Structural, rheological properties and antioxidant activities analysis of the exopolysaccharide produced by Rhizobium leguminosarum bv. viciae VF39

Microbial exopolysaccharide is an eco-friendly and non-toxic biopolymeric materials widely used in various industrial fields such as pharmaceutical, food and cosmetics based on its structural, rheological and physiochemical properties. A microbial exopolysaccharide (VF39-EPS) was directly isolated from Rhizobium leguminosarum bv. viciae VF39. Structural analysis using FTIR and 2D NMR spectroscopy confirmed the complete chemical structures of VF39-EPS as 3-hydroxybutanoylglycan with octasaccharide repeating units containing two pyruvyl, two acetyl, and one 3-hydroxybutanoyl group. VF39-EPS exhibited thermal stability up to 275 °C and showed characteristic rheological behaviors of structural fluid with weak gel-like properties above 4 % the aqueous solution, suggesting VF39-EPS as a potential effective thickener or hydrogel scaffolder. Flow behavior tests validated broad stability at a wide range of both pHs from 2 to 12 and temperatures from 25 to 75 °C, and even in the presence of various salts. Furthermore, VF39-EPS showed excellent antioxidant effects of 78.5 and 62.4 % (n = 3, p < 0.001) in DPPH scavenging activity and hydroxyl radical scavenging activity, respectively. Therefore, those structural, rheological and antioxidant properties suggest that VF39-EPS could be one of the excellent biomaterial candidates for cosmetic, food and pharmaceutical industries based on its characteristic rheological behaviors in various condition and excellent antioxidant activity.

Development of Novel Polysaccharide Membranes for Guided Bone Regeneration: In Vitro and In Vivo Evaluations

INTRODUCTION

Guided bone regeneration (GBR) procedures require selecting suitable membranes for oral surgery. Pullulan and/or dextran-based polysaccharide materials have shown encouraging results in bone regeneration as bone substitutes but have not been used to produce barrier membranes. The present study aimed to develop and characterize pullulan/dextran-derived membranes for GBR.

MATERIALS AND METHODS

Two pullulan/dextran-based membranes, containing or not hydroxyapatite (HA) particles, were developed. In vitro, cytotoxicity evaluation was performed using human bone marrow mesenchymal stem cells (hBMSCs). Biocompatibility was assessed on rats in a subcutaneous model for up to 16 weeks. In vivo, rat femoral defects were created on 36 rats to compare the two pullulan/dextran-based membranes with a commercial collagen membrane (Bio-Gide®). Bone repair was assessed radiologically and histologically.

RESULTS

Both polysaccharide membranes demonstrated cytocompatibility and biocompatibility. Micro-computed tomography (micro-CT) analyses at two weeks revealed that the HA-containing membrane promoted a significant increase in bone formation compared to Bio-Gide®. At one month, similar effects were observed among the three membranes in terms of bone regeneration.

CONCLUSION

The developed pullulan/dextran-based membranes evidenced biocompatibility without interfering with bone regeneration and maturation. The HA-containing membrane, which facilitated early bone regeneration and offered adequate mechanical support, showed promising potential for GBR procedures.

Nanoparticles loaded with pharmacologically active plant-derived natural products: Biomedical applications and toxicity

Pharmacologically active natural products have played a significant role in the history of drug development. They have acted as sources of therapeutic drugs for various diseases such as cancer and infectious diseases. However, most natural products suffer from poor water solubility and low bioavailability, limiting their clinical applications. The rapid development of nanotechnology has opened up new directions for applying natural products and numerous studies have explored the biomedical applications of nanomaterials loaded with natural products. This review covers the recent research on applying plant-derived natural products (PDNPs) nanomaterials, including nanomedicines loaded with flavonoids, non-flavonoid polyphenols, alkaloids, and quinones, especially their use in treating various diseases. Furthermore, some drugs derived from natural products can be toxic to the body, so the toxicity of them is discussed. This comprehensive review includes fundamental discoveries and exploratory advances in natural product-loaded nanomaterials that may be helpful for future clinical development.

