Photopolymerization of methacrylated chitosan/PNIPAAm hybrid dual-sensitive hydrogels as carrier for drug delivery

Modelling methacrylated chitosan hydrogel properties through an experimental design approach: from composition to material properties

Hydrogels of biopolymers are gradually substituting synthetic hydrogels in tissue engineering applications due to their properties. However, biopolymeric hydrogels are difficult to standardize because of the intrinsic variability of the material and the reversibility of physical crosslinking processes. In this work, we synthesized a photocrosslinkable derivative of chitosan (Cs), namely methacrylated chitosan (CsMA), in which the added methacrylic groups allow the formation of hydrogels through radical polymerization triggered by UV exposure. We then performed a systematic study to link the physical properties of the materials to its preparation parameters to standardize its preparation according to specific applications. We studied the properties of CsMA solutions and the derived hydrogels using a statistical method, namely, response surface method, which allowed us to build empirical models describing material properties in terms of several selected processing factors. In particular, we studied the viscosity of CsMA solutions as a function of CsMA concentration, temperature, and shear rate, while hydrogel compression modulus, morphology, degradation and solubilization were investigated as a function of CsMA concentration, photoinitiator concentration and UV exposure. CsMA solutions resulted in shear thinning and were thus suitable for extrusion-based 3D printing. The CsMA hydrogel was found to be highly tunable, with a stiffness in the 12-64 kPa range, and was stable over a long timeframe (up to 60 days). Finally, the possibility to engineer hydrogel stiffness through an empirical model allowed us to hypothesize a number of possible applications based on the mechanical properties of several biological tissues reported in the literature.

Facile fabrication of a thermal/pH responsive IPN hydrogel drug carrier based on cellulose and chitosan through simultaneous dual-click strategy

Herein, an interpenetrating network hydrogel (IPN-Gel) based on cellulose and chitosan was synthesized via simultaneous amino-anhydride and azide-alkyne click reaction in water in one pot. The samples were characterized by various analytical methods including FTIR, SEM, XRD, XPS, 1H NMR and so forth. The fabrication conditions were optimized by single factor experiments with water uptake (WU) and gel mass fraction (GMF) as two indexes. The WU and GMF of the IPN-Gel prepared under optimized conditions were 1192.37 % and 74.00 %, respectively. Its WU descended with the ascension in temperature, and first descended and then gradually ascended with the ascension in pH, confirming that the IPN-Gel had thermal/pH dual responsiveness. Using 5-Fu as a model drug, the release behavior of 5-Fu in IPN-Gel was explored. Its release behavior could be regulated by changing temperature and pH values, and it followed the Korsmeyer Peppas model. The viability of 4 T1 cells and HUVEC cells exceeded 80 % after 48 h of incubation at a high concentration of 200 μg/mL IPN-Gel, and hemolytic percentage was below the allowed limit of 5 %. The study provides a new strategy for the preparation of the IPN-Gel with biocompatibility, swelling reversibility and controllable drug release.

Exosome-loaded hydrogels for craniofacial bone tissue regeneration

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

A superabsorbent and pH-responsive copolymer-hydrogel based on acemannan from Aloe vera (Aloe barbadensis M.): A smart material for drug delivery

Combining natural polysaccharides with synthetic materials improves their functional properties which are essential for designing sustained-release drug delivery systems. In this context, the Aloe vera leaf mucilage/hydrogel (ALH) was reacted with acrylic acid (AA) to synthesize a copolymerized hydrogel, i.e., ALH-grafted-Polyacrylic acid (ALH-g-PAA) through free radical copolymerization. Concentrations of the crosslinker N,N'-methylene-bis-acrylamide (MBA), and the initiator potassium persulfate (KPS) were optimized to study their effects on ALH-g-PAA swelling. The FTIR and solid-state NMR (CP/MAS 13C NMR) spectra witnessed the formation of ALH-g-PAA. Scanning electron microscopy (SEM) analysis revealed superporous nature of ALH-g-PAA. The gel fraction (%) of ALH-g-PAA was directly related to the concentrations of AA and MBA whereas the sol fraction was inversely related to the concentrations of AA and MBA. The porosity (%) of ALH-g-PAA directly depends on the concentration of AA and MBA. The ALH-g-PAA swelled admirably at pH 7.4 and insignificantly at pH 1.2. The ALH-g-PAA offered on/off switching properties at pH 7.4/1.2. The metoprolol tartrate was loaded on different formulations of ALH-g-PAA. The ALH-g-PAA showed pH, time, and swelling-dependent release of metoprolol tartrate (MT) for 24 h following the first-order kinetic and Korsmeyer-Peppas model. Haemocompatibility studies ascertained the non-thrombogenic and non-hemolytic behavior of ALH-g-PAA.

