Nano-hydroxyapatite/polyacrylamide composite hydrogels with high mechanical strengths and cell adhesion properties

Exosome-loaded hydrogels for craniofacial bone tissue regeneration

It is common for maladies and trauma to cause significant bone deterioration in the craniofacial bone, which can cause patients to experience complications with their appearance and their ability to function. Regarding grafting procedures' complications and disadvantages, the newly emerging field of tissue regeneration has shown promise. Tissue -engineered technologies and their applications in the craniofacial region are increasingly gaining prominence with limited postoperative risk and cost. MSCs-derived exosomes are widely applied in bone tissue engineering to provide cell-free therapies since they not only do not cause immunological rejection in the same way that cells do, but they can also perform a cell-like role. Additionally, the hydrogel system is a family of multipurpose platforms made of cross-linked polymers with considerable water content, outstanding biocompatibility, and tunable physiochemical properties for the efficient delivery of commodities. Therefore, the promising exosome-loaded hydrogels can be designed for craniofacial bone regeneration. This review lists the packaging techniques for exosomes and hydrogel and discusses the development of a biocompatible hydrogel system and its potential for exosome continuous delivery for craniofacial bone healing.

Calcium Orthophosphate (CaPO4) Containing Composites for Biomedical Applications: Formulations, Properties, and Applications

The goal of this review is to present a wide range of hybrid formulations and composites containing calcium orthophosphates (abbreviated as CaPO4) that are suitable for use in biomedical applications and currently on the market. The bioactive, biocompatible, and osteoconductive properties of various CaPO4-based formulations make them valuable in the rapidly developing field of biomedical research, both in vitro and in vivo. Due to the brittleness of CaPO4, it is essential to combine the desired osteologic properties of ceramic CaPO4 with those of other compounds to create novel, multifunctional bone graft biomaterials. Consequently, this analysis offers a thorough overview of the hybrid formulations and CaPO4-based composites that are currently known. To do this, a comprehensive search of the literature on the subject was carried out in all significant databases to extract pertinent papers. There have been many formulations found with different material compositions, production methods, structural and bioactive features, and in vitro and in vivo properties. When these formulations contain additional biofunctional ingredients, such as drugs, proteins, enzymes, or antibacterial agents, they offer improved biomedical applications. Moreover, a lot of these formulations allow cell loading and promote the development of smart formulations based on CaPO4. This evaluation also discusses basic problems and scientific difficulties that call for more investigation and advancements. It also indicates perspectives for the future.

Advancements in gradient bone scaffolds: enhancing bone regeneration in the treatment of various bone disorders

Bone scaffolds are widely employed for treating various bone disorders, including defects, fractures, and accidents. Gradient bone scaffolds present a promising approach by incorporating gradients in shape, porosity, density, and other properties, mimicking the natural human body structure. This design offers several advantages over traditional scaffolds. A key advantage is the enhanced matching of human tissue properties, facilitating cell adhesion and migration. Furthermore, the gradient structure fosters a smooth transition between scaffold and surrounding tissue, minimizing the risk of inflammation or rejection. Mechanical stability is also improved, providing better support for bone regeneration. Additionally, gradient bone scaffolds can integrate drug delivery systems, enabling controlled release of drugs or growth factors to promote specific cellular activities during the healing process. This comprehensive review examines the design aspects of gradient bone scaffolds, encompassing structure and drug delivery capabilities. By optimizing the scaffold's inherent advantages through gradient design, bone regeneration outcomes can be improved. The insights presented in this article contribute to the academic understanding of gradient bone scaffolds and their applications in bone tissue engineering.

Self-assembled chitosan/gelatin nanofibrous aggregates incorporated thermosensitive nanocomposite bioink for bone tissue engineering

Chitosan-based thermosensitive bioink can be a potential option as bioinks for bone tissue engineering because of their excellent biocompatibility and crosslinker-free gelation at physiological temperature. However, their low mechanical strength, poor printability, and low post-printing cell viability are some of their limitations. In this work, self-assembled nanofibrous aggregates of chitosan and gelatin were prepared and incorporated in chitosan-based bioinks to enhance printability, mechanical properties, post-printing cell viability, and proliferation. Subsequently, the optimal concentration of nanohydroxyapatite was determined, and the potential of the nanocomposite bioink was evaluated. Physiochemical, mechanical, and in vitro characterizations were carried out for the developed nanocomposite bioink. The bioink had optimum printability at 10 % nanohydroxyapatite and cell viability >88 %. The composite bioink had a low water uptake capacity (2.5 %) and degraded within 3 weeks in the presence of lysozyme. Mechanical characterization revealed an elastic modulus of about 15.5 kPa. Rheological analysis indicated a higher storage modulus of the bioink samples at 37 °C. ALP activity of 36.8 units/ml after 14 days of scaffold culture in osteogenic media indicated high cellular activity. These results suggested that the incorporation of osteogenic nanohydroxyapatite and nanofibrous aggregates improved the overall osteogenic and physiochemical potential of the thermosensitive bioink.

