Polysaccharide-Based Hydrogels: The Key Role of Water in Affecting Mechanical Properties

Topical film prepared with Rhus verniciflua extract-loaded pullulan hydrogel for atopic dermatitis treatment

Atopic dermatitis (AD) is characterized by relapsing pruritus and skin dryness. Due to the pathogenic multiplicity and the adverse effects associated with the current therapeutics, development of transdermal drug delivery system is becoming an area of interest. Here, a novel topical film prepared with Rhus verniciflua extract (RVE)-loaded pullulan hydrogel (RVE@PH) was synthesized and tested its therapeutic efficacy on the AD rats modeled by neonatal capsaicin injection method. The RVE@PH was characterized by a Fourier-transform infrared spectroscopy and an in vitro release assay. Rat pups were randomly divided into two groups: vehicle-treated (VEH; n = 5) and capsaicin-treated (n = 15). The latter were given capsaicin subcutaneously at 24 h after birth for AD induction and further divided into three groups (n = 5 per each): not treated (CAP), pullulan hydrogel-applied (PH), and RVE@PH-applied (RVE-PH). The pullulan hydrogel and RVE@PH were topically applied on shoulder lesions for 14 days (from 42 to 56 days after birth). Their phenotypes were compared based on the dermatitis score, epidermal thickness, mast cell infiltration, and serum myeloperoxidase (MPO) activities. The PH group showed significant attenuation in all the aforementioned values compared to the CAP group, suggesting that pullulan hydrogel itself has therapeutic activity against AD. Notably, the attenuations were more potent in the RVE-PH group than the PH group, indicating that the therapeutic efficacy against AD is augmented by the presence of RVE, a loaded pharmaceutic. Collectively, these results indicate that RVE@PH inhibits AD through exerting the dual roles, that is, the pullulan hydrogel-mediated physical and RVE-mediated pharmaceutical actions. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2325-2334, 2019.

Redox-responsive cisplatin nanogels for anticancer drug delivery

Inspired by cisplatin's deactivation by glutathione (GSH) in cancer, a GSH responsive nanogel loaded with doxorubicin (Dox) was prepared using hyaluronan as a matrix and cisplatin as a crosslinker. The elevated GSH depletes the cisplatin crosslinker in the nanogel, enhances Dox release and boosts cytotoxicity, thus providing a new GSH responsive platform to reverse cisplatin resistance.

Recent Advances in Edible Polymer Based Hydrogels as a Sustainable Alternative to Conventional Polymers

The over increasing demand of eco-friendly materials to counter various problems, such as environmental issues, economics, sustainability, biodegradability, and biocompatibility, open up new fields of research highly focusing on nature-based products. Edible polymer based materials mainly consisting of polysaccharides, proteins, and lipids could be a prospective contender to handle such problems. Hydrogels based on edible polymer offer many valuable properties compared to their synthetic counterparts. Edible polymers can contribute to the reduction of environmental contamination, advance recyclability, provide sustainability, and thereby increase its applicability along with providing environmentally benign products. This review is highly emphasizing on toward the development of hydrogels from edible polymer, their classification, properties, chemical modification, and their potential applications. The application of edible polymer hydrogels covers many areas including the food industry, agricultural applications, drug delivery to tissue engineering in the biomedical field and provide more safe and attractive products in the pharmaceutical, agricultural, and environmental fields, etc.

Hyaluronan enhancement of expanded polytetrafluoroethylene cardiovascular grafts

Heart disease continues to be the leading cause of death in the United States. The demand for cardiovascular bypass procedures increases annually. Expanded polytetrafluoroethylene is a popular material for replacement implants, but it does have drawbacks such as high thrombogenicity and low patency, particularly in small diameter grafts. Hyaluronan, a naturally occurring polysaccharide in the human body, is known for its wound healing and anticoagulant properties. In this work, we demonstrate that treating the luminal surface of expanded polytetrafluoroethylene grafts with hyaluronan improves hemocompatibility without notably changing its mechanical properties and without significant cytotoxic effects. Surface characterization such as ATR-FTIR and contact angle goniometry demonstrates that hyaluronan treatment successfully changes the surface chemistry and increases hydrophilicity. Tensile properties such as elastic modulus, tensile strength, yield stress and ultimate strain are unchanged by hyaluronan enhancement. Durability data from flow loop studies demonstrate that hyaluronan is durable on the expanded polytetrafluoroethylene inner lumen. Hemocompatibility tests reveal that hyaluronan-treated expanded polytetrafluoroethylene reduces blood clotting and platelet activation. Together our results indicate that hyaluronan-enhanced expanded polytetrafluoroethylene is a promising candidate material for cardiovascular grafts.

