Synthesis and characterization of osteoinductive visible light-activated adhesive composites with antimicrobial properties.

Orthopedic surgical procedures based on the use of conventional biological graft tissues are often associated with serious post-operative complications such as immune rejection, bacterial infection, and poor osseointegration. Bioresorbable bone graft substitutes have emerged as attractive alternatives to conventional strategies because they can mimic the composition and mechanical properties of the native bone. Among these, bioactive glasses (BGs) hold great potential to be used as biomaterials for bone tissue engineering owing to their biomimetic composition and high biocompatibility and osteoinductivity. Here, we report the development of a novel composite biomaterial for bone tissue engineering based on the incorporation of a modified strontium- and lithium-doped 58S BG (i.e., BG-5/5) into gelatin methacryloyl (GelMA) hydrogels. We characterized the physicochemical properties of the BG formulation via different analytical techniques. Composite hydrogels were then prepared by directly adding BG-5/5 to the GelMA hydrogel precursor, followed by photocrosslinking of the polymeric network via visible light. We characterized the physical, mechanical, and adhesive properties of GelMA/BG-5/5 composites, as well as their in vitro cytocompatibility and osteoinductivity. In addition, we evaluated the antimicrobial properties of these composites in vitro, using a strain of methicillin-resistant Staphylococcus Aureus. GelMA/BG-5/5 composites combined the functional characteristics of the inorganic BG component, with the biocompatibility, biodegradability, and biomimetic composition of the hydrogel network. This novel biomaterial could be used for developing osteoinductive scaffolds or implant surface coatings with intrinsic antimicrobial properties and higher therapeutic efficacy

Interpenetrating network gelatin methacryloyl (GelMA) and pectin-g-PCL hydrogels with tunable properties for tissue engineering.

The design of new hydrogel-based biomaterials with tunable physical and biological properties is essential for the advancement of applications related to tissue engineering and regenerative medicine. For instance, interpenetrating polymer network (IPN) and semi-IPN hydrogels have been widely explored to engineer functional tissues due to their characteristic microstructural and mechanical properties. Here, we engineered IPN and semi-IPN hydrogels comprised of a tough pectin grafted polycaprolactone (pectin-g-PCL) component to provide mechanical stability, and a highly cytocompatible gelatin methacryloyl (GelMA) component to support cellular growth and proliferation. IPN hydrogels were formed by calcium ion (Ca2+)-crosslinking of pectin-g-PCL chains, followed by photocrosslinking of the GelMA precursor. Conversely, semi-IPN networks were formed by photocrosslinking of the pectin-g-PCL and GelMA mixture, in the absence of Ca2+ crosslinking. IPN and semi-IPN hydrogels synthesized with varying ratios of pectin-g-PCL to GelMA, with and without Ca2+-crosslinking, exhibited a broad range of mechanical properties. For semi-IPN hydrogels, the aggregation of microcrystalline cores led to formation of hydrogels with compressive moduli ranging from 3.1 to 10.4 kPa. For IPN hydrogels, the mechanistic optimization of pectin-g-PCL, GelMA, and Ca2+ concentrations resulted in hydrogels with comparatively higher compressive modulus, in the range of 39 kPa-5029 kPa. Our results also showed that IPN hydrogels were cytocompatible in vitro and could support the growth of three-dimensionally (3D) encapsulated MC3T3-E1 preosteoblasts in vitro. The simplicity, technical feasibility, low cost, tunable mechanical properties, and cytocompatibility of the engineered semi-IPN and IPN hydrogels highlight their potential for different tissue engineering and biomedical applications

Local Immunomodulation Using an Adhesive Hydrogel Loaded with miRNA-Laden Nanoparticles Promotes Wound Healing.

Chronic wounds are characterized by impaired healing and uncontrolled inflammation, which compromise the protective role of the immune system and may lead to bacterial infection. Upregulation of miR-223 microRNAs (miRNAs) shows driving of the polarization of macrophages toward the anti-inflammatory (M2) phenotype, which could aid in the acceleration of wound healing. However, local-targeted delivery of microRNAs is still challenging, due to their low stability. Here, adhesive hydrogels containing miR-223 5p mimic (miR-223*) loaded hyaluronic acid nanoparticles are developed to control tissue macrophages polarization during wound healing processes. In vitro upregulation of miR-223* in J774A.1 macrophages demonstrates increased expression of the anti-inflammatory gene Arg-1 and a decrease in proinflammatory markers, including TNF-α, IL-1β, and IL-6. The therapeutic potential of miR-223* loaded adhesive hydrogels is also evaluated in vivo. The adhesive hydrogels could adhere to and cover the wounds during the healing process in an acute excisional wound model. Histological evaluation and quantitative polymerase chain reaction (qPCR) analysis show that local delivery of miR-223* efficiently promotes the formation of uniform vascularized skin at the wound site, which is mainly due to the polarization of macrophages to the M2 phenotype. Overall, this study demonstrates the potential of nanoparticle-laden hydrogels conveying miRNA-223* to accelerate wound healing

