Morteza Rasoulianboroujeni

From solvent-free microspheres to bioactive gradient scaffolds

A solvent-free microsphere sintering technique was developed to fabricate scaffolds with pore size gradient for tissue engineering applications. Poly(D,L-Lactide) microspheres were fabricated through an emulsification method where TiO2 nanoparticles were employed both as particulate emulsifier in the preparation procedure and as surface modification agent to improve bioactivity of the scaffolds. A fine-tunable pore size gradient was achieved with a pore volume of 30±2.6%. SEM, EDX, XRD and FTIR analyses all confirmed the formation of bone-like apatite at the 14th day of immersion in Simulated Body Fluid (SBF) implying the ability of our scaffolds to bond to living bone tissue. In vitro examination of the scaffolds showed progressive activity of the osteoblasts on the scaffold with evidence of increase in its mineral content. The bioactive scaffold developed in this study has the potential to be used as a suitable biomaterial for bone tissue engineering and hard tissue regeneration.

Development of a DNA-liposome complex for gene delivery applications

The association structures formed by cationic liposomes and DNA (Deoxyribonucleic acid)-liposome have been effectively utilized as gene carriers in transfection assays. In this research study, cationic liposomes were prepared using a modified lipid film hydration method consisting of a lyophilization step for gene delivery applications. The obtained results demonstrated that the mean particle size had no significant change while the polydispersity (PDI) increased after lyophilization. The mean particle size slightly reduced after lyophilization (520±12nm to 464±25nm) while the PDI increased after lyophilization (0.094±0.017 to 0.220±0.004). In addition. The mean particle size of vesicles increases when DNA is incorporated to the liposomes (673±27nm). According to the Scanning Electron Microscopy (SEM) and transmission electron microscopy (TEM) images, the spherical shape of liposomes confirmed their successful preservation and reconstitution from the powder. It was found that liposomal formulation has enhanced transfection considerably compared to the naked DNA as negative control. Finally, liposomal formulation in this research had a better function than Lipofectamine® 2000 as a commercialized product because the cellular activity (cellular protein) was higher in the prepared lipoplex than Lipofectamine® 2000.

Preparation of natural chitosan from shrimp shell with different deacetylation degree

Abstract The main aim of the present study was to produce natural chitosan with different deacetylation degree from shrimp shells. Three deacetylation degrees of chitosan were obtained through boiling the chitin in NaOH (50% (w/v)) at 110 °C for 4 h. The samples were labelled as NCS1, NCS2 and NCS3 according to the number of times they were treated with alkaline solution. The functional groups of the obtained products and the degree of deacetylation were determined through Fourier transformed infra-red spectroscopy. Scanning electron microscope was employed to characterise the morphology of the produced materials. Cell viability assay was carried out using mesenchymal stem cells cultured on the samples for 7 days. The results showed that the deacetylation degree of chitin, NCS1, NCS2 and NCS3 became 50.1, 73.5, 82.3 and 82.5%, respectively. The natural chitin had carnation-like morphology. NCS1, NCS2 and NCS3 had the raised hills with the smaller and denser Gulbergs, however, there was no significant difference between NCS2 and NCS3 regarding the structure and deacetylation degree. Moreover, the result of the cell culture experiment indicated that the number of cells on the NCS1 was less than that of the NCS2 after 7 days.

Development of chitosan/gelatin/keratin composite containing hydrocortisone sodium succinate as a buccal mucoadhesive patch to treat desquamative gingivitis

Abstract The aim of this research was to develop chitosan/gelatin/keratin composite containing hydrocortisone sodium succinate as a buccal mucoadhesive patch to treat desquamative gingivitis, which was fabricated through an environmental friendly process. Mucoadhesive films increase the advantage of higher efficiency and drug localization in the affected region. In this research, mucoadhesive films, for the release of hydrocortisone sodium succinate, were prepared using different ratios of chitosan, gelatin and keratin. In the first step, chitosan and gelatin proportions were optimized after evaluating the mechanical properties, swelling capacity, water uptake, stability, and biodegradation of the films. Then, keratin was added at different percentages to the optimum composite of chitosan and gelatin together with the drug. The results of surface pH showed that none of the samples were harmful to the buccal cavity. FTIR analysis confirmed the influence of keratin on the structure of the composite. The presence of a higher amount of keratin in the composite films resulted in high mechanical, mucoadhesive properties and stability, low water uptake and biodegradation in phosphate buffer saline (pH = 7.4) containing 104 U/ml lysozyme. The release profile of the films ascertained that keratin is a rate controller in the release of the hydrocortisone sodium succinate. Finally, chitosan/gelatin/keratin composite containing hydrocortisone sodium succinate can be employed in dental applications.