Structural analysis of adsorption processes of 5FU and imiquimodon hydrogels using AMBER/PM3 hybrid model

El modelo hibrido AMBER/PM3permitió determinar las propiedades estructurales del 5FU e imiquimod individualmente y después de la adsorción en hidrogeles de quitosano entrecruzados con genipina, respectivamente. Se observó que la energía libre de Gibbs (ΔG) disminuye con la adsorción, sin embargo, en ambos procesos se encontró estabilidad termodinámica y espontaneidad; ΔG fue verificado mediante el incremento en los momentos dipolares. Por otro lado, el coeficiente de partición estableció el carácter hidrofìlico con respecto al agua presente en el hidrogel, el cual aumenta con la adsorción. El FTIR evidenció que existen desplazamientos en las señales. Se observaron las bandas de puente de hidrógeno, atribuidas a la formación de enlaces, para realizar la adsorción de los fármacos. La adsorción fue verificada mediante los MESP y los análisis de superficie, en donde se apreció la distribución de zonas nucleofílicas y electrofílicas.

Cross-linked and hydrophobized hyaluronic acid-based controlled drug release systems

This work demonstrates the preparation, structural characterization, and the kinetics of the drug release of hyaluronic acid (HyA)-based colloidal drug delivery systems which contain hydrophobic ketoprofen (KP) as model molecule. Because of the highly hydrophilic character of HyA the cross-linked derivatives at different cross-linking ratio have been synthesized. The hydrophobized variants of HyA have also been produced by modifying the polymer chains with cetyltrimethylammonium bromide (CTAB) at various HyA/CTAB ratios. Due to modifications the coherent structure of HyA changes into an incoherent colloidal system that were verified by rheological investigations. Nearly 70% of the encapsulated KP dissolve from the totally cross-linked HyA carrier but the release rate of KP is about 20% (after 8 h) from the CTAB-modified colloidal system at HyA monomer/CTAB 1:0.8 mass ratio. It has been verified that the modified HyA may be a potential candidate for controlled drug release of hydrophobic KP molecules.

Preparation, Characterization and Application of Polysaccharide-Based Metallic Nanoparticles: A Review

Polysaccharides are natural biopolymers that have been recognized to be the most promising hosts for the synthesis of metallic nanoparticles (MNPs) because of their outstanding biocompatible and biodegradable properties. Polysaccharides are diverse in size and molecular chains, making them suitable for the reduction and stabilization of MNPs. Considerable research has been directed toward investigating polysaccharide-based metallic nanoparticles (PMNPs) through host⁻guest strategy. In this review, approaches of preparation, including top-down and bottom-up approaches, are presented and compared. Different characterization techniques such as scanning electron microscopy, transmission electron microscopy, dynamic light scattering, UV-visible spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction and small-angle X-ray scattering are discussed in detail. Besides, the applications of PMNPs in the field of wound healing, targeted delivery, biosensing, catalysis and agents with antimicrobial, antiviral and anticancer capabilities are specifically highlighted. The controversial toxicological effects of PMNPs are also discussed. This review can provide significant insights into the utilization of polysaccharides as the hosts to synthesize MPNs and facilitate their further development in synthesis approaches, characterization techniques as well as potential applications.

