A chitosan/beta-glycerophosphate thermo-sensitive gel for the delivery of ellagic acid for the treatment of brain cancer

In-Situ Forming pH and Thermosensitive Injectable Hydrogels to Stimulate Angiogenesis: Potential Candidates for Fast Bone Regeneration Applications

Biomaterials that promote angiogenesis are required for repair and regeneration of bone. In-situ formed injectable hydrogels functionalised with bioactive agents, facilitating angiogenesis have high demand for bone regeneration. In this study, pH and thermosensitive hydrogels based on chitosan (CS) and hydroxyapatite (HA) composite materials loaded with heparin (Hep) were investigated for their pro-angiogenic potential. Hydrogel formulations with varying Hep concentrations were prepared by sol-gel technique for these homogeneous solutions were neutralised with sodium bicarbonate (NaHCO3) at 4 °C. Solutions (CS/HA/Hep) constituted hydrogels setting at 37 °C which was initiated from surface in 5-10 minutes. Hydrogels were characterised by performing injectability, gelation, rheology, morphology, chemical and biological analyses. Hydrogel solutions facilitated manual dropwise injection from 21 Gauge which is highly used for orthopaedic and dental administrations, and the maximum injection force measured through 19 G needle (17.191 ± 2.296N) was convenient for manual injections. Angiogenesis tests were performed by an ex-ovo chick chorioallantoic membrane (CAM) assay by applying injectable solutions on CAM, which produced in situ hydrogels. Hydrogels induced microvascularity in CAM assay this was confirmed by histology analyses. Hydrogels with lower concentration of Hep showed more efficiency in pro-angiogenic response. Thereof, novel injectable hydrogels inducing angiogenesis (CS/HA/Hep) are potential candidates for bone regeneration and drug delivery applications.

A novel multiple emulsion enhanced immunity via its biomimetic delivery approach

A special emulsion with biomimetic structural dynamic properties was fabricated, inducing efficient vaccine–cell interaction and robust immunity.

Improving Topical Skin Delivery of Monocrotaline Via Liposome Gel-based Nanosystems

Background:

In this study, a liposomal gel based on a pH-gradient method was used to increase the skin-layer retention of monocrotaline (MCT) for topical administration.

Methods:

Using the Box-Behnken design, different formulations were designed to form liposome suspensions with optimal encapsulation efficiency (EE%) and stability factor (KE). In order to keep MCT in liposomes and accumulate in skin slowly and selectively, MCT liposome suspensions were engineered into gels.

Results:

A pH-gradient method was used to prepare liposome suspensions. The optimal formulation of liposome suspensions (encapsulation efficiency: 83.10 ± 0.21%) was as follows: MCT 12 mg, soybean phosphatidyl choline (sbPC) 200 mg, cholesterol (CH) 41 mg, vitamin E (VE) 5 mg, and citric acid buffer solution (CBS) 4.0 10 mL (pH 7.0). The final formulation of liposomal gels consisted of 32 mL liposome suspensions, 4.76 mL deionized water, 0.40 g Carbopol-940, 1.6 g glycerol, 0.04 g methylparaben, and a suitable amount of triethanolamine for pH value adjustment. The results of in vitro drug release showed that MCT in liposomal gels could be released in 12 h constantly in physiological saline as a Ritger-Peppas model. Compared with plain MCT in gel form, liposomal MCT in gel had higher skin retention in vitro.

Conclusion:

In this study, liposomal gels were formed for greater skin retention of MCT. It is potentially beneficial for reducing toxicities of MCT by topical administration with liposomal gel.

An injectable thermosensitive hydrogel for sustained release of apelin-13 to enhance flap survival in rat random skin flap

With the advantage of handy process, random pattern skin flaps are generally applied in limb reconstruction and wound repair. Apelin-13 is a discovered endogenous peptide, that has been shown to have potent multiple biological functions. Recently, thermosensitive gel-forming systems have gained increasing attention as wound dressings due to their advantages. In the present study, an apelin-13-loaded chitosan (CH)/β-sodium glycerophosphate (β-GP) hydrogel was developed for promoting random skin flap survival. Random skin flaps were created in 60 rats after which the animals were categorized to a control hydrogel group and an apelin-13 hydrogel group. The water content of the flap as well as the survival area were then measured 7 days post-surgery. Hematoxylin and eosin staining was used to evaluate the flap angiogenesis. Cell differentiation 34 (CD34) and vascular endothelial growth factor (VEGF) levels were detected by immunohistochemistry and Western blotting. Tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were assessed by enzyme linked immunosorbent assays (ELISAs). Oxidative stress was estimated via the activity of tissue malondialdehyde (MDA) and superoxide dismutase (SOD). Our results showed that CH/β-GP/apelin-13 hydrogel could not only reduce the tissue edema, but also improve the survival area of flap. CH/β-GP/apelin-13 hydrogel also upregulated levels of VEGF protein and increased mean vessel densities. Furthermore, CH/β-GP/apelin-13 hydrogel was shown to significantly inhibit the expression of TNF-α and IL-6, along with increasing the activity of SOD and suppressing the MDA content. Taken together, these results indicate that this CH/β-GP/apelin-13 hydrogel may be a potential therapeutic way for random pattern skin flap.

