Superporous Hydrogels Research Articles

GASTRO RETENTIVE NON-FLOATING DRUG DELIVERY APPROACH: A REVIEW

Gastro retardation is attractive approach to enhance bioavailability of narrow absorption window drugs. Drug retardation in stomach is more beneficial for certain gastro intestinal disorders like gastro esophageal reflex disease, ulcer and other gastro intestinal conditions. Gastric site retardation is one of the challenging technique, however various techniques are applied to keep the drug and achieve the enhancement of bioavailability. To achieve gastro retentive commonly two approaches are considered, they are floating drug delivery system and non-floating gastro retentive drug delivery system. The floating drug made-up by low density polymers, this approach was not fit many of the drug molecule and floating drug has some limitations like sufficient level fluids in stomach and not to be dosed just before going to bed. In this review describe the various high density (sinking) system (non-floating) drug delivery systems like super porous hydrogels, expanding system, bio/mucoadhesives system, and magnetic system and mechanism, desirable drug characters, advantages and disadvantages. Keyword: Bioavailability, gastro retentive, magnetic system, mucoadhesive, non-floating and sinking system.

GASTRORETENTIVE DRUG DELIVERY SYSTEM

Oral route of drug administration is the most preferable route because of its flexibility in formulation, ease of administration, and patient compliance. But this route has certain limitations like limited gastric residence time (GRT) for sustained drug delivery system and for the drugs which are absorb from specific region of gastrointestinal tract (GIT). To overcome these limitations, various approaches have been proposed to increase the gastric retention time of the delivery system in the upper part of gastrointestinal tract. Gastroretentive dosage form (GRDF) prolongs the GRT by targeting site-specific drug release in upper part of GIT. GRDFs enable continuous and the extended duration of drug release and improve bioavailability of drugs that have narrow therapeutic window, by this way they prolong dosing interval and increase compliance of the patient. The purpose of this article is to compile the various gastroretentive approaches. In order to understand various physiological difficulties to achieve gastric retention, we have summarized important factors controlling gastric retention. Finally the evaluation parameters of gastroretentive drug delivery systems are covered. The present review addresses briefly about the current status of various leading gastroretentive drug delivery technologies, developed until now, i.e. high density (sinking), floating, bio- or mucoadhesive, expandable, unfoldable, super porous hydrogel, magnetic systems etc. In addition, important factors controlling gastroretention, advantages and finally, future potential are discussed.Keywords: Floating Delivery, Gastro retentive system.Â

Effect of gas foaming and porosigen techniques on the properties of superporous hydrogels

Hydrogels is a type of hydrophilic polymers which exist in three dimension network that absorb significant amount of water. However, most of the dried hydrogels take long time to be swollen, which limits their applications. In order to overcome this problem, superporous hydrogels (SPHs) which are novel hydrogel materials that can exhibit fast swelling and superabsorbent properties was introduced. As the SPHs foaming techniques influenced the morphology, swelling behavior and structure of the SPHs, this research was mainly focused to study on the effect of the two different foaming techniques (gas blowing and porosigen technique) on the physical and swelling properties of the SPHs. In the preparation of SPHs, the cross linking polymerization reaction was used to prepare poly-(acrylic acid-co-acrylamide) SPHs by using monomers of acrylic acid (AA), and acrylamide (AM). Besides that, the swelling ratio was determined in order to investigate water absorbency properties of SPHs on both techniques. The final products were characterized by using Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR), respectively. Based on the results, the SPHs prepared by gas blowing technique had shown higher water absorbency value, Q which is 194.13 ± 2.43 (g/g) compared with the SPHs prepared by porosigen technique which is 176.31 ± 1.30 (g/g). The formation of various size pores in or between the structures SPHs allowing the penetration of water into the SPHs structure. Based on FTIR results, both SPHs had same types of bond which are O-H, C=C, N-H, C-H, C-O, and C=O that corresponding to the swelling properties of SPHs. In conclusion, SPHs prepared by gas blowing technique gave better performance on water absorbency than SPHs that prepared by porosigen technique