Engineered human liver based on pullulan-dextran hydrogel promotes mice survival after liver failure

Liver tissue engineering approaches aim to support drug testing, assistance devices, or transplantation. However, their suitability for clinical application remains unsatisfactory. Herein, we demonstrate the beneficial and biocompatible use of porous pullulan-dextran hydrogel for the self-assembly of hepatocytes and biliary-like cells into functional 3D microtissues. Using HepaRG cells, we obtained 21 days maintenance of engineered liver polarity, functional detoxification and excretion systems, as well as glycogen storage in hydrogel. Implantation on two liver lobes in mice of hydrogels containing 3800 HepaRG 3D structures of 100 ​μm in diameter, indicated successful engraftment and no signs of liver toxicity after one month. Finally, after acetaminophen-induced liver failure, when mice were transplanted with engineered livers on left lobe and peritoneal cavity, the survival rate at 7 days significantly increased by 31.8% compared with mice without cell therapy. These findings support the clinical potential of pullulan-dextran hydrogel for liver failure management.

Removal of Methylene Blue Dye from Aqueous Solutions by Pullulan Polysaccharide/Polyacrylamide/Activated Carbon Complex Hydrogel Adsorption

In this study, composite hydrogels were prepared using a simple synthetic technique to adsorb methylene blue (MB) from water. The hydrogel comprised potassium persulfate (KPS) as the initiator, N,N'-methylene bisacrylamide as the crosslinking agent, and sodium hydroxide (NaOH) as the activator. It was employed to adsorb MB at different concentrations from water. The morphology and properties of PUL/PAM/GO composites were characterized through thermogravimetric analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. Moreover, the adsorption properties, adsorption isotherms, adsorption kinetics, adsorption thermodynamics, and swelling properties of the hydrogel for MB were investigated. The optimal ratio of PUL to AC was obtained as 6:1 by fixing the amount of PUL and loading AC of different masses. The maximum adsorption capacity was obtained as 591.4 mg/g. It also exhibited certain mechanical strength. The adsorption of MB conforms to pseudo-first-order kinetics and Langmuir isotherms. In this study, an environment-friendly, cheap, simple, and efficient way was presented for the composite hydrogel in the direction of water treatment.

The UCST phase transition of a dextran based copolymer in aqueous media with tunable thermoresponsive behavior

A hydrogen bonded UCST polymer has been developed by grafting of methacrylamide and acrylic acid on dextran via free radical polymerization.

Modification of cyclodextrin and use in environmental applications

Water pollution, which has become a global problem in parallel with environmental pollution, is a problem that needs to be solved urgently, considering the gradual depletion of water resources. The inadequacy of the water treatment methods and the materials used somehow directed the researchers to look for dual character structures such as biocompatible and biodegradable β-cyclodextrin (β-CD). β-CD, which is normally insoluble in water, is used in demanding wastewater applications by being modified with the help of different agents to be water soluble or transformed into polymeric adsorbents as a result of co-polymerization via cross-linkers. In this way, in addition to the host-guest interactions offered by β-CD, secondary forces arising from these interactions provide advantages in terms of regeneration and reusability. However, the adsorption efficiency and synthesis steps need to be improved. Based on the current studies presented in this review, in which cross-linkers and modification methods are also mentioned, suggestions for novel synthesis methods of new-generation β-CD-based materials, criticisms, and recent methods of removal of micropollutants such as heavy metals, industrial dyes, harmful biomolecules, and pharmaceutics wastes are mentioned.

Tuning Physicochemical Properties of a Macroporous Polysaccharide-Based Scaffold for 3D Neuronal Culture

Central nervous system (CNS) lesions are a leading cause of death and disability worldwide. Three-dimensional neural cultures in biomaterials offer more physiologically relevant models for disease studies, toxicity screenings or in vivo transplantations. Herein, we describe the development and use of pullulan/dextran polysaccharide-based scaffolds for 3D neuronal culture. We first assessed scaffolding properties upon variation of the concentration (1%, 1.5%, 3% w/w) of the cross-linking agent, sodium trimetaphosphate (STMP). The lower STMP concentration (1%) allowed us to generate scaffolds with higher porosity (59.9 ± 4.6%), faster degradation rate (5.11 ± 0.14 mg/min) and lower elastic modulus (384 ± 26 Pa) compared with 3% STMP scaffolds (47 ± 2.1%, 1.39 ± 0.03 mg/min, 916 ± 44 Pa, respectively). Using primary cultures of embryonic neurons from PGKCre, Rosa26tdTomato embryos, we observed that in 3D culture, embryonic neurons remained in aggregates within the scaffolds and did not attach, spread or differentiate. To enhance neuronal adhesion and neurite outgrowth, we then functionalized the 1% STMP scaffolds with laminin. We found that treatment of the scaffold with a 100 μg/mL solution of laminin, combined with a subsequent freeze-drying step, created a laminin mesh network that significantly enhanced embryonic neuron adhesion, neurite outgrowth and survival. Such scaffold therefore constitutes a promising neuron-compatible and biodegradable biomaterial.