Investigation on solution-to-gel characteristic of thermosensitive and mucoadhesive biopolymers for the development of moxifloxacin-loaded sustained release periodontal in situ gels

The objectives of present research were to develop and characterize thermosensitive and mucoadhesive polymer-based sustained release moxifloxacin in situ gels for the treatment of periodontal diseases. Poloxamer- and chitosan-based in situ gels are in liquid form at room temperature and transform into gel once administered into periodontal pocket due to raise in temperature to 37 °C. Besides solution-to-gel characteristic of polymers, their mucoadhesive nature aids the gel to adhere to mucosa in periodontal pocket for prolonged time and releases the drug in sustained manner. These formulations were prepared using cold method and evaluated for pH, solution-gel temperature, syringeability and viscosity. In vitro drug release studies were conducted using dialysis membrane at 37 °C and 50 rpm. Antimicrobial studies carried out against Aggregatibacter actinomycetemcomitans (A.A.) and Streptococcus mutans (S. Mutans) using agar cup-plate method. The prepared formulations were clear and pH was at 7.01-7.40. The viscosity of formulations was found to be satisfactory. Among the all, formulations comprising of 21% poloxamer 407 and 2% poloxamer 188 (P5) and in combination with 0.5% HPMC (P6) as well as 2% chitosan and 70% β-glycerophosphate (C6) demonstrated an ideal gelation temperature (33-37 °C) and sustained the drug release for 8 h. Formulations P6 and C6 showed promising antimicrobial efficacy with zone of inhibition of 27 mm for A.A. and 55 mm for S. Mutans. The developed sustained release in situ gel formulations could enhance patient's compliance by reducing the dosing frequency and also act as an alternative treatment to curb periodontitis.

Scaffolding Strategies for Tissue Engineering and Regenerative Medicine Applications

During the past two decades, tissue engineering and the regenerative medicine field have invested in the regeneration and reconstruction of pathologically altered tissues, such as cartilage, bone, skin, heart valves, nerves and tendons, and many others. The 3D structured scaffolds and hydrogels alone or combined with bioactive molecules or genes and cells are able to guide the development of functional engineered tissues, and provide mechanical support during in vivo implantation. Naturally derived and synthetic polymers, bioresorbable inorganic materials, and respective hybrids, and decellularized tissue have been considered as scaffolding biomaterials, owing to their boosted structural, mechanical, and biological properties. A diversity of biomaterials, current treatment strategies, and emergent technologies used for 3D scaffolds and hydrogel processing, and the tissue-specific considerations for scaffolding for Tissue engineering (TE) purposes are herein highlighted and discussed in depth. The newest procedures focusing on the 3D behavior and multi-cellular interactions of native tissues for further use for in vitro model processing are also outlined. Completed and ongoing preclinical research trials for TE applications using scaffolds and hydrogels, challenges, and future prospects of research in the regenerative medicine field are also presented.

Injectable chitosan/gelatin/bioactive glass nanocomposite hydrogels for potential bone regeneration: In vitro and in vivo analyses

The present work describes in vitro and in vivo behaviors of thermosensitive composite hydrogels based on polymers/bioactive glass nanoparticles. Assays in SBF (simulated body fluid) solution showed that loss of hydrogel mass in vitro was decreased by 4.3% when bioactive glass nanoparticles (nBG) were incorporated, and confirmed the bioactivity of nBG containing hydrogels. In vitro assays demonstrated the cytocompatibility of the hydrogels with encapsulated rat bone marrow mesenchymal stem cells (BMSC). Crystal violet assays showed a 27% increase in cell viability when these cells were seeded in hydrogels containing nBG. In vivo biocompatibility was examined by injecting hydrogels into the dorsum of Swiss rats. The results indicated that the prepared hydrogels were nontoxic upon subcutaneous injection, and could be candidates for a safe in situ gel-forming system. Injection of the hydrogels into a rat tibial defect allowed preliminary evaluation of the hydrogels' regenerative potential. Micro Computed Tomography analysis suggested that more new tissue was formed in the defects treated with the hydrogels. Taken together, our data suggest that the developed injectable composite hydrogels possess properties which make them suitable candidates for use as temporary injectable matrices for bone regeneration.