Gastro retentive drug delivery systems: An overview

Orally administered gastro retentive dosage forms draws great attention in the pharmaceutical research industry. These systems improved patient compliance with increased therapeutic index of drugs increase importance of gastro-retentive drug delivery systems (GRDDS). Numerous physiological constraints associated with gastroretentive dosage forms such as short gastric retentive time, variations in gastric emptying time can be reduced by various technological advanced utilized in the design and fabrication of gastroretentive dosage. Currently different development approaches are utilized to increase gastric retention time, including High density systems, Expanding systems, Unfoldable and Swellable systems and Superporous hydrogels. The present review briefly addresses various gastroretentive dosage forms for prolongation gastric residence time.

Enhancement of Curcumin Bioavailability Using Nanocellulose Reinforced Chitosan Hydrogel.

A unique biodegradable, superporous, swellable and pH sensitive nanocellulose reinforced chitosan hydrogel with dynamic mechanical properties was prepared for oral administration of curcumin. Curcumin, a less water-soluble drug was used due to the fact that the fast swellable, superporous hydrogel could release a water-insoluble drug to a great extent. CO2 gas foaming was used to fabricate hydrogel as it eradicates using organic solvents. Field emission scanning electron microscope images revealed that the pore size significantly increased with the formation of widely interconnected porous structure in gas foamed hydrogels. The maximum compression of pure chitosan hydrogel was 25.9 ± 1 kPa and it increased to 38.4 ± 1 kPa with the introduction of 0.5% cellulose nanocrystals. In vitro degradation of hydrogels was found dependent on the swelling ratio and the amount of CNC of the hydrogel. All the hydrogels showed maximum swelling ratios greater than 300%. The 0.5% CNC-chitosan hydrogel showed the highest swelling ratio of 438% ± 11%. FTIR spectrum indicated that there is no interaction between drug and ingredients present in hydrogels. The drug release occurred in non-Fickian (anomalous) manner in simulated gastric medium. The drug release profiles of hydrogels are consistent with the data obtained from the swelling studies. After gas foaming of the hydrogel, the drug loading efficiency increased from 41% ± 2.4% to 50% ± 2.0% and release increased from 0.74 to 1.06 mg/L. The drug release data showed good fitting to Ritger-Peppas model. Moreover, the results revealed that the drug maintained its chemical activity after in vitro release. According to the results of this study, CNC reinforced chitosan hydrogel can be suggested to improve the bioavailability of curcumin for the absorption from stomach and upper intestinal tract.

Salicyl-imine-chitosan hydrogels: Supramolecular architecturing as a crosslinking method toward multifunctional hydrogels

Hydrogels based on chitosan and salicyladehyde were obtained by dynamic covalent chemistry. The unusual chitosan gelling in the presence of the monoaldehyde has been deciphered following and correlating data of NMR, FTIR, single crystal and wide angle XRD, POM and optical measurements. Of significant importance in understanding the crosslinking features was the synthesis of a model compound and the successfully growth as single crystal allowing the study of its supramolecular peculiarities. The hydrogels exhibited in SEM a porous or fibrous morphology, in good correlation with the crosslinking degree. They swelled very fast, similar to the superporous hydrogels of third generation and exhibited self-healing properties. Rheological investigation demonstrated good mechanical properties, thermosensitivity and thixotropy. The paper revealed a hydrogel with suitable properties for use in bio-medical applications, and moreover, revealed a new concept of obtaining chitosan hydrogels using monoaldehydes − which are widespread in nature, cheap and beneficial to the human body.