Selenium release kinetics and mechanism from Cordyceps sinensis exopolysaccharide-selenium composite nanoparticles in simulated gastrointestinal conditions

This work investigated selenium (Se) release kinetics and mechanism from exopolysaccharide-selenium nanoparticles (EPS-SeNPs, Se/EPS = 1/20, 1/1 and 4/3) in simulated gastric (SGF) and intestinal fluids (SIF) using kinetics models of Zero order, First order, Higuchi, Hixson-Crowell and Korsmeyer-Peppas. EPS-SeNPs showed an increase in size from 80-125 nm to 250-320 nm and more ambiguous boundary after gastrointestinal digestion. Se/EPS ratio and pH had significant influence on Se release. Se release kinetics from EPS-SeNPs (Se/EPS = 1/1 and 4/3 in SGF) followed a classical Fickian diffusion, in contrast to an erosion governed by macromolecular chains relaxation for Se/EPS = 1/20 in SIF. Se release from EPS-SeNPs (Se/EPS = 1/1 and 4/3 in SIF) was well-fitted to Korsmeyer-Peppas model and followed a non-Fickian mechanism controlled by both diffusion and erosion. Additionally, EPS-SeNPs (Se/EPS = 1/20) showed a low Se release after SGF digestion, but a high release after SIF digestion, suggesting its application in controlled release of Se-enriched supplements for Se-deficiency treatment.

Hydroxyethyl starch based smart nanomedicine

In the past decades, the vigorous development of nanomedicine has opened up a new world for drug delivery. Hydroxyethyl starch (HES), a clinical plasma volume expander which has been widely used for years, is playing an attracting role as drug carriers. Compared with all other polysaccharides, HES has proven its unique characteristics for drug delivery platforms, including good manufacture practice, biodegradability, biocompatibility, abundant groups for chemical modification, excellent water solubility, and tailorability. In this review, an overview of various types of HES based drug delivery systems is provided, including HES-drug conjugates, HES-based nano-assemblies, HES-based nanocapsules, and HES-based hydrogels. In addition, the current challenges and future opportunities for design and application of HES based drug delivery systems are also discussed. The available studies show that HES based drug delivery systems has significant potential for clinical translation.

Fabrication and Characterization of Polysaccharide Metallohydrogel Obtained from Succinoglycan and Trivalent Chromium

In the present study, a polysaccharide metallohydrogel was successfully fabricated using succinoglycan and trivalent chromium and was verified via Fourier transform infrared spectroscopy, differential scanning calorimetry analysis, thermogravimetric analysis (TGA), field emission scanning electron microscopy, and rheological measurements. Thermal behavior analysis via TGA indicated that the final mass loss of pure succinoglycan was 87.8% although it was reduced to 65.8% by forming a hydrogel with trivalent chromium cations. Moreover, succinoglycan-based metallohydrogels exhibited improved mechanical properties based on the added concentration of Cr³⁺ and displayed a 10 times higher compressive stress and enhanced storage modulus (G′) of 230% at the same strain. In addition, the pore size of the obtained SCx could be adjusted by changing the concentration of Cr³⁺. Gelation can also be adjusted based on the initial pH of the metallohydrogel formulation. This was attributed to crosslinking between chromium trivalent ions and hydroxyl/carboxyl groups of succinoglycan, each of which exhibits a specific pH-dependent behavior in aqueous solutions. It could be used as a soft sensor to detect Cr³⁺ in certain biological systems, or as a soft matrix for bioseparation that allows control of pore size and mechanical strength by tuning the Cr³⁺ concentration.

