Bora Garipcan

Utilization of cell derived decellularized extracellular matrices (dECM) is a highly versatile way to introduce complex cell specific native-like microenvironment in vitro. While dECMs have been used in various applications, surface functionalization of biomaterials with cell-derived dECMs that maintain their structural integrity for investigating cell behavior is rarely reported. In this study, we developed and characterized a platform combining native bone surface topography mimicked polydimethylsiloxane (BSM PDMS) surfaces with pre-osteoblast derived dECM to mimic both physical and biochemical cues of the bone microenvironment. Decellularized ECM on PDMS and BSM PDMS surfaces preserved their structure and specific matrix components, in addition to having a significant influence on microscale surface topography. Recellularization of BSM PDMS + dECM surfaces supported cell attachment and proliferation of both pre-osteoblasts and adipose derived mesenchymal stem cells (hADMSC). BSM PDMS + dECM surfaces showed significantly elevated glycosaminoglycan (GAG) content, as well as, resulted in induction and topography dependent calcification of hADMSCs. Osteogenic induction and dECM presence on BSM PDMS synergistically increased RUNX2 expression of hADMSCs while keeping YAP expression relatively unaltered. This work provides insights for designing biomimetic platforms integrating biochemical and biophysical cues for advanced bone tissue engineering.

In this study, human fetal osteoblasts behavior was investigated on titanium surfaces that has been modified with amino acid conjugated self-assembled molecules. For this purpose, 3-aminopropyltriethoxysilane (APTES) was conjugated by histidine and leucine and these newly synthesized molecules were used in different combinations to modify titanium surfaces via creating amino acid conjugated self-assembled monolayers (SAM) on titanium surfaces. The modification of the surfaces to introduce hydrophilic and hydrophobic regions on the surface was achieved with varying concentrations (v/v,100:0 20:80, 50:50, 80:20, 0:100). X-ray photoelectron spectroscopy (XPS) analysis and water contact angle measurements were performed for characterizing all of the modified surfaces in order to verify presence of amino acid specific bonds and wettability behavior to find suitable concentrations to support initial cell adhesion. In order to confirm that the surface modification supported cell adhesion and proliferation, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed. Our results have shown that, amino acid SAM modification can be used to fine tune surface wettability and adherent cells were able to proliferate at different rates using different mixture concentrations. This presented approach can prove useful for expanding fine tuning surface chemistry methods for more specific applications and research.

Surface structure plays a crucial role in determining cell behavior on biomaterials, influencing cell adhesion, proliferation, differentiation, as well as immune cells and macrophage polarization. While grooves and ridges stimulate M2 polarization and pits and bumps promote M1 polarization, these structures do not accurately mimic the real bone surface. Consequently, the impact of mimicking bone surface topography on macrophage polarization remains unknown. Understanding the synergistic sequential roles of M1 and M2 macrophages in osteoimmunomodulation is crucial for effective bone tissue engineering. Thus, exploring the impact of bone surface microstructure mimicking biomaterials on macrophage polarization is critical. In this study, we aimed to sequentially activate M1 and M2 macrophages using Poly-l-Lactic acid (PLA) membranes with bone surface topographical features mimicked through the soft lithography technique. To mimic the bone surface topography, a bovine femur was used as a model surface, and the membranes were further modified with collagen type-I and hydroxyapatite to mimic the bone surface microenvironment. To determine the effect of these biomaterials on macrophage polarization, we conducted experimental analysis that contained estimating cytokine release profiles and characterizing cell morphology. Our results demonstrated the potential of the hydroxyapatite-deposited bone surface-mimicked PLA membranes to trigger sequential and synergistic M1 and M2 macrophage polarizations, suggesting their ability to achieve osteoimmunomodulatory macrophage polarization for bone tissue engineering applications. Although further experimental studies are required to completely investigate the osteoimmunomodulatory effects of these biomaterials, our results provide valuable insights into the potential advantages of biomaterials that mimic the complex microenvironment of bone surfaces.