Recombinant spider silk-based bioinks

Bioinks, 3D cell culture systems which can be printed, are still in the early development stages. Currently, extensive research is going into designing printers to be more accommodating to bioinks, designing scaffolds with stiff materials as support structures for the often soft bioinks, and modifying the bioinks themselves. Recombinant spider silk proteins, a potential biomaterial component for bioinks, have high biocompatibility, can be processed into several morphologies and can be modified with cell adhesion motifs to enhance their bioactivity. In this work, thermally gelled hydrogels made from recombinant spider silk protein encapsulating mouse fibroblast cell line BALB/3T3 were prepared and characterized. The bioinks were evaluated for performance in vitro both before and after printing, and it was observed that unprinted bioinks provided a good platform for cell spreading and proliferation, while proliferation in printed scaffolds was prohibited. To improve the properties of the printed hydrogels, gelatin was given as an additive and thereby served indirectly as a plasticizer, improving the resolution of printed strands. Taken together, recombinant spider silk proteins and hydrogels made thereof show good potential as a bioink, warranting further development.

Properties of Water Bound in Hydrogels

In this review, the importance of water in hydrogel (HG) properties and structure is analyzed. A variety of methods such as ¹H NMR (nuclear magnetic resonance), DSC (differential scanning calorimetry), XRD (X-ray powder diffraction), dielectric relaxation spectroscopy, thermally stimulated depolarization current, quasi-elastic neutron scattering, rheometry, diffusion, adsorption, infrared spectroscopy are used to study water in HG. The state of HG water is rather non-uniform. According to thermodynamic features of water in HG, some of it is non-freezing and strongly bound, another fraction is freezing and weakly bound, and the third fraction is non-bound, free water freezing at 0 °C. According to structural features of water in HG, it can be divided into two fractions with strongly associated and weakly associated waters. The properties of the water in HG depend also on the amounts and types of solutes, pH, salinity, structural features of HG functionalities.

Fabrication of complex-shaped hydrogels by diffusion controlled gelation of nanocellulose crystallites

In this study we investigated the fabrication of small hydrogel objects by the coordination-driven assembly of supramolecular rod-like crystallites of nanocellulose, using ionotropic gelation as a methodological approach and Ca²⁺ as a gelling agent. We proved that the gelation process is diffusion-mediated and fitting the equations modelling this process to the profile of the Ca²⁺ front, a Ca²⁺ diffusion coefficient in the incipient hydrogel of (4.5 ± 1.1) × 10^-6 cm² s^-1 was calculated. At the steady-state a spatially homogeneous distribution of Ca²⁺-crosslinked sites in the hydrogel network was observed. External ionotropic gelation produced beads, wires or disks, while core-shell capsules were obtained by inverse ionotropic gelation. We demonstrated that equilibrium and dynamics of the distribution of Ca²⁺ offer the opportunity to design precisely the size and shape of these small hydrogel objects. In particular, the core size and the shell thickness of the capsules can be tailored under kinetic controlled conditions. The proposed approach, with supramolecular structures of the natural source as assembling components and the water-in-water fabrication process, is fast, simple, and requires only sustainable chemistry and is easily implementable in automatic microfluidic platforms.

Role of sonication pre-treatment and cation valence in the sol-gel transition of nano-cellulose suspensions

Sol-gel transition of carboxylated cellulose nanocrystals has been investigated using rheology, SAXS, NMR and optical spectroscopies to unveil the distinctive roles of ultrasound treatments and addition of various cations. Besides cellulose fiber fragmentation, sonication treatment induces fast gelling of the solution. The gelation is independent of the addition of cations, while the final rheological properties are highly influenced by the type, concentration and sequence of the operations since the cations must be added prior to sonication to produce stiff gels. The gel elastic modulus was found to increase proportionally to the ionic charge rather than the cationic size. In cases where ions were added after sonication, SAXS analysis of the Na+ hydrogel and Ca2+ hydrogel indicated the presence of structurally ordered domains in which water is confined, and 1H-NMR investigation showed the dynamics of water exchange within the hydrogels. Conversely, separated phases containing essentially free water were characteristic of the hydrogels obtained by sonication after Ca2+ addition, confirming that this ion induces irreversible fiber aggregation. The rheological properties of the hydrogels depend on the duration of the ultrasound treatments, enabling the design of programmed materials with tailored energy dissipation response.

