Surface characteristics of additively manufactured CoCr and Ti6Al4V dental alloys: The effects of carbon and gold thin film coatings, and alkali-heat treatment.

This study investigates the impact of surface modifications on additively manufactured CoCr and Ti6Al4V dental alloys, focusing on surface properties. Thin film carbon (C) and gold (Au) coatings, as well as alkali-heat treatment, were applied to the high- and low-polished specimens. Scanning electron microscopy (SEM) showed that thin film coatings retained the underlying surface topography, while the alkali-heat treatment induced distinct morphological changes. Energy-dispersive x-ray spectroscopy (EDS) analysis revealed that C-coating enriched surfaces with C, and Au-coating introduced detectable amounts of Au. Nevertheless, signs of coating delamination were observed in the high-polished specimens. Alkali-heat treatment led to the formation of a sodium titanate layer on Ti6Al4V surfaces, confirmed by sodium presence and Fourier transform infrared spectroscopy (FTIR) results showing carbonate bands. Surface roughness measurements with atomic force microscopy (AFM) showed that C-coating increased surface roughness in both high- and low-polished alloys. Au-coating slightly increased roughness, except for low-polished Au-coated Ti6Al4V, where a decrease in roughness was observed compared to low-polished bare Ti6Al4V, likely due to surface defects present in the latter resulting from the additive manufacturing process. Alkali-heat treatment led to a pronounced increase in roughness for both alloys, particularly for Ti6Al4V. Both thin film coatings decreased the water contact angles in all specimens in varying magnitudes, indicating an increase in wettability. However, the alkali-heat treatment caused a substantial decrease in contact angles, resulting in a highly hydrophilic state for Ti6Al4V. These findings underscore the substantial impact of surface modifications on additively manufactured dental alloys, potentially influencing their clinical performance. RESEARCH HIGHLIGHTS: Thin film coatings and chemical/heat treatment modify the surface properties of additively manufactured dental alloys. The surfaces of the alloys get rougher and more hydrophilic after alkali-heat treatment. Thin gold coatings exhibit potential adhesion challenges.

Characterization of Collagen from Jellyfish Aurelia aurita and Investigation of Biomaterials Potentials.

Marine collagen sources are potent alternatives due to abundant yield, low pathogen infection risk, high biocompatibility, and any religious and ethical restrictions compared to terrestrial collagen sources. In this research, we aim to investigate the biomaterials potential of the collagen from Aurelia aurita, which is a native jellyfish species in the Marmara Sea. Spectroscopic techniques were used to investigate the structure of jellyfish collagen (JCol) from acid-soluble fraction and compared to Jellagen® from Rhizostoma pulmo. MALDI-TOF showed the main peak of Jellagen® at 276,765.161 Da and jellyfish collagen at 276,761.687 Da. SDS-PAGE indicated α1 and α2 bands at about 122 kDa and 140 kDa, respectively. In FTIR and Raman spectra, the locations of amide bands of both species were almost the same. The pI of JCol was determined as 4.46. The particle size decreased abruptly at 43 oC from 890 to 290 nm. Water, organic and inorganic ratios of collagen were determined at 7.14%, 63.59, and 29.27 respectively. In DSC, the denaturation temperature (Td) of JCol was found at 43.7 oC and found to be higher than that of the collagens from jellyfishes that have been reported so far in the literature. Biocompatibility testing by metabolic assay revealed significantly higher fibroblast proliferation on collagen film than on the Tissue Culture Plate. To conclude, Aurelia aurita collagen would be a suitable source of collagen when biomaterials are needed to have high biocompatibility and unique macromolecular properties such as high denaturation temperatures.

Evaluating Oxygen Tensions Related to Bone Marrow and Matrix for MSC Differentiation in 2D and 3D Biomimetic Lamellar Scaffolds.