Sustained Releasing of Methotrexate from Injectable and Thermosensitive Chitosan-Carbon Nanotube Hybrid Hydrogels Effectively Controls Tumor Cell Growth

Injectable thermosensitive hydrogels have been widely investigated for drug delivery systems. Chitosan (CH) is one of the most abundant natural polymers, and its biocompatibility and biodegradability make it a favorable polymer for thermosensitive hydrogel formation. The addition of nanoparticles can improve its drug release behavior, remote actuation capability, and biological interactions. Carbon nanotubes (CNTs) have been studied for the use in drug delivery systems, and they can act as drug delivery vehicles to improve the delivery of different types of therapeutic agents. In this work, carbon nanotubes were incorporated into a thermosensitive and injectable hydrogel formed by chitosan and β-glycerophosphate (β-GP) (CH-β-GP-CNTs). The hybrid hydrogels loaded with methotrexate (MTX) were liquid at room temperature and became a solidified gel at body temperature. A number of tests including scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray diffraction were utilized to characterize the MTX-loaded CH-β-GP-CNT hybrid hydrogels. The cell viability (alamarBlue) assay showed that hydrogels containing CNT (0.1%) were not toxic to the 3T3 cells. In vitro MTX release study revealed that CNT-containing hydrogels (with 0.1% CNT) demonstrated a decreased MTX releasing rate compared with control hydrogels without CNT. The cultured MCF-7 breast cancer cells were used to evaluate the efficacy of CH-β-GP-CNT hybrid hydrogels delivering MTX on the control of tumor cell growth. Results demonstrated that CNT (0.1%) in the hydrogel enhanced the MTX antitumor function. Our study indicates that a thermosensitive CH-β-GP-CNT hybrid hydrogel can be used as a potential breast cancer therapy system for controlled delivery of MTX.

Chitosan/β-glycerophosphate in situ gelling mucoadhesive systems for intravesical delivery of mitomycin-C

The development of mucoadhesive in situ gelling formulations for intravesical application may improve the therapeutic outcomes of bladder cancer patients. In this work, chitosan/β-glycerophosphate (CHIGP) thermosensitive formulations have been prepared using three different chitosan grades (62, 124 and 370 kDa). Their ability to form in situ gelling systems triggered by changes in temperature upon administration to urinary bladder were evaluated using vial inversion and rheological methods. Texture analysis was used to study their mucoadhesive properties as well as syringeability through the urethral catheter. The retention of CHIGP formulations, with fluorescein sodium as the model drug, was studied on porcine urinary bladder mucosa ex vivo using the flow-through technique and fluorescent microscopy. CHIGP formulations containing mitomycin-C were prepared and drug release was studied using in vitro dialysis method. It was established that the molecular weight of chitosan influenced the thermogelling, mucoadhesive and drug release behaviour of the in situ gelling delivery systems. Formulations prepared from chitosan with greatest molecular weight (370 kDa) were found to be the most promising for intravesical application due to their superior gelling properties and in vitro retention in the bladder.

The effect of complexation with cyclodextrins on the antioxidant and antimicrobial activity of ellagic acid

PURPOSE

The aim of the paper was to develop the simple procedures for preparation of inclusion complexes of ellagic acid (EA) with cyclodextrins (CDs) and to investigate their antioxidant and antimicrobial activity.

METHODS

The structural characterization was carried out using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR) methods. The phase solubility technique was used to investigate the interactions between 'host' and 'guest' molecules and to estimate the molar ratio between them. The antioxidant and antimicrobial activity of EA and inclusion complexes were determined.

RESULTS

The apparent stability constants were found to be 117 dm³ mol^-1 for the complex with β-CD and 161 dm³ mol^-1 for the complex with (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD). The results of phase-solubility studies showed that EA formed the inclusion complexes with CDs in the molar ratio of 1:1. The calculated half-maximal inhibitory concentration was 41.18 μg cm^-3 for butyl hydroxy toluene, 1.96 μg cm^-3 for EA, 0.88 μg cm^-3 for inclusion complex with HP-β-CD, and 1.27 μg cm^-3 for inclusion complex with β-CD.