Facile fabrication of temperature/pH dual sensitive hydrogels based on cellulose and polysuccinimide through aqueous amino-succinimide reaction

A temperature/pH dual sensitive hydrogel with a semi-interpenetrating network (semi-IPN) structure was synthesized through an aqueous amino-succinimide reaction between water-soluble polysuccinimide and polyethyleneimine in the presence of thermosensitive cellulose derivatives. Single-factor experiments were carried out to optimize the preparation conditions of the semi-IPN hydrogel. The swelling behavior and cytotoxicity assay of the hydrogel were tested. Finally, taking 5- fluorouracil (5-Fu) as a model drug, the release performance of the 5-Fu-loaded hydrogel was investigated. The results indicated that the swelling ratio (SR) first decreased and then increased when the pH of the solutions ascended from 2 to 10. The SR decreased with the increase in temperature. In addition, the swelling behavior of the hydrogel was reversible and reproducible under different pH values and temperatures. The prepared hydrogels had good cytocompatibility. The release behavior of 5-Fu was most consistent with the Korsmeyer-Peppas model and followed the case II diffusion. The acidic environment was beneficial for the release of 5-Fu. The preparation process of the semi-IPN hydrogel is simple and the reaction can proceed quickly in water. The strategy introduced here has great potential for application in the preparation of drug carriers.

Chitosan Poly(vinyl alcohol) Methacrylate Hydrogels for Tissue Engineering Scaffolds

A major challenge in tissue engineering scaffolds is controlling scaffold degradation rates during healing while maintaining mechanical properties to support tissue formation. Hydrogels are three-dimensional matrices that are widely applied as tissue scaffolds based on their unique properties that can mimic the extracellular matrix. In this study, we develop a hybrid natural/synthetic hydrogel platform to tune the properties for tissue engineering scaffold applications. We modified chitosan and poly(vinyl alcohol) (PVA) with photo-cross-linkable methacrylate functional groups and then synthesized a library of chitosan PVA methacrylate hydrogels (ChiPVAMA) with two different photoinitiators, Irgacure 2959 (I2959) and lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP). ChiPVAMA hydrogels showed tunability in degradation rates and mechanical properties based on both the polymer content and photoinitiator type. This tunability could enable their application in a range of tissue scaffold applications. In a 2D scratch wound healing assay, all hydrogel samples induced faster wound closure compared to a gauze clinical wound dressing control. NIH/3T3 cells encapsulated in hydrogels showed a high viability (∼92%) over 14 days, demonstrating the capacity of this system as a supportive cell scaffold. In addition, hydrogels containing a higher chitosan content demonstrated a high antibacterial capacity. Overall, ChiPVAMA hydrogels provide a potential tissue engineering scaffold that is tunable, degradable, and suitable for cell growth.