Synthesis, Characterization, and Investigation of Doxorubicin Drug Release Properties of Poly(acrylamide-co-acrylic Acid/Maleic Acid)-Hydroxyapatite Composite Hydrogel

BACKGROUND

Hydroxyapatite and its derivatives have been used for a lot of applications. One of them is drug release studies. Due to its low adhesion strength and lack of the strength and durability required for load-carrying applications, there is a need to improve the properties of hydroxyapatite. For this aim, the most important factors are increasing pH sensitivity and preventing coagulation. Mixing it with multifunctional polymers is the best solution.

OBJECTIVES

The main objectives are: 1- preparing poly(acrylamide-co-acrylic acid/maleic acid)- hydroxyapatite (PAm-co-PAA/PMA-HApt), 2- assessment of (PAm-co-PAA/PMA-HApt) and dox-loaded poly(acrylamide-co-acrylic acid/maleic acid) (Dox-(PAm-co-PAA/PMA-HApt)) composite hydrogels, and 3- elucidating the difference in behavior of drug release studies between hydroxyapatite (HApt) and poly(acrylamide-co-acrylic acid/maleic acid) composite hydrogels.

METHODS

A composite of PAm-co-PAA/PMA-HApt was prepared by direct polymerization of acrylamide-co-acrylic acid/maleic acid in a suspension of HApt. The drug loading and release features of PAm-co-PAA/PMA-HApt and HApt were then investigated for doxorubicin (dox) release. Using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TG/DTA), this unique composite hydrogel has been physicochemically investigated. Also, a colorimetric assay was used to assess the in vitro biocompatible support and anticancer activity of HApt and the newly developed composite hydrogel XTT (2,3-Bis-(2-Methoxy-4-Nitro-5-Sulfophenyl)-2H-Tetrazolium-5-Carboxanilide) assay.

RESULTS

According to the results of drug release studies of this new material, it is pH sensitive, and PAm-co-PAA/PMA-HApt demonstrated a faster release than HApt at 37°C in the acidic solution of pH 4.5 than in the neutral solution of pH 7.4. The XTT assay outcomes also demonstrated the biocompatibility of PAm-co-PAA/PMA-HApt and HApt and the cytotoxic effect of dox-loaded PAm-co-PAA/PMA-HApt.

CONCLUSION

It should be inferred that the drug release profile was improved at pH 4.5 by the newly produced pH-sensitive composite hydrogel.

Injectable antibacterial Ag-HA/ GelMA hydrogel for bone tissue engineering

Background: Fracture or bone defect caused by accidental trauma or disease is a growing medical problem that threats to human health.Currently, most orthopedic implant materials must be removed via follow-up surgery, which requires a lengthy recovery period and may result in bacterial infection. Building bone tissue engineering scaffolds with hydrogel as a an efficient therapeutic strategy has outstanding bionic efficiency.By combining some bionic inorganic particles and hydrogels to imitate the organic-inorganic characteristics of natural bone extracellular matrix, developing injectable multifunctional hydrogels with bone tissue repair effects and also displaying excellent antibacterial activity possesses attractive advantages in the field of minimally invasive therapy in clinical. Methods: In the present work, a multifunctional injectable hydrogel formed by photocrosslinking was developed by introducing hydroxyapatite (HA) microspheres to Gelatin Methacryloyl (GelMA) hydrogel. Results: The composite hydrogels exhibited good adhesion and bending resistance properties due to the existence of HA. In addition, when the concentration of GelMA is 10% and the concentration of HA microspheres is 3%, HA/GelMA hydrogel system displayed increased microstructure stability, lower swelling rate, increased viscosity, and improved mechanical properties. Furthermore, the Ag-HA/GelMA demonstrated good antibacterial activity against Staphylococcus aureus and Escherichia coli, which could signifificantly lower the risk of bacterial infection following implantation. According to cell experiment, the Ag-HA/GelMA hydrogel is capable of cytocompatibility and has low toxicity to MC3T3 cell. Conclusion: Therefore, the new photothermal injectable antibacterial hydrogel materials proposed in this study will provide a promising clinical bone repair strategy and is expected to as a minimally invasive treatment biomaterial in bone repair fields.

Advanced Hydrogel systems for mandibular reconstruction

Mandibular defect becomes a prevalent maxillofacial disease resulting in mandibular dysfunctions and huge psychological burdens to the patients. Considering the routine presence of oral contaminations and aesthetic restoration of facial structures, the current clinical treatments are however limited, incapable to reconstruct the structural integrity and regeneration, spurring the need for cost-effective mandibular tissue engineering. Hydrogel systems possess great merit for mandibular reconstruction with precise involvement of cells and bioactive factors. In this review, current clinical treatments and distinct mode(s) of mandible formation and pathological resorption are summarized, followed by a review of hydrogel-related mandibular tissue engineering, and an update on the advanced fabrication of hydrogels with improved mechanical property, antibacterial ability, injectable form, and 3D bioprinted hydrogel constructs. The exploration of advanced hydrogel systems will lay down a solid foundation for a bright future with more biocompatible, effective, and personalized treatment in mandibular reconstruction.