Effect of Foaming Agent on the Properties of Superporous Hydrogels Prepared via Solution Polymerization Method

Background/Objectives: Superporous hydrogels (SPHs) are three dimensional network polymers that often crosslinked through chemical or physical interactions. It can swell to an equilibrium state and retain a significant amount of water molecule due to the presences of interconnected microscopic pores. The swelling rate of most of the dried hydrogel (i.e. xerogels) typically low and take a longer time to reach equilibrium due to slow water absorption capability. This disadvantage further limits the possible application of the hydrogel to be utilized in various field, includes as drug delivery material and as soil conditioner in agriculture field. Therefore, there is a significant interest in developing synthesis method and the selection of material in preparation of the superporous hydrogel that can exhibit both fast swelling absorption properties. Methods/Statistical Analysis: In this study, SPHs were prepared from monomer of acrylamide (AM) by a solution polymerization reaction process with the assistance of ammonium persulphate (APS) as an initiator and N’N’-methylenebisacrylamide (MBA) as cross linker. The effect of sodium bicarbonate (NaHCO3) amount as foaming agent to generate pore structure was investigated in term of morphology, water absorbency, and swelling properties of SPHs. Findings: Based on the results, the water absorbency of SPHs increased 65% by comparing with control sample (0wt%). Based on the comparison, the increasing foaming agent from 0-0.4 wt% of sodium bicarbonate shows that water absorbency reached the optimum condition at 0.4 wt% which is 99.10±3.35 g/g. Then, the interaction between hydrogels shows the best fit at 0.4 wt% with K value of 1.1905E- 05. Application/Improvements: SPHs was produced in order to be used in other applications such as agriculture, electrical and separation technology according to its porosity improvement.

Microwave-induced biomimetic approach for hydroxyapatite coatings of chitosan scaffolds

Simulated body fluid (SBF) can form calcium phosphates on osteoinductive materials, so it is widely used for coating of bone scaffolds to mimic natural extracellular matrix (ECM). However, difficulties of bulk coating in 3D scaffolds and the necessity of long process times are the common problems for coating with SBF. In the present study, a microwave-assisted process was developed for rapid and internal coating of chitosan scaffolds. The scaffolds were fabricated as superporous hydrogel (SPH) by combining microwave irradiation and gas foaming methods. Then, they were immersed into 10x SBF-like solution and homogenous bone-like hydroxyapatite (HA) coating was achieved by microwave treatment at 600W without the need of any nucleating agent. Cell culture studies with MC3T3-E1 preosteoblasts showed that microwave-assisted biomimetic HA coating process could be evaluated as an efficient and rapid method to obtain composite scaffolds for bone tissue engineering.

Novel biodegradable hydrogel sponge containing curcumin and honey for wound healing.

To develop and evaluate a biodegradable superporous hydrogel based wound healing composite of chitosan and alginate incorporated with curcumin and honey. A 3(2) factorial design was adopted to optimise the honey-curcumin hydrogel composite sponge (CHS). Sodium alginate and chitosan were dissolved in deionised water and 1% aqueous acetic acid solution at room temperature, respectively. Ethanolic solution of curcumin was poured into the chitosan solution followed by an addition of sodium alginate solution. In situ polymerisation was carried out by adding acrylamide base components to the polymeric solution of curcumin. Finally, honey was added with slow stirring and a sponge was cast on a glass surface by solvent evaporation at 45ºC. The produced sponge was assessed for swelling capacity, moisture loss, tensile strength, biocompatibility, bioadhesion, biodegradation, drug diffusion and wound healing properties. The morphology of CHS was studied by scanning electron microscopy (SEM). The optimised CHS demonstrated a high swelling capacity (111.05 ± 05%), tensile strength (4323gm/mm(2)), in vitro drug diffusion (75.03 ± 3.59%/20days), bioadhesion (20 ± 0.2mg force) and ability of water vapour transmission. A rapid induction of tissue granulation and re-epithelialisation was observed. Time to complete healing (94.14 ± 1.04% wound contraction) was 7 ± 2 days. This study has shown that honey-curcumin hydrogel composite sponge can be formulated by a simple mixing and in situ polymerisation method. The hydrogel base provided a dry wound bed due to excellent fluid absorption capacity. Chitosan and honey contributed to effective faster wound healing. We recommend further clinical studies of the soft sponge wound healing composite for diabetic foot or pressure ulcers.