A Photocurable Polysaccharide-Based Hydrogel Delivery of Polydeoxyribonucleotide-Loaded Vectors for Wound Treatment

The wounds caused by war, accidents, and diseases require timely and effective treatment. Polysaccharides, as natural macromolecules, have good biocompatibility and unique functions, and are excellent substrates for constructing new wound dressings. Short-chain chitosan (SCS) has good water solubility and, importantly, retains a large number of active amino groups. We first introduce double bonds to SCS. This chitosan derivative can be entangled with sodium alginate (SA) through electrostatic interaction. The flowing sol can be applied to a wound with an irregular shape. Under the initiation of a photoinitiator, the internal double bonds are broken and cross-linked to form a gel. The prepared hydrogel wound dressing exhibited good antibacterial properties and can provide a microenvironment conducive to wound repair. A polydeoxyribonucleotide (PDRN) has been proven to have encouraging therapeutic effects for wound healing. PDRN can be condensed by branched polyethylenimine (PEI) to form a nucleic acid delivery system, which can be efficiently uptaken by cells. The cooperation of hydrogel and nucleic-acid-based therapy presented good results in a mouse full-thickness skin wound model.

Synergistic Effect of Thermoresponsive and Photocuring Methacrylated Chitosan-Based Hybrid Hydrogels for Medical Applications

The thermoresponsive drug-loaded hydrogels have attracted widespread interest in the field of medical applications due to their ease of delivery to structurally complex tissue defects. However, drug-resistant infections remain a challenge, which has prompted the development of new non-antibiotic hydrogels. To this end, we prepared chitosan-methacrylate (CTSMA)/gelatin (GEL) thermoresponsive hydrogels and added natural phenolic compounds, including tannic acid, gallic acid, and pyrogallol, to improve the efficacy of hydrogels. This hybrid hydrogel imparted initial crosslinking at physiological temperature, followed by photocuring to further provide a mechanically robust structure. Rheological analysis, tensile strength, antibacterial activity against E. coli, S. aureus, P. gingivalis, and S. mutans, and L929 cytotoxicity were evaluated. The experimental results showed that the hybrid hydrogel with CTSMA/GEL ratio of 5/1 and tannic acid additive had a promising gelation temperature of about 37 °C. The presence of phenolic compounds not only significantly (p < 0.05) enhanced cell viability, but also increased the tensile strength of CTSMA/GEL hybrid hydrogels. Moreover, the hydrogel containing tannic acid revealed potent antibacterial efficacy against four microorganisms. It was concluded that the hybrid hydrogel containing tannic acid could be a potential composite material for medical applications.

Temperature/pH-Sensitive Double Cross-Linked Hydrogels as Platform for Controlled Delivery of Metoclopramide

Novel double cross-linked (DC) hydrogels with pH-/temperature-sensitive properties were designed and developed. Therefore, linear pH-sensitive poly(methyl vinyl ether-alt-maleic acid) (P(VME/MA)) macromolecules were absorbed within a thermosensitive poly(N-isopropylacrylamide-co-hydroxyethylacrylamide)-hydrogel (PNH) and, subsequently, cross-linked together through a solvent-free thermal method. As a novelty, double cross-linked hydrogels were obtained from previously purified polymers in the absence of any solvent or cross-linking agent, which are generally harmful for the body. The new DC structures were characterized by FT-IR spectroscopy, SEM, swelling kinetic measurements, and mechanical tests. The resulting scaffolds exhibited interconnected pores and a flexible pattern, compared to the brittle structure of conventional PNH. The swelling kinetics of DC hydrogels were deeply affected by temperature (25 and 37 °C) and pH (7.4 and 1.2). Furthermore, the hydrogels absorbed a great amount of water in a basic environment and displayed improved mechanical properties. Metoclopramide (Met) was loaded within DC hydrogels as a model drug to investigate the ability of the support to control the drug release rate. The results obtained recommended them as convenient platforms for the oral administration of drugs, with the release of the largest part of the active principle occurring in the colon.

Intelligent hydrogel with both redox and thermo-response based on cellulose nanofiber for controlled drug delivery

The purpose of this study is to develop a hydrogel with temperature and redox response to control drug delivery. However, the strength of temperature sensitive N-isopropylacrylamide (NIPAM) hydrogel is weak. Therefore, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidized cellulose nanofiber (CNF) is introduced to improve this problem. The compressive strength of hydrogels increased by 360% after CNF addition. Meanwhile, N,N'-bis(acryloyl)cystamine (BACy) is introduced into the hydrogels as a cross-linker, imparting redox responsive properties to the hydrogels. Tumor therapeutic drugs are used as model drugs for in vitro release studies. The drug release rate of hydrogel is regulated by temperature and reducing environment. The maximum cumulative release rate of doxorubicin (DOX) is 39.56%, and the Berberine (BBR) is 99.50% after 60 h. The swelling and transparency of hydrogels showed dramatic changes in the range of 30-40 °C. Cytotoxicity experiments demonstrated that the hydrogel had almost no cytotoxicity.