A pH-Controlled Solid Inhibitor Based on PAM Hydrogel for Steel Corrosion Protection in Wide Range pH NaCl Medium

To provide carbon steel a long-term corrosion protection effect in NaCl solutions with different pH values, based on poly-acrylamide (PAM) and oleate imidazoline (OIM), a solid corrosion inhibitor with the properties of pH-controlled release was synthesized. SEM, FTIR and TGA results indicated that the OIM inhibitors were successfully loaded into PAM hydrogel with a high OIM encapsulation content (39.64 wt.%). The OIM release behavior from the hydrogel structure has two stages, quick release and sustained release. The pH of solutions could affect the initial release kinetics of OIM inhibitors and the diffusion path in the hydrogel structure. Weight loss measurement of L80 steel in different pH solutions with OIM@PAM proved the inhibitor responsive release mechanism and anticorrosion performance. The inhibition efficiency of OIM@PAM can maintain over 80% after long-term immersion in a harsh corrosive environment (pH 3), which is much higher than the inhibition efficiency of OIM@PAM in a moderate corrosive solution.

A bioactive glass functional hydrogel enhances bone augmentation via synergistic angiogenesis, self-swelling and osteogenesis

Bone augmentation materials usually cannot provide enough new bone for dental implants due to the material degradation and mucosal pressure. The use of hydrogels with self-swelling properties may provide a higher bone augmentation, although swelling is generally considered to be a disadvantage in tissue engineering. Herein, a double-crosslinked gelatin-hyaluronic acid hydrogels (GH) with self-swelling properties were utilized. Meanwhile, niobium doped bioactive glasses (NbBG) was dispersed in the hydrogel network to prepare the GH-NbBG hydrogel. The composite hydrogel exhibited excellent biocompatibility and the addition of NbBG significantly improved the mechanical properties of the hydrogel. In vivo results found that GH-NbBG synergistically promoted angiogenesis and increased bone augmentation by self-swelling at the early stage of implantation. In addition, at the late stage after implantation, GH-NbBG significantly promoted new bone formation by activating RUNX2/Bglap signaling pathway. Therefore, this study reverses the self-swelling disadvantage of hydrogels into advantage and provides novel ideas for the application of hydrogels in bone augmentation.

Comparison of physical, mechanical and biological effects of leucocyte-PRF and advanced-PRF on polyacrylamide nanofiber wound dressings: In vitro and in vivo evaluations

Platelet-rich fibrin (PRF) is extracted from the blood without biochemical interference and, also, with the ability of a long-term release of growth factors that can stimulate tissue repair and regerenation. Here, leucocyte- and platelet-rich fibrin (L-PRF) and advanced platelet-rich fibrin (A-PRF) were extracted and utilized for the creation of nanofibers containing polyacrylamide (PAAm), PAAm / L-PRF and PAAm / A-PRP through electrospinning processing technique. The effect of the type of PRF on the physical, mechanical and biological properties of the resultant nanofiberous wound dressings are thoroughly evaluated. The results presented in the current study reveals that the fiber diameter is grealtly reduced through the utilization of L-PRF. In addition, mechanical property is also positively affected by L-PRF and the degradation rate is found to be higher compared to A-PRF group. The L929 cells proliferation and adhesion, angiogenesis potential and wound healing ability was significantly higher in PAAm/A-PRF nanofibers compared to pure PAAm and PAAm/L-PRF nanofibers owed to the release of vascular endothelial growth factor (VEGF) and platelet derived growth factor (PDGF). Overall, the utilization of L-PRF or A-PRF can improve the physical, mechanical and biological behavior of nanofiber making them an ideal candidate for wound dressings, with the emphasis on the skin tissue repair and regeneration applications.

Unmodified Gum Arabic/Chitosan/Nanohydroxyapatite Nanocomposite Hydrogels as Potential Scaffolds for Bone Regeneration

In this work, physical cross-linking was used to create nanocomposite hydrogels composed of unmodified gum arabic (GA), chitosan (Ch), and natural nanohydroxyapatite (nHA), using an acrylic acid (AA) solvent. Different GA/chitosan contents (15%, 25%, and 35% of the used AA) as well as different nHA contents (2, 5, and 10 wt.%), were used and studied. The natural nHA and the fabricated GA/Ch/nHA nanocomposite hydrogels were characterized using different analysis techniques. Using acrylic acid solvent produced novel hydrogels with compressive strength of 15.43–22.20 MPa which is similar to that of natural cortical bone. The addition of natural nHA to the hydrogels resulted in a significant improvement in the compressive strength of the fabricated hydrogels. In vitro studies of water absorption and degradation—and in vivo studies—confirmed that the nanocomposite hydrogels described here are biodegradable, biocompatible, and facilitate apatite formation while immersed in the simulated body fluid (SBF). In light of these findings, the GA/Ch/nHA nanocomposite hydrogels are recommended for preparing bioactive nanoscaffolds for testing in bone regeneration applications.