CONCLUSION

The stability constants indicated the rapid release of EA from the inclusion complexes in the aqueous medium at 25 °C. The antioxidant activity of EA was increased, while the antimicrobial activity was preserved after complexation with CDs.

Novel application of pluronic lecithin organogels (PLOs) for local delivery of synergistic combination of docetaxel and cisplatin to improve therapeutic efficacy against ovarian cancer

The synergistic combination of docetaxel (DTX) and cisplatin (CIS) by local drug delivery with a pluronic lecithin organogel (PLO) to facilitate high drug concentrations at tumor sites and less nonspecific distribution to normal organs is thought to be beneficial in chemotherapy. In this study, using Capryol-90 (C90) with the addition of lecithin as the oil phase was developed to carry DTX, which was then incorporated into a PLO-containing CIS to formulate a dual-drug injectable PLO for local delivery. An optimal PLO composite, P₁₃L_0.15O_1.5, composed of PF127:lecithin:C90 at a 13:0.15:1.5 weight ratio was obtained. The sol-gel transition temperature of P₁₃L_0.15O_1.5 was found to be 33 °C. Tumor inhibition studies illustrated that DTX/CIS-loaded P₁₃L_0.15O_1.5 could efficiently suppress tumor growth by both intratumoral and peritumoral injections in SKOV-3 xenograft mouse model. Pharmacokinetic studies showed that subcutaneous administration of P₁₃L_0.15O_1.5 was able to sustain the release of DTX and CIS leading to their slow absorption into the systemic circulation resulting in lower area under the plasma concentration curve at 0-72 h (AUC_0-72) and maximum concentration (C_max) values but longer half-life (T_1/2) and mean residence time (MRT) values. An in vivo biodistribution study showed lower DTX and CIS concentrations in organs compared to other treatment groups after IT administration of the dual drug-loaded P₁₃L_0.15O_1.5. It was concluded that the local co-delivery of DTX and CIS by PLOs may be a promising and effective platform for local anticancer drug delivery with minimal systemic toxicities.

Injectable dynamic covalent hydrogels of boronic acid polymers cross-linked by bioactive plant-derived polyphenols

We report here the development of hydrogels formed at physiological conditions using PEG (polyethylene glycol) based polymers modified with boronic acids (BAs) as backbones and the plant derived polyphenols ellagic acid (EA), epigallocatechin gallate (EGCG), tannic acid (TA), nordihydroguaiaretic acid (NDGA), rutin trihydrate (RT), rosmarinic acid (RA) and carminic acid (CA) as linkers. Rheological frequency sweep and single molecule force spectroscopy (SMFS) experiments show that hydrogels linked with EGCG and TA are mechanically stiff, arising from the dynamic covalent bond formed by the polyphenol linker and boronic acid functionalized polymer. Stability tests of the hydrogels in physiological conditions revealed that gels linked with EA, EGCG, and TA are stable. We furthermore showed that EA- and EGCG-linked hydrogels can be formed via in situ gelation in pH 7.4 buffer, and provide long-term steady state release of bioactive EA. In vitro experiments showed that EA-linked hydrogel significantly reduced the viability of CAL-27 human oral cancer cells via gradual release of EA.

Evaluation of a novel oxiconazole nitrate formulation: The thermosensitive gel

Superficial fungal infections caused by Candida species are common skin diseases. Therefore, this study aimed to develop a new formulation containing oxiconazole nitrate, which is an azole group derivative for antifungal treatment, as a thermosensitive gel since there has been no literature study until now. MIC value of the novel thermosensitive formulation against three Candida species was calculated and time-dependent antifungal activity analysis was performed. Viscosity, transition temperature Tsol-gel (°C) and gelation time of the thermosensitive gel formulation were also determined in the viscometer. The measurements performed on the tensilometer device were analyzed for adhesion hardness and elongation percentages of the formulation. In the FT-IR spectrometer, the spectrum of solution and gel state was compared between 650 and 4000 cm-1 and it was found that there is no difference between them. It was found that the temperature is reversible on the formulation and did not cause any disruption of its components. Characterization parameters of the thermosensitive gel formulation containing oxiconazole nitrate and time-dependent activity against Candida species was observed to be the same as those of the solution containing only oxiconazole nitrate. MIC, MFC and time-dependent antifungal analysis did not show any particular difference between formulation and oxiconazole nitrate itself. Thermosensitive gel formulation containing oxiconazole nitrate was found to be effective on superficial fungal infections. We believe it is also appropriate for in vivo usage, but it is necessary to perform animal and human research. It is also needed to evaluate the formulation against other etiologic agents of superficial fungal infections.

