"A lactose-modified chitosan accelerates chondrogenic differentiation in mesenchymal stem cells spheroids"

Spheroids derived from human mesenchymal stem cells (hMSCs) are of limited use for cartilage regeneration, as the viability of the cells progressively decreases during the period required for chondrogenic differentiation (21 days). In this work, spheroids based on hMSCs and a lactose-modified chitosan (CTL) were formed by seeding cells onto an air-dried coating of CTL. The polymer coating can inhibit cell adhesion and it is simultaneously incorporated into spheroid structure. CTL-spheroids were characterized from a morphological and biological perspective, and their properties were compared with those of spheroids obtained by seeding the cells onto a non-adherent surface (agar gel). Compared to the latter, smaller and more viable spheroids form in the presence of CTL as early as 4 days of culture. At this time point, analysis of stem cells differentiation in spheroids showed a remarkable increase in collagen type-2 (COL2A1) gene expression (~700-fold compared to day 0), whereas only a 2-fold increase was observed in the control spheroids at day 21. These results were confirmed by histological and transmission electron microscopy (TEM) analyses, which showed that in CTL-spheroids an early deposition of collagen with a banding structure already occurred at day 7. Overall, these results support the use of CTL-spheroids as a novel system for cartilage regeneration, characterized by increased cell viability and differentiation capacity within a short time-frame. This will pave the way for approaches aimed at increasing the success rate of procedures and reducing the time required for tissue regeneration.

Ionic Strength Impacts the Physical Properties of Agarose Hydrogels

Agarose is a natural polysaccharide known for its ability to form thermoreversible hydrogels. While the effects of curing temperature and polysaccharide concentration on mechanical properties have been discussed in the literature, the role of ionic strength has been less studied. In the present manuscript, we investigate the effects of supporting salt concentration and the role of cation (i.e. Na+ or Li+, neighbors in the Hofmeister series), on the setting and performance of agarose hydrogels. Compressive and rheological measurements show that the supporting salts reduce the immediate elastic response of agarose hydrogels, with Li+ showing a stronger effect than Na+ at high ionic strength, while they significantly increase the extent of linear stress-strain response (i.e., linear elasticity). The presence of increasing amounts of added supporting salt also leads to a reduction in hysteresis during mechanical deformation due to loading and unloading cycles, which is more pronounced with Li+ than with Na+. The combination of rheological measurements and NMR relaxometry shows a mesh size in agarose hydrogels in the order of 6-17 nm, with a thickness of the water layer bound to the biopolymer of about 3 nm. Of note, the different structuring of the water within the hydrogel network due to the different alkali seems to play a role for the final performance of the hydrogels.

Antibacterial and bioactive multilayer electrospun wound dressings based on hyaluronic acid and lactose-modified chitosan

Antibacterial multilayer electrospun matrices based on hyaluronic acid (HA) and a lactose-modified chitosan (CTL) were synthetized (i) by combining electrospun polycaprolactone (PCL) and polysaccharidic matrices in a bilayer device and (ii) by sequentially coating the PCL mat with CTL and HA. In both cases, the antibacterial activity was provided by loading rifampicin within the PCL support. All matrices disclosed suitable morphology and physicochemical properties to be employed as wound dressings. Indeed, both the bilayer and coated fibers showed an optimal swelling capacity (3426 ± 492 % and 1435 ± 251 % after 7 days, respectively) and water vapor permeability (160 ± 0.78 g/m2h and 170 ± 12 g/m2h at 7 days, respectively). On the other hand, the polysaccharidic dressings were completely wettable in the presence of various types of fluids. Depending on the preparation method, a different release of both polysaccharides and rifampicin was detected, and the immediate polysaccharide dissolution from the bilayer structure impacted the antibiotic release (42 ± 4 % from the bilayer structure against 25 ± 2 % from the coated fibers in 4 h). All the multilayer matrices, regardless of their production strategy and composition, revealed optimal biocompatibility and bioactivity with human dermal fibroblasts, as the released bioactive polysaccharides induced a faster wound closure in the cell monolayer (100 % in 24 h) compared to the controls (78 ± 8 % for untreated cells and 89 ± 5 % for cells treated with PCL alone, after 24 h). The inhibitory and bactericidal effects of the rifampicin loaded matrices were assessed on S. aureus, S. epidermidis, E. coli, and P. aeruginosa. The antibacterial matrices were found to be highly effective except for E. coli, which was more resistant even at higher amounts of rifampicin, with a bacterial concentration of 6.4 ± 0.4 log CFU/mL and 6.8 ± 0.3 log CFU/mL after 4 h in the presence of the rifampicin-loaded bilayer and coated matrices, respectively.