Tunable mechanical properties of Mo3Se3-poly vinyl alcohol-based/silk fibroin-based nanowire ensure the regeneration mechanism in tenocytes derived from human bone marrow stem cells

Silk fibroin (SF) and poly vinyl alcohol (PVA)-based nanomaterial has exceptional attention in regenerative medicine. However, the preparation of SF and PVA-based nanomaterials in the desired form is complex due to their poor mechanical strength, brittleness, and compatibility. To this end, Mo₃Se₃ is chosen as a bio-nanowire to fabricate by combining PVA and SF to improve the mechanical properties. Physicochemical and structural features of the Mo₃Se₃-PVA-SF nanowire hydrogel (Mo₃Se₃-PVA-SF-NWH) were characterized by field emission scanning electron microscope (FE-SEM). Mechanical properties, degradation ratio, hydrophilicity, water uptake capacity, biocompatibility, and biological activity of the hydrogel were also studied. Superior interactions were formed between the reinforcing molecules of Mo₃Se₃ and PVA/SF in the hydrogel network by introducing Mo₃Se₃ nanowire (NW) into the hydrogel. Conversely, Mo₃Se₃ NW imparts mechanical stability and robustness to the blends (hydrogel) with predictable long-term degradation characteristics. It was proven by in vitro biodegradable rate, and swelling behaviour was varied depending on the concentration of Mo₃Se₃ NW. Mo₃Se₃ reinforced the hydrogels and found high porosity with superior biocompatibility. Excellent cellular adaptation was analyzed by MTT assay, live/dead staining, western blot, and quantitative real-time polymerase chain reaction (qRT-PCR). It revealed moderate toxicity at a concentration of 0.02% among the control samples. There was no discernible difference in 0.01% and 0.005% of Mo₃Se₃-PVA-SF-NWH in tenocytes derived from human bone marrow mesenchymal stem cells (hBMSC). Hence, this Mo₃Se₃-PVA-SF-NWH might be considered biocompatible due to its biological activities and appropriate mechanical properties. Overall, the Mo₃Se₃-PVA-SF-NWH might be considered a biocompatible scaffold for the possible biomedical applications of tendon tissue engineering.

Lignin grafted hydroxyapatite entrapped in polyacrylamide: Characterization and adsorptive features for Th4+ and bovine serum albumin

Water-soluble sulfolignin (SL) was grafted onto hydroxyapatite (Hap) by using epichlorohydrin. SLgHap was then entrapped in cross-linked polyacrylamide by in situ polymerizations of acrylamide and N, N'-methylenebisacrylamide to obtain the composite of PSLgHap. The composite was characterized by FT-IR, BET- porosity, XRD, EDXRF, SEM-EDX, TGA-DTG, PZC, CEC, and swelling tests. The adsorptive features of PSLgHAP were investigated for Th⁴⁺ and BSA in view of its dependence on pH, ionic intensity, concentration, temperature, and time. The results of characterization tests confirmed the formation of PSLgHap. The grafting efficiency concerning sulfur contents of PSLgHap was 96% by EDXRF. The isotherms were best represented by the Sips model, Langmuir adsorption capacities were 369 and 390 mg g_SLgHap^-1 for BSA and Th⁴⁺. The enthalpy and entropy changes were positive whilst Gibbs energy was negative by entropy controlled. The adsorption kinetics of both species was obeyed to pseudo second-order model, whereas it was first-order for BSA and hybrid-order for Th⁴⁺ of Langmuir model.

Nano-hybrid gradient scaffold for articular repair

Osteoarthritis disease can easily lead to articular cartilage degeneration and subchondral bone damage, so the demand for suitable articular substitutes is gradually increasing. In order to simulate the complex environment of different layers in natural joint, we fabricate the continuous one-phase gradient scaffold. In the study, CS (chitosan) was modified with SH (sodium hyaluronate) and GO (graphene oxide) to form the whole scaffold. nHAP (Nano-hydroxyapatite) was in situ generated with gradient distribution in the scaffold. Continuous interface can better imitate the combination style of cartilage and subchondral bone at joint. The diverseness of scaffold's different layer in water absorption/retention rate and mechanical property is similar to the difference of articular cartilage and subchondral bone. Meanwhile, the cell experiments demonstrated that the bionic scaffold can well promote the proliferation of bone marrow mesenchymal stem cell. Articular defect model further confirmed that the scaffold can better induce articular regeneration. Herein, the prepared scaffold might be an excellent candidate for endogenous articular repair.