Bioprinting of a Cell-Laden Conductive Hydrogel Composite.

Bioprinting has gained significant attention for creating biomimetic tissue constructs with potential to be used in biomedical applications such as drug screening or regenerative medicine. Ideally, biomaterials used for three-dimensional (3D) bioprinting should match the mechanical, hydrostatic, bioelectric, and physicochemical properties of the native tissues. However, many materials with these tissue-like properties are not compatible with printing techniques without modifying their compositions. In addition, integration of cell-laden biomaterials with bioprinting methodologies that preserve their physicochemical properties remains a challenge. In this work, a biocompatible conductive hydrogel composed of gelatin methacryloyl (GelMA) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) was synthesized and bioprinted to form complex, 3D cell-laden structures. The biofabricated conductive hydrogels were formed by an initial cross-linking step of the PEDOT:PSS with bivalent calcium ions and a secondary photopolymerization step with visible light to cross-link the GelMA component. These modifications enabled tuning the mechanical properties of the hydrogels, with Young's moduli ranging from ∼40-150 kPa, as well as tunable conductivity by varying the concentration of PEDOT:PSS. In addition, the hydrogels degraded in vivo with no substantial inflammatory responses as demonstrated by haematoxylin and eosin (H&E) and immunofluorescent staining of subcutaneously implanted samples in Wistar rats. The parameters for forming a slurry of microgel particles to support 3D bioprinting of the engineered cell-laden hydrogel were optimized to form constructs with improved resolution. High cytocompatibility and cell spreading were demonstrated in both wet-spinning and 3D bioprinting of cell-laden hydrogels with the new conductive hydrogel-based bioink and printing methodology. The synergy of an advanced fabrication method and conductive hydrogel presented here is promising for engineering complex conductive and cell-laden structures

An Antimicrobial Dental Light Curable Bioadhesive Hydrogel for Treatment of Peri-Implant Diseases.

Dental implants constitute the standard of care to replace the missing teeth, which has led to an increase in the number of patients affected by peri-implant diseases (PIDs). Here, we report the development of an antimicrobial bioadhesive, GelAMP, for the treatment of PIDs. The hydrogel is based on a visible light-activated naturally-derived polymer (gelatin) and an antimicrobial peptide (AMP). The optimized formulation of GelAMP could be rapidly crosslinked using commercial dental curing systems. When compared to commercial adhesives, the bioadhesives exhibited significantly higher adhesive strength to physiological tissues and titanium. Moreover, the bioadhesive showed high cytocompatibility and could efficiently promote cell proliferation and migration in vitro. GelAMP also showed remarkable antimicrobial activity against Porphyromonas gingivalis. Furthermore, it could support the growth of autologous bone after sealing calvarial bone defects in mice. Overall, GelAMP could be used as a platform for the development of more effective therapeutics against PIDs

Structural Biology: Modeling applications and techniques at a glance

As recent advancements in biology shows, the molecular machines specially proteins, RNA and complex molecules play the main role of the so called cell functionality. It means a very big part of the system biology is concerned with the interactions of such molecular components. Drug industries and research institutes are trying hard to better understand the concepts underlying these interactions and are highly dependent on the issues regarding these molecular elements. However the costs for such projects are so high and in many cases these projects will be funded by governments or profit making companies. With this in mind it has to be said that the techniques like stimulation are always a very good candidate to decrease such costs and to provide scientists with a bright future of the project results before undergoing costly experiments. However the costs involved projects that determine an approximation for the problem is not that much high but they are also costly. So it is of utmost importance to invent special techniques for the concept of stimulation that can also decrease the project costs and also predict much accurately. Since the system biology and proteomics as the study of the proteins and their functions are in the center of consideration for the purpose of drug discovery, understanding the cell functionalities and the underlying causes behind diseases; so we need advance software and algorithms that can predict the structure of the molecular components and to provide researchers with the computational tools to analyze such models. In this paper we make review of the importance of molecular modeling, its limitations and applications

Gelatin Methacryloyl Bioadhesive Improves Survival and Reduces Scar Burden in a Mouse Model of Myocardial Infarction.

