Dual pH‐ and thermal‐responsive nanocomposite hydrogels for controllable delivery of hydrophobic drug baicalein

Hydrogels have been widely used as mild biomaterials due to their bio‐affinity, high drug loading capability and controllable release profiles. However, hydrogel‐based carriers are greatly limited for the delivery of hydrophobic payloads due to the lack of hydrophobic binding sites. Herein, nano‐liposome micelles were embedded in semi‐interpenetrating poly[(N‐isopropylacrylamide)‐co‐chitosan] (PNIPAAm‐co‐CS) and poly[(N‐isopropylacrylamide)‐co‐(sodium alginate)] (PNIPAAm‐co‐SA) hydrogels which were responsive to both temperature and pH, thereby establishing tunable nanocomposite hydrogel delivery systems. Nano‐micelles formed via the self‐assembly of phospholipid could serve as the link between hydrophobic drug and hydrophilic hydrogel due to their special amphiphilic structure. The results of transmission and scanning electron microscopies and infrared spectroscopy showed that the porous hydrogels were successfully fabricated and the liposomes encapsulated with baicalein could be well contained in the network. In addition, the experimental results of response release in vitro revealed that the smart hydrogels showed different degree of sensitiveness under different pH and temperature stimuli. The results of the study demonstrate that combining PNIPAAm‐co‐SA and PNIPAAm‐co‐CS hydrogels with liposomes encapsulated with hydrophobic drugs is a feasible method for hydrophobic drug delivery and have potential application prospects in the medical field. © 2018 Society of Chemical Industry     

In situ incorporation of monodisperse drug nanoparticles into hydrogel scaffolds for hydrophobic drug release

The effective and locally sustained delivery of hydrophobic drug with hydrogels as carriers is still a challenge owing to the inherent incompatibility of hydrophilic hydrogel network and hydrophobic drug. One promising approach is to use porous hydrogels to encapsulate and deliver hydrophobic drug in the form of nanoparticles to the disease sites. However, this approach is currently limited by the inability to load concentrated hydrophobic drug nanoparticles into the hydrogels because of the severe nanoparticle aggregation during the loading process. In this article, we firstly designed and fabricated efficient drug nanoparticles embedded hydrogels for hydrophobic drug delivery by incorporating monodisperse silybin (hydrophobic drug for liver protection) nanoparticles into acrylated hyaluronic acid (HA‐AC) based hydrogels through in situ cross‐linking. The silybin nanoparticles embedded hydrogel scaffolds proved to be a good sustained release system with a long period of 36 h. The drug release from this hybrid hydrogels could be modulated by tuning HA‐AC concentration, cross‐linking ratio, chain length of cross‐linker and drug loading amount. The different kinetic models were applied, and it was observed that the release profile of silybin best followed the Hixson‐Crowell model for the release of drug from the hydrogels embedding silybin nanoparticles. It could be envisioned that this process would significantly advance the potential applications of hydrogel scaffolds mediated hydrophobic drug delivery in clinical therapies. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43111.     

Cytocompatibility and Suitability of Protein-Based Biomaterials as Potential Candidates for Corneal Tissue Engineering

The vision impairments suffered by millions of people worldwide and the shortage of corneal donors show the need of substitutes that mimic native tissue to promote cell growth and subsequent tissue regeneration. The current study focused on the in vitro assessment of protein-based biomaterials that could be a potential source for corneal scaffolds. Collagen, soy protein isolate (SPI), and gelatin films cross-linked with lactose or citric acid were prepared and physicochemical, transmittance, and degradation measurements were carried out. In vitro cytotoxicity, cell adhesion, and migration studies were performed with human corneal epithelial (HCE) cells and 3T3 fibroblasts for the films’ cytocompatibility assessment. Transmittance values met the cornea’s needs, and the degradation profile revealed a progressive biomaterials’ decomposition in enzymatic and hydrolytic assays. Cell viability at 72 h was above 70% when exposed to SPI and gelatin films. Live/dead assays and scanning electron microscopy (SEM) analysis demonstrated the adhesion of both cell types to the films, with a similar arrangement to that observed in controls. Besides, both cell lines were able to proliferate and migrate over the films. Without ruling out any material, the appropriate optical and biological properties shown by lactose-crosslinked gelatin film highlight its potential for corneal bioengineering.     

