main classes of bioceramic nanoparticles, that is, calcium phosphate (CaP) and silicate-based nanoparticles. While most reviews in literature focus on either CaP or silicate-based nanoparticles, our review evaluates both classes of bioceramic nanoparticles simultaneously. This combined review offers the opportunity to analyze differences and similarities with respect to the historic development and emerging trends within both fields of bioceramics research.

Contains fulltext : 282850.pdf (Publisher’s version ) (Open Access)

Item does not contain fulltext, Implant coatings are frequently applied to modulate tissue response and delivery of drugs. Copper (Cu)-containing coatings on dental implant abutments have been proposed to improve soft tissue integration and reduce the risk for peri-implant infections. However, precise control over Cu loading and release kinetics remains a major challenge. In this study, we introduced a bottom-up coating deposition method based on nanoparticle assembly to allow for local release of Cu ions from implant surfaces. We first doped mesoporous bioactive glass (MBG) nanoparticles with various amounts of Cu. Subsequently, we suspended these Cu-doped MBG (Cu-MBG), Cu-free MBG nanoparticles, or mixtures thereof in chitosan solution and prepared a series of composite coatings on commercially pure titanium disks as model surfaces for transmucosal components of bone implants through electrophoretic deposition (EPD). By changing the Cu-MBG:MBG ratio of the composite coatings, we controlled the Cu release kinetics without changing other coating properties. Human gingival fibroblasts proliferated on the composite coatings except for coatings with the highest amount of Cu, which inhibited their proliferation. The migration rate of human umbilical vein endothelial cells cultured on the composite coatings was highest on coatings containing equal amounts of Cu-MBG and Cu-free MBG. Antibacterial tests confirmed that Cu-containing coatings reduced the growth of Porphyromonas gingivalis up to fivefold compared with uncoated implants. In conclusion, our data indicate that the EPD method is suitable to deposit nanoparticle-based coatings onto dental implants, which enhance endothelial cell migration and reduce bacterial growth. Impact statement Precise control over the release of therapeutic agents remains a major challenge for implant coatings. In this study, we introduce a simple and cost-effective way to tune the release of angiogenic and antibacterial copper ions using the electrophoretic deposition te

Contains fulltext : 283838.pdf (Publisher’s version ) (Open Access)

Item does not contain fulltext, OBJECTIVE: This study aimed to investigate the wear behaviour of direct composite restorations after 5 years and associated patient factors. METHODS: 38 patients (6 females, 32 males; 35.2 ± 7.6y) from the Radboud Tooth Wear Project with generalized moderate to severe tooth wear were treated with direct composite restorations on all teeth. Ethical approval was sought and granted before the study was undertaken. Intraoral 3D scans were recorded at 1 month (baseline) and 5 years (recall) after treatment. The amount of height loss was measured at six index teeth (first molars and upper central incisors). Patient factors (age, vertical dimension of occlusion increase, bite force, aetiology score, jaw position and bearing/ non-bearing cusps) were included in the analysis. Multilevel multiple regression with bootstrapping was used to analyse the influence of these factors on wear behaviour of restorations. Observer reliability was tested by paired t-tests and Band-Altman plots (p<0.05) RESULTS: After 5 years, the mean height loss was 0.23± 0.19 mm for incisors and 0.43± 0.24 mm for molars (p≤0.001). Patient factors did not show any significant influence on height loss of the composite restorations, while bearing cusps showed significant more wear compared to non-bearing cusps (p≤0.001). The observer reliability tests confirmed the repeatability (correlation of 0.809, DME 0.103). CONCLUSIONS: Wear of composite restorations is a significant and relevant factor over time in patients treated with severe tooth wear. Within the limitations of this clinical study, patient factors were found not to have a significant effect on wear behaviour of direct composite restorations.