Controlled Quenching of Agarose Defines Hydrogels with Tunable Structural, Bulk Mechanical, Surface Nanomechanical, and Cell Response in 2D Cultures

The scaffolding of agarose hydrogel networks depends critically on the rate of cooling (quenching) after heating. Efforts are made to understand the kinetics and evolution of biopolymer self-assembly upon cooling, but information is lacking on whether quenching might affect the final hydrogel structure and performance. Here, a material strategy for the fine modulation of quenching that involves temperature-curing steps of agarose is reported. Combining microscopy techniques, standard and advanced macro/nanomechanical tools, it is revealed that agarose accumulates on the surface when the curing temperature is set at 121 °C. The inhomogeneity can be mostly recovered when it is reduced to 42 °C. This has a drastic effect on the stiffness of the surface, but not on the viscoelasticity, roughness, and wettability. When hydrogels are strained at small/large deformations, the curing temperature has no effect on the viscoelastic response of the hydrogel bulk but does play a role in the onset of the non-linear region. Cells cultured on these hydrogels exhibit surface stiffness-sensing that affects cell adhesion, spreading, F-actin fiber tension, and assembly of vinculin-rich focal adhesions. Collectively, the results indicate that the temperature curing of agarose is an efficient strategy to produce networks with tunable mechanics and is suitable for mechanobiology studies.

Immediate stress dissipation in dual cross-link hydrogels controls osteogenic commitment of mesenchymal stem cells

In vitro studies of mesenchymal stem cells (MSCs) differentiation have been predominantly performed with non-physiologically elastic materials. Here we report the effect of different viscoplastic ECM mimics on the osteogenic engagement of MSCs in 2D. We have developed soft hydrogels, composed of a lactose-modified chitosan, using a combination of permanent and temporary cross-links. The presence of temporary cross-links has a minor effect on the shear modulus of the hydrogels, but causes an immediate relaxation (dissipation) of the applied stress. This material property leads to early osteogenic commitment of MSCs, as evidenced by gene expression of runt-related transcription factor 2 (RUNX2), type 1 collagen (COL1A1), osteocalcin (OCN), alkaline phosphatase enzyme activity (ALP) and calcium deposit formation. In contrast, cells cultured on purely elastic hydrogels with only permanent cross-link begin to differentiate only after a longer period of time, indicating a dissipation-mediated mechano-sensing in the osteogenic commitment of MSCs.

Hydrogels based on methylated-alginates as a platform to investigate the effect of material properties on cell activity. The role of material compliance

Alginate-based hydrogels with tunable mechanical properties are developed by chemical methylation of the polysaccharide backbone, which was performed either in homogeneous phase (in solution) or in heterogeneous phase (on hydrogels). Nuclear Magnetic Resonance (NMR) and Size Exclusion Chromatography (SEC-MALS) analyses of methylated alginates allow to identify the presence and location of methyl groups on the polysaccharide, and to investigate the influence of methylation on the stiffness of the polymer chains. The methylated polysaccharides are employed for the manufacturing of calcium-reticulated hydrogels for cell growth in 3D. The rheological characterization shows that the shear modulus of hydrogels is dependent on the amount of cross-linker used. Methylated alginates represent a platform to explore the effect of mechanical properties on cell activity. As an example, the effect of compliance is investigated using hydrogels displaying similar shear modulus. An osteosarcoma cell line (MG-63) was encapsulated in the alginate hydrogels and the effect of material compliance on cell proliferation and localization of YAP/TAZ protein complex is investigated by flow cytometry and immunohistochemistry, respectively. The results point out that an increase of material compliance leads to an increase of the proliferative rate of cells and correlates with the translocation of YAP/TAZ inside the cell nucleus.

Correction: CTL-doxorubicin (DOX)-gold complex nanoparticles (DOX-AuGCs): from synthesis to enhancement of therapeutic effect on liver cancer model

[This corrects the article DOI: 10.1039/D0NA00758G.].

DOTAREM (DOTA)-Gold-Nanoparticles: Design, Spectroscopic Evaluation to Build Hybrid Contrast Agents to Applications in Nanomedecine

Introduction

The realization of MRI contrast agents through chemical protocols of functionalization is a strong domain of research. In this work, we developed and formulated a novel hybrid gold nanoparticle system in which a gold salt (HAuCl₄) is combined with dotarem, an MRI contrast agent (DOTA) by chelation (Method IN) and stabilized by a lactose-modified chitosan polymer (CTL; Chitlac) to form DOTA IN-CTL AuNPs.

Result and Discussion

The authors demonstrate the biological efficiency of these nanoparticles in the case of three cell lines: Mia PaCa-2 (human pancreatic cancer cell line), TIB-75 (murine liver cell line) and KKU-M213 (cholangiocarcinoma cell line). DOTA IN-CTL AuNPs are stable under physiological conditions, are nontoxic, and are very efficient as PTT agents. The highlights, such as high stability and preliminary MRI in vitro and in vivo models, may be suitable for diagnosis and therapy.