The Effect of Network Solvation on the Viscoelastic Response of Polymer Hydrogels

The majority of investigations consider the deformation response of hydrogels, fully controlled by the deformation behavior of their polymer network, neglecting the contribution caused by the presence of water. Here, we use molecular dynamics simulation in an attempt to include the effect of physically bound water via polymer chain solvation on the viscoelastic response of hydrogels. Our model allows us to control the solvation of chains as an independent variable. The solvation of the chain is independent of other factors, mainly the effect (pH) which interferes significantly in experiments. The solvation of hydrophilic chains was controlled by setting a partial charge on the chains and quantified by the Bjerrum length (BL). The BL was calculated from the partial electric charge of the solvent and macromolecular network. When the BL is short, the repulsive Van der Waals interactions are predominant in the vicinity of macromolecules and solvation is not observed. For a long BL, the water molecules in the solvation zone of network are in the same range as attractive intermolecular forces and the solvation occurs. The model also allows the consideration of molecules of water attached to two chains simultaneously, forming a temporary bridging. By elucidating the relations between solvation of the network and structural changes during the network deformation, one may predict the viscoelastic properties of hydrogels knowing the molecular structure of its polymer chains.

Synthesis and characterization of psyllium seed mucilage grafted with N,N-methylene bisacrylamide

Psyllium seed polysaccharide was modified to investigate its use as multifunctional pharmaceutical excipient. The objective of this study was isolation of psyllium seed polysaccharide and crosslinking with acrylic acid using N,N-methylene bisacrylamide and its characterization. Acrylic acid was used as monomer and ammonium persulfate as initiator. A full factorial design was employed to optimize the crosslinking. The modified polysaccharide was characterized by FTIR, DSC, PXRD, loss on drying, pH, viscosity, micromeritics properties and swelling studies in 0.1N HCl, 0.5N NaOH, phosphate buffer pH 6.8. It was observed that swelling of crosslinked polysaccharide increased with decreased concentration of monomer and increasing concentration of crosslinker. Greater degree of grafting was observed with increase in crosslinker and monomer concentration. Dispersions of 1% w/v of PPS and APPS show pseudoplastic behavior. No clinical signs of toxicity were evident in repeat dose toxicity studies conducted in rats. Administration of up to 350mg/kg/day of APPS was well tolerated by the animals. Modification of psyllium via graft copolymerization and network formation with the crosslinker, improved the property profile and utility of psyllium polysaccharide. The modified polysaccharide can be used for designing controlled release drug delivery systems due to its swelling ability.

Probing the adhesion properties of alginate hydrogels: a new approach towards the preparation of soft colloidal probes for direct force measurements

The adhesion of alginate hydrogels to solid surfaces was probed by atomic force microscopy (AFM) in the sphere/plane geometry. For this purpose a novel approach has been developed for the immobilization of soft colloidal probes onto AFM-cantilevers, which is inspired by techniques originating from cell biology. The aspiration and consecutive manipulation of hydrogel beads by micropipettes allows the entire manipulation sequence to be carried-out in situ. Hence, any alteration of the hydrogel beads upon drying can be excluded. The adhesive behaviour of alginate hydrogels was first evaluated by determining the distribution of pull-off forces on self-assembled monolayers (SAMs) terminating in different functional groups (-CH₃, -OH, -NH₂, -COOH). It was demonstrated that solvent exclusion plays practically no role in the adhesion process, in clear difference to solid colloidal probes. The adhesion of alginate beads is dominated by chemical interactions rather than solvent exclusion, in particular in the case of amino-terminated SAMs. The data set acquired on the SAMs provided the framework to relate the adhesion of alginate beads on recombinant spider silk protein films to specific functional groups. The preparation of soft colloidal probes and the presented approach in analysing the adhesive behaviour is not limited to alginate hydrogel beads but can be generally applied for probing and understanding the adhesion behaviour of hydrogels on a wide range of substrates, which would be relevant for various applications such as biomedical surface modification or tissue engineering.