Preparation and characterization of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)/pullulan-gelatin electrospun nanofibers with shell-core structure

In this study, hydrophilic pullulan, which is favorable for cell adhesion, proliferation, and differentiation, was selected as a modifier for the preparation of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB))/pullulan nanofibers via electrospinning to improve the biocompatibility of P(3HB-co-4HB) and increase the drug loading of composite fibers. Alkyl polyglycoside was used as the emulsifying agent to promote emulsification and stabilize the P(3HB-co-4HB)/pullulan composite solution. Drug-loading property of the nanofibers with a shell-core structure is increased because gelatin was not formed into fibers via electrospinning, thereby forming a stable drug-containing gelatin solution in the core layer. Finally, P(3HB-co-4HB)/pullulan-gelatin shell-core nanofibers were prepared. The intermolecular interaction, morphology, crystallization properties, mechanical properties, morphology, sustained release, and biocompatibility of composite nanofibers were characterized. Results show that the crystallization property of P(3HB-co-4HB)/pullulan composite nanofibers increases continuously with an increase in the pullulan content. As the pullulan content increases, the strain and stress of P(3HB-co-4HB)/pullulan nanofibers increase initially and decrease later. At the mass ratio of P(3HB-co-4HB) to pullulan of 10:2, P(3HB-co-4HB)/pullulan composite nanofibers exhibit a uniform morphology with an average diameter of 590 nm and porosity of 70.71%. At this mass ratio, the P(3HB-co-4HB)/pullulan-gelatin/drug shell-core structure, which sustained a release effect for more than 180 h, has potential applications as biomaterials without cytotoxicity.

Gd(DOTA)-grafted submicronic polysaccharide-based particles functionalized with fucoidan as potential MR contrast agent able to target human activated platelets

Early detection of thrombotic events remains a big medical challenge. Dextran-based submicronic particles bearing Gd(DOTA) groups and functionalized with fucoidan have been produced via a simple and green water-in-oil emulsification/co-crosslinking process. Their capacity to bind to human activated platelets was evidenced in vitro as well as their cytocompatibility with human endothelial cells. The presence of Gd(DOTA) moieties was confirmed by elemental analysis and total reflection X-ray fluorescence (TRXF) spectrometry. Detailed characterization of particles was performed in terms of size distribution, morphology, and relaxation rates. In particular, longitudinal and transversal proton relaxivities were respectively 1.7 and 5.0 times higher than those of DOTAREM. This study highlights their potential as an MRI diagnostic platform for atherothrombosis.

Development of 3D Hepatic Constructs Within Polysaccharide-Based Scaffolds with Tunable Properties

Organoids production is a key tool for in vitro studies of physiopathological conditions, drug-induced toxicity assays, and for a potential use in regenerative medicine. Hence, it prompted studies on hepatic organoids and liver regeneration. Numerous attempts to produce hepatic constructs had often limited success due to a lack of viability or functionality. Moreover, most products could not be translated for clinical studies. The aim of this study was to develop functional and viable hepatic constructs using a 3D porous scaffold with an adjustable structure, devoid of any animal component, that could also be used as an in vivo implantable system. We used a combination of pharmaceutical grade pullulan and dextran with different porogen formulations to form crosslinked scaffolds with macroporosity ranging from 30 µm to several hundreds of microns. Polysaccharide scaffolds were easy to prepare and to handle, and allowed confocal observations thanks to their transparency. A simple seeding method allowed a rapid impregnation of the scaffolds with HepG2 cells and a homogeneous cell distribution within the scaffolds. Cells were viable over seven days and form spheroids of various geometries and sizes. Cells in 3D express hepatic markers albumin, HNF4α and CYP3A4, start to polarize and were sensitive to acetaminophen in a concentration-dependant manner. Therefore, this study depicts a proof of concept for organoid production in 3D scaffolds that could be prepared under GMP conditions for reliable drug-induced toxicity studies and for liver tissue engineering.

Astaxanthin Complexes to Attenuate Muscle Damage after In Vivo Femoral Ischemia-Reperfusion

(1) Background: Reperfusion injury refers to the cell and tissue damage induced, when blood flow is restored after an ischemic period. While reperfusion reestablishes oxygen supply, it generates a high concentration of radicals, resulting in tissue dysfunction and damage. Here, we aimed to challenge and achieve the potential of a delivery system based on astaxanthin, a natural antioxidant, in attenuating the muscle damage in an animal model of femoral hind-limb ischemia and reperfusion. (2) Methods: The antioxidant capacity and non-toxicity of astaxanthin was validated before and after loading into a polysaccharide scaffold. The capacity of astaxanthin to compensate stress damages was also studied after ischemia induced by femoral artery clamping and followed by varied periods of reperfusion. (3) Results: Histological evaluation showed a positive labeling for CD68 and CD163 macrophage markers, indicating a remodeling process. In addition, higher levels of Nrf2 and NQO1 expression in the sham group compared to the antioxidant group could reflect a reduction of the oxidative damage after 15 days of reperfusion. Furthermore, non-significant differences were observed in non-heme iron deposition in both groups, reflecting a cell population susceptible to free radical damage. (4) Conclusions: Our results suggest that the in situ release of an antioxidant molecule could be effective in improving the antioxidant defenses of ischemia/reperfusion (I/R)-damaged muscles.