Conclusion

We proved that DOTA IN-CTL AuNPs have several advantages: i) Biological efficacy on three cell lines: MIA PaCa-2 (human pancreatic cancer cell line), TIB-75 (murine liver cell line) and KKU-M213 (cholangiocarcinoma cell line); ii) high stability, and no-toxicity; iii) high efficiency as a PPT agent. The study conducted on MRI in vitro and in vivo models will be suitable for diagnosis and therapy.

Alginate bone scaffolds coated with a bioactive lactose modified chitosan for human dental pulp stem cells proliferation and differentiation

Bioactive and biodegradable porous scaffolds can hasten the healing of bone defects; moreover, patient stem cells seeded onto scaffolds can enhance the osteoinductive and osteoconductive properties of these biomaterials. In this work, porous alginate/hydroxyapatite scaffolds were functionalized with a bioactive coating of a lactose-modified chitosan (CTL). The highly interconnected porous structure of the scaffold was homogeneously coated with CTL. The scaffolds showed remarkable stability up to 60 days of aging. Human Dental Pulp Stem Cells (hDPSCs) cultured in the presence of CTL diluted in culture medium, showed a slight and negligible increase in terms of proliferation rate; on the contrary, an effect on osteogenic differentiation of the cells was observed as a significant increase in alkaline phosphatase activity. hDPSCs showed higher cell adhesion on CTL-coated scaffolds than on uncoated ones. CTL coating did not affect cell proliferation, but stimulated cell differentiation as shown by alkaline phosphatase activity analysis.

Development of di-methacrylate quaternary ammonium monomers with antibacterial activity

Nine antibacterial di-methacrylate monomers based on bis-quaternary ammonium salts (bis-QAMs) were synthesized and structurally characterized. The biological activity of the bis-QAMs was tested in terms of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) on different bacterial strains achieving promising results and, in most cases, a complete bactericidal effect using a bis-QAM concentration lower than 1 mg/mL. Two of the structures showed comparable and superior activity against S. mutans than the commercial monomer 12-methacryloyloxydodecyl pyridinium bromide (MDBP). All the bis-QAMs here described were able to inhibit S. mutans biofilm formation at a concentration equal to the MIC value. From the analysis of the obtained data, some correlation regarding the structure and the antibacterial activity of the bis-QAMs could be drawn: a flexible alkyl C₁₂ spacer between the two quaternary ammonium moieties increased the monomer antibacterial effect in comparison to the aromatic ones; the equilibrium between hydrophobic and hydrophilic moieties was directly correlated to the bactericidal range of action; the increase of the steric hindrance of the ammonium side groups might be both advantageous or disadvantageous to the antibacterial efficacy depending on the whole monomer chemical structure. Even though the possible correlation between the monomer structures and their bacteriostatic or bactericidal effect is under investigation, the monomers exhibited low cytotoxicity on human dental pulp stem cells, confirming their promising potential in the dental materials' field. STATEMENT OF SIGNIFICANCE: The use of dental resins with antibacterial monomers might prevent the formation of secondary caries at the restoration margins. For this purpose, a series of di-methacrylate bis-quaternary ammonium monomers (QAMs) was developed. Unlike antibacterial mono-methacrylate monomers already described in the literature, the synthesized di-methacrylate monomers have the potential of acting as cross-linkers stabilizing the polymeric network and bear two quaternary ammonium groups that increase their antibacterial ability. The QAMs exert bactericidal activity on both Gram(+) and Gram(-) bacterial strains maintaining at the same time good biocompatibility with the oral environment. Some structural elements of the monomers were clearly related to high antibacterial properties, and this can help design new active structures and better understand their mechanism of action.

Strain Hardening in Highly Acetylated Chitosan Gels

Strain hardening has recently emerged as a near-universal response of biological tissues to mechanical stimulation as well as a powerful regulator of cell fate. Understanding the mechanistic basis for this nonlinear elasticity is crucial for developing bioinspired materials that mimic extracellular matrix mechanics. Here, we show that covalent networks built from highly acetylated chitosans exhibit strain hardening at physiological pH and osmolarity. While varying the chitosan physical-chemical composition and network connectivity, we provide evidence that temporary nodes arising from the entangling of chains between stable cross-links are at the root of nonlinear elasticity. The contour length (L_c) of the said chains revealed that the larger the chain length between the cross-links, the greater is the entanglement over disentanglement upon network stretching. To this end, we calculated that the minimum number of Khun's segments in L_c that contributes to the onset of strain hardening is 15. Furthermore, we identified a relationship between critical strain marking nonlinear elasticity and the network connectivity, being similar to that found for the cytoskeletal collagen matrix, indicating the potential use of semiflexible (neutral pH-soluble) chitosans in assembling extracellular matrix mimics.