The physiological O2 microenvironment of mesenchymal stem cells (MSCs) and osteoblasts and the dimensionality of a substrate are known to be important in regulating cell phenotype and function. By providing the physiologically normoxic environments of bone marrow (5%) and matrix (12%), we assessed their potential to maintain stemness, induce osteogenic differentiation, and enhance the material properties in the micropatterned collagen/silk fibroin scaffolds that were produced in 2D or 3D. Expression of osterix (OSX) and vascular endothelial growth factor A (VEGFA) was significantly enhanced in the 3D scaffold in all oxygen environments. At 21% O2, OSX and VEGFA expressions in the 3D scaffold were respectively 13,200 and 270 times higher than those of the 2D scaffold. Markers for assessing stemness were significantly more pronounced on tissue culture polystyrene and 2D scaffold incubated at 5% O2. At 21% O2, we measured significant increases in ultimate tensile strength (p < 0.0001) and Young's modulus (p = 0.003) of the 3D scaffold compared to the 2D scaffold, whilst 5% O2 hindered the positive effect of cell seeding on tensile strength. In conclusion, we demonstrated that the 3D culture of MSCs in collagen/silk fibroin scaffolds provided biomimetic cues for bone progenitor cells toward differentiation and enhanced the tensile mechanical properties.

Surface modification strategies for hemodialysis catheters to prevent catheter-related infections: A review.

Insertion of a central venous catheter is one of the most common invasive procedures applied in hemodialysis therapy for end-stage renal disease. The most important complication of a central venous catheter is catheter-related infections that increase hospitalization and duration of intensive care unit stay, cost of treatment, mortality, and morbidity rates. Pathogenic microorganisms, such as, bacteria and fungi, enter the body from the catheter insertion site and the surface of the catheter can become colonized. The exopolysaccharide-based biofilms from bacterial colonies on the surface are the main challenge in the treatment of infections. Catheter lock solutions and systemic antibiotic treatment, which are commonly used in the treatment of hemodialysis catheter-related infections, are insufficient to prevent and terminate the infections and eventually the catheter needs to be replaced. The inadequacy of these approaches in termination and prevention of infection revealed the necessity of coating of hemodialysis catheters with bactericidal and/or antiadhesive agents. Silver compounds and nanoparticles, anticoagulants (e.g., heparin), antibiotics (e.g., gentamicin and chlorhexidine) are some of the agents used for this purpose. The effectiveness of few commercial hemodialysis catheters that were coated with antibacterial agents has been tested in clinical trials against catheter-related infections of pathogenic bacteria, such as Staphylococcus aureus and Staphylococcus epidermidis with promising results. Novel biomedical materials and engineering techniques, such as, surface micro/nano patterning and the conjugation of antimicrobial peptides, enzymes, metallic cations, and hydrophilic polymers (e.g., poly [ethylene glycol]) on the surface, has been suggested recently.

Bioprinting Technologies in Tissue Engineering.

Bioprinting technology is a strong tool in producing living functional tissues and organs from cells, biomaterial-based bioinks, and growth factors in computer-controlled platform. The aim of this chapter is to present recent progresses in bioprinting of nerve, skin, cardiac, bone, cartilage, skeletal muscle, and other soft tissues and highlight the challenges in these applications. Various composite bioinks with bioactive ceramic-based scaffolds having patient-specific design and controlled micro-architectures were used at clinical and preclinical applications successfully for regeneration of bone. In nerve tissue engineering, bioprinting of alginate- and gelatin-based gel bioinks by extrusion presented a controllable 3D microstructures and showed satisfactory cytocompatibility and axonal regeneration. Bioprinting of cardiac progenitors in biopolymers resulted in limited success, while the use of bioinks from extracellular matrix induced satisfactory results in cardiac regeneration. Osteochondral scaffold bioprinting is challenging due to the complex hierarchical structure and limited chondral regeneration. Therefore, current approaches focused on osteochondral scaffold with vascular network and mimicking hierarchical structures. The applications of bioprinting in other types of tissues were also studied, and results showed significant potentials in regeneration of tissues such as cornea, liver, and urinary bladder.

Human adipose derived stem cells are superior to human osteoblasts (HOB) in bone tissue engineering on a collagen-fibroin-ELR blend.

