Alireza Moshaverinia

Revisiting structure-property relationship of pH-responsive polymers for drug delivery applications.

&NA; pH‐responsive polymers contain ionic functional groups as pendants in their structure. The total number of charged groups on polymer chains determines the overall response of the system to changes in the external pH. This article reviews various pH‐responsive polymers classified as polyacids (e.g., carboxylic acid based polymers, sulfonamides, anionic polysaccharides, and anionic polypeptides) and polybases (e.g., polyamines, pyridine and imidazole containing polymers, cationic polysaccharides, and cationic polypeptides). We correlate the pH variations in the body at the organ level (e.g., gastrointestinal tract and vaginal environment), tissue level (e.g., cancerous and inflamed tissues), and cellular level (e.g., sub‐cellular organelles), with the intrinsic properties of pH‐responsive polymers. This knowledge could help to select more effective (‘smart’) polymeric systems based on the biological target. Considering the pH differences in the body, various drug delivery systems can be designed by utilizing smart biopolymeric compounds with the required pH‐sensitivity. We also review the pharmaceutical application of pH‐responsive polymeric carriers including hydrogels, polymer‐drug conjugates, micelles, dendrimers, and polymersomes. Graphical abstract Figure. No caption available.

Nanostructured Fibrous Membranes with Rose Spike-Like Architecture

Nanoparticles have been used for engineering composite materials to improve the intrinsic properties and/or add functionalities to pristine polymers. The majority of the studies have focused on the incorporation of spherical nanoparticles within the composite fibers. Herein, we incorporate anisotropic branched-shaped zinc oxide (ZnO) nanoparticles into fibrous scaffolds fabricated by electrospinning. The addition of the branched particles resulted in their protrusion from fibers, mimicking the architecture of a rose stem. We demonstrated that the encapsulation of different-shape particles significantly influences the physicochemical and biological activities of the resultant composite scaffolds. In particular, the branched nanoparticles induced heterogeneous crystallization of the polymeric matrix and enhance the ultimate mechanical strain and strength. Moreover, the three-dimensional (3D) nature of the branched ZnO nanoparticles enhanced adhesion properties of the composite scaffolds to the tissues. In addition, the rose stem-like constructs offered excellent antibacterial activity, while supporting the growth of eukaryote cells.

Muscle Tissue Engineering Using Gingival Mesenchymal Stem Cells Encapsulated in Alginate Hydrogels Containing Multiple Growth Factors

Repair and regeneration of muscle tissue following traumatic injuries or muscle diseases often presents a challenging clinical situation. If a significant amount of tissue is lost the native regenerative potential of skeletal muscle will not be able to grow to fill the defect site completely. Dental-derived mesenchymal stem cells (MSCs) in combination with appropriate scaffold material, present an advantageous alternative therapeutic option for muscle tissue engineering in comparison to current treatment modalities available. To date, there has been no report on application of gingival mesenchymal stem cells (GMSCs) in three-dimensional scaffolds for muscle tissue engineering. The objectives of the current study were to develop an injectable 3D RGD-coupled alginate scaffold with multiple growth factor delivery capacity for encapsulating GMSCs, and to evaluate the capacity of encapsulated GMSCs to differentiate into myogenic tissue in vitro and in vivo where encapsulated GMSCs were transplanted subcutaneously into immunocompromised mice. The results demonstrate that after 4xa0weeks of differentiation in vitro, GMSCs as well as the positive control human bone marrow mesenchymal stem cells (hBMMSCs) exhibited muscle cell-like morphology with high levels of mRNA expression for gene markers related to muscle regeneration (MyoD, Myf5, and MyoG) via qPCR measurement. Our quantitative PCR analyzes revealed that the stiffness of the RGD-coupled alginate regulates the myogenic differentiation of encapsulated GMSCs. Histological and immunohistochemical/fluorescence staining for protein markers specific for myogenic tissue confirmed muscle regeneration in subcutaneous transplantation in our in vivo animal model. GMSCs showed significantly greater capacity for myogenic regeneration in comparison to hBMMSCs (pxa0<xa00.05). Altogether, our findings confirmed that GMSCs encapsulated in RGD-modified alginate hydrogel with multiple growth factor delivery capacity is a promising candidate for muscle tissue engineering.