Enhanced mechanical, biomineralization, and cellular response of nanocomposite hydrogels by bioactive glass and halloysite nanotubes for bone tissue regeneration

In the present study, the synergistic effect of the bioactive glass (BG) and halloysite nanotubes (HNTs) (i.e. BG@HNT) was evaluated on physicochemical and bioactive properties of polyacrylamide/poly (vinyl alcohol) (PMPV) based nanocomposite hydrogels. Here, a double-network hydrogel composed of organic-inorganic components was successfully developed by using in-situ free-radical polymerization and freeze-thawing process. Structural analyses confirmed the successful formation of the nanocomposite hydrogels through physical and chemical interactions. Morphological analysis showed that all hydrogel scaffolds are containing highly porous 3D microstructure and pore-interconnectivity. The equilibrium swelling ratio of the hydrogels was decreased by the addition of BG or BG@HNT and thereby the lower porosity and pore-size reduced the penetration of media and slow down the degradation process. Enhanced biomineralization ability of PMPV/BG@HNT was observed via apatite-forming ability (Ca/P: 1.21 ± 0.14) after immersion in the simulated body fluid as well as significantly enhanced dynamic mechanical properties (compressive strength: 102.1 kPa at 45% of strain and stiffness: 3115.0 N/m at 15% of strain). Furthermore, an enhanced attachment and growth of hFOB1.19 osteoblast cells on PMPV/BG@HNT was achieved compared to PMPV or PMPV/BG hydrogels over 14 days. The PMPV/BG@HNT nanocomposite hydrogel could have a promising application in low-load bearing bone tissue regeneration.

A new cancellous bone material of silk fibroin/cellulose dual network composite aerogel reinforced by nano-hydroxyapatite filler

Composites materials comprised of biopolymeric aerogel matrices and inorganic nano-hydroxyapatite (n-HA) fillers have received considerable attention in bone engineering. Although with significant progress in aerogel-based biomaterials, the brittleness and low strengths limit the application. The improvements in toughness and mechanical strength of aerogel-based biomaterials are in great need. In this work, an alkali urea system was used to dissolve, regenerate and gelate cellulose and silk fibroin (SF) to prepare composite aerosol. A dual network structure was shaped in the composite aerosol materials interlaced by sheet-like SF and reticular cellulose wrapping n-HA on the surface. Through uniaxial compression, the density of the composite aerogel material was close to the one of natural bone, and mechanical strength and toughness were high. Our work indicates that the composite aerogel has the same mechanical strength range as cancellous bone when the ratio of cellulose, n-HA and SF being 8:1:1. In vitro cell culture showed HEK-293T cells cultured on composite aerogels had high ability of adhesion, proliferation and differentiation. Totally, the presented biodegradable composite aerogel has application potential in bone tissue engineering.

Facile manufacturing of fused deposition modelled composite scaffold for tissue engineering - An embedment model with plasticity for incorporation of additives

Fused deposition modeling (FDM) process is carried out at an elevated temperature, preventing the addition of biological factors, drugs, bioactive compounds, etc., during fabrication. To surpass this disadvantage, 3D interlinked porous PLA (Polylactic acid) scaffold was fabricated by FDM, followed by embedment of PCL (polycaprolactone) scaffold into the pores of PLA at room temperature yielding PLA-PCL scaffold. In addition, PLA-PCL scaffold with nanohydroxyapatite (PLA-PCL-nHAP) and multiwalled carbon nanotubes (PLA-PCL-MWCNT) were also fabricated. Herein, FDM fabricated PLA scaffold functions as a "structural component" whereas embedded PCL scaffold acts as "functional component" which provides a provision to functionalize the scaffolds with desired chemical or biological materials. The embedment process is straightforward, cost effective, and does not require sophistication. Mechanical characterization of scaffolds suggests Young's modulus of PLA-PCL scaffold (16.02 MPa) was higher than FDM fabricated PLA (9.98 MPa) scaffold by virtue of embedded PCL matrix. Besides, Finite element analysis showed, von Mises stress on mandible with scaffolds at 4.04 MPa, whereas mandible with the defect was 6.7 MPa suggesting stress distribution efficiency and mechanical stability of these scaffolds. Further, field emission scanning electron microscope (FESEM) analysis implied interlinked porous structures with a pore diameter of 50 µm to 300 µm. X-Ray diffraction (XRD) results revealed an increased crystallinity (%) of embedment models (PLA-PCL, PLA-PCL-nHAP and PLA-PCL-MWCNT) compared to PLA printed scaffold. Additionally, Raman analysis revealed that the embedment process did not impart chemical alterations in polymeric chains. In vitro analysis with human osteoblasts exhibited osteoconductive nature of the scaffold by supporting mineralization. In brief, the advantages the model is that, it helps to overcome the hassles of manufacturing a filament with desired additives for FDM, and offers provision to incorporate desired concentrations of heat labile bioactive molecules during embedment process at ambient temperature.