Radboud University, 03 oktober 2022, Promotores : Leeuwenburgh, S.C.G., Loomans, B.A.C. Co-promotor : Yang, F., Contains fulltext : 281489.pdf (Publisher’s version ) (Open Access)

Radboud University, 13 september 2022, Promotores : Beucken, J.J.J.P van den, Leeuwenburgh, S.C.G., Contains fulltext : 252890.pdf (Publisher’s version ) (Open Access)

Item does not contain fulltext, The large number of animal models used in spinal cord injury (SCI) research complicates the objective selection of the most appropriate model to investigate the efficacy of biomaterial-based therapies. This systematic review aims to identify a list of relevant animal models of SCI by evaluating the confirmation of SCI and animal survival in all published SCI models used in biomaterials research up until April 2021. A search in PubMed and Embase based on "spinal cord injury," "animal models," and "biomaterials" yielded 4606 papers, 393 of which were further evaluated. A total of 404 individual animal experiments were identified based on type of SCI, level of SCI, and the sex, species, and strain of the animals used. Finally, a total of 149 unique animal models were comparatively evaluated, which led to the generation of an evidence-based list of well-documented mid-thoracic rat models of SCI. These models were used most often, clearly confirmed SCI, and had relatively high survival rates, and therefore could serve as a future starting point for studying novel biomaterial-based therapies for SCI. Furthermore, the review discusses (1) the possible risk of bias in SCI animal models, (2) the difficulty in replication of such experiments due to frequent poor reporting of the methods and results, and (3) the clinical relevance of the currently utilized models. Systematic review registration: The study was prospectively registered in PROSPERO, registration number CRD42019141162. Impact statement Studies on biomaterial-based therapies within the field of spinal cord injury (SCI) research show a large inconsistency concerning the selection of animal models. This review goes beyond summarizing the existing gaps between experimental and clinical SCI by systematically evaluating all animal models used within this field. The models identified by this work were used most often, clearly confirmed SCI, and had a relatively high survival rate. This evidence-based list of well-documen

Item does not contain fulltext, Bone tissue engineering aims to restore and maintain the function of bone by means of biomaterial-based scaffolds. This review specifically focuses on the use of fibers in biomaterials used for bone tissue engineering as suitable environment for bone tissue repair and regeneration. We present a bioinspired rationale behind the use of fibers in bone tissue engineering and provide an overview of the most common fiber fabrication methods, including solution, melt, and microfluidic spinning. Subsequently, we provide a brief overview of the composition of fibers that are used in bone tissue engineering, including fibers composed of (i) natural polymers (e.g., cellulose, collagen, gelatin, alginate, chitosan, and silk, (ii) synthetic polymers (e.g., polylactic acid [PLA], polycaprolactone, polyglycolic acid [PGA], polyethylene glycol, and polymer blends of PLA and PGA), (iii) ceramic fibers (e.g., aluminium oxide, titanium oxide, and zinc oxide), (iv) metallic fibers (e.g., titanium and its alloys, copper and magnesium), and (v) composite fibers. In addition, we review the most relevant fiber modification strategies that are used to enhance the (bio)functionality of these fibers. Finally, we provide an overview of the applicability of fibers in biomaterials for bone tissue engineering, with a specific focus on mechanical, pharmaceutical, and biological properties of fiber-functionalized biomaterials for bone tissue engineering. Impact statement Natural bone is a complex composite material composed of an extracellular matrix of mineralized fibers containing living cells and bioactive molecules. Consequently, the use of fibers in biomaterial-based scaffolds offers a wide variety of opportunities to replicate the functional performance of bone. This review provides an overview of the use of fibers in biomaterials for bone tissue engineering, thereby contributing to the design of novel fiber-functionalized bone-substituting biomaterials of improved functionality regarding the

Item does not contain fulltext, Osteoclasts are multinucleated cells derived from the hematopoietic monocyte/macrophage lineage that possess the unique capacity to resorb bone. Due to the crucial role of osteoclasts in maintaining bone homeostasis and pathologies, this cell type is pivotal in multiple research areas dedicated to bone physiology in health and disease. Although numerous methods for generation of human osteoclasts are already available, those rely either on cell labeling-based purification or an intermediate adhesion step after which cells are directly differentiated toward osteoclasts. While the former requires additional reagents and equipment, the latter harbors the risk of variable osteoclast formation due to varying numbers of osteoclast precursors available for different donors. In this study, we report a facile and reliable three-step method for the generation of human osteoclasts from blood-derived precursor cells. Monocytes were obtained after adhering peripheral blood-derived mononuclear cells to plastic substrates followed by macrophage induction and proliferation resulting in a homogeneous population of osteoclast precursors. Finally, macrophages were seeded into suitable culture vessels and differentiated toward osteoclasts. Osteoclastogenesis was monitored longitudinally using nondestructive techniques, while the functionality of mature osteoclasts was confirmed after 14 days of culture by analysis of functional (e.g., elevated tartrate-resistant acid phosphatase [TRAP]-activity, resorption) and morphological (e.g., presence of TRAP, actin ring, and integrin β(3)) characteristics. Furthermore, we propose to use combinatory staining of three morphological osteoclast markers, rather than previously reported staining of a single or maximal two markers, to clearly distinguish osteoclasts from undifferentiated mononuclear cells. Impact statement Research related to bone biology requires a standardized and reliable method for in vitro generation of human osteoclasts. We here