Bone tissue engineering with scaffold-supported perfusion co-cultures of human stem cell-derived osteoblasts and cell line-derived osteoclasts

The aim of this study was to investigate the effects of perfusion co-culture on bone tissue regeneration in vitro. Human mesenchymal stem cell (hMSC)-derived osteoblasts and THP-1 human acute monocytic leukemia cell line-derived osteoclasts were dynamically co-cultured on the chitosan-hydroxyapatite (chitosan-HA) superporous hydrogel. In the perfusion bioreactor set-up, bidirectional recycled perfusion with 6 mL/h flow rate was applied and cell seeding was realized in two-steps with a preculture time of 12 days. Outcomes were compared to static cultures. Two-step cell seeding and long preculture ensured good adhesion of cells on the scaffold surface and minimized cell loss during perfusion. The perfusion bioreactor enhanced mass transfer throughout the scaffolds, thus increased cellularity and provided flow-induced mechanical stimulation for osteoblastic and osteoclastogenic differentiation. The results indicated that osteoblast and osteoclast co-cultures in perfusion bioreactors provide a one-step approach to in vitro bone tissue engineering and emphasized the significance of enhanced mass transfer and mechanical stimulation on cellular activity and differentiation.

Synthesis and Characterisation of PVA/PVOH Based Super Porous Hydrogel

The present paper explains the synthesis of super porous hydrogel (SPH) with reinforcement of different concentrations (0.05, 0.1, 0.15 and 0.2 g) of PVA by solution polymerization. The polymerisation process is conducted at a pH value of 5. The corollaries of PVA on different characteristics of super porous hydrogel were studied. The characterization study involves measurement of apparent density, swelling, mechanical strength and microstructure. The PVA added SPH are treated for a total time of 550 minutes in double distilled water and acid salt solution to analyse the swelling properties. The result shows that inclusion of PVA to SPH reduces its swelling tendency culminating that; the empathy for swelling is more in double distilled water than acid medium.

Inverse high internal phase emulsion polymerization (i-HIPE) of GMMA, HEMA and GDMA for the preparation of superporous hydrogels as a tissue engineering scaffold.

A series of novel superporous hydrogels for regenerative medicine were prepared by oil-in-water (o/w) or inverse high internal phase emulsion (i-HIPE) copolymerization of glycerol monomethacrylate (GMMA), 2-hydroxy ethyl methacrylate (HEMA) and glycerol dimethacrylate (GDMA) as a cross-linker using a non toxic solvent and a redox initiator system at the physiological temperature (37 °C). The monomer GMMA was synthesized from glycidyl methacrylate (GMA) by an alternative facile method using Amberlyst-15. The described i-HIPEs showed a significantly wider stability window. The polyHIPE hydrogels were characterized by FTIR, BET method for surface area, mercury porosimetry, SEM, DSC, TGA, XRD, compressive strain and strain recovery. The swelling ratio of the hydrogels and their degradation in 0.007 M NaOH and lipase B (Candida antarctica) solutions were determined gravimetrically and the rate of degradation was explained in terms of the molecular structure of the hydrogels. The morphological studies showed that the pore diameter varied between 20 and 30 μm and the pore throats (interconnecting windows) diameter was in the range of 4-8 μm. The described polyHIPE hydrogels were found to have an open cell morphology and interconnected pore architecture, which are important characteristics for scaffold applications. The initial cytotoxicity study performed according to ISO-10993-5 indicated cytocompatibility (97% cell viability) and the subsequent cell seeding and proliferation study exhibited 55-88% cell viability (increased monotonously from GHG-1 to GHG-5), which could be attributed to modulation of the physical and chemical properties of the hydrogels. The described super porous hydrogels are considered as potential candidates for scaffold materials in tissue engineering applications.