Hydrogel elasticity and microarchitecture regulate dental-derived mesenchymal stem cell-host immune system cross-talk

The host immune system (T-lymphocytes and their pro-inflammatory cytokines) has been shown to compromise bone regeneration ability of mesenchymal stem cells (MSCs). We have recently shown that hydrogel, used as an encapsulating biomaterial affects the cross-talk among host immune cells and MSCs. However, the role of hydrogel elasticity and porosity in regulation of cross-talk between dental-derived MSCs and immune cells is unclear. In this study, we demonstrate that the modulus of elasticity and porosity of the scaffold influence T-lymphocyte-dental MSC interplay by regulating the penetration of inflammatory T cells and their cytokines. Moreover, we demonstrated that alginate hydrogels with different elasticity and microporous structure can regulate the viability and determine the fate of the encapsulated MSCs through modulation of NF-kB pathway. Our in vivo data show that alginate hydrogels with smaller pores and higher elasticity could prevent pro-inflammatory cytokine-induced MSC apoptosis by down-regulating the Caspase-3- and 8- associated proapoptotic cascades, leading to higher amounts of ectopic bone regeneration. Additionally, dental-derived MSCs encapsulated in hydrogel with higher elasticity exhibited lower expression levels of NF-kB p65 and Cox-2 in vivo. Taken together, our findings demonstrate that the mechanical characteristics and microarchitecture of the microenvironment encapsulating MSCs, in addition to presence of T-lymphocytes and their pro-inflammatory cytokines, affect the fate of encapsulated dental-derived MSCs.nnnSTATEMENT OF SIGNIFICANCEnIn this study, we demonstrate that alginate hydrogel regulates the viability and the fate of the encapsulated dental-derived MSCs through modulation of NF-kB pathway. Alginate hydrogels with smaller pores and higher elasticity prevent pro-inflammatory cytokine-induced MSC apoptosis by down-regulating the Caspase-3- and 8- associated proapoptotic cascade, leading to higher amounts of ectopic bone regeneration. MSCs encapsulated in hydrogel with higher elasticity exhibited lower expression levels of NF-kB p65 and Cox-2 in vivo. These findings confirm that the fate of encapsulated MSCs are affected by the stiffness and microarchitecture of the encapsulating hydrogel biomaterial, as well as presence of T-lymphocytes/pro-inflammatory cytokines providing evidence concerning material science, stem cell biology, the molecular mechanism of dental-derived MSC-associated therapies, and the potential clinical therapeutic impact of MSCs.

Alginate/hyaluronic acid hydrogel delivery system characteristics regulate the differentiation of periodontal ligament stem cells toward chondrogenic lineage

Cartilage tissue regeneration often presents a challenging clinical situation. Recently, it has been shown that Periodontal Ligament Stem Cells (PDLSCs) possess high chondrogenic differentiation capacity. In this study, we developed a stem cell delivery system based on alginate/hyaluronic acid (HA) loaded with TGF-β1 ligand, encapsulating PDLSCs; and investigated the chondrogenic differentiation of encapsulated cells in alginate/HA hydrogel microspheres in vitro and in vivo. The results showed that PDLSCs, as well as human bone marrow mesenchymal stem cells (hBMMSCs), as the positive control, were stained positive for both toluidine blue and alcian blue staining, while exhibiting high levels of gene expression related to chondrogenesis (Col II, Aggrecan and Sox-9), as assessed via qPCR. The quantitative PCR analyses exhibited that the chondrogenic differentiation of encapsulated MSCs can be regulated by the modulus of elasticity of hydrogel delivery system, confirming the vital role of the microenvironment, and the presence of inductive signals for viability and differentiation of MSCs. In vivo, histological and immunofluorescence staining for chondrogenic specific protein markers confirmed ectopic cartilage-like tissue regeneration inside transplanted hydrogels. PDLSCs presented significantly greater capability for chondrogenic differentiation than hBMMSCs (Pu2009<u20090.05). Altogether, our findings confirmed that alginate/HA hydrogels encapsulating PDLSCs are a promising candidate for cartilage regeneration.Graphical abstract