Chitosan/Alginate Hydrogel Dressing Loaded FGF/VE-Cadherin to Accelerate Full-Thickness Skin Regeneration and More Normal Skin Repairs

The process of full-thickness skin regeneration is complex and has many parameters involved, which makes it difficult to use a single dressing to meet the various requirements of the complete regeneration at the same time. Therefore, developing hydrogel dressings with multifunction, including tunable rheological properties and aperture, hemostatic, antibacterial and super cytocompatibility, is a desirable candidate in wound healing. In this study, a series of complex hydrogels were developed via the hydrogen bond and covalent bond between chitosan (CS) and alginate (SA). These hydrogels exhibited suitable pore size and tunable rheological properties for cell adhesion. Chitosan endowed hemostatic, antibacterial properties and great cytocompatibility and thus solved two primary problems in the early stage of the wound healing process. Moreover, the sustained cytocompatibility of the hydrogels was further investigated after adding FGF and VE-cadherin via the co-culture of L929 and EC for 12 days. The confocal 3D fluorescent images showed that the cells were spherical and tended to form multicellular spheroids, which distributed in about 40–60 μm thick hydrogels. Furthermore, the hydrogel dressings significantly accelerate defected skin turn to normal skin with proper epithelial thickness and new blood vessels and hair follicles through the histological analysis of in vivo wound healing. The findings mentioned above demonstrated that the CS/SA hydrogels with growth factors have great potential as multifunctional hydrogel dressings for full-thickness skin regeneration incorporated with hemostatic, antibacterial, sustained cytocompatibility for 3D cell culture and normal skin repairing.     

Porous hydroxyapatite ceramics by ice templating: Freezing characteristics and mechanical properties

Ice templating produces porous hydroxyapatite (HA) scaffolds with a lamellar morphology and aligned channels when using aqueous HA slurries. We investigated the freezing characteristics of HA slurries with regard to the pore structures of the porous HA scaffolds. We found that by increasing the cooling rate, the lamellar spacing decreased. The average lamellar spacing is about 785.7 μm at a cooling rate of 1.3 °C/min. The porous geometry changes from lamella and well aligned channels to a partial dendrite and partially aligned cavities with a decrease in the initial nucleation temperature and an increase in the degree of supercooling. Additionally, we determined the relationship between compressive strength and porosity. The compressive strength of the porous HA scaffolds reach 6.7 MPa at a porosity of 64% and the lamellar spacing is about 124 μm.     

Effect of hydroxyapatite and tricalcium phosphate addition on protein foaming-consolidation porous alumina

Porous alumina-hydroxyapatite (HA) and alumina-tricalcium phosphate (TCP) composites have been fabricated to investigate the effect of HA and ??-TCP addition on protein foaming-consolidation derived porous alumina. HA and ??-TCP loadings along with yolk content, starch content, and sintering temperature were varied to modulate performance of the porous composites. The rheological behavior of slurry shifted from pseudoplastic flow to a Newtonian fluid with increasing yolk concentration. The foaming capacity of slurry increased with yolk addition. The addition of starch into slurry resulted in bigger pore size and avoided the porous bodies from cracks. The shrinkage of sintered bodies increased with increasing HA loading, but decreased with increasing ??-TCP loading. The compressive strength of porous alumina-HA body was found 2.9?MPa at 45.8% porosity and 20.4?MPa at 36.8% porosity. The increasing porosity of porous alumina-TCP body from 56.1 to 61.6% improved the compressive strength from 3.1 to 4.2?MPa. Increasing sintering temperature resulted in large grain size among powder particles, thus improving the compressive strength of porous bodies. Preliminary results of DF-1 cells culture on the surface of porous alumina and alumina-TCP samples are also reported.     