Effect of Sodium Trimetaphosphate on Chitosan-Methylcellulose Composite Films: Physicochemical Properties and Food Packaging Application

Environmentally friendly food packaging currently attracts much interest. Sodium trimetaphosphate (STMP) finds specialized applications in food, but it is rarely used as a crosslinking agent. In this study, STMP was used as a crosslinking agent to prepare chitosan/methylcellulose composite films. Both antibacterial and physicochemical properties of the composite film were improved by crosslinking with STMP. The crosslinked films, with good antibacterial activity (~99%), had increased tensile strength, a higher elongation at break, a lower swelling ratio and solubility, and a lower enzymatic degradation than the non-crosslinked films. Furthermore, the crosslinked films showed an excellent preservative effect on fresh-cut wax gourd after three days at room temperature. The obtained films crosslinked by STMP can be potentially applied to the food industry, such as food functional packaging, providing a novel alternative to traditional plastic packages.

Effect of cross-linking on the physicochemical and in vitro properties of pullulan/dextran microbeads

Hydrogels are very promising for tissue engineering as they provide scaffolds and a suitable microenvironment to control cell behavior and tissue regeneration. We used a patented method to obtain beads of pullulan/dextran cross-linked with sodium trimetaphosphate (STMP), that were already described for in vivo bone repair. The aim of this study was to provide a comparative analysis of microbeads made of polysaccharides prepared using three different STMP feeding ratio of 1.5, 2.25 or 3 % w/w. The morphology, swelling and biodegradability of these structures were assessed. Mesenchymal stem cells were also seeded to evaluate the cell organization onto the beads. We found that the amount of phosphorus resulting from the cross-linking was proportional to the introduced STMP concentration. An increase of cross-linking decreased the in vitro enzymatic degradability, and also decreased the swelling in PBS or water. The microstructures observed by SEM and confocal microscopy indicated that homogeneous spherical microbeads were obtained, except for the lower cross-linking ratio where the shapes were altered. Beads hydrated in PBS exhibited a mean diameter ranging from 400 to 550 µm with the decrease of STMP ratio. Cells adhered to the surface of microbeads even in the absence of protein coating. Cell viability studies revealed an increase in cell numbers over two weeks for the highest cross-linked beads, whereas the two lowest STMP concentrations induced a decrease of cell viability. Overall, this study demonstrated that pullulan/dextran hydrogels can be designed as microbeads with adjustable physicochemical and biological properties to fulfill requirements for tissue engineering approaches.

A New Bone Substitute Developed from 3D-Prints of Polylactide (PLA) Loaded with Collagen I: An In Vitro Study

Although a lot of research has been performed, large segmental bone defects caused by trauma, infection, bone tumors or revision surgeries still represent big challenges for trauma surgeons. New and innovative bone substitutes are needed. Three-dimensional (3D) printing is a novel procedure to create 3D porous scaffolds that can be used for bone tissue engineering. In the present study, solid discs as well as porous cage-like 3D prints made of polylactide (PLA) are coated or filled with collagen, respectively, and tested for biocompatibility and endotoxin contamination. Microscopic analyses as well as proliferation assays were performed using various cell types on PLA discs. Stromal-derived factor (SDF-1) release from cages filled with collagen was analyzed and the effect on endothelial cells tested. This study confirms the biocompatibility of PLA and demonstrates an endotoxin contamination clearly below the FDA (Food and Drug Administration) limit. Cells of various cell types (osteoblasts, osteoblast-like cells, fibroblasts and endothelial cells) grow, spread and proliferate on PLA-printed discs. PLA cages loaded with SDF-1 collagen display a steady SDF-1 release, support cell growth of endothelial cells and induce neo-vessel formation. These results demonstrate the potential for PLA scaffolds printed with an inexpensive desktop printer in medical applications, for example, in bone tissue engineering.

Photocrosslinkable polysaccharide hydrogel composites based on dextran or pullulan–amylose blends with cytokines for a human co-culture model of human osteoblasts and endothelial cells

Polysaccharide hyrogel composites demonstrate fundamental potential as biomaterials for bone regeneration in vitro.