Background Delivery of hydrogels to the heart is a promising strategy for mitigating the detrimental impact of myocardial infarction (MI). Challenges associated with the in vivo delivery of currently available hydrogels have limited clinical translation of this technology. Gelatin methacryloyl (GelMA) bioadhesive hydrogel could address many of the limitations of available hydrogels. The goal of this proof-of-concept study was to evaluate the cardioprotective potential of GelMA in a mouse model of MI. Methods and Results The physical properties of GelMA bioadhesive hydrogel were optimized in vitro. Impact of GelMA bioadhesive hydrogel on post-MI recovery was then assessed in vivo. In 20 mice, GelMA bioadhesive hydrogel was applied to the epicardial surface of the heart at the time of experimental MI. An additional 20 mice underwent MI but received no GelMA bioadhesive hydrogel. Survival rates were compared for GelMA-treated and untreated mice. Left ventricular function was assessed 3 weeks after experimental MI with transthoracic echocardiography. Left ventricular scar burden was measured with postmortem morphometric analysis. Survival rates at 3 weeks post-MI were 89% for GelMA-treated mice and 50% for untreated mice (P=0.011). Left ventricular contractile function was better in GelMA-treated than untreated mice (fractional shortening 37% versus 26%, P<0.001). Average scar burden in GelMA-treated mice was lower than in untreated mice (6% versus 22%, P=0.017). Conclusions Epicardial GelMA bioadhesive application at the time of experimental MI was performed safely and was associated with significantly improved post-MI survival compared with control animals. In addition, GelMA treatment was associated with significantly better preservation of left ventricular function and reduced scar burden

HYDROGEL-BASED BIOADHESIVES FOR TISSUE ENGINEERING AND SURGICAL APPLICATIONS

Sutures, wires, and staples constitute the conventional standard of care for reconnecting tissues after surgical procedures to restore their structure and function. These methods generally have several limitations. For example, they are time-consuming and may cause further tissue damage and lead to infection. In addition, they may not provide immediate and adequate sealing to stop body fluid and air leakages. Using adhesive biomaterials is a suitable alternative for wound closure due to their characteristics, such as simple and painless application, and short implementation time. In this regard, various types of surgical materials have been used for sealing, reconnecting tissues, or attaching devices to the tissues. Based on the final application and the anatomical parts involved in the medical intervention, it is important to design these tissue adhesives with some specific characteristics such as: i) high biocompatibility, ii) easy and rapid application, iii) strong adhesion to the target tissue, iv) biomimetic mechanical properties, v) permeability to nutrients and gases, vi) supporting tissue regeneration, and vii) antimicrobial properties in the case of infected wounds. However, commercially available surgical adhesives have many drawbacks and generally only possess one of the properties mentioned above. In this project, we aimed to combine different types of highly biocompatible biopolymers (e.g. gelatin, elastin like polypeptides, and hyaluronic acid) with different nanomaterials to engineer novel bioadhesives with the combined properties mentioned above. These biopolymers were first chemically modified to form photocrosslinakble hydrogels through a short exposure to visible light in the presence of a highly biocompatible photoinitiator (Eosin Y). The engineered adhesives exhibited tunable physical properties and could be tailored for a variety of surgical and tissue engineering applications. As the first step of the project, a flexible and transparent gelatin-based adhesive was designed for corneal tissue sealing and repair. The mechanical properties of the engineered hydrogel adhesive were optimized to mimic the stiffness of the native cornea. In addition, the formulation of the adhesive was modified to obtain high adhesion to the cornea, while retaining appropriate biodegradability and high cytocompatibility in vitro. Our data showed that the engineered hydrogel adhesives had higher adhesive strength than commercially available adhesives used for cornea such as ReSure� (Ocular Therapeutix, Inc., USA), based on standard adhesion tests by the American Society for Testing and Materials (ASTM). In addition, ex vivo tests on explanted rabbit eyes demonstrated that the adhesives possessed high retention and were resistant to burst pressure. Furthermore, in vivo tests were conducted using a rabbit stromal cornea defect model to test the biocompatibility and retention of the biomaterial, as well as corneal regeneration after the application. In the second part of this proposal, we modified our engineered hydrogels to fabricate multifunctional adhesives through incorporation of different drugs and nanomaterials. In particular, we engineered antimicrobial adhesives by incorporating ZnO nanoparticles (NPs) or antimicrobial peptides (Tet213) to the structure of the biopolymer prior to photopolymerization. In addition, we showed that the incorporation of laponite (disc shaped silicate NPs) could lead to the formation of osteoinductive adhesives that can be used for a wide range of applications, such as bone and dental tissue engineering. These multifunctional adhesive hydrogels exhibited high biocompatibility, mechanical stability and tissue integration in different animal models such as subcutaneous implantation in rats, and a mouse calvarial defect model. Our engineered multifunctional adhesives with tunable physical and adhesive properties can be used as a platform for sealing and repair of various tissues such as bone, lung, skin, and arteries