Fabrication and Characterisation of a Photo-Responsive,Injectable Nanosystem for Sustained Delivery of Macromolecules

The demand for biodegradable sustained release carriers with minimally invasive and less frequent administration properties for therapeutic proteins and peptides has increased over the years. The purpose of achieving sustained minimally invasive and site-specific delivery of macromolecules led to the investigation of a photo-responsive delivery system. This research explored a biodegradable prolamin, zein, modified with an azo dye (DHAB) to synthesize photo-responsive azoprolamin (AZP) nanospheres loaded with Immunoglobulin G (IgG). AZP nanospheres were incorporated in a hyaluronic acid (HA) hydrogel to develop a novel injectable photo-responsive nanosystem (HA-NSP) as a potential approach for the treatment of chorio-retinal diseases such as age-related macular degeneration (AMD) and diabetic retinopathy. AZP nanospheres were prepared via coacervation technique, dispersed in HA hydrogel and characterised via infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Size and morphology were studied via scanning electron microscopy (SEM) and dynamic light scattering (DLS), UV spectroscopy for photo-responsiveness. Rheological properties and injectability were investigated, as well as cytotoxicity effect on HRPE cell lines. Particle size obtained was <200 nm and photo-responsiveness to UV = 365 nm by decreasing particle diameter to 94 nm was confirmed by DLS. Encapsulation efficiency of the optimised nanospheres was 85% and IgG was released over 32 days up to 60%. Injectability of HA-NSP was confirmed with maximum force 10 N required and shear-thinning behaviour observed in rheology studies. In vitro cell cytotoxicity effect of both NSPs and HA-NSP showed non-cytotoxicity with relative cell viability of ≥80%. A biocompatible, biodegradable injectable photo-responsive nanosystem for sustained release of macromolecular IgG was successfully developed.     

Three dimensional polyurethane/ hydroxyapatite bioactive scaffolds: The role of hydroxyapatite on pore generation

Fabrication of a suitable scaffold with highly interconnected and well-distributed pores for cell proliferation and growth in the field of bone tissue engineering is of high importance. In this study, three-dimensional porous polyurethane (PU) scaffolds, with 0, 15, 25, and 32 wt% hydroxyapatite (HA), were fabricated. In this regard, HA was incorporated into PU constituents prior to starting in-situ polymerization of PU. Porosity and density measurement of the scaffolds revealed that higher amount of HA in the scaffolds led to increasing the former and decreasing the latter quantity. The field emission scanning electron microscopy (FESEM) images revealed that by increasing HA content, the pore size showed a descending trend while the number of pores increased. This would be attributed to the type of interactions between HA and PU, and the role of HA in pore formation. Mechanical test revealed that Young's Modulus of the samples was reduced by increasing scaffold porosity caused by the increase of HA content. Bioactivity tests in the simulated body fluid (SBF) showed the ability of scaffolds forming apatite precipitates. MTT assay showed that by increasing HA content, MG63 osteoblast cell viability increased and FESEM images revealed proper attachment of the cells to the scaffold surface.     

Preparation and characterization of gelatin/hydroxyapatite nanocomposite for bone tissue engineering

Homogeneous gelatin/hydroxyapatite (GEL/HA) nano‐composites were synthesized by a novel in situ precipitation method, and its corresponding characterizations, including composition, morphology, pore structure, thermal stability, mechanical strength, and biocompatibility, were carried out. High‐magnified scanning electron microscope (SEM) images indicated that nano‐HA with particle size ranging from 20 to 50 nm were uniformly distributed in GEL matrix and tightly integrated with organic phase. Wide angle X‐ray diffraction (XRD) analysis and transmission electron microscope (TEM) images showed that, during the process of mineralization, there existed preferred oriented growth of HA crystals along (002) and (211) crystal planes. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) indicated that, the thermal stability of GEL molecules enhanced by hybridizing with HA nanocrystals. Interconnected porous GEL/HA nanocomposites with pore size ranging between 50 and 350 μm were prepared by a freeze‐drying method. This pore size was adequate for bone tissue engineering (BTE) applications. In addition, in vitro MG63 osteoblast‐like cell culture illuminated that GEL/HA nanocomposites had excellent cytocompatibility and could promote proliferation of cells. These results suggested that GEL/HA nanocomposite might be an ideal bone substitute. POLYM. COMPOS., 38:1579–1590, 2017. © 2015 Society of Plastics Engineers     