Near-infrared triggered on-demand local anesthesia using a jammed microgels system

To conveniently modulate the degree of local analgesia in response to changes in patients' needs and level of activity, a NIR-activated drug delivery system based on jammed microgels was introduced in the present study to realize on-demand local anesthesia. Chemically cross-linked gelatin microgels (5-15 μm) containing N-isopropylacrylamide (NIPAM), methylallyl polyethylene glycol (APEG) and graphene oxide (GOs) were fabricated through emulsion. After the in situ free radical polymerization, the physical network was formed, producing microgels with double networks (DN microgels). The DN microgels exhibited thermosensitive properties. The copolymerization of APEG resulted in the increase of lower critical solution temperature (LCST) of microgels. The maximum volume shrinkage ratio of DN microgels (NIPAM40 + APEG60) increased with the increase of the content of physical cross-linking network. The DN microgels also exhibited NIR-responsive ability. Under the NIR irradiance of 272 mW/cm², the temperature of DN microgels with 3 mg/mL GOs reached 40 °C within 60 s, resulting in the volume shrinkage of 14%. Ropivacaine release from DN microgels could be effectively triggered by NIR irradiation in vitro. After centrifugation, a jammed microgels system was produced where microgels packed densely, displaying shear-thinning behavior for achieving injection. The jammed DN microgels carrying ropivacaine were injected subcutaneously into rat footpad. NIR irradiation produced on-demand and repeated infiltration anesthesia in the rat footpad. The jammed DN microgels system thus was beneficial in the management of pain.

Assessment of the Release of Vascular Endothelial Growth Factor from 3D-Printed Poly-ε-Caprolactone/Hydroxyapatite/Calcium Sulfate Scaffold with Enhanced Osteogenic Capacity

Vascular endothelial growth factor (VEGF) is one of the most crucial growth factors and an assistant for the adjustment of bone regeneration. In this study, a 3D scaffold is fabricated using the method of fused deposition modeling. Such a fabricated method allows us to fabricate scaffolds with consistent pore sizes, which could promote cellular ingrowth into scaffolds. Therefore, we drafted a plan to accelerate bone regeneration via VEGF released from the hydroxyapatite/calcium sulfate (HACS) scaffold. Herein, HACS will gradually degrade and provide a suitable environment for cell growth and differentiation. In addition, HACS scaffolds have higher mechanical properties and drug release compared with HA scaffolds. The drug release profile of the VEGF-loaded scaffolds showed that VEGF could be loaded and released in a stable manner. Furthermore, initial results showed that VEGF-loaded scaffolds could significantly enhance the proliferation of human mesenchymal stem cells (hMSCs) and human umbilical vein endothelial cells (HUVEC). In addition, angiogenic- and osteogenic-related proteins were substantially increased in the HACS/VEGF group. Moreover, in vivo results revealed that HACS/VEGF improved the regeneration of the rabbit’s femur bone defect, and VEGF loading improved bone tissue regeneration and remineralization after implantation for 8 weeks. All these results strongly imply that the strategy of VEGF loading onto scaffolds could be a potential candidate for future bone tissue engineering.

A novel bovine serum albumin and sodium alginate hydrogel scaffold doped with hydroxyapatite nanowires for cartilage defects repair

Cartilage tissue engineering has become the trend of cartilage defect repair owing to the engineered biomimetic tissue that can mimic the structural, biological and functional characteristics of natural cartilage. Biomaterials with high biocompatibility and regeneration capacity are expected to be used in cartilage tissue engineering. Herein, in this study, a dual-network bovine serum albumin/sodium alginate with hydroxyapatite nanowires composite (B-S-H) hydrogel scaffold has been prepared for cartilage repair. The obtained B-S-H hydrogel scaffold exhibits ideal physical properties, such as excellent mechanical strength, high porosity and swelling ratio, as well as the excellent biological activity to promote the human bone marrow derived mesenchymal stem cells (hBMSCs) proliferation and differentiation. The in vivo study further shows that the B-S -H hydrogel scaffold can obviously promote the generation of new cartilage that integrates well with surrounding tissues and is similar to adjacent cartilage in terms of thickness. It is considered that the B-S-H hydrogel scaffold has great potential in the application of cartilage defects repair.

Integration of Human Umbilical Cord Mesenchymal Stem Cells-Derived Exosomes with Hydroxyapatite-Embedded Hyaluronic Acid-Alginate Hydrogel for Bone Regeneration

The treatment of bone defects has plagued clinicians. Exosomes, the naturally secreted nanovesicles by cells, exhibit great potential in bone defect regeneration to realize cell-free therapy. In this work, we successfully revealed that human umbilical cord mesenchymal stem cells-derived exosomes could effectively promote the proliferation, migration, and osteogenic differentiation of a murine calvariae preosteoblast cell line in vitro. Considering the long period of bone regeneration, to effectively exert the reparative effect of exosomes, we synthesized an injectable hydroxyapatite (HAP)-embedded in situ cross-linked hyaluronic acid-alginate (HA-ALG) hydrogel system to durably retain exosomes at the defect sites. Then, we combined the exosomes with the HAP-embedded in situ cross-linked HA-ALG hydrogel system to repair bone defects in rats in vivo. The results showed that the combination of exosomes and composite hydrogel could significantly enhance bone regeneration. Our experiment provides a new strategy for exosome-based therapy, which shows great potential in future tissue and organ repair.