The ultrastructure of the bone provides a unique mechanical strength against compressive, torsional and tensional stresses. An elastin-like recombinamer (ELR) with a nucleation sequence for hydroxyapatite was incorporated into films prepared from a collagen - silk fibroin blend carrying microchannel patterns to stimulate anisotropic osteogenesis. SEM and fluorescence microscopy showed the alignment of adipose-derived stem cells (ADSCs) and the human osteoblasts (HOBs) on the ridges and in the grooves of microchannel patterned collagen-fibroin-ELR blend films. The Young's modulus and the ultimate tensile strength (UTS) of untreated films were 0.58 ± 0.13 MPa and 0.18 ± 0.05 MPa, respectively. After 28 days of cell culture, ADSC seeded film had a Young's modulus of 1.21 ± 0.42 MPa and UTS of 0.32 ± 0.15 MPa which were about 3 fold higher than HOB seeded films. The difference in Young's modulus was statistically significant (p: 0.02). ADSCs attached, proliferated and mineralized better than the HOBs. In the light of these results, ADSCs served as a better cell source than HOBs for bone tissue engineering of collagen-fibroin-ELR based constructs used in this study. We have thus shown the enhancement in the tensile mechanical properties of the bone tissue engineered scaffolds by using ADSCs.

Pullulan microcarriers for bone tissue regeneration.

Microcarrier systems offer a convenient way to repair bone defects as injectable cell carriers that can be applied with small incisions owing to their small size and spherical shape. In this study, pullulan (PULL) microspheres were fabricated and characterized as cell carriers for bone tissue engineering applications. PULL was cross-linked by trisodium trimetaphosphate (STMP) to enhance the stability of the microspheres. Improved cytocompatibility was achieved by silk fibroin (SF) coating and biomimetic mineralization on the surface by incubating in simulated body fluid (SBF). X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescent microscopy analysis confirmed biomimetic mineralization and SF coating on microspheres. The degradation analysis revealed that PULL microspheres had a slow degradation rate with 8% degradation in two weeks period indicating that the microspheres would support the formation of new bone tissue. Furthermore, the mechanical tests showed that the microspheres had a high mechanical stability that was significantly enhanced with the biomimetic mineralization. In vitro cell culture studies with SaOs-2 cells showed that cell viability was higher on SF and SBF coated microspheres on 7th day compared to PULL ones under dynamic conditions. Alkaline phosphatase activity was higher for SF coated microspheres in comparison to uncoated microspheres when dynamic culture condition was applied. The results suggest that both organic and inorganic surface modifications can be applied on PULL microspheres to prepare a biocompatible microcarrier system with suitable properties for bone tissue engineering.

Nanoparticles Based on Plasma Proteins for Drug Delivery Applications.

BACKGROUND: Nanoparticulate delivery systems receive a lot of attention in pharmaceutical research and market due to their in vivo stability, ability to protect entrapped drug, and ease of cellular penetration. The hemocompatibility and the clearance half-life are important parameters of the nanodelivery systems that will be administered through intravenous route. Natural components, like blood plasma proteins are ideal sources of biomaterial for such systems with their long in vivo half-lives. METHODS: The aim of this work is to review in vitro, in vivo and clinical findings of nanocarriers based on blood plasma proteins, namely albumin, lipoproteins, fibrin/fibrinogen, transferrin. Plasma protein based nanocarriers loaded with different bioactive molecules (i.e., anti-cancer, antiviral, anti-epileptic drugs, DNA) have been developed using different preparation methods like desolvation, emulsification, nab-technology, complexation methods. RESULTS: Human serum albumin has attracted the most attention in the last decade as nanocarrier due to its biocompatibility, high binding capacity to various drugs, and easy derivatization by covalent methods. Commercial products of albumin nanoparticles have emerged on the market after its recognition. Low and high density lipoproteins have recently been considered as valuable natural material for preparing hemocompatible small (app 20 nm) lipid-protein vesicles. For other proteins of plasma, however, there are a limited number of studies that explored their potential as nanocarrier formulation. Therefore, there is huge research potential for investigating the proteins like globulins, fibrinogen and transferrin as part of nanocarrier core. CONCLUSION: Plasma protein based nanoparticulate delivery systems, especially albumin based ones have opened up and also will continue to open new treatment strategy options for treating cancer, AIDS and other complex life threatening diseases with advances in nanotechnology and science.