3D-printed membrane for guided tissue regeneration

Three-dimensional (3D) printing is currently being intensely studied for a diverse set of applications, including the development of bioengineered tissues, as well as the production of functional biomedical materials and devices for dental and orthopedic applications. The aim of this study was to develop and characterize a 3D-printed hybrid construct that can be potentially suitable for guided tissue regeneration (GTR). For this purpose, the rheology analyses have been performed on different bioinks and a specific solution comprising 8% gelatin, 2% elastin and 0.5% sodium hyaluronate has been selected as the most suitable composition for printing a structured membrane for GTR application. Each membrane is composed of 6 layers with strand angles from the first layer to the last layer of 45, 135, 0, 90, 0 and 90°. Confirmed by 3D Laser Measuring imaging, the membrane has small pores on one side and large pores on the other to be able to accommodate different cells like osteoblasts, fibroblasts and keratinocytes on different sides. The ultimate cross-linked product is a 150μm thick flexible and bendable membrane with easy surgical handling. Static and dynamic mechanical testing revealed static tensile modules of 1.95±0.55MPa and a dynamic tensile storage modulus of 314±50kPa. Through seeding the membranes with fibroblast and keratinocyte cells, the results of in vitro tests, including histological analysis, tissue viability examinations and DAPI staining, indicated that the membrane has desirable in vitro biocompatibility. The membrane has demonstrated the barrier function of a GTR membrane by thorough separation of the oral epithelial layer from the underlying tissues. In conclusion, we have characterized a biocompatible and bio-resorbable 3D-printed structured gelatin/elastin/sodium hyaluronate membrane with optimal biostability, mechanical strength and surgical handling characteristics in terms of suturability for potential application in GTR procedures.

3D printed TCP-based scaffold incorporating VEGF-loaded PLGA microspheres for craniofacial tissue engineering

OBJECTIVE Vascularization is a critical process during bone regeneration/repair and the lack of tissue vascularization is recognized as a major challenge in applying bone tissue engineering methods for cranial and maxillofacial surgeries. The aim of our study is to fabricate a vascular endothelial growth factor (VEGF)-loaded gelatin/alginate/β-TCP composite scaffold by 3D printing method using a computer-assisted design (CAD) model. METHODS The paste, composed of (VEGF-loaded PLGA)-containing gelatin/alginate/β-TCP in water, was loaded into standard Nordson cartridges and promptly employed for printing the scaffolds. Rheological characterization of various gelatin/alginate/β-TCP formulations led to an optimized paste as a printable bioink at room temperature. RESULTS The in vitro release kinetics of the loaded VEGF revealed that the designed scaffolds fulfill the bioavailability of VEGF required for vascularization in the early stages of tissue regeneration. The results were confirmed by two times increment of proliferation of human umbilical vein endothelial cells (HUVECs) seeded on the scaffolds after 10 days. The compressive modulus of the scaffolds, 98±11MPa, was found to be in the range of cancellous bone suggesting their potential application for craniofacial tissue engineering. Osteoblast culture on the scaffolds showed that the construct supports cell viability, adhesion and proliferation. It was found that the ALP activity increased over 50% using VEGF-loaded scaffolds after 2 weeks of culture. SIGNIFICANCE The 3D printed gelatin/alginate/β-TCP scaffold with slow releasing of VEGF can be considered as a potential candidate for regeneration of craniofacial defects.

Surface modification of dental implants

Abstract Dental implant surface advancement techniques have been developing rapidly to facilitate osseointegration and bone formation on the implant surface and to enhance the predictability of accelerated implant therapy. Surface modifications have been proven effective on capitalizing the features of titanium that make it the material of choice in dental implantology. Some of these features include wettability, surface area, and osteogenic potential. The following chapter is a brief review of commercial methods of surface modification processing and demonstrates the advantages and disadvantages of each, noting potential for improvement when applicable. Prospective studies in surface modification of implants attempt to address problems in conventional implant treatment, from promoting soft-tissue adherence and antimicrobial properties to induction of osteogenic processes. Overall, prospective trends indicate a shift in the focus to increase the success rate in compromised patients, such as those suffering from osteoporosis, as well as improving soft-tissue integration onto the implant surface to reduce the risk of development of periimplant disease. Surface roughness continues to be optimized, with prospects of configuration at a nanoscale.