V. B, Velswamy P, T. S. U, Perumal PT. Design and development of a piscine collagen blended pullulan hydrogel for skin tissue engineering

This present study was designed to prepare a super-absorbent tailor-made collagen–pullulan hydrogel with improved mechanical stability and well-defined biocompatibility for skin tissue engineering.

Three-Dimensional Environment Sustains Hematopoietic Stem Cell Differentiation into Platelet-Producing Megakaryocytes

Hematopoietic stem cells (HSC) differentiate into megakaryocytes (MK), whose function is to release platelets. Attempts to improve in vitro platelet production have been hampered by the low amplification of MK. Providing HSC with an optimal three-dimensional (3D) architecture may favor MK differentiation by mimicking some crucial functions of the bone marrow structure. To this aim, porous hydrogel scaffolds were used to study MK differentiation from HSC as well as platelet production. Flow cytometry, qPCR and perfusion studies showed that 3D was suitable for longer kinetics of CD34+ cell proliferation and for delayed megakaryocytic differentiation far beyond the limited shelf-life observed in liquid culture but also increased production of functional platelets. We provide evidence that these 3D effects were related to 1) persistence of MK progenitors and precursors and 2) prolongation of expression of EKLF and c-myb transcription factors involved in early MK differentiation. In addition, presence of abundant mature MK with increased ploidy and impressive cytoskeleton elongations was in line with expression of NF-E2 transcription factor involved in late MK differentiation. Platelets produced in flow conditions were functional as shown by integrin αIIbβ3 activation following addition of exogenous agonists. This study demonstrates that spatial organization and biological cues synergize to improve MK differentiation and platelet production. Thus, 3D environment constitutes a powerful tool for unraveling the physiological mechanisms of megakaryopoiesis and thrombopoiesis in the bone marrow environment, potentially leading to an improved amplification of MK and platelet production.

The use of total human bone marrow fraction in a direct three-dimensional expansion approach for bone tissue engineering applications: focus on angiogenesis and osteogenesis

Current approaches in bone tissue engineering have shown limited success, mostly owing to insufficient vascularization of the construct. A common approach consists of co-culture of endothelial cells and osteoblastic cells. This strategy uses cells from different sources and differentiation states, thus increasing the complexity upstream of a clinical application. The source of reparative cells is paramount for the success of bone tissue engineering applications. In this context, stem cells obtained from human bone marrow hold much promise. Here, we analyzed the potential of human whole bone marrow cells directly expanded in a three-dimensional (3D) polymer matrix and focused on the further characterization of this heterogeneous population and on their ability to promote angiogenesis and osteogenesis, both in vitro and in vivo, in a subcutaneous model. Cellular aggregates were formed within 24 h and over the 12-day culture period expressed endothelial and bone-specific markers and a specific junctional protein. Ectopic implantation of the tissue-engineered constructs revealed osteoid tissue and vessel formation both at the periphery and within the implant. This work sheds light on the potential clinical use of human whole bone marrow for bone regeneration strategies, focusing on a simplified approach to develop a direct 3D culture without two-dimensional isolation or expansion.

Pullulan/dextran/nHA macroporous composite beads for bone repair in a femoral condyle defect in rats

The repair of bone defects is of particular interest for orthopedic, oral, maxillofacial, and dental surgery. Bone loss requiring reconstruction is conventionally addressed through bone grafting. Depending on the size and the location of the defect, this method has limits and risks. Biomaterials can offer an alternative and have features supporting bone repair. Here, we propose to evaluate the cellular penetration and bone formation of new macroporous beads based on pullulan/dextran that has been supplemented with nanocrystalline hydroxyapatite in a rat model. Cross-linked beads of 300–500 µm diameters were used in a lateral femoral condyle defect and analyzed by magnetic resonance imaging, micro-computed tomography, and histology in comparison to the empty defects 15, 30, and 70 days after implantation. Inflammation was absent for both conditions. For empty defects, cellularisation and mineralization started from the periphery of the defect. For the defects containing beads, cellular structures filling out the spaces between the scaffolds with increasing interconnectivity and trabecular-like organization were observed over time. The analysis of calcified sections showed increased mineralization over time for both conditions, but was more pronounced for the samples containing beads. Bone Mineral Density and Bone Mineral Content were both significantly higher at day 70 for the beads in comparison to empty defects as well as compared with earlier time points. Analysis of newly formed tissue around the beads showed an increase of osteoid tissue, measured as percentage of the defect surface. This study suggests that the use of beads for the repair of small size defects in bone may be expanded on to meet the clinical need for a ready-to-use fill-up material that can favor bone formation and mineralization, as well as promote vessel ingrowth into the defect site.