Therapeutic nanoemulsions in ophthalmic drug administration: Concept in formulations and characterization techniques for ocular drug delivery

The eye is the specialized part of the body and is comprised of numerous physiological ocular barriers that limit the drug absorption at the action site. Regardless of various efforts, efficient topical ophthalmic drug delivery remains unsolved, and thus, it is extremely necessary to advance the contemporary treatments of ocular disorders affecting the anterior and posterior cavities. Nowadays, the advent of nanotechnology-based multicomponent nanoemulsions for ophthalmic drug delivery has gained popularity due to the enhancement of ocular penetrability, improve bioavailability, increase solubility, and stability of lipophilic drugs. Nanoemulsions offer the sustained/controlled drug release and increase residence time which depend on viscosity, compositions, and stabilization process, etc.; hence, decrease the instillation frequency and improve patient compliance. Further, due to the nanosized of nanoemulsions, the sterilization process is easy as conventional solutions and cause no blur vision. The review aims to summarizes the various ocular barriers, manufacturing techniques, possible mechanisms to the retention and deep penetration into the eye, and appropriate excipients with their under-lying selection principles to prevent destabilization of nanoemulsions. This review also discusses the characterization parameters of ocular drug delivery to spike the interest of those contemplating a foray in this field. Here, in short, nanoemulsions are abridged with concepts to design clinically advantageous ocular drug delivery.

Drug delivery system of dual-responsive PF127 hydrogel with polysaccharide-based nano-conjugate for textile-based transdermal therapy

Pluronic F-127 based dual-responsive (pH/temperature) hydrogel drug delivery system was developed involving polysaccharide-based nano-conjugate of hyaluronic acid and chitosan oligosaccharide lactate and applied for loading of gallic acid which is the principal component of traditional Chinese medicine Cortex Moutan recommended in the treatment of atopic dermatitis. The polysaccharide-based nano-conjugate was used as pH-responsive compound in the formulation and its amphiphilic character was determined colorimetrically. Microstructure analysis by SEM and TEM indicated highly porous hydrogel network and well-dispersed micellar structures, respectively, after modification with the nano-conjugate, and so, release property of the hydrogel for drug was significantly improved. Different pH-conditions were applied here to see pH-responsiveness of the formulation and increase in acidity of external environment gradually diminished mechanical stability of the hydrogel and that was reflected on the drug release property. Rheology was performed to observe sol-gel transition of the formulation and showed better rheological properties after modification with nano-conjugate. In this study, the cytotoxicity results of PF127 based formulations loaded with/without gallic acid showed cell viability of > 80.0 % for human HaCaT keratinocytes in the concentration range of 0.0-20.0 μg/ml.

Extravascular gelation shrinkage-derived internal stress enables tumor starvation therapy with suppressed metastasis and recurrence

Despite the efficacy of current starvation therapies, they are often associated with some intrinsic drawbacks such as poor persistence, facile tumor metastasis and recurrence. Herein, we establish an extravascular gelation shrinkage-derived internal stress strategy for squeezing and narrowing blood vessels, occluding blood & nutrition supply, reducing vascular density, inducing hypoxia and apoptosis and eventually realizing starvation therapy of malignancies. To this end, a biocompatible composite hydrogel consisting of gold nanorods (GNRs) and thermal-sensitive hydrogel mixture was engineered, wherein GRNs can strengthen the structural property of hydrogel mixture and enable robust gelation shrinkage-induced internal stresses. Systematic experiments demonstrate that this starvation therapy can suppress the growths of PANC-1 pancreatic cancer and 4T1 breast cancer. More significantly, this starvation strategy can suppress tumor metastasis and tumor recurrence via reducing vascular density and blood supply and occluding tumor migration passages, which thus provides a promising avenue to comprehensive cancer therapy.