Contains fulltext : 244204.pdf (Publisher’s version ) (Open Access), The development of bone glues based on bone-adhesive hydrogels to allow for facile bone fracture fixation remains a major challenge. Herein, dual crosslinked hydrogels that combine tunable stiffness, ductility, and self-healing capacity are successfully synthesized. The resulting double network hydrogel is formed by chemical crosslinking of N-hydroxysuccinimide-functionalized poly(2-oxazoline)s(POx-NHS)"?> with amine-functionalized poly(2-oxazoline)s, and physical crosslinking of alendronate-functionalized poly(2-oxazoline)s (POx-Ale) with calcium ions in solution. The use of an excess of alendronate-functionalized POx-Ale polymers also ensures affinity toward calcium cations in the mineral phase of bone, thereby rendering these hydrogels adhesive to bone. The mechanical and bone-adhesive properties of these novel hydrogels are superior to commercially available fibrin sealants. Moreover, hydrogels retain their bone-adhesive properties under wet conditions. Although the dual crosslinked hydrogels swell considerably, they are stable upon immersion in phosphate-buffered saline (up to 12 d) and even in ethylenediaminetetraacetic acid solution. The enhanced mechanical and bone-adhesive properties of these hydrogels, as well as their in vitro stability, indicate that they have much application potential as bone-adhesive glues.

Contains fulltext : 244261.pdf (Publisher’s version ) (Open Access), To investigate the delivery of next-generation macromolecular drugs, such as engineered proteins and mRNA-containing nanoparticles, there is an increasing push towards the use of physiologically relevant disease models that incorporate human cells and do not face ethical dilemmas associated with animal use. Here, we illustrate the versatility and ease of use of a microfluidic platform for studying drug delivery using high-resolution microscopy in 3D. Using this microfluidic platform, we successfully demonstrate the specific targeting of carbonic anhydrase IX (CAIX) on cells overexpressing the protein in a tumor-mimicking chip system using affibodies, with CAIX-negative cells and non-binding affibodies as controls. Furthermore, we demonstrate this system's feasibility for testing mRNA-containing biomaterials designed to regenerate bone defects. To this end, peptide- and lipid-based mRNA formulations were successfully mixed with colloidal gelatin in microfluidic devices, while translational activity was studied by the expression of a green fluorescent protein. This microfluidic platform enables the testing of mRNA delivery from colloidal biomaterials of relatively high densities, which represents a first important step towards a bone-on-a-chip platform. Collectively, by illustrating the ease of adaptation of our microfluidic platform towards use in distinct applications, we show that our microfluidic chip represents a powerful and flexible way to investigate drug delivery in 3D disease-mimicking culture systems that recapitulate key parameters associated with in vivo drug application.

Contains fulltext : 232237.pdf (Publisher’s version ) (Open Access)

Contains fulltext : 237694.pdf (Publisher’s version ) (Open Access), The aim of the current study is to assess the biological performance of self-healing hydrogels based on calcium phosphate (CaP) nanoparticles and bisphosphonate (BP) conjugated hyaluronan (HA) in a critical size segmental femoral bone defect model in rats. Additionally, these hydrogels are loaded with bone morphogenetic protein 2 (BMP-2) and their performance is compared in healthy and osteoporotic bone conditions. Treatment groups comprise internal plate fixation and placement of a PTFE tube containing hydrogel (HA(BP) -CaP) or hydrogel loaded with BMP-2 in two dosages (HA(BP) -CaP-lowBMP2 or HA(BP) -CaP-highBMP2). Twelve weeks after bone defect surgery, bone formation is analyzed by X-ray examination, micro-CT analysis, and histomorphometry. The data show that critical size, segmental femoral bone defects cannot be healed with HA(BP) -CaP gel alone. Loading of the HA(BP) -CaP gel with low dose BMP-2 significantly improve bone formation and resulted in defect bridging in 100% of the defects. Alternatively, high dose BMP-2 loading of the HA(BP) -CaP gel does not improve bone formation within the defect area, but leads to excessive bone formation outside the defect area. Bone defect healing is not affected by osteoporotic bone conditions.