Molecularly regulated release of growth factors from programmable hydrogels for angiogenesis

Event Abstract Back to Event Molecularly regulated release of growth factors from programmable hydrogels for angiogenesis Yong Wang1*, Nan Zhao1, Xiaolong Zhang1*, Li-Juan Duan2* and Guo-Hua Fong2* 1 Penn State University, Department of Biomedical Engineering, United States 2 UConn Health Center, Center for Vascular Biology, United States Introduction: Vascularization is important to treatment of ischemic diseases and survival of tissue-engineered constructs[1]. Delivery of growth factors is a promising strategy for vascularization. However, polymeric systems for growth factor delivery face several challenges including denaturation of growth factors, difficulty of controlling growth factor release kinetics, and/or lack of macroporous structures for cell growth[2]. The purpose of this work was to demonstrate that oligonucleotide aptamers and macroporous hydrogels could be used to develop a multifunctional biomaterial with great potential of overcoming all of these challenges. Materials and Methods: The multifunctional hydrogel was synthesized in a cylindrical mold with free radical polymerization and gas formation[3]. The key components in the pregel solution were oligonucleotide aptamers and acrylated gelatin that were incorporated into the hydrogel during the polymerization. The incorporation efficiency was determined by protein and oligonucleotide staining assays. The hydrogel was thoroughly washed to remove unreacted monomers and immersed in solution with VEGF and PDGF-BB for growth factor sequestration. The kinetics of growth factor release was examined using ELISA. The bioactivity of released or retained growth factors was measured using the standard HUVEC tube formation assay. To demonstrate directly the ability of this new hydrogel in promoting angiogenesis, the hydrogels with growth factors were subcutaneously implanted into a mouse model. The hydrogels were collected and analyzed after 4-week implantation. Endothelial cell surface biomarker CD31 was stained to examine populated vascular lumens in the hydrogels and tissues adjacent to the hydrogels. Results and Discussion: Macroporous hydrogels were successfully synthesized with free radical polymerization coupled with gas formation. The SEM images show that macroporous structures had an average pore diameter of 50 microns (Figure 1a). Both aptamers and gelatin were efficiently incorporated into the hydrogel network. Importantly, growth factors could be rapidly sequestered into the hydrogel network. When the superporous hydrogels were immersed into release media, aptamers effectively reduced the burst release effect and prolonged the growth factor release with desired kinetics. Moreover, the released and retained growth factors maintained high bioactivity (Figure 1b). For instance, at the end of two weeks, VEGF could maintain ~50% bioactivity that is much higher than the data reported in the literature. The animal studies showed that the multifunctional hydrogel stimulated angiogenesis much more effectively than the control hydrogels without aptamers (Figure 1c). Conclusions: Aptamer-functionalized hydrogels are a promising multifunctional biomaterial for controlled growth factor release. They hold great potential to stimulate vascularization for treatment of ischemic diseases or enhance survival of tissue-engineered constructs. U.S. NSF CAREER program under award number DMR-1332351; the National Heart, Lung, and Blood Institute of the NIH under award number R01HL122311

Classification, processing and application of hydrogels: A review.

This article aims to review the literature concerning the choice of selectivity for hydrogels based on classification, application and processing. Super porous hydrogels (SPHs) and superabsorbent polymers (SAPs) represent an innovative category of recent generation highlighted as an ideal mould system for the study of solution-dependent phenomena. Hydrogels, also termed as smart and/or hungry networks, are currently subject of considerable scientific research due to their potential in hi-tech applications in the biomedical, pharmaceutical, biotechnology, bioseparation, biosensor, agriculture, oil recovery and cosmetics fields. Smart hydrogels display a significant physiochemical change in response to small changes in the surroundings. However, such changes are reversible; therefore, the hydrogels are capable of returning to its initial state after a reaction as soon as the trigger is removed.