A photo-switchable and thermal-enhanced fluorescent hydrogel prepared from N-isopropylacrylamide with water-soluble spiropyran derivative

Herein, a photo-switchable and thermal-enhanced fluorescent hydrogel has been fabricated from N-isopropylacrylamide (NIPAAm) with a mixture of water-soluble acryloyl-α-cyclodextrin/acryloyl-α-cyclodextrin-spiropyran (acryloyl-α-CD/ acryloyl-α-CD-SP) as cross-linkers. The physical properties, photochromic properties, and fluorescent behavior of the hydrogel were characterized. The fluorescence emission of the hydrogel can be reversibly switched 'on/off' by UV/visible light irradiation, and meanwhile the fluorescence intensity can be enhanced by increasing the temperature above the volume phase transition temperature (VPTT) of the hydrogel. The hydrogel also shows spatiotemporal fluorescent behavior, excellent cytocompatibility, and fatigue resistance in photochromic and photo-switchable fluorescent behaviors.

Influence of Ethylene Glycol Methacrylate to the Hydration and Transition Behaviors of Thermo-Responsive Interpenetrating Polymeric Network Hydrogels

The influence of ethylene glycol methacrylate (EGMA) to the hydration and transition behaviors of thermo-responsive interpenetrating polymeric network (IPN) hydrogels containing sodium alginate, N-isopropylacrylamide (NIPAAm), and EGMA were investigated. The molar ratios of NIPAAm and EGMA were varied from 20:0 to 19.5:0.5 and 18.5:1.5 in the thermo-responsive alginate-Ca2+/P(NIPAAm-co-EGMA) IPN hydrogels. Due to the more hydrophilicity and high flexibility of EGMA, the IPN hydrogels exhibited higher lower critical solution temperature (LCST) and lower glass transition temperature (Tg) when the ratio of EGMA increases. The swelling/deswelling kinetics of the IPN hydrogels could be controlled by adjusting the NIPAAm/EGMA molar ratio. A faster water uptake rate and a slower water loss rate could be realized by increase the amount of EGMA in the IPN hydrogel (the shrinking rate constant was decreased from 0.01207 to 0.01195 and 0.01055 with the changing of NIPAAm/EGMA ratio from 20:0, 19.5:0.5 to 18.5:1.5). By using 2-Isopropylthioxanthone (ITX) as a photo initiator, the obtained alginate-Ca2+/P(NIPAAm-co-EGMA360) IPN hydrogels were successfully immobilized on cotton fabrics. The surface and cross section of the hydrogel were probed by scanning electron microscopy (SEM). They all exhibited a porous structure, and the pore size was increased with the amount of EGMA. Moreover, the LCST values of the fabric-grafted hydrogels were close to those of the pure IPN hydrogels. Their thermal sensitivity remained unchanged. The cotton fabrics grafted with hydrogel turned out to be much softer with the continuous increase of EGMA amount. Therefore, compared with alginate-Ca2+/PNIPAAm hydrogel, alginate-Ca2+/P(NIPAAm-co-EGMA360) hydrogel is a more promising candidate for wound dressing in the field of biomedical textile.

Photopolymerized maleilated chitosan/thiol-terminated poly (vinyl alcohol) hydrogels as potential tissue engineering scaffolds

Photocrosslinkable hydrogels composed of natural materials exhibit great application potential in tissue engineering scaffolds. However, weak formation and poor mechanical property can usually be a limitation. Herein, the photo-clickable thiol-ene hydrogels based chitosan were synthesized using photopolymerization of maleic chitosan (MCS) and thiol-terminated poly (vinyl alcohol) (TPVA) in the presence of a biocompatible photoinitiator. Rheological property and absorbing behavior of the MCS/TPVA hydrogels could be tailored by varying the amount of TPVA in the feed. There was strong intermolecular hydrogen bonding between the molecules of MCS and TPVA. Notably, the MCS/TPVA hydrogel (MT-3) exhibited rapid gelation behavior (<120 s), improved stiff (G' = ∼5500 Pa) and compressive strength (0.285 ± 0.014 MPa), which were important for hydrogel scaffolds, especially for injectable hydrogel scaffolds. Photocrosslinked MCS/TPVA hydrogels was cytocompatible and could promote the L929 cells attachment and proliferation, showing their potential as tissue engineering scaffolds.