Investigation on solution-to-gel characteristic of thermosensitive and mucoadhesive biopolymers for the development of moxifloxacin-loaded sustained release periodontal in situ gels

The objectives of present research were to develop and characterize thermosensitive and mucoadhesive polymer-based sustained release moxifloxacin in situ gels for the treatment of periodontal diseases. Poloxamer- and chitosan-based in situ gels are in liquid form at room temperature and transform into gel once administered into periodontal pocket due to raise in temperature to 37 °C. Besides solution-to-gel characteristic of polymers, their mucoadhesive nature aids the gel to adhere to mucosa in periodontal pocket for prolonged time and releases the drug in sustained manner. These formulations were prepared using cold method and evaluated for pH, solution-gel temperature, syringeability and viscosity. In vitro drug release studies were conducted using dialysis membrane at 37 °C and 50 rpm. Antimicrobial studies carried out against Aggregatibacter actinomycetemcomitans (A.A.) and Streptococcus mutans (S. Mutans) using agar cup-plate method. The prepared formulations were clear and pH was at 7.01-7.40. The viscosity of formulations was found to be satisfactory. Among the all, formulations comprising of 21% poloxamer 407 and 2% poloxamer 188 (P5) and in combination with 0.5% HPMC (P6) as well as 2% chitosan and 70% β-glycerophosphate (C6) demonstrated an ideal gelation temperature (33-37 °C) and sustained the drug release for 8 h. Formulations P6 and C6 showed promising antimicrobial efficacy with zone of inhibition of 27 mm for A.A. and 55 mm for S. Mutans. The developed sustained release in situ gel formulations could enhance patient's compliance by reducing the dosing frequency and also act as an alternative treatment to curb periodontitis.

Efficacy of thermosensitive chitosan/β-glycerophosphate hydrogel loaded with β-cyclodextrin-curcumin for the treatment of cutaneous wound infection in rats

Wound infection has been a persistent problem that is common and costly. Thermosensitive hydrogel has been demonstrated to be a suitable dressing candidate due to its high moldability, easy administration and ability to maintain a moist topical environment at the wound bed. In the present study, a novel thermosensitive hydrogel was successfully prepared and characterized to have a porous inner structure and a sustained curcumin-releasing profile. The wound healing ability of the hydrogel was investigated in a wound infection model in rats. On analysis, it was observed that the hydrogel complex-dressed wounds exhibited a faster wound closure rate compared with gauze-covered wounds, which was paralleled with improved histological outcomes that were observed. Additionally, the results of in vitro antimicrobial, anti-oxidant, western blot analysis and reverse transcription-quantitative polymerase chain reaction assays indicated that the hydrogel complex had distinct anti-oxidative, antimicrobial and anti-nuclear factor-κB-signaling capacities. These results suggest that this novel hydrogel may be a suitable candidate for facilitating the healing of infected cutaneous wounds in rats.

Thermosensitive hydrogels a versatile concept adapted to vaginal drug delivery

Vaginal drug delivery represents an attractive strategy for local and systemic delivery of drugs otherwise poorly absorbed after oral administration. The rather dense vascular network, mucus permeability and the physiological phenomenon of the uterine first-pass effect can all be exploited for therapeutic benefit. However, several physiological factors such as an acidic pH, constant secretion, and turnover of mucus as well as varying thickness of the vaginal epithelium can impact sustained drug delivery. In recent years, polymers have been designed to tackle challenges mentioned above. In particular, thermosensitive hydrogels hold great promise due to their stability, biocompatibility, adhesion properties and adjustable drug release kinetics. Here, we discuss the physiological and anatomical uniqueness of the vaginal environment and how it impacts the safe and efficient vaginal delivery and also reviewed several thermosensitive hydrogels deemed suitable for vaginal drug delivery by addressing specific characteristics, which are essential to engage the vaginal environment successfully.

In vitro and in vivo acute response towards injectable thermosensitive chitosan/TEMPO-oxidized cellulose nanofiber hydrogel

TEMPO-oxidized cellulose nanofiber (TOCNF) is a natural material with many promising properties, including biocompatibility and degradability. In this study, we integrated TOCNF at different concentrations (0.2, 0.4, 0.6, 0.8% w/v) with chitosan (CS) and created a thermosensitive injectable hydrogel intended for biomedical applications. These hydrogels can undergo sol-gel transition at body temperature through interactions between chitosan and β-glycerophosphate. The addition of TOCNF resulted in faster gelation time and increased porosity. These hydrogels with TOCNF showed improved biocompatibility both in vitro and in vivo compared to CS hydrogel. Both MC3T3-E1 pre-osteoblast cells and L929 fibroblast cells showed biocompatibility towards CS/TOCNF 0.4. After 7days of implantation, initial inflammatory response to CS/TOCNF 0.4 was found. Such response was significantly subsided within 14days. Cell infiltration within the hydrogel was also prominent, showing anti-inflammatory or wound healing (M2) macrophage at 14days after implantation. These results showed that the addition of TOCNF could significantly improve the biocompatibility of CS hydrogel as a biomaterial for biomedical application.