In vitro and in vivo evaluation of blood coagulation activation of polyvinyl alcohol hydrogel plus dextran-based vascular grafts

Polyvinyl alcohol hydrogel (PVA) is a water-soluble synthetic polymer that is commonly used in biomedical applications including vascular grafting. It was argued that the copolymerization of PVA with dextran (Dx) can result in improvement of blood-biomaterial interactions. The focus of this experimental study was to assess that interaction through an in vivo and in vitro evaluation of the coagulation system activation. The thrombogenicity of the copolymer was determined by quantification of platelet adhesion through the lactate dehydrogenase assay, determination of whole blood clotting time, and by quantification of platelet activation by flow cytometry. The thrombin-antithrombin complex blood levels were also determined. The obtained results for the in vitro assays suggested a non-thrombogenic profile for PVA/Dx. Additionally in vivo coagulation and hematological parameters were determined in an animal model after PVA/Dx vascular graft implantation. For coagulation homeostasis assessment, the intrinsic and extrinsic pathway's activation was determined by measuring prothrombin time (PT) and activated partial thromboplastin time (aPTT). Other markers of coagulation and inflammation activation including d-dimers, interleukin-6, and C-reactive protein were also assessed. The PVA/Dx copolymer tended to inhibit platelet adhesion/activation process and the contact activation process for coagulation. These results were also confirmed with the in vivo experiments where the measurements for APTT, interleukin-6, and C-reactive protein parameters were normal considering the species normal range of values. The response to those events is an indicator of the in vitro and in vivo hemocompatibility of PVA/Dx and it allows us to select this biomaterial for further preclinical trials in vascular reconstruction.

Biocompatibility and hemocompatibility of polyvinyl alcohol hydrogel used for vascular grafting--In vitro and in vivo studies

Polyvinyl alcohol hydrogel (PVA) is a synthetic polymer with an increasing application in the biomedical field that can potentially be used for vascular grafting. However, the tissue and blood-material interactions of such gels and membranes are unknown in detail. The objectives of this study were to: (a) assess the biocompatibility and (b) hemocompatibility of PVA-based membranes in order to get some insight into its potential use as a vascular graft. PVA was evaluated isolated or in copolymerization with dextran (DX), a biopolymer with known effects in blood coagulation homeostasis. The effects of the mesenchymal stem cells (MSCs) isolated from the umbilical cord Wharton's jelly in the improvement of PVA biocompatibility and in the vascular regeneration were also assessed. The biocompatibility of PVA was evaluated by the implantation of membranes in subcutaneous tissue using an animal model (sheep). Histological samples were assessed and the biological response parameters such as polymorphonuclear neutrophilic leucocytes and macrophage scoring evaluated in the implant/tissue interface by International Standards Office (ISO) Standard 10993-6 (annex E). According to the scoring system based on those parameters, a total value was obtained for each animal and for each experimental group. The in vitro hemocompatibility studies included the classic hemolysis assay and both human and sheep bloods were used. Relatively to biocompatibility results, PVA was slightly irritant to the surrounding tissues; PVA-DX or PVA plus MSCs groups presented the lowest score according to ISO Standard 10993-6. Also, PVA was considered a nonhemolytic biomaterial, presenting the lowest values for hemolysis when associated to DX.

Polysaccharides as Cell Carriers for Tissue Engineering: the Use of Cellulose in Vascular Wall Reconstruction

Polysaccharides are long carbohydrate molecules of monosaccharide units joined together by glycosidic bonds. These biological polymers have emerged as promising materials for tissue engineering due to their biocompatibility, mostly good availability and tailorable properties. This complex group of biomolecules can be classified using several criteria, such as chemical composition (homo- and heteropolysaccharides), structure (linear and branched), function in the organism (structural, storage and secreted polysaccharides), or source (animals, plants, microorganisms). Polysaccharides most widely used in tissue engineering include starch, cellulose, chitosan, pectins, alginate, agar, dextran, pullulan, gellan, xanthan and glycosaminoglycans. Polysaccharides have been applied for engineering and regeneration of practically all tissues, though mostly at the experimental level. Polysaccharides have been tested for engineering of blood vessels, myocardium, heart valves, bone, articular and tracheal cartilage, intervertebral discs, menisci, skin, liver, skeletal muscle, neural tissue, urinary bladder, and also for encapsulation and delivery of pancreatic islets and ovarian follicles. For these purposes, polysaccharides have been applied in various forms, such as injectable hydrogels or porous and fibrous scaffolds, and often in combination with other natural or synthetic polymers or inorganic nanoparticles. The immune response evoked by polysaccharides is usually mild, and can be reduced by purifying the material or by choosing appropriate crosslinking agents.