Development and Characterisation of the Imiquimod Poly(2-(2-methoxyethoxy)ethyl Methacrylate) Hydrogel Dressing for Keloid Therapy

The imiquimod-poly(2-(2-methoxyethoxy)ethyl methacrylate) hydrogel (poly(MEO₂MA) hydrogel) dressing was developed for the keloid therapy application. Four groups of the hydrogels, including the imiquimod-poly(MEO₂MA) hydrogel, crosslinked with 0.2 mol %, 0.4 mol %, 0.6 mol %, and 0.8 mol % of di(ethylene glycol) dimethacrylate cross-linker (DEGDMA), were synthesised and characterised for fabricating the imiquimod-poly(MEO₂MA) hydrogel pad. The lower critical solution temperature (LCST) of the poly(MEO₂MA) hydrogel was measured at approximately 28 °C and was used as a trigger to control the imiquimod loading and release. The loaded amounts of the imiquimod in the poly(MEO₂MA) hydrogel, crosslinked with 0.2 mol % and 0.8 mol % of DEGDMA, were about 27.4 μg and 14.1 μg per 1 mm³ of the hydrogel, respectively. The imiquimod-release profiles of two samples were characterised in a phosphate buffered saline (PBS) solution at 37 °C and the released imiquimod amount were about 45% and 46% of the total loaded imiquimod. The Cell Counting Kit-8 (CCK-8) assay was utilised to analyse the cell viability of keloid fibroblasts cultured on the samples of imiquimod-poly(MEO₂MA) hydrogel, crosslinked with 0.2 mol % and 0.8 mol % of DEGDMA. There was around a 34% decrease of the cell viabilities after 2 days, compared with the pure-poly(MEO₂MA) hydrogel samples. Therefore, the developed imiquimod-poly(MEO₂MA) hydrogel dressing can affect the proliferation of keloid fibroblasts. It should be possible to utilise the hydrogel dressing for the keloid therapy application.

Degradable poly(ethylene glycol)-based hydrogels: Synthesis, physico-chemical properties and in vitro characterization

Designing degradable hydrogels is complicated by the structural and temporal complexities of the gel and evolving tissue. A major challenge is to create scaffolds with sufficient mechanical properties to restore initial function while simultaneously controlling temporal changes in the gel structure to facilitate tissue formation. Poly(ethylene glycol) was used in this work, to form biodegradable poly(ethylene glycol)-based hydrogels with hydrolyzable poly-l-lactide segments in the backbone. Non-degradable poly(ethylene glycol) was also introduced in the formulation to obtain control of the degradation profile that encompasses cell growth and new tissue formation. The dependence on polymer composition was observed by higher degradation profiles and decreased mechanical properties as the content of degradable segments was increased in the formulation. Based on in vitro tests, no toxicity of extracts or biomaterial in direct contact with human adipose tissue stem cells was observed, and the ultraviolet light treatment did not affect the proliferation capacity of the cells.

pH dependent poly[2-(methacryloyloxyethyl)trimetylammonium chloride-co-methacrylic acid]hydrogels for enhanced targeted delivery of 5-fluorouracil in colon cancer cells