Microenvironmental Control of MUC1 Aptamer-Guided Acid-Labile Nanoconjugate within Injectable Microporous Hydrogels

Although aptamers are well-known as cell-specific membrane biomarkers for tumor-targeted therapy, it is important to avoid their degradation by nucleases in vivo. In this study, we developed a MUC1 aptamer-doxorubicin nanoconjugate (APT-DOX) through an acid-labile linkage and embedded APT-DOX into a thermosensitive hydrogel for antitumor therapy. The hydrogels exhibit a sol-gel transition upon intratumoral injection, resulting in the protection and controlled release control of APT-DOX with the shielding of the gel network. Moreover, the released APT-DOX was prone to be enriched at the tumor cells due to specific intracellular transport by the overexpressing MUC1 protein; however, APT-DOX regained the free DOX form via the rupture of the linkage under tumor cells lysosome acidic conditions and achieved increased concentration in the nucleus for antitumor treatment.

Nanodiamond-based injectable hydrogel for sustained growth factor release: Preparation, characterization and in vitro analysis

Nanodiamonds (NDs) represent an emerging class of carbon nanomaterials that possess favorable physical and chemical properties to be used as multifunctional carriers for a variety of bioactive molecules. Here we report the synthesis and characterization of a new injectable ND-based nanocomposite hydrogel which facilitates a controlled release of therapeutic molecules for regenerative applications. In particular, we have formulated a thermosensitive hydrogel using gelatin, chitosan and NDs that provides a sustained release of exogenous human vascular endothelial growth factor (VEGF) for wound healing applications. Addition of NDs improved the mechanical properties of the injectable hydrogels without affecting its thermosensitive gelation properties. Biocompatibility of the generated hydrogel was verified by in vitro assessment of apoptotic gene expressions and anti-inflammatory interleukin productions. NDs were complexed with VEGF and the inclusion of this complex in the hydrogel network enabled the sustained release of the angiogenic growth factor. These results suggest for the first time that NDs can be used to formulate a biocompatible, thermosensitive and multifunctional hydrogel platform that can function both as a filling agent to modulate hydrogel properties, as well as a delivery platform for the controlled release of bioactive molecules and growth factors.

STATEMENT OF SIGNIFICANCE

One of the major drawbacks associated with the use of conventional hydrogels as carriers of growth factors is their inability to control the release kinetics of the loaded molecules. In fact, in most cases, a burst release is inevitable leading to diminished therapeutic effects and unsuccessful therapies. As a potential solution to this issue, we hereby propose a strategy of incorporating ND complexes within an injectable hydrogel matrix. The functional groups on the surface of the NDs can establish interactions with the model growth factor VEGF and promote a prolonged release from the polymer network, therefore, providing a longer therapeutic effect. Our strategy demonstrates the efficacy of using NDs as an essential component for the design of a novel injectable nanocomposite system with improved release capabilities.

Structural and biological properties of thermosensitive chitosan-graphene hybrid hydrogels for sustained drug delivery applications

Chitosan has the ability to make injectable thermosensitive hydrogels which has been highly investigated for drug delivery applications. The addition of nanoparticles is one way to increase the mechanical strength of thermosensitive chitosan hydrogel and subsequently and control the burst release of drug. Graphene nanoparticles have shown unique mechanical, optical and electrical properties which can be exploited for biomedical applications, especially in drug delivery. This study, have focused on the mechanical properties of a thermosensitive and injectable hybrid chitosan hydrogel incorporated with graphene nanoparticles. Scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD) have been used for morphological and chemical characterization of graphene infused chitosan hydrogels. The cell viability and cytotoxicity of graphene-contained hydrogels were analyzed using the alamarBlue^® technique. In-vitro methotrexate (MTX) release was investigated from MTX-loaded hybrid hydrogels as well. As a last step, to evaluate their efficiency as a cancer treatment delivery system, an in vitro anti-tumor test was also carried out using MCF-7 breast cancer cell lines. Results confirmed that a thermosensitive chitosan-graphene hybrid hydrogel can be used as a potential breast cancer therapy system for controlled delivery of methotrexate. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2381-2390, 2017.