Physicochemical Properties and the Gelation Process of Supramolecular Hydrogels: A Review

Supramolecular polysaccharide-based hydrogels have attracted considerable research interest recently due to their high structural functionality, low toxicity, and potential applications in foods, cosmetics, catalysis, drug delivery, tissue engineering and the environment. Modulation of the stability of hydrogels is of paramount importance, especially in the case of stimuli-responsive systems. This review will update the recent progress related to the rational design of supramolecular hydrogels with the objective of understanding the gelation process and improving their physical gelation properties for tailored applications. Emphasis will be given to supramolecular host⁻guest systems with reference to conventional gels in describing general aspects of gel formation. A brief account of the structural characterization of various supramolecular hydrogels is also provided in order to gain a better understanding of the design of such materials relevant to the nature of the intermolecular interactions, thermodynamic properties of the gelation process, and the critical concentration values of the precursors and the solvent components. This mini-review contributes to greater knowledge of the rational design of supramolecular hydrogels with tailored applications in diverse fields ranging from the environment to biomedicine.

Monitoring Endothelial and Tissue Responses to Cobalt Ferrite Nanoparticles and Hybrid Hydrogels

Iron oxide nanoparticles (NPs) have been proposed for many biomedical applications as in vivo imaging and drug delivery in cancer treatment, but their toxicity is an ongoing concern. When NPs are intravenously administered, the endothelium represents the first barrier to tissue diffusion/penetration. However, there is little information about the biological effects of NPs on endothelial cells. In this work we showed that cobalt-ferrite (CoFe2O4) NPs affect endothelial cell integrity by increasing permeability, oxidative stress, inflammatory profile and by inducing cytoskeletal modifications. To overcome these problems, NPs have be loaded into biocompatible gels to form nanocomposite hybrid material (polysaccharide hydrogels containing magnetic NPs) that can be further conjugated with anticancer drugs to allow their release close to the target. The organic part of hybrid biomaterials is a carboxymethylcellulose (CMC) polymer, while the inorganic part consists of CoFe2O4 NPs coated with (3-aminopropyl)trimethoxysilane. The biological activity of these hybrid hydrogels was evaluated in vitro and in vivo. Our findings showed that hybrid hydrogels, instead of NPs alone, were not toxic on endothelial, stromal and epithelial cells, safe and biodegradable in vivo. In conclusion, biohydrogels with paramagnetic NPs as cross-linkers can be further exploited for antitumor drug loading and delivery systems.

Impact of biopolymer matrices on relaxometric properties of contrast agents

Properties of water molecules at the interface between contrast agents (CAs) for magnetic resonance imaging and macromolecules could have a valuable impact on the effectiveness of metal chelates. Recent studies, indeed, demonstrated that polymer architectures could influence CAs' relaxivity by modifying the correlation times of the metal chelate. However, an understanding of the physico-chemical properties of polymer/CA systems is necessary to improve the efficiency of clinically used CAs, still exhibiting low relaxivity. In this context, we investigate the impact of hyaluronic acid (HA) hydrogels on the relaxometric properties of Gd-DTPA, a clinically used CA, to understand better the determining role of the water, which is crucial for both the relaxation enhancement and the polymer conformation. To this aim, water self-diffusion coefficients, thermodynamic interactions and relaxometric properties of HA/Gd-DTPA solutions are studied through time-domain NMR relaxometry and isothermal titration calorimetry. We observed that the presence of Gd-DTPA could alter the polymer conformation and the behaviour of water molecules at the HA/Gd-DTPA interface, thus modulating the relaxivity of the system. In conclusion, the tunability of hydrogel structures could be exploited to improve magnetic properties of metal chelates, inspiring the development of new CAs as well as metallopolymer complexes with applications as sensors and memory devices.

Effect of Carboxymethylation on the Rheological Properties of Hyaluronan

Chemical modifications made to hyaluronan to enable covalent crosslinking to form a hydrogel or to attach other molecules may alter the physical properties as well, which have physiological importance. Here we created carboxymethyl hyaluronan (CMHA) with varied degree of modification and investigated the effect on the viscosity of CMHA solutions. Viscosity decreased initially as modification increased, with a minimum viscosity for about 30-40% modification. This was followed by an increase in viscosity around 45-50% modification. The pH of the solution had a variable effect on viscosity, depending on the degree of carboxymethyl modification and buffer. The presence of phosphates in the buffer led to decreased viscosity. We also compared large-scale production lots of CMHA to lab-scale and found that large-scale required extended reaction times to achieve the same degree of modification. Finally, thiolated CMHA was disulfide crosslinked to create hydrogels with increased viscosity and shear-thinning aspects compared to CMHA solutions.