Contains fulltext : 236827.pdf (Publisher’s version ) (Open Access)

Contains fulltext : 238876.pdf (Publisher’s version ) (Open Access), To create a novel generation of barrier membranes with bone-adhesive properties, three-component membranes were successfully developed using a solvent-free approach by combining an occlusive polyester backing layer with a bone-adhesive fibrous gelatin carrier impregnated with calcium-binding alendronate-functionalized poly(2-oxazoline)s (POx-Ale). The mechanical properties of these novel membranes were similar to other commercially available barrier membranes. In contrast, the adhesion of our membranes towards bone was by far superior (i.e. 62-fold) compared to conventional commercially available Bio-Gide® membranes. Moreover, alendronate-functionalized membranes retained their bone-adhesive properties under wet conditions in phosphate-buffered saline (PBS) solutions with and without collagenase. Finally, the in vitro degradation of the membranes was studied by monitoring their weight loss upon immersion in PBS solutions with and without collagenase. The membranes degraded in a sustained manner, which was accelerated by the presence of collagenase due to enzymatic degradation of the carrier. In conclusion, our results show that surface functionalization of barrier membranes with alendronate moieties renders them adhesive to bone. As such, the biomaterials design strategy presented herein opens up new avenues of research on bone-adhesive membranes for guided bone regeneration.

Contains fulltext : 228689.pdf (publisher's version ) (Open Access)

Radboud University, 02 november 2021, Promotores : Leeuwenburgh, S.C.G., Hest, J.C.M. van Co-promotor : Felix Lanao, R.P., Contains fulltext : 238955.pdf (Publisher’s version ) (Open Access)

Radboud University, 28 juni 2021, Promotores : Jansen, J.A., Leeuwenburgh, S.C.G. Co-promotor : Yang, F., Contains fulltext : 233900.pdf (Publisher’s version ) (Open Access)

Contains fulltext : 231106.pdf (publisher's version ) (Open Access)

Radboud University, 25 januari 2021, Promotor : Leeuwenburgh, S.C.G., Contains fulltext : 230410.pdf (publisher's version ) (Open Access)

Radboud University, 11 juni 2021, Promotor : Leeuwenburgh, S.C.G. Co-promotor : Beucken, J.J.J.P van den, Contains fulltext : 233567.pdf (Publisher’s version ) (Open Access)

Contains fulltext : 220012.pdf (Publisher’s version ) (Open Access)

Contains fulltext : 219813.pdf (Publisher’s version ) (Closed access)

Contains fulltext : 220688.pdf (Publisher’s version ) (Open Access), Calcium phosphate cements (CPCs) are frequently used as synthetic bone substitute materials due to their favorable osteocompatibility and handling properties. However, CPCs alone are inherently brittle and exhibit low strength and toughness, which restricts their clinical applicability to non-load bearing sites. Mechanical reinforcement of CPCs using fibers has proven to be an effective strategy to toughen these cements by transferring stress from the matrix to the fibers through frictional sliding at the interface. Therefore, tailoring the fiber-matrix affinity is paramount in designing highly toughened CPCs. However, the mechanistic correlation between this interaction and the macromechanical properties of fiber-reinforced CPCs has hardly been investigated to date. The aim of this study was to tailor the fiber-matrix interface affinity by modifying the surface of poly(vinyl alcohol) (PVA) fibers and correlate their interfacial properties to macromechanical properties (i.e. fracture toughness, work-of-fracture and tensile strength) of CPCs. Results from single fiber pullout tests reveal that the surface modification of PVA fibers increased their hydrophilicity and improved their affinity to the CPC matrix. This observation was evidenced by an increase in the interfacial shear strength and a reduction in the critical fiber embedment length (i.e. maximum embedded length from which a fiber can be pulled out without rupture). This increased interface affinity facilitated energy dissipation during fracture of CPCs subjected to macromechanical three-point flexure and tensile tests. The fracture toughness also significantly improved, even for CPCs reinforced with fibers of lengths greater than their critical fiber embedment length, suggesting that other crack-arresting mechanisms also play an important role in mechanically reinforcing CPCs. Overall, these basic insights will improve the understanding of the correlation between micro- and macromechanical characteristics of