Non-covalently crosslinked chitosan nanofibrous mats prepared by electrospinning as substrates for soft tissue regeneration

Chitosan (CS) membranes obtained by electrospinning are potentially ideal substrates for soft tissue engineering as they combine the excellent biological properties of CS with the extracellular matrix (ECM)-like structure of nanofibrous mats. However, the high amount of acid solvents required to spun CS solutions interferes with the biocompatibility of CS fibres. To overcome this limitation, novel CS based solutions were investigated in this work. Low amount of acidic acid (0.5M) was used and dibasic sodium phosphate (DSP) was introduced as ionic crosslinker to improve nanofibres water stability and to neutralize the acidic pH of electrospun membranes after fibres soaking in biological fluids. Randomly oriented and aligned nanofibres (128±19nm and 140±41nm, respectively) were obtained through electrospinning process (voltage of 30kV, 30μL/min flow rate and temperature of 39°C) showing mechanical properties similar to those of soft tissues (Young Modulus lower than 40MPa in dry condition) and water stability until 7 days. C2C12 myoblast cell line was cultured on CS fibres showing that the aligned architecture of substrate induces cell orientation that can enhance skeletal muscle regeneration.

Recent advances in engineered chitosan-based nanogels for biomedical applications

Recent progress in the preparation and biomedical applications of engineered chitosan-based nanogels has been comprehensively reviewed.

Novel low temperature (<37 °C) chitosan hydrogel fabrication under the synergistic effect of graphene oxide

A low temperature chitosan hydrogel was fabricated under the synergistic effect of graphene oxide, and may be applied in hydrogel medical coatings.

Development of a dual drug-loaded hydrogel delivery system for enhanced cancer therapy: in situ formation, degradation and synergistic antitumor efficiency

A stimuli-responsive, biodegradable, and dual drug-loaded hydrogel delivery system was formed in situ for combination drug therapy of cancer in vivo.

Hydrogels for central nervous system therapeutic strategies

The central nervous system shows a limited regenerative capacity, and injuries or diseases, such as those in the spinal, brain and retina, are a great problem since current therapies seem to be unable to achieve good results in terms of significant functional recovery. Different promising therapies have been suggested, the aim being to restore at least some of the lost functions. The current review deals with the use of hydrogels in developing advanced devices for central nervous system therapeutic strategies. Several approaches, involving cell-based therapy, delivery of bioactive molecules and nanoparticle-based drug delivery, will be first reviewed. Finally, some examples of injectable hydrogels for the delivery of bioactive molecules in central nervous system will be reported, and the key features as well as the basic principles in designing multifunctional devices will be described.

In vitro proliferation and osteogenic differentiation of human dental pulp stem cells in injectable thermo-sensitive chitosan/β-glycerophosphate/hydroxyapatite hydrogel

Injectable thermo-sensitive hydrogels have a potential application in bone tissue engineering for their sensitivities and minimal invasive properties. Human dental pulp stem cells have been considered a promising tool for tissue reconstruction. The objective of this study was to investigate the proliferation and osteogenic differentiation of dental pulp stem cells in injectable thermo-sensitive chitosan/β-glycerophosphate/hydroxyapatite hydrogel in vitro. The chitosan /β-glycerophosphate hydrogel and chitosan/β-glycerophosphate/hydroxyapatite hydrogel were prepared using the sol-gel method. The injectability of chitosan /β-glycerophosphate hydrogel and chitosan/β-glycerophosphate/hydroxyapatite hydrogel was measured using a commercial disposable syringe. Scanning electron microscopy was used to observe the inner structure of hydrogels. Then dental pulp stem cells were seeded in chitosan /β-glycerophosphate hydrogel and chitosan/β-glycerophosphate/hydroxyapatite hydrogel, respectively. The growth of dental pulp stem cells was periodically observed under an inverted microscope. The proliferation of dental pulp stem cells was detected by using an Alamar Blue kit, while cell apoptosis was determined by using a Live/Dead Viability/Cytotoxicity kit. The osteogenic differentiations of dental pulp stem cells in chitosan /β-glycerophosphate hydrogel and chitosan/β-glycerophosphate/hydroxyapatite hydrogel were evaluated by alkaline phosphatase activity assay and mRNA expression of osteogenesis gene for 21 days in osteogenic medium. The results indicated that there was no significant difference between chitosan /β-glycerophosphate hydrogel and chitosan/β-glycerophosphate/hydroxyapatite hydrogel in injectability. Cells within the chitosan/β-glycerophosphate/hydroxyapatite hydrogel displayed a typical adherent cell morphology and rapid proliferation with high cellular viability after 14 days of culture. Dental pulp stem cells seeded in chitosan/β-glycerophosphate/hydroxyapatite hydrogels had a higher alkaline phosphatase activity and better up-regulation of gene expression levels of Runx-2, Collagen I, alkaline phosphatase and osteocalcin than in chitosan /β-glycerophosphate hydrogels after osteogenic differentiation. These results demonstrated that the chitosan/β-glycerophosphate/hydroxyapatite hydrogel had excellent cellular compatibility and the superiority in promoting dental pulp stem cells osteogenic differentiation in vitro, showing that the combination of dental pulp stem cells and chitosan/β-glycerophosphate/hydroxyapatite hydrogel has the potential to be used for bone tissue engineering.