HYDROGEL-BASED BIOADHESIVES FOR TISSUE ENGINEERING AND SURGICAL APPLICATIONS

Sutures, wires, and staples constitute the conventional standard of care for reconnecting tissues after surgical procedures to restore their structure and function. These methods generally have several limitations. For example, they are time-consuming and may cause further tissue damage and lead to infection. In addition, they may not provide immediate and adequate sealing to stop body fluid and air leakages. Using adhesive biomaterials is a suitable alternative for wound closure due to their characteristics, such as simple and painless application, and short implementation time. In this regard, various types of surgical materials have been used for sealing, reconnecting tissues, or attaching devices to the tissues. Based on the final application and the anatomical parts involved in the medical intervention, it is important to design these tissue adhesives with some specific characteristics such as: i) high biocompatibility, ii) easy and rapid application, iii) strong adhesion to the target tissue, iv) biomimetic mechanical properties, v) permeability to nutrients and gases, vi) supporting tissue regeneration, and vii) antimicrobial properties in the case of infected wounds. However, commercially available surgical adhesives have many drawbacks and generally only possess one of the properties mentioned above. In this project, we aimed to combine different types of highly biocompatible biopolymers (e.g. gelatin, elastin like polypeptides, and hyaluronic acid) with different nanomaterials to engineer novel bioadhesives with the combined properties mentioned above. These biopolymers were first chemically modified to form photocrosslinakble hydrogels through a short exposure to visible light in the presence of a highly biocompatible photoinitiator (Eosin Y). The engineered adhesives exhibited tunable physical properties and could be tailored for a variety of surgical and tissue engineering applications. As the first step of the project, a flexible and transparent gelatin-based adhesive was designed for corneal tissue sealing and repair. The mechanical properties of the engineered hydrogel adhesive were optimized to mimic the stiffness of the native cornea. In addition, the formulation of the adhesive was modified to obtain high adhesion to the cornea, while retaining appropriate biodegradability and high cytocompatibility in vitro. Our data showed that the engineered hydrogel adhesives had higher adhesive strength than commercially available adhesives used for cornea such as ReSure� (Ocular Therapeutix, Inc., USA), based on standard adhesion tests by the American Society for Testing and Materials (ASTM). In addition, ex vivo tests on explanted rabbit eyes demonstrated that the adhesives possessed high retention and were resistant to burst pressure. Furthermore, in vivo tests were conducted using a rabbit stromal cornea defect model to test the biocompatibility and retention of the biomaterial, as well as corneal regeneration after the application. In the second part of this proposal, we modified our engineered hydrogels to fabricate multifunctional adhesives through incorporation of different drugs and nanomaterials. In particular, we engineered antimicrobial adhesives by incorporating ZnO nanoparticles (NPs) or antimicrobial peptides (Tet213) to the structure of the biopolymer prior to photopolymerization. In addition, we showed that the incorporation of laponite (disc shaped silicate NPs) could lead to the formation of osteoinductive adhesives that can be used for a wide range of applications, such as bone and dental tissue engineering. These multifunctional adhesive hydrogels exhibited high biocompatibility, mechanical stability and tissue integration in different animal models such as subcutaneous implantation in rats, and a mouse calvarial defect model. Our engineered multifunctional adhesives with tunable physical and adhesive properties can be used as a platform for sealing and repair of various tissues such as bone, lung, skin, and arteries