Novel sensor platform for rapid detection and quantification of coliforms on food contact surfaces

In this paper, a novel sensor platform based on screen printed carbon electrode coated by graphene modified polyacrylamide gel (GR/PAAGC) was developed and implemented for sampling, detection and enumeration of coliform bacteria (coliforms) on food contact surfaces. The optimized formula of polyacrylamide (PAA) and agar-agar increased the adhesive properties of the gel, being crucial for the coliforms recovery, attached to food contact surfaces. The 6-Chloro-3-indoxyl-β-D-galactopyranoside (6-CIGP) was used as a new electrochemical reporter for β-D-galactosidase activity. The released 6,6'-Dichloro-Indigo (6-DI) was directly detected by GR/PAAGC sensor. The presence of Isopropyl-β-D-thiogalactopyranoside (IPTG) and n-Octyl-β-D-thiogalactopyranoside (OBDG) in the gel contributed to reduction of the detection time. The addition of graphene enhanced the voltammetric signal and increased the conductivity of PAA gel. The anodic and cathodic peaks of the released product were directly proportional to the concentration of coliforms. Bacterial cell concentrations ranging from 1.6log₁₀CFU/mL to 6.6log₁₀CFU/mL were detected. Well-shaped, sharp voltammetric curves were generated within 3 h. Redox peaks exhibited good sensitivity with detection limits (LOD) < 0.6log₁₀CFU/mL. After series of optimization experiments, coliforms ranging from 0.6log₁₀CFU/cm² to 6.6₁₀CFU/cm² on stainless steel surfaces have been detected within 30 min with a LOD of 0.1log₁₀CFU/cm². The developed rapid, sensitive, reproducible and specific sensor successfully applied for single detection as well as for real-time monitoring of growth of coliform bacteria on stainless steel surfaces during food processing.

Nanocomposite Hydrogels: Advances in Nanofillers Used for Nanomedicine

The ongoing progress in the development of hydrogel technology has led to the emergence of materials with unique features and applications in medicine. The innovations behind the invention of nanocomposite hydrogels include new approaches towards synthesizing and modifying the hydrogels using diverse nanofillers synergistically with conventional polymeric hydrogel matrices. The present review focuses on the unique features of various important nanofillers used to develop nanocomposite hydrogels and the ongoing development of newly hydrogel systems designed using these nanofillers. This article gives an insight in the advancement of nanocomposite hydrogels for nanomedicine.

Preparation and Characterization of Hydrophobic-Associated Microspheres for Deep Profile Control in Offshore Oilfields

Microspheres have excellent sealing performances such as injectivity, bridging-off, deep migration, and deformation performances, but their plugging effects are limited by the fast swelling rate and poor viscoelasticity. In this study, we synthesized a novel modified microsphere with polymerizable surfactant monomers and cationic monomers. We investigated the influence factors on the swelling performance and rheological properties of the microspheres and explored the ways to improve the plugging performance of hydrophobic-associating microspheres. The association behaviors in aqueous media of poly(acrylamide-co-methacry loyloxyethyl trimethyl ammonium chloride-co-n-dodecyl poly(etheroxy acrylate) P(AM-DMC-DEA) are proven to be mediated by the DEA content. Moreover, the hydrophobic association interaction has a strong effect on the performance of microspheres such as swelling properties, the rheological performance, and plugging properties. The swelling properties of microsphere studies exhibited the slow swelling rate. The rheological performance measurements showed significant improvements; yield stress, and creep compliance increased rapidly from 404 to 2060 Pa and 3.89 × 10−4 to 1.41 × 10−2 1/Pa, respectively, with DEA content in microspheres rising from 0.0% to 0.22%. The plugging properties of microspheres were enhanced by the slow swelling performance and good viscoelasticity.

Nanocomposite Hydrogels and Their Applications in Tissue Engineering

Nanocomposite (NC) hydrogels, organic-inorganic hybrid materials, are of great interest as artificial three-dimensional (3D) biomaterials for biomedical applications. NC hydrogels are prepared in water by chemically or physically cross-linking organic polymers with nanomaterials (NMs). The incorporation of hard inorganic NMs into the soft organic polymer matrix enhances the physical, chemical, and biological properties of NC hydrogels. Therefore, NC hydrogels are excellent candidates for artificial 3D biomaterials, particularly in tissue engineering applications, where they can mimic the chemical, mechanical, electrical, and biological properties of native tissues. A wide range of functional NMs and synthetic or natural organic polymers have been used to design new NC hydrogels with novel properties and tailored functionalities for biomedical uses. Each of these approaches can improve the development of NC hydrogels and, thus, provide advanced 3D biomaterials for biomedical applications.