Injectable hydrogel-based drug delivery systems for local cancer therapy

Common chemotherapy is often associated with adverse effects in normal cells and tissues. As an alternative approach, localized chemotherapy can diminish the toxicity of systemic chemotherapy while providing a sustained release of the chemotherapeutics at the target tumor site. Therefore, injectable biodegradable hydrogels as drug delivery systems for chemotherapeutics have become a matter of importance. Here, we review the application of a variety of injectable hydrogel-based drug delivery systems, including thermosensitive, pH-sensitive, photosensitive, dual-sensitive, as well as active targeting hydrogels, for the treatment of different types of cancer. Generally, injectable hydrogel-based drug delivery systems are found to be more efficacious than the conventional systemic chemotherapy in terms of cancer treatment.

Sodium dodecyl sulfate/β-cyclodextrin vesicles embedded in chitosan gel for insulin delivery with pH-selective release

In an answer to the challenge of enzymatic instability and low oral bioavailability of proteins/peptides, a new type of drug-delivery vesicle has been developed. The preparation, based on sodium dodecyl sulfate (SDS) and β-cyclodextrin (β-CD) embedded in chitosan gel, was used to successfully deliver the model drug-insulin. The self-assembled SDS/β-CD vesicles were prepared and characterized by particle size, zeta potential, appearance, microscopic morphology and entrapment efficiency. In addition, both the interaction of insulin with vesicles and the stability of insulin loaded in vesicles in the presence of pepsin were investigated. The vesicles were crosslinked into thermo-sensitive chitosan/β-glycerol phosphate solution for an in-situ gel to enhance the dilution stability. The in vitro release characteristics of insulin from gels in media at different pH values were investigated. The insulin loaded vesicles–chitosan hydrogel (IVG) improved the dilution stability of the vesicles and provided pH-selective sustained release compared with insulin solution–chitosan hydrogel (ISG). In vitro, IVG exhibited slow release in acidic solution and relatively quick release in neutral solutions to provide drug efficacy. In simulated digestive fluid, IVG showed better sustained release and insulin protection properties compared with ISG. Thus IVG might improve the stability of insulin during its transport in vivo and contribute to the bioavailability and therapeutic effect of insulin.

Effective Enhancement of Hypoglycemic Effect of Insulin by Liver-Targeted Nanoparticles Containing Cholic Acid-Modified Chitosan Derivative

Liver is responsible for the balance of blood glucose level. In this study, cholic acid and N-(2-hydroxy)-propyl-3-trimethylammonium chloride modified chitosan (HTCC-CA) was used as a liver-targeted vehicle for insulin delivery. A novel approach was developed to effectively load insulin by mixing insulin and HTCC-CA in 50% ethanol and water mixed solvent at pH 2 and then dialysis against pH 7.4 phosphate buffer subsequently against water. The insulin-loaded HTCC-CA nanoparticles have an average diameter of 86 nm and insulin loading efficiency of 98.7%. Due to random distribution of the hydrophobic cholic acid groups in HTCC-CA, some of the cholic acid groups located on the nanoparticle surface. Compared with free insulin, the nanoparticles increased in vitro cellular uptake of insulin to 466%, and the nanoparticles accumulated in liver for more time after subcutaneous injection into mice. The therapy for diabetic rats displayed that the nanoparticles increased the pharmacological bioavailability of insulin to 475% relative to free insulin, and the nanoparticles could maintain the hypoglycemic effect for more than 24 h. This study demonstrates that the nanoparticles with cholic acid groups on their surface possess liver-targeted property and biocompatible insulin-loaded HTCC-CA nanoparticles can effectively enhance the hypoglycemic effect of insulin.