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.

²H Solid-State NMR Analysis of the Dynamics and Organization of Water in Hydrated Chitosan

Understanding water–biopolymer interactions, which strongly affect the function and properties of biopolymer-based tissue engineering and drug delivery materials, remains a challenge. Chitosan, which is an important biopolymer for the construction of artificial tissue grafts and for drug delivery, has attracted extensive attention in recent decades, where neutralization with an alkali solution can substantially enhance the final properties of chitosan films cast from an acidic solution. In this work, to elucidate the effect of water on the properties of chitosan films, we investigated the dynamics and different states of water in non-neutralized (CTS-A) and neutralized (CTS-N) hydrated chitosan by mobility selective variable-temperature (VT) ²H solid-state NMR spectroscopy. Four distinct types of water exist in all of the samples with regards to dynamic behavior. First, non-freezable, rigid and strongly bound water was found in the crystalline domain at low temperatures. The second component consists of weakly bound water, which is highly mobile and exhibits isotropic motion, even below 260 K. Another type of water undergoes well-defined 180° flips around their bisector axis. Moreover, free water is also present in the films. For the CTS-A sample in particular, another special water species were bounded to acetic acid molecules via strong hydrogen bonding. In the case of CTS-N, the onset of motions of the weakly bound water molecules at 260 K was revealed by ²H-NMR spectroscopy. This water is not crystalline, even below 260 K, which is also the major contribution to the flexibility of chitosan chains and thus toughness of materials. By contrast, such motion was not observed in CTS-A. On the basis of the ²H solid-state NMR results, it is concluded that the unique toughness of CTS-N mainly originates from the weakly bound water as well as the interactions between water and the chitosan chains.

Sundew adhesive: a naturally occurring hydrogel

Bioadhesives have drawn increasing interest in recent years, owing to their eco-friendly, biocompatible and biodegradable nature. As a typical bioadhesive, sticky exudate observed on the stalked glands of sundew plants aids in the capture of insects and this viscoelastic adhesive has triggered extensive interests in revealing the implied adhesion mechanisms. Despite the significant progress that has been made, the structural traits of the sundew adhesive, especially the morphological characteristics in nanoscale, which may give rise to the viscous and elastic properties of this mucilage, remain unclear. Here, we show that the sundew adhesive is a naturally occurring hydrogel, consisting of nano-network architectures assembled with polysaccharides. The assembly process of the polysaccharides in this hydrogel is proposed to be driven by electrostatic interactions mediated with divalent cations. Negatively charged nanoparticles, with an average diameter of 231.9 ± 14.8 nm, are also obtained from this hydrogel and these nanoparticles are presumed to exert vital roles in the assembly of the nano-networks. Further characterization via atomic force microscopy indicates that the stretching deformation of the sundew adhesive is associated with the flexibility of its fibrous architectures. It is also observed that the adhesion strength of the sundew adhesive is susceptible to low temperatures. Both elasticity and adhesion strength of the sundew adhesive reduce in response to lowering the ambient temperature. The feasibility of applying sundew adhesive for tissue engineering is subsequently explored in this study. Results show that the fibrous scaffolds obtained from sundew adhesive are capable of increasing the adhesion of multiple types of cells, including fibroblast cells and smooth muscle cells, a property that results from the enhanced adsorption of serum proteins. In addition, in light of the weak cytotoxic activity exhibited by these scaffolds towards a variety of mammal cells, evidence is sufficient to propose that sundew adhesive is a promising nanomaterial worth further exploitation in the field of tissue engineering.