A Hyaluronan and Platelet-Rich Plasma Hydrogel for Mesenchymal Stem Cell Delivery in the Intervertebral Disc: An Organ Culture Study

The purpose of the present pilot study was to evaluate the effect of a hydrogel composed of hyaluronic acid (HA) and platelet-rich plasma (PRP) as a carrier for human mesenchymal stem cells (hMSCs) for intervertebral disc (IVD) regeneration using a disc organ culture model. HA was mixed with batroxobin (BTX) and PRP to form a hydrogel encapsulating 1 × 10⁶ or 2 × 10⁶ hMSCs. Bovine IVDs were nucleotomized and filled with hMSCs suspended in ~200 μL of the PRP/HA/BTX hydrogel. IVDs collected at day 0 and nucleotomized IVDs with no hMSCs and/or hydrogel alone were used as controls. hMSCs encapsulated in the hydrogel were also cultured in well plates to evaluate the effect of the IVD environment on hMSCs. After 1 week, tissue structure, scaffold integration, hMSC viability and gene expression of matrix and nucleus pulposus (NP) cell markers were assessed. Histological analysis showed a better preservation of the viability of the IVD tissue adjacent to the gel in the presence of hMSCs (~70%) compared to the hydrogel without hMSCs. Furthermore, disc morphology was maintained, and the hydrogel showed signs of integration with the surrounding tissues. At the gene expression level, the hydrogel loaded with hMSCs preserved the normal metabolism of the tissue. The IVD environment promoted hMSC differentiation towards a NP cell phenotype by increasing cytokeratin-19 (KRT19) gene expression. This study demonstrated that the hydrogel composed of HA/PRP/BTX represents a valid carrier for hMSCs being able to maintain a good cell viability while stimulating cell activity and NP marker expression.     

Strontium incorporated hydroxyapatite/hydrothermally reduced graphene oxide nanocomposite as a cytocompatible material

Hydroxyapatite (HA)/reduced graphene oxide (rGO) composites with different mol% of strontium and 1?wt% of GO were fabricated through a green hydrothermal reduction method and this combination has been reported for the first time. All the synthesized composites had strontium incorporated onto the crystal structure of HA as can be substantiated from XRD and FTIR. This paper also discusses a possible role of surface and pore characteristics on the in vitro cytocompatibility and the contribution of graphene oxide in directing the nucleation points resulting in dispersed strontium incorporated hydroxyapatite (SHA) based on P-31 NMR and TEM studies. In addition, a reasonable speculation also has been made to correlate the cytocompatibility with the selective occupancy of strontium ions in the apatite lattice. The in vitro cytocompatibility of SHA/rGO composites (SHAG) has been evaluated using cell proliferation tests with MG-63 cells, under a wider range of concentrations (1000–7.8?µg/ml) and by varying Sr/(Ca+Sr) molar ratio. SHAG with strontium substitution of 10?mol% exhibited the maximum viability among the samples tested. These results suggest that the SHAG composites will be a promising material for biomedical application.     

Self-ordering of anodic porous alumina formed in organic acid electrolytes

New self-ordering porous alumina films were fabricated in organic acid electrolytes. Highly ordered cell arrangements of porous alumina films were realized in malonic acid at 120 V and tartaric acid at 195 V having 300 nm and 500 nm pore intervals, respectively. Self-organization was achieved at the maximum voltage required to induce high-current-density anodization while preventing burning, i.e., an extremely high-current flow concentrated at local points. The cells of the film grown at a high field must be pressed against each other, so that the self-ordering proceeds with the porous layer growth. When the self-ordering of cell arrangement proceeds, the cells became smaller. To improve the regularity of the cell configuration, a low electrolyte temperature and a relatively high electrolyte concentration were effective for maintaining a high-current-density to prevent burning. Surface flatness was an essential factor for self-ordering, however, the surface oxide film produced by electropolishing an aluminum substrate prevented quick pore growth in the organic acids having a low dissociation constant. It is confirmed that electropolishing followed by alkaline treatment was most appropriate as the pre-treatment in preparing flat surfaces.     