Transcriptome profiling reveals differential expression of interferon family induced by dengue virus 2 in human endothelial cells on tissue culture plastic and polyacrylamide hydrogel

A cell model is critical for studying the molecular mechanisms of dengue virus 2 (DENV-2) invasions and cell bioactivity can be easily affected by the substrate matrix. Tissue culture plastic (TCP) and polyacrylamide hydrogel (PAMH) are two kinds of matrices widely used for cells. The effects of different matrices on the cultured cells with DENV-2 invasion remain unknown. To address the issue, the effects of TCP and PAMH were explored in primary human umbilical vein endothelial cells (HUVECs) with DENV-2 invasion. HUVECs were assigned into four groups: group A (cultured on TCP), group B (cultured on PAMH), group C (cultured on TCP with DENV-2 invasion), and group D (cultured on PAMH with DENV-2 invasion). Flow cytometry was performed on HUVECs after 48-hr culture. Gene expression patterns were analyzed by gene microarray. The levels of interleukin-29 (IL-29) were measured by real-time qRT-PCR and ELISA. There were no cell apoptosis induced by DENV-2 in HUVECs cultured on TCP and PAMH (P > 0.05). After DENV-2 invasion, the up-regulated genes involve in the activities of oligoadenylate synthetase (OAS), interferon-related cytokine, and growth factors so on. The up-regulated pathways involve in the responses to DENV-2 and innate immunity. IL-29 was induced in the HUVECs on PAMH when compared with the cells on TCP (P < 0.05). Thus, different matrices cause different immune responses, which should be considered in the cell models for exploring the molecular mechanisms of DENV-induced diseases.

Composite Hydrogels for Bone Regeneration

Over the past few decades, bone related disorders have constantly increased. Among all pathological conditions, osteoporosis is one of the most common and often leads to bone fractures. This is a massive burden and it affects an estimated 3 million people only in the UK. Furthermore, as the population ages, numbers are due to increase. In this context, novel biomaterials for bone fracture regeneration are constantly under development. Typically, these materials aim at favoring optimal bone integration in the scaffold, up to complete bone regeneration; this approach to regenerative medicine is also known as tissue engineering (TE). Hydrogels are among the most promising biomaterials in TE applications: they are very flexible materials that allow a number of different properties to be targeted for different applications, through appropriate chemical modifications. The present review will focus on the strategies that have been developed for formulating hydrogels with ideal properties for bone regeneration applications. In particular, aspects related to the improvement of hydrogels' mechanical competence, controlled delivery of drugs and growth factors are treated in detail. It is hoped that this review can provide an exhaustive compendium of the main aspects in hydrogel related research and, therefore, stimulate future biomaterial development and applications.

Photocrosslinkable and elastomeric hydrogels for bone regeneration

Nanocomposite biomaterials are extensively investigated for cell and tissue engineering applications due their unique physical, chemical and biological characteristics. Here, we investigated the mechanical, rheological, and degradation properties of photocrosslinkable and elastomeric nanocomposite hydrogels from nanohydroxyapatite (nHAp) and gelatin methacryloyl (GelMA). The addition of nHAp resulted in a significant increase in mechanical stiffness and physiological stability. Cells readily adhere and proliferate on the nanocomposite surfaces. Cyclic stretching of cells on the elastomeric nanocomposites revealed that nHAp elicited a stronger alignment response in the direction of strain. In vitro studies highlight enhanced bioactivity of nanocomposites as determined by alkaline phosphate (ALP) activity. Overall, the elastomeric and photocrosslinkable nanocomposite hydrogels can be used for minimally invasive therapy for bone regeneration.

Calcium Orthophosphate-Containing Biocomposites and Hybrid Biomaterials for Biomedical Applications

The state-of-the-art on calcium orthophosphate (CaPO4)-containing biocomposites and hybrid biomaterials suitable for biomedical applications is presented. Since these types of biomaterials offer many significant and exciting possibilities for hard tissue regeneration, this subject belongs to a rapidly expanding area of biomedical research. Through the successful combinations of the desired properties of matrix materials with those of fillers (in such systems, CaPO4 might play either role), innovative bone graft biomaterials can be designed. Various types of CaPO4-based biocomposites and hybrid biomaterials those are either already in use or being investigated for biomedical applications are extensively discussed. Many different formulations in terms of the material constituents, fabrication technologies, structural and bioactive properties, as well as both in vitro and in vivo characteristics have been already proposed. Among the others, the nano-structurally controlled biocomposites, those containing nanodimensional compounds, biomimetically fabricated formulations with collagen, chitin and/or gelatin, as well as various functionally graded structures seem to be the most promising candidates for clinical applications. The specific advantages of using CaPO4-based biocomposites and hybrid biomaterials in the selected applications are highlighted. As the way from a laboratory to a hospital is a long one and the prospective biomedical candidates have to meet many different necessities, the critical issues and scientific challenges that require further research and development are also examined.