Stimuli responsive hydrogels have shown enormous potential as a carrier for targeted drug delivery. In this study we have developed novel pH responsive hydrogels for the delivery of 5-fluorouracil (5-FU) in order to alleviate its antitumor activity while reducing its toxicity. We used 2-(methacryloyloxyethyl) trimetylammonium chloride a positively charged monomer and methacrylic acid for fabricating the pH responsive hydrogels. The released 5-FU from all except hydrogel (GEL-5) remained biologically active against human colon cancer cell lines [HT29 (IC50 = 110-190 μg ml(-1)) and HCT116 (IC50 = 210-390 μg ml(-1))] but not human skin fibroblast cells [BJ (CRL2522); IC50 ≥ 1000 μg ml(-1)]. This implies that the copolymer hydrogels (1-4) were able to release 5-FU effectively to colon cancer cells but not normal human skin fibroblast cells. This is probably due to the shorter doubling time that results in reduced pH in colon cancer cells when compared to fibroblast cells. These pH sensitive hydrogels showed well defined cell apoptosis in HCT116 cells through series of events such as chromatin condensation, membrane blebbing, and formation of apoptotic bodies. No cell killing was observed in the case of blank hydrogels. The results showed the potential of these stimuli responsive polymer hydrogels as a carrier for colon cancer delivery.

Facile Synthesis of Magnetic Copolymer Microspheres Based on Poly(glycidyl methacrylate-co-N-isopropylacrylamide)/Fe3O4by Suspension Photopolymerization

Magnetic copolymer based on poly(glycidyl methacrylate-co-N-isopropylacrylamide) microspheres was prepared by 2,2-dimethoxy-2-phenylacetophenone- (DMPP-) photo initiated and poly(vinyl alcohol)- (PVA-) stabilized single step suspension photopolymerization. The effect of chemical interaction, morphology, and thermal properties by adding 0.1% w/v Fe3O4in the copolymer was investigated. Infrared analysis (FTIR) showed that (C=C) band disappeared after copolymerization, indicating that the magnetic copolymer microspheres were successfully synthesized and two important bands at 908 cm−1and 1550 cm−1appear. These are associated with the epoxy group stretching of GMA and secondary amide (N–H/C–H) deformation vibration of NIPAAm in magnetic microspheres. The X-ray diffraction (XRD) result proved the incorporation of Fe3O4nanoparticles with copolymer microspheres as peak of Fe3O4was observed. Morphology study revealed that magnetic copolymer exhibited uniform spheres and smoother appearance when entrapped with Fe3O4nanoparticles. The lowest percentage of Fe3O4nanoparticles leached from the copolymer microspheres was obtained at pH 7. Finally, thermal property of the copolymer microspheres was improved by adding a small amount of Fe3O4nanoparticles that has been shown from the thermogram.

One-pot synthesis of superabsorbent hybrid hydrogels based on methacrylamide gelatin and polyacrylamide. Effortless control of hydrogel properties through composition design

Network-forming polymerization of methacrylamide gelatin and acrylamide generates scaffolds with controlled biocompatibility and water affinity.

Visible light crosslinkable chitosan hydrogels for tissue engineering

In situ gelling constructs, which form a hydrogel at the site of injection, offer the advantage of delivering cells and growth factors to the complex structure of the defect area for tissue engineering. In the present study, visible light crosslinkable hydrogel systems were presented using methacrylated glycol chitosan (MeGC) and three blue light initiators: camphorquinone (CQ), fluorescein (FR) and riboflavin (RF). A minimal irradiation time of 120 s was required to produce MeGC gels able to encapsulate cells with CQ or FR. Although prolonged irradiation up to 600 s improved the mechanical strength of CQ- or FR-initiated gels (compressive modulus 2.8 or 4.4 kPa, respectively), these conditions drastically reduced encapsulated chondrocyte viability to 5% and 25% for CQ and FR, respectively. Stable gels with 80-90% cell viability could be constructed using radiofrequency (RF) with only 40s irradiation time. Increasing irradiation time up to 300s significantly improved the compressive modulus of the RF-initiated MeGC gels up to 8.5 kPa without reducing cell viability. The swelling ratio and degradation rate were smaller at higher irradiation time. RF-photoinitiated hydrogels supported proliferation of encapsulated chondrocytes and extracellular matrix deposition. The feasibility of this photoinitiating system as in situ gelling hydrogels was further demonstrated in osteochondral and chondral defect models for potential cartilage tissue engineering. The MeGC hydrogels using RF offer a promising photoinitiating system in tissue engineering applications.