Nitrogen doped nanoporous graphene: an efficient metal-free electrocatalyst for the oxygen reduction reaction

The oxygen reduction reaction (ORR) is an important half reaction, which occurs at the cathode within a fuel cell and limits their range of applications due to slow electrochemical kinetics. To overcome this issue, electrocatalysts are sought, which need to be an alternative to expensive and unsustainable metallic catalysts. Herein we report the synthesis of nitrogen doped nanoporous graphene (NPG), which is a competitive alternative to currently employed metallic catalysts. The NPG is synthesised through a chemical vapour deposition methodology followed by a chemical functionalization step introducing oxygen functional groups (carbonyl and hydroxyl groups), which is then doped with nitrogen via ortho-phenylenediamine (OPDA). The NPG is physiochemically and electrochemically characterised. The NPG demonstrates outstanding electrocatalytic activity towards the ORR in alkaline media proceeding via a favourable 4-electron pathway and is comparable to commercially available platinum–carbon (20%). We demonstrate that the electrochemical activity of the NPG is tailorable such that through increased nitrogen doping the ORR transforms from a 2-electron process to that of the favourable 4-electron process via increasing the proportion of pyridinic nitrogen while the content of graphitic nitrogen remains almost constant. The NPG exhibits excellent electrochemical performance towards the ORR in alkaline media, long-term stability and appropriate methanol crossover as benchmarked to commercialised Pt/C electrodes; this outstanding electrocatalytic activity is related to the high proportion of defects, high porosity and (pyridinic) doping.

Collagenous matrix supported by a 3D-printed scaffold for osteogenic differentiation of dental pulp cells

OBJECTIVE A systematic characterization of hybrid scaffolds, fabricated based on combinatorial additive manufacturing technique and freeze-drying method, is presented as a new platform for osteoblastic differentiation of dental pulp cells (DPCs). METHODS The scaffolds were consisted of a collagenous matrix embedded in a 3D-printed beta-tricalcium phosphate (β-TCP) as the mineral phase. The developed construct design was intended to achieve mechanical robustness owing to 3D-printed β-TCP scaffold, and biologically active 3D cell culture matrix pertaining to the Collagen extracellular matrix. The β-TCP precursor formulations were investigated for their flow-ability at various temperatures, which optimized for fabrication of 3D printed scaffolds with interconnected porosity. The hybrid constructs were characterized by 3D laser scanning microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and compressive strength testing. RESULTS The in vitro characterization of scaffolds revealed that the hybrid β-TCP/Collagen constructs offer superior DPCs proliferation and alkaline phosphatase (ALP) activity compared to the 3D-printed β-TCP scaffold over three weeks. Moreover, it was found that the incorporation of TCP into the Collagen matrix improves the ALP activity. SIGNIFICANCE The presented results converge to suggest the developed 3D-printed β-TCP/Collagen hybrid constructs as a new platform for osteoblastic differentiation of DPCs for craniomaxillofacial bone regeneration.

Effect of sodium chloride on gene expression of Streptococcus mutans and zeta potential of demineralized dentin

Purpose In this work, the effects of sodium chloride (NaCl) on gene expression of planktonic Streptococcus mutans cells are investigated. Also assessed are the effects of NaCl on zeta potential of sound and demineralized dentin. Methods The relative level of glucosyltransferase B (gtfB), gtfC and gtfD transcription of S. mutans in the presence of NaCl was evaluated by quantitative polymerase chain reaction (qPCR). The osmolality of varying salt (NaCl) concentrations and their influence on the zeta potential of sound and demineralized dentin was investigated as well. Results NaCl significantly reduced the expression of gtfB and C genes in planktonic S. mutans; whereas, gtf D gene expression significantly increased in the presence of NaCl (P < 0.05). NaCl at concentrations of 37.5 mg/ml reduced zeta potential of demineralized dentin, while no significant decrease of zeta potential was found when sound dentin was exposed to this concentration. Conclusion NaCl reduces the expression of some gtfs in S. mutans and increases negative potential charge of demineralized dentin.