Effect of particle size and freezing conditions on freeze-casted scaffold

Freeze casting is one of the emerging and novel manufacturing routes to fabricate porous scaffolds for various applications including orthopedic implants, drug delivery, energy storing devices etc. Thus, it becomes important to understand this process in a deeper sense. Present work was focused to study the effect/influence of basic parameters, particle sizes, and freezing conditions on the mechanical properties and microstructures of porous scaffold fabricated by freeze casting. β-tricalcium phosphate (β-TCP) and hydroxyapatite (HAp) powder with particle sizes of 10?μm and 20?nm were used. Prepared slurries were freeze casted at constant freezing temperature (5?°C) and constant freezing rate (1.86?°C/min) to study the effect of freezing conditions on mechanical and microstructural properties of the porous scaffold. It was observed that porous scaffold fabricated by nanoparticles has given better porosity (63.22–76.16%), than scaffold fabricated by microparticles (13–43.05%) at given solid loading of both freezing conditions. Although, the range of pore size of the scaffold fabricated by nanoparticles (CFR: 2.60–0.84?μm; CFT: 1.66–0.46?μm) was lower than that of scaffold fabricated by microparticles (CFR: 9.45–4.83?μm; CFT: 4.72–2.84?μm). The compressive strength of scaffolds prepared by nanoparticles was in the range of trabecular bone. Moreover, the results of present work will pave the way for the fabrication of porous scaffold with desired pore size and porosity for various implants, energy, and drug delivery applications.     

Generation of Large Pore Channels for Bone Tissue Engineering Using Camphene-Based Freeze Casting

The present study reports an innovative way to produce large pore channels with a size >100 μm for applications in bone tissue engineering using the camphene-based freeze casting method, and using an unusually high freezing temperature, which is close to the solidification temperature of the slurry, in order to allow the formation of excessively overgrown camphene dendrites due to the extremely low solidification velocity. To accomplish this, hydroxyapatite (HA)/slurries with various solid loadings (10, 15, and 20 vol%) were frozen at 35°C for 20 h. The frozen samples were freeze dried and sintered at 1250°C for 3 h. All of the fabricated samples showed highly porous structures with large pore channels >100 μm in size and dense HA walls without any noticeable defects, such as cracks or pores. As the initial solid loading was increased from 10 to 20 vol%, the porosity of the sample decreased linearly from 76% to 55%, while the pore channels became narrower. However, the compressive strength was remarkably improved from 2.5 to 16.7 MPa.     

Synthesis and characterization of new injectable and degradable dextran-based hydrogels

Injectable and degradable hydrogels are very interesting networks for drug delivery and cell transplantation applications since they can be administered in the human body in a minimally invasive way. In most cases, the crosslinking reaction occurs by photopolymerisation or free radical polymerisation; however, the use of chemical initiators may promote cell death. In the current work, injectable and degradable dextran-based hydrogels were prepared without the use of initiators. Dextran, a natural glucose-containing polysaccharide, was oxidized with sodium periodate (dexOx) and the derivatives characterized by NMR and FTIR spectroscopy's as well as by colorimetric techniques. The oxidized derivatives were crosslinked with adipic acid dihydrazide (AAD), forming a gel within 2-4 min. The obtained hydrogels were characterized by their mechanical properties, swelling and degradation behavior under physiologic conditions. In addition, the hydrogel interior morphology as well as porous structure was evaluated by scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). MIP analysis showed that dexOx hydrogels crosslinked with 10% of AAD were macroporous with pore sizes ranging from 0.32 to 0.08 μm. As expected, the average pore size increased during hydrogel degradation as confirmed by SEM and MIP studies.     

Preparation of chitosan-sodium alginate/bioactive glass composite cartilage scaffolds with high cell activity and bioactivity