Inosculation potential of angiopoietin-4-immobilized pHEMA-based bone scaffolds

Although angiopoietin-1has potential therapeutic use in angiogenesis, the biological role of angiopoietin-4, especially in its immobilized form, is already unknown. In this study, vascularization potential of angiopoietin-4 either alone or in combination with vascular endothelial growth factor (VEGF) was investigated following its immobilization onto the poly(2-hydroxyethyl methacrylate)-based bone scaffolds. Poly(2-hydroxyethyl methacrylate) (pHEMA)-based superporous hydrogels (SPHs) were synthesized by radical polymerization of hydroxyethyl methacrylate in the presence of gelatin or chitosan and the porosity was achieved by gas foaming. However, only pHEMA-gelatin SPHs fulfill the structural and biological characteristics of a bone scaffold. Therefore, angiopoietin-4 and/or VEGF were immobilized successfully onto the pHEMA–gelatin SPHs using carbodiimide chemistry. The cell culture studies that were performed with human umbilical vein endothelial cells (HUVECs) for 28 days showed that immobilized angiopoietin-4 supported sprout formation more than that of other groups, while the immobilized VEGF including scaffolds promoted proliferation of HUVECs.

Hydrodynamically Balanced Gastro-Retentive Site Specific Drug Delivery System: An Innovative Approach

Conventional oral dosage forms suffer with many disadvantages. To avoid such limitations controlled release dosage forms are preferred. When these controlled release dosage forms administered by oral route retained in the stomach and release the drug in a controlled fashion continuously in gastrointestinal tract [1]. Controlled release systems also suffer with some limitations such as short gastric retention time and unpredictable short gastric emptying time, which leads to incomplete drug release in the absorption zone results into reduced efficiency of the dose administered [2]. To achieve a desirable prolonged gastric residence time, it is essential to design a site-specific controlled oral dosage form. The prolonged gastric retention of a dosage form increases the total duration of drug release, improves bioavailability, minimizes the drug loss and enhances solubility of poorly soluble drugs in gastric environment [3]. Furthermore, prolonged gastric retention time in the stomach also leads to effective local action in the upper part of the small intestine especially in the treatment of peptic ulcer. Hydrodynamically balanced gastric retentive drug delivery is an innovative approach play important role in prolonging gastric residence time by targeting site specific drug release in the upper intestine for local as well as systemic effect. Over the last few decades different kinds of gastroretentive drug delivery systems being developed. Main among these are: high density (sinking) systems that are designed to sink into the gastric fluid and settle at the bottom of stomach [4], low density (floating) systems that are designed to float on the gastric fluid causing buoyancy [5-7], mucoadhesive systems that are designed to adhere to stomach mucosa [8], unfoldable, extendable, or swellable systems that are designed to limit the emptying of the dosage forms through the pyloric sphincter of stomach [9], superporous hydrogel systems [10] and magnetic systems [11]. The current editorial focused mainly on concise information about hydrodynamically balanced site specific gastroretentive approach for orally administered controlled release dosage forms.

Microwave‐Promoted Synthesis of Smart Superporous Hydrogel for the Development of Gastroretentive Drug Delivery System

ABSTRACTSmart superporous hydrogels (SPHs) based on dimethylaminoethyl methacrylate and acrylamide monomers with and without magnetic nanoparticles (MNPs) were synthesized via a microwave procedure. The synthesized samples were confirmed by various techniques such as Fourier transform spectroscopy, x‐ray diffraction, thermogravimetric analysis, scanning electron microscopy, vibrating sample magnetometry, and transmission electron microscopy. The parameters such as pH, irradiation time, and MNPs content on the swelling behavior of products were studied. The results of swelling studies in artificial gastric and intestine media exhibited a higher swelling ratio of SPHs in lower pH, confirming smart performance of SPHs for gastroretentive drug delivery (GDD). The metronidazole (MTZ) was used as an effective antibiotic administered in peptic ulcer therapy. The in vitro release studies showed that the presence of MNPs into the hydrogel network provided the sustained release pattern for MTZ. It was concluded that our developed SPHs and MSPHs fabricated via a facile method have potential to be used in GDD.