In vitro osteogenic and odontogenic differentiation of human dental pulp stem cells seeded on carboxymethyl cellulose-hydroxyapatite hybrid hydrogel

Stem cells from human dental pulp have been considered as an alternative source of adult stem cells in tissue engineering because of their potential to differentiate into multiple cell lineages. Recently, polysaccharide based hydrogels have become especially attractive as matrices for the repair and regeneration of a wide variety of tissues and organs. The incorporation of inorganic minerals as hydroxyapatite nanoparticles can modulate the performance of the scaffolds with potential applications in tissue engineering. The aim of this study was to verify the osteogenic and odontogenic differentiation of dental pulp stem cells (DPSCs) cultured on a carboxymethyl cellulose—hydroxyapatite hybrid hydrogel. Human DPSCs were seeded on carboxymethyl cellulose—hydroxyapatite hybrid hydrogel and on carboxymethyl cellulose hydrogel for 1, 3, 5, 7, 14, and 21 days. Cell viability assay and ultramorphological analysis were carried out to evaluate biocompatibility and cell adhesion. Real Time PCR was carried out to demonstrate the expression of osteogenic and odontogenic markers. Results showed a good adhesion and viability in cells cultured on carboxymethyl cellulose—hydroxyapatite hybrid hydrogel, while a low adhesion and viability was observed in cells cultured on carboxymethyl cellulose hydrogel. Real Time PCR data demonstrated a temporal up-regulation of osteogenic and odontogenic markers in dental pulp stem cells cultured on carboxymethyl cellulose—hydroxyapatite hybrid hydrogel. In conclusion, our in vitro data confirms the ability of DPSCs to differentiate toward osteogenic and odontogenic lineages in presence of a carboxymethyl cellulose—hydroxyapatite hybrid hydrogel. Taken together, our results provide evidence that DPSCs and carboxymethyl cellulose—hydroxyapatite hybrid hydrogel could be considered promising candidates for dental pulp complex and periodontal tissue engineering.

On the Mechanism of Drug Release from Polysaccharide Hydrogels Cross-Linked with Magnetite Nanoparticles by Applying Alternating Magnetic Fields: the Case of DOXO Delivery

The chemical, biological and physical properties of carboxymethylcellulose (CMC) hydrogels with silanized magnetite (Fe₃O₄) nanoparticles (NPs) as cross-linker were investigated and compared with the analogous hydrogel obtained by using 1,3-diaminopropane (DAP) as cross-linker. The magnetic hydrogel was characterized from the chemical point of view by FT-IR, whereas the morphology of the hydrogel was investigated by FESEM and STEM. The water uptake and rheological measurements reveal how much the swelling and mechanical properties change when CMC is cross-linked with silanized magnetite NPs instead of with DAP. As far as the biological properties, the hybrid hydrogel neither exerts any adverse effect nor any alteration on the cells. The magnetic hydrogels show magnetic hysteresis at 2.5 K as well as at 300 K. Magnetic measurements show that the saturation magnetization, remanent magnetization and coercive field of the NPs are not influenced significantly by the silanization treatment. The magnetic hydrogel was tested as controlled drug delivery system. The release of DOXO from the hydrogel is significantly enhanced by exposing it to an alternating magnetic field. Under our experimental conditions (2 mT and 40 kHz), no temperature increase of the hydrogel was measured, testifying that the mechanism for the enhancement of drug release under the AMF involves the twisting of the polymeric chains. A static magnetic field (0.5 T) does not influence the drug release from the hydrogel, compared with that without magnetic field.

New Formulations of Polysaccharide-Based Hydrogels for Drug Release and Tissue Engineering

Polysaccharide-based hydrogels are very promising materials for a wide range of medical applications, ranging from tissue engineering to controlled drug delivery for local therapy. The most interesting property of this class of materials is the ability to be injected without any alteration of their chemical, mechanical and biological properties, by taking advantage of their thixotropic behavior. It is possible to modulate the rheological and chemical-physical properties of polysaccharide hydrogels by varying the cross-linking agents and exploiting their thixotropic behavior. We present here an overview of our synthetic strategies and applications of innovative polysaccharide-based hydrogels: hyaluronan-based hydrogel and new derivatives of carboxymethylcellulose have been used as matrices in the field of tissue engineering; while guar gum-based hydrogel and hybrid magnetic hydrogels, have been used as promising systems for targeted controlled drug release. Moreover, a new class of materials, interpenetrating hydrogels (IPH), have been obtained by mixing various native thixotropic hydrogels.

Modified biopolymer-dextrin based crosslinked hydrogels: application in controlled drug delivery

This review describes hydrogels and their classifications along with the synthesis and properties of biopolymer-dextrin based crosslinked hydrogels towards potential application in controlled drug delivery.