Human Periodontal Ligament- and Gingiva-derived Mesenchymal Stem Cells Promote Nerve Regeneration When Encapsulated in Alginate/Hyaluronic Acid 3D Scaffold

Repair or regeneration of damaged nerves is still a challenging clinical task in reconstructive surgeries and regenerative medicine. Here, it is demonstrated that periodontal ligament stem cells (PDLSCs) and gingival mesenchymal stem cells (GMSCs) isolated from adult human periodontal and gingival tissues assume neuronal phenotype in vitro and in vivo via a subcutaneous transplantation model in nude mice. PDLSCs and GMSCs are encapsulated in a 3D scaffold based on alginate and hyaluronic acid hydrogels capable of sustained release of human nerve growth factor (NGF). The elasticity of the hydrogels affects the proliferation and differentiation of encapsulated MSCs within scaffolds. Moreover, it is observed that PDLSCs and GMSCs are stained positive for βIII-tubulin, while exhibiting high levels of gene expression related to neurogenic differentiation (βIII-tubulin and glial fibrillary acidic protein) via quantitative polymerase chain reaction (qPCR). Western blot analysis shows the importance of elasticity of the matrix and the presence of NGF in the neurogenic differentiation of encapsulated MSCs. In vivo, immunofluorescence staining for neurogenic specific protein markers confirms islands of dense positively stained structures inside transplanted hydrogels. As far as it is known, this study is the first demonstration of the application of PDLSCs and GMSCs as promising cell therapy candidates for nerve regeneration.

Effect of different thermo–light polymerization on flexural strength of two glass ionomer cements and a glass carbomer cement

Statement of problem. Whether polymerization lights can be used for heating glass ionomer cements (GICs) or glass carbomer (GCP) to improve their mechanical properties is not well established. Purpose. The purpose of this in vitro study was to assess the effect of thermo–light polymerization on the flexural strength (FS) of 2 GICs (Fuji IX GP Fast, Ketac Molar) and a GCP. Material and methods. Specimens (n=10) were prepared in stainless steel molds (2×2×25 mm), compressed, exposed to 3 polymerization lights (500, 1000, 1200 mW/cm2) for 2 cycles of 40 seconds on each side, and stored in petroleum jelly (37°C, 24 hours). Results. Significant FS differences were detected among groups after different thermo–light polymerization regimens (F=50.926, df=11, P<.001). GCP showed the highest mean FS (˜5 times, P<.001) after thermo–light polymerization with power outputs of 1000 (127.1 ±25.8 MPa) and 1200 mW/cm2 (117.4 ±18.5 MPa), with no significance difference between them (P=.98), compared with 500 mW/cm2 (24.1 ±1.7 MPa). For Ketac Molar, compared with autopolymerization setting (15.5 ±3.1 MPa), a significant increase in mean FS (˜2.5 times) was only observed in specimens treated with 1200 mW/cm2 polymerization light (P=.03). For Fuji IX GP Fast, only the light with 1000 mW/cm2 output significantly increased the FS (98.9 ±23.4 MPa, P<.001) compared with the autopolymerization setting (34.9 ±6.4 MPa). Conclusions. Thermo–light polymerization accelerated the development of FS in the tested GICs, potentially protecting against saliva contamination during the first 3 to 4 minutes after mixing GIC. Thermo–light polymerization of the glass carbomer with power outputs of 1000 and 1200 mW/cm2 also substantially increased FS. The clinical advantages of the findings should be validated by in vivo studies.

Comparison of dimensional accuracy of conventionally and digitally manufactured intracoronal restorations