A nano-hydroxyapatite--pullulan/dextran polysaccharide composite macroporous material for bone tissue engineering

Research in bone tissue engineering is focused on the development of alternatives to allogenic and autologous bone grafts that can stimulate bone healing. Here, we present scaffolds composed of the natural hydrophilic polysaccharides pullulan and dextran, supplemented or not with nanocrystalline hydroxyapatite particles (nHA). In vitro studies revealed that these matrices induced the formation of multicellular aggregates and expression of early and late bone specific markers with human bone marrow stromal cells in medium deprived of osteoinductive factors. In absence of any seeded cells, heterotopic implantation in mice and goat, revealed that only the composite macroporous scaffold (Matrix + nHA) (i) retained subcutaneously local growth factors, including Bone Morphogenetic Protein 2 (BMP2) and VEGF165, (ii) induced the deposition of a biological apatite layer, (iii) favored the formation of a dense mineralized tissue subcutaneously in mice, as well osteoid tissue after intramuscular implantation in goat. The composite scaffold was thereafter implanted in orthotopic preclinical models of critical size defects, in small and large animals, in three different bony sites, i.e. the femoral condyle of rat, a transversal mandibular defect and a tibial osteotomy in goat. The Matrix + nHA induced a highly mineralized tissue in the three models whatever the site of implantation, as well as osteoid tissue and bone tissue regeneration in direct contact to the matrix. We therefore propose this composite matrix as a material for stimulating bone cell differentiation of host mesenchymal stem cells and bone formation for orthopedic and maxillofacial surgical applications.

Paclitaxel-incorporated nanoparticles of hydrophobized polysaccharide and their antitumor activity

The aim of this study was to characterize paclitaxel-incorporated polysaccharide nanoparticles and evaluate their antitumor activity in vitro and in vivo. Pullulan was hydrophobically modified using acetic anhydride to make the paclitaxel-incorporated nanoparticles. Pullulan acetate (PA) was used to encapsulate paclitaxel using the nanoprecipitation method. The particles had spherical shapes under electron microscopy with sizes <100 nm. The sizes of paclitaxel-incorporated nanoparticles increased to >100 nm, and higher drug feeding induced higher particle size and drug content. Initial drug burst release was observed until 2 days and then the drug was continuously released over 1 week. Intrinsic cytotoxicity of empty PA nanoparticles was tested with RAW264.7 macrophage cells for biocompatibilty. The viability of RAW264.7 cells was >93% at all concentrations of empty PA nanoparticles, indicating that the PA nanoparticles are not acutely cytotoxic to normal human cells. The nanoparticles showed lower antitumor activity in vitro against HCT116 human colon carcinoma cells than that of paclitaxel itself, indicating the sustained release properties of nanoparticles. An in vivo study using HCT116 human colon carcinoma-bearing mice showed that paclitaxel-incorporated PA nanoparticles reduced tumor growth more than that of paclitaxel itself. These results indicate that PA paclitaxel-incorporated nanoparticles are a promising candidate for antitumor drug delivery.

In vitro studies and preliminary in vivo evaluation of silicified concentrated collagen hydrogels

Hybrid and nanocomposite silica-collagen materials derived from concentrated collagen hydrogels were evaluated in vitro and in vivo to establish their potentialities for biological dressings. Silicification significantly improved the mechanical and thermal stability of the collagen network within the hybrid systems. Nanocomposites were found to favor the metabolic activity of immobilized human dermal fibroblasts while decreasing the hydrogel contraction. Cell adhesion experiments suggested that in vitro cell behavior was dictated by mechanical properties and surface structure of the scaffold. First-to-date in vivo implantation of bulk hydrogels in subcutaneous sites of rats was performed over the vascular inflammatory period. These materials were colonized and vascularized without inducing strong inflammatory response. These data raise reasonable hope for the future application of silica-collagen biomaterials as biological dressings.