Chitosan-sodium alginate/bioactive glass (CSB) composite cartilage scaffold with outstanding in vitro mineralization property and cytocompatibility is synthesized by freeze drying method. The effect of bioactive glass (BG) addition on the microstructure, porosity, swelling/degradation ratio, in vitro mineralization property and cytocompatibility of CSB scaffold is investigated by the characterization techniques of SEM, XRD, FTIR and BET. Results showed that CSB composite cartilage scaffold had a three-dimensional (3D) porous structure, and both porosity and average pore size met the requirements of cartilage tissue repair. Among, the typical CSB-1.0 had the largest overall pore size and lowest compressive modulus (1.083 ± 0.002 MPa). As the amount of BG increased, pore volume and porosity of CSB scaffolds gradually decreased, and the swelling and degradation ratios gradually reduced. After immersing in SBF for 3 d, cauliflower like hydroxyapatite (HA) was formed on CSB surface, indicating that the scaffold had good in vitro mineralization property. Moreover, the introduction of BG into the composite scaffold can improve the relative cell viability of MC3T3-E1 cells, and CSB-1.0 has the strongest ability to promote the proliferation of cells. Therefore, the as-obtained CSB scaffold can be used as a strong candidate for cartilage tissue engineering scaffold to meet clinical needs.     

Reinforcement of pH‐responsive γ‐poly(glutamic acid)/chitosan hydrogel for orally administrable colon‐targeted drug delivery

Orally administrable hydrogel was prepared by crosslinking chitosan (CS) with γ‐poly(glutamic acid) (γ‐PGA) for an excellent pH‐responsive colon‐targeted drug delivery system. The stable crosslinked amide bond appeared in the shifted region of FTIR spectroscopy, and the tensile strength and elastic modulus were also reduced by crosslinking of CS and γ‐PGA. The surfaces of crosslinked hydrogel have a homogeneous pore array with pore size corresponding to the varied blending ratio. The swelling ratio was dramatically changed by increasing the pH from 3 to 6, and the responsiveness of swelling ratio to the reversible pH changes between 3 and 10 was reliable for 72 h. The drug diffusion rate was mainly dependent on the pH, and a water‐soluble tetrazolium (WST‐1) assay indicated that cytocompatibility of the hydrogel was in an acceptable range. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci. 2013     

Interpenetrating networks hydrogels based on hyaluronic acid for drug delivery and tissue engineering

There are several techniques for preparing hydrogel biomaterials. Among these techniques, preparation of interpenetrating polymer networks hydrogel (IPNs) has been more interested during last years. IPNs are fabricated by the incorporation of monomers or polymeric chains in hydrogel network. Natural polymers such as hyaluronic acids have some advantages such as biocompatibility, biodegradability and non-toxicity. In this review, we would have a brief view to the interpenetrating polymer networks hydrogel based on hyaluronic acids and its applications as a drug delivery system and tissue engineering applications.     

Fabrication and compressive strength of porous hydroxyapatite scaffolds with a functionally graded core/shell structure

A novel type of porous hydroxyapatite (HA) scaffolds with a functionally graded core/shell structure was fabricated by freeze casting HA/camphene slurries with various HA contents into fugitive molds containing a graphite template with three-dimensionally interconnected pores for the creation of a highly porous core. All the fabricated samples had functionally graded core/shell structures with 3-D periodic pore networks in a core surrounded by a relatively dense shell. The overall porosity of the sample decreased from 60 to 38 vol% with increasing HA content in the HA/camphene slurry from 20 to 36 vol% due to a decrease in porosity in both the core and shell regions. In addition, the compressive strength was improved remarkably from 12 ± 1.1 to 32 ± 3.0 MPa. The in vitro cell test using a pre-osteoblast cell line showed that the samples had good biocompatibility.     

Fabrication and characterization of porous silver powder prepared by spray drying and calcining technology

High porosity porous silver powder with about 100 µm average size and 5 µm pore size was fabricated by spray drying and calcining technology. Effects of calcining temperature and process of spray-dried powder on the phases, grain size, particle morphology and pore microstructure of silver powder were investigated. The results showed that porous silver with approximately spherical shape and via hole structure was obtained using 0.25 mol Ag₂CO₃ solution of ammonia water, which was spray-dried at 200 °C and calcined at 400 °C for 30 min with heat treatment technology curve of gradient temperature in air. And there were not Ag₂CO₃, Ag₂O and AgO phases existing in the porous silver. However, using 0.25 mol Ag₂CO₃ solution of ammonia water, the porous silver powder could not be fabricated by spray pyrolysis technology with a solution feed rate of 300 mL/h, flux of carrier gas of 0.30 MPa, and 640 °C furnace set temperature.