Statement of problem. Advances have been made in digital dentistry for the fabrication of dental prostheses, but evidence regarding the efficacy of digital techniques for the fabrication of intracoronal restorations is lacking. Purpose. The purpose of this in vitro study was to compare the dimensional accuracy of intracoronal restorations fabricated with digital and conventional techniques. Material and methods. A sound mandibular molar tooth received a standard onlay preparation, and onlays were fabricated with 1 of 3 fabrication techniques. In group CC, the onlays were made after conventional impression and conventional fabrication of a resin pattern. In group CP, the onlays were made after conventional impression and 3‐dimensional (3D) printing of the pattern. In group IP, the onlays were made after intraoral scanning, and 3D printing produced the resin pattern. Ten specimens in each group (N=30) were evaluated. Glass‐ceramic restorations were fabricated using the press technique. The replica technique was used to assess the marginal fit. Each replica was assessed at 8 points. One‐way ANOVA was used to compare the marginal discrepancy among the 3 groups. The Tukey honest significant differences test was applied for pairwise comparisons of the groups (&agr;=.05). Results. No significant differences were noted in the marginal discrepancy at the gingival margin among the 3 groups (P=.342), but significant differences were noted among the 3 groups in the pulpal (P=.025) and lingual (P=.031) areas. Comparison of the absolute discrepancy among the 3 groups revealed that only groups CC and CP were significantly different (P=.020) from each other. Conclusions. Within the limitations of this in vitro study, the conventional method yielded more accuracy than the 3D printing method, and no differences were found between the methods which used the 3D printer (groups CP and IP).

Regulation of the fate of dental‐derived mesenchymal stem cells using engineered alginate‐GelMA hydrogels

Mesenchymal stem cells (MSCs) derived from dental and orofacial tissues provide an alternative therapeutic option for craniofacial bone tissue regeneration. However, there is still a need to improve stem cell delivery vehicles to regulate the fate of the encapsulated MSCs for high quality tissue regeneration. Matrix elasticity plays a vital role in MSC fate determination. Here, we have prepared various hydrogel formulations based on alginate and gelatin methacryloyl (GelMA) and have encapsulated gingival mesenchymal stem cells (GMSCs) and human bone marrow MSCs (hBMMSCs) within these fabricated hydrogels. We demonstrate that addition of the GelMA to alginate hydrogel reduces the elasticity of the hydrogel mixture. While presence of GelMA in an alginate-based scaffold significantly increased the viability of encapsulated MSCs, increasing the concentration of GelMA downregulated the osteogenic differentiation of encapsulated MSCs in vitro due to decrease in the stiffness of the hydrogel matrix. The osteogenic suppression was rescued by addition of a potent osteogenic growth factor such as rh-BMP-2. In contrast, MSCs encapsulated in alginate hydrogel without GelMA were successfully osteo-differentiated without the aid of additional growth factors, as confirmed by expression of osteogenic markers (Runx2 and OCN), as well as positive staining using Xylenol orange. Interestingly, after two weeks of osteo-differentiation, hBMMSCs and GMSCs encapsulated in alginate/GelMA hydrogels still expressed CD146, an MSC surface marker, while MSCs encapsulated in alginate hydrogel failed to express any positive staining. Altogether, our findings suggest that it is possible to control the fate of encapsulated MSCs within hydrogels by tuning the mechanical properties of the matrix. We also reconfirmed the important role of the presence of inductive signals in guiding MSC differentiation. These findings may enable the design of new multifunctional scaffolds for spatial and temporal control over the fate and function of stem cells even post-transplantation.

Mechanobiological Mimicry of Helper T Lymphocytes to Evaluate Cell–Biomaterials Crosstalk

The unique properties of immune cells have inspired many efforts in engineering advanced biomaterials capable of mimicking their behaviors. However, an inclusive model capable of mimicking immune cells in different situations remains lacking. Such models can provide invaluable data for understanding immune-biomaterial crosstalk. Inspired by CD4+ T cells, polymeric microparticles with physicochemical properties similar to naïve and active T cells are engineered. A lipid coating is applied to enhance their resemblance and provide a platform for conjugation of desired antibodies. A novel dual gelation approach is used to tune the elastic modulus and flexibility of particles, which also leads to elongated circulation times. Furthermore, the model is enriched with magnetic particles so that magnetotaxis resembles the chemotaxis of cells. Also, interleukin-2, a proliferation booster, and interferon-γ cytokines are loaded into the particles to manipulate the fates of killer T cells and mesenchymal stem cells, respectively. The penetration of these particles into 3D environments is studied to provide in vitro models of immune-biomaterials crosstalk. This biomimicry model enables optimization of design parameters required for engineering more efficient drug carriers and serves as a potent replica for understanding the mechanical behavior of immune cells.