Amniotic membrane extract (AME) and Wharton's jelly mesenchymal stem cells derived‐exosomes (WJ‐MSC‐Exos) are promising therapeutic solutions explored for their potential in tissue engineering and regenerative medicine, particularly in skin and corneal wound healing applications. AME is an extract form of human amniotic membrane and known to contain a plethora of cytokines and growth factors, making it a highly attractive option for topical applications. Similarly, WJ‐MSC‐Exos have garnered significant interest for their wound healing properties. Although WJ‐MSC‐Exos and AME have been used separately for wound healing research, their combined synergistic effects have not been studied extensively. In this study, we evaluated the effects of both AME and WJ‐MSC‐Exos, individually and together, on the proliferation of corneal keratocytes as well as their ability to promote in vitro cell migration, wound healing, and their impact on cellular morphology. Our findings indicated that the presence of both exosomes (3 × 10⁵ Exo/mL) and AME (50 μg/mL) synergistically enhance the proliferation of corneal keratocytes. Combined use of these solutions (3 × 10⁵ Exo/mL + 50 μg/mL) increased cell proliferation compared to only 50 μg/mL AME treatment on day 3 (**** p < 0.0001). This mixture treatment (3 × 10⁵ Exo/mL + 50 μg/mL) increased wound closure rate compared to isolated WJ‐MSC‐Exo treatment (3 × 10⁵ Exo/mL) (*p < 0.05). Overall, corneal keratocytes treated with AME and WJ‐MSC‐Exo (3 × 10⁵ Exo/mL + 50 μg/mL) mixture resulted in enhanced proliferation and wound healing tendency. Utilization of combined use of AME and WJ‐MSC‐Exo can pave the way for a promising foundation for corneal repair research.

Herein, polydimethylsiloxane (PDMS) surfaces are coated with hydroxyapatite (HA) using immobilization and biomineralization techniques with the aid of small molecules, namely, l‐aspartic acid (AA), l‐glutamic acid, and citric acid, in an effort to develop biointeractive surfaces for bone tissue‐related research. The efficacy of biomineralization and immobilization techniques and the impact of small molecules on HA deposition on PDMS surfaces are investigated by chemical and morphological analysis of surfaces, besides in vitro cell culture studies. Characteristic peaks of phosphate groups at wavelengths of 569 and 603 cm⁻¹ in Fourier transform infrared spectroscopy analysis and HA's characteristic patterns identified at 26.1°, 31.7°, and 45.5° in X‐ray diffraction analysis demonstrate the successful deposition of HA particles on PDMS surfaces which are also observed on scanning electron microscopy micrographs. The interaction of human fetal osteoblast cells (hFOB 1.19) with HA‐deposited PDMS surfaces is evaluated with in vitro cell culture studies, which reveals increased cell metabolic activity and growth across all groups as compared to plain PDMS, with HA deposited on AA‐PDMS surfaces through biomineralization being the most stimulating group. Overall, small‐molecule effect on deposition of HA on PDMS substrates merits further investigation, particularly on substrates mimicking bone surface chemical and morphological features.

Protein adsorption behavior can play a critical role in defining the outcome of a material by affecting the subsequent in vivo response to it. To date, the effect of surface properties on protein adsorption behavior has been mainly focused on surface chemistry, but research on the effect of nanoscale surface topography remains limited. In this study, the adsorption behavior of human serum albumin, immunoglobulin G, and fibrinogen in terms of the adsorbed amount and conformational changes were investigated on bare and anodized titanium (Ti) samples (40 and 60 V applied voltages). While the surface chemistry, RMS surface roughness, and arithmetic surface roughness of the anodized samples were similar, they had distinctly different nanomorphologies identified by atomic force microscopy and scanning electron microscopy, and the surface statistical parameters, surface skewness Ssk and kurtosis Sku. The Feret pore size distribution was more uniform on the 60 V sample, and surface nanostructures were more symmetrical with higher peaks and deeper pores. On the other hand, the 40 V sample surface presented a nonuniform pore size distribution and asymmetrical surface nanostructures with lower peaks and shallower pores. The amount of surface-adsorbed protein increased on the sample surfaces in the order of Ti < 40 V < 60 V with the predominant factor affecting the amount of surface-adsorbed protein being the increased surface area attained by pore formation. The secondary structure of all adsorbed proteins deviated from that of their native counterparts. While comparing the secondary structure components of proteins on anodized surfaces, it was observed that all three proteins retained more of their secondary structure composition on the surface with more uniform and symmetrical nanofeatures than the surface having asymmetrical nanostructures. Our results suggest that the nanomorphology of the peaks and outer walls of the nanotubes can significantly influence the conformation of adsorbed serum proteins, even for surfaces having similar roughness values.