Topical vaginal drug delivery system based on superporous hydrogel hybrids.

In this investigation a novel approach based on mucoadhesive superporous hydrogel hybrids (SPHHs) for topi- cal vaginal drug delivery for Metronidazole was tried. SPHHs were synthesized by solution polymerization tech- nique. The synthesized SPHHs were characterized for tensile strength, swelling behavior, porosity, density, mucoadhesion time, SEM, DSC and FT-IR studies. In vitro drug release study from prepared vaginal formulation based on SPHH was performed in simulated vaginal fluid. Different mathematical models were applied to ascertain the drug release mecha- nism. SPHHs have shown good tensile strength, mucoadhesion time and drug release for 24 hour. SEM images reflected the formation of pores and interconnected capillary channels. The release kinetic of drug from the prepared system was best explained by Korsmeyer-Peppas and Higuchi models and shown anomalous transport. The proposed novel drug de- livery system based on SPHH was successfully prepared and SPHH-DDS might be promising candidate for topical vagi- nal delivery of Metronidazole.

Graphene-reinforced collagen hydrogels with through-thickness porosity

Collagen, an extracellular protein abundant in animal tissues, is an excellent candidate for tissue engineering and other biomedical applications. Superporous hydrogels for gastric retention drug delivery systems and ice-templated materials, which have distinct advantages in cell interations, are some examples. Although it has been one of the most preferred biomaterials for in vivo medical applications, its difficult processing and poor mechanical properties have been the barriers to its use. The poor mechanical properties of collagen led previous researchers to use reinforcing particles for strengthening purpose. Hydroxyapatite nanoparticles have been the primary choice for researchers interested in bone tissue engineering. Silica nanoparticles and carbon nanotubes have also been employed, and carbon nanotubes functionalized with carboxyl groups were able to dramatically improve the mechanical properties. With advances in preparation techniques and the understanding of graphene, experimental and theoretical studies of graphene composite scaffolds have been increasingly explored. So far, no systematic experimental study of graphene/collagen combination has been reported to the best of our knowledge, and only several theoretical predictions that surface ripples or charged functional groups are critical for mechanical strengthening in graphene/collagen composites have recently been reported. This study demonstrates the successful reinforcement effects of reduced graphene oxide (rGO, Figure S1, Supporting Information) in superporous collagen hydrogels with a pore morphology engineered by directional cooling crystallization of water. The resulting composite hydrogels can be used as strong, biocompatible hydrogels for tissue engineering, drug delivery systems, and sensors. Furthermore, the directional cylindrical pores are expected to have the ability to guide cells, and the incorporation of rGO is expected to provide electrical conductivity.

Preparation of PCL/PEG superporous hydrogel containing drug-loaded nanoparticles: The effect of hydrophobic–hydrophilic interface on the physical properties

A series of novel amphiphilic hydrogels were synthesized by photopolymerization of diacrylated polyethylene glycol as hydrophilic parts and polycaprolactone (PCL) terminated with linear acrylates (G0.5) and dendritic ones (G1.5) as hydrophobic segments in the presence of Irgacure 2959 as initiator. Water absorbency, water content percentage and in-vitro degradation of all hydrogels were determined. Due to their fast swelling and high swelling ratios, these hydrogels have the capability of using as superporous hydrogels. Tandem acrylation/Michael addition by acryloyl chloride and diethanolamine were used to prepare the second generation of aminoester–polycaprolactone–aminoester triblock copolymer (G2) with dendritic–linear–dendritic structure. All steps were characterized by FT-IR and 1H NMR spectroscopy. In order to evaluate the ability of synthesized hydrogels as biodevice materials, the release profile of hydrogels containing quercetin-loaded nanoparticles was determined and compared with the free nanoparticles. Drug-loaded nanoparticles with 88nm in diameter were prepared by nanoprecipitation method using G2 as polymeric carrier.