Osteogenic differentiation of adipose derived stem cells on high and low aspect ratio micropatterns.

Adipose derived stem cells (ADSCs) were cultured on collagen-silk fibroin films with microchannel and micropillar patterns to investigate the effects of cell morphology changes on osteogenic differentiation. Channel and pillar micropatterned films were prepared from collagen type I and silk fibroin. While higher ADSC proliferation profiles were obtained on micropillar blend film, microchannel blend films, however, caused twice higher aspect ratio and effective orientation of cells. Alkaline phosphatase activity of ADSCs was several times higher on microchannel surface when the measured activities were normalized to cell number. Effective deposition of collagen type I and mineral by the cells were observed for patterned and unpatterned films, and these extracellular matrix components were oriented along the axis of the microchannels. In conclusion, the use of collagen-fibroin blend film with microchannel topography increased the aspect ratio and alignment of cells significantly, and was also effective in the differentiation of ADSCs into osteogenic lineage.

Protein-based materials in load-bearing tissue-engineering applications.

Proteins such as collagen and elastin are robust molecules that constitute nanocomponents in the hierarchically organized ultrastructures of bone and tendon as well as in some of the soft tissues that have load-bearing functions. In the present paper, the macromolecular structure and function of the proteins are reviewed and the potential of mammalian and non-mammalian proteins in the engineering of load-bearing tissue substitutes are discussed. Chimeric proteins have become an important structural biomaterial source and their potential in tissue engineering is highlighted. Processing of proteins challenge investigators and in this review rapid prototyping and microfabrication are proposed as methods for obtaining precisely defined custom-built tissue engineered structures with intrinsic microarchitecture.

Performance of biodegradable microcapsules of poly(butylene succinate), poly(butylene succinate-co-adipate) and poly(butylene terephthalate-co-adipate) as drug encapsulation systems.

Poly(butylene succinate) (PBSu), poly(butylene succinate-co-adipate) (PBSA) and poly(butylene terephthalate-co-adipate) (PBTA) microcapsules were prepared by the double emulsion/solvent evaporation method. The effect of polymer and poly(vinyl alcohol) (PVA) concentration on the microcapsule morphologies, drug encapsulation efficiency (EE) and drug loading (DL) of bovine serum albumin (BSA) and all-trans retinoic acid (atRA) were all investigated. As a result, the sizes of PBSu, PBSA and PBTA microcapsules were increased significantly by varying polymer concentrations from 6 to 9%. atRA was encapsulated into the microcapsules with an high level of approximately 95% EE. The highest EE and DL of BSA were observed at 1% polymer concentration in values of 60 and 37%, respectively. 4% PVA was found as the optimum concentration and resulted in 75% EE and 14% DL of BSA. The BSA release from the capsules of PBSA was the longest, with 10% release in the first day and a steady release of 17% until the end of day 28. The release of atRA from PBSu microcapsules showed a zero-order profile for 2 weeks, keeping a steady release rate during 4 weeks with a 9% cumulative release. Similarly, the PBSA microcapsules showed a prolonged and a steady release of atRA during 6 weeks with 12% release. In the case of PBTA microcapsules, after a burst release of 10% in the first day, showed a parabolic release profile of atRA during 42 days, releasing 36% of atRA.

Solid-phase enzyme modification via affinity chromatography.

In the present study antileukemic enzyme L-asparaginase (ASNase) and catalase (as a model enzyme) were modified in solid-phase with activated polyethylene glycol (PEG(2)) by using ligand-immobilized affinity column systems L-asparagine-Sepharose CL-4B and Procion red-Sepharose CL-4B, respectively. Studies on change of specific activity with modification time showed negligible differences between batches of modified catalase. Modification of ASNase for 1 h resulted in 50.2% recovery of the specific activity and the attachment of 69 molecules of PEG(2) per molecule of ASNase forming 'PEGylated ASNase'. Sequential modification of ASNase by activated PEG and heparin resulted in coupling of about nine molecules of heparin per molecule of PEGylated ASNase. Intravenous (i.v.) administration of PEG(2)-modified ASNase showed prolonged presence in the blood circulation and no adverse effects or symptoms of anaphylaxis were observed in presensitized mice.