Insights into Mechanical Behavior and Biological Properties of Chia Seed Mucilage Hydrogels

In this contribution we report insights on the rheological properties of chia (Salvia hispanica) seed mucilage hydrogels. Creep experiments performed in steady state conditions allowed calculation of Newtonian viscosities for chia hydrogels with different polymer concentration, pointing at inter-chain interactions as the main responsible for the different behavior toward network slipping under constant stress. A combination of oscillatory frequency and stress sweep tests highlighted a moderate effect of temperature in influencing hydrogel mechanics. The latter results prompted us to investigate potential biological functions for this set of biomaterials. Lactate Dehydrogenase assay proved the lack of cytotoxicity of chia suspensions toward Human Mesenchymal Stem Cells from adipose tissue used here as a cell model. Differentiation experiments were finally undertaken to verify the influence of chia samples on osteo-induction triggered by chemical differentiation factors. Alkaline Phosphatase enzyme activity assay and Alizarin red staining demonstrated that chia mucilage did not alter in vitro stem cell differentiation. Collectively, this set of experiments revealed an almost inert role associated with chia suspensions, indicating a possible application of chia-based networks as scaffold models to study osteogenesis in vitro.

CTL-doxorubicin (DOX)-gold complex nanoparticles (DOX-AuGCs): from synthesis to enhancement of therapeutic effect on liver cancer model

In this work, we bring back a rapid way to conceive doxorubicin (DOX) hybrid gold nanoparticles, in which DOX and Au(iii) ions were complexed with a hydrochloride-lactose-modified chitosan, named CTL and dicarboxylic acid-terminated polyethylene-glycol (PEG), leading to hybrid polymer-sugar-metal nanoparticles (DOX-AuGSs). All formulations were assessed by spectroscopic techniques (Raman and UV-Vis) and transmission electron microscopy (TEM). To estimate the therapeutic effect of DOX-AuGSs in liver cancer, murine HepG2 cells were used to induce a hepatic carcinoma model in nude mice. The survival time of the tumor-bearing mice, body weight and tumor volume were measured and recorded. The cytokines were used to detect the serum inflammatory factors, and the blood cell analyzer was used to determine the blood cell content of different groups of nude mice. The outcomes demonstrate that DOX-AuGCs significantly suppressed the tumor growth derived from human HepG2 injection and reduce the tumor index without affecting the body weight of mice. Moreover, DOX-AuGCs significantly reduced the serum levels of cytokines IL-6, TNF-α and IL-12 P70. Finally, a histological analysis of the heart tissue sections indicated that DOX-AuGCs significantly reduce the chronic myocardial toxicity of DOX during the period of treatment.

On the Mechanism of Genipin Binding to Primary Amines in Lactose-Modified Chitosan at Neutral pH

The present manuscript deals with the elucidation of the mechanism of genipin binding by primary amines at neutral pH. UV-VIS and CD measurements both in the presence of oxygen and in oxygen-depleted conditions, combined with computational analyses, led to propose a novel mechanism for the formation of genipin derivatives. The indications collected with chiral and achiral primary amines allowed interpreting the genipin binding to a lactose-modified chitosan (CTL or Chitlac), which is soluble at all pH values. Two types of reaction and their kinetics were found in the presence of oxygen: (i) an interchain reticulation, which involves two genipin molecules and two polysaccharide chains, and (ii) a binding of one genipin molecule to the polymer chain without chain-chain reticulation. The latter evolves in additional interchain cross-links, leading to the formation of the well-known blue iridoid-derivatives.

Binary Solutions of Hyaluronan and Lactose-Modified Chitosan: The Influence of Experimental Variables in Assembling Complex Coacervates

A miscibility study between oppositely charged polyelectrolytes, namely hyaluronic acid and a lactose-modified chitosan, is here reported. Experimental variables such as polymers' weight ratios, pH values, ionic strengths and hyaluronic acid molecular weights were considered. Transmittance analyses demonstrated the mutual solubility of the two biopolymers at a neutral pH. The onset of the liquid-liquid phase separation due to electrostatic interactions between the two polymers was detected at pH 4.5, and it was found to be affected by the overall ionic strength, the modality of mixing and the polymers' weight ratio. Thorough Dynamic Light Scattering (DLS) measurements were performed to check the quality of the formed coacervates by investigating their dimensions, homogeneity and surface charge. The whole DLS results highlighted the influence of the hyaluronic acid molecular weight in affecting coacervates' dispersity and size.

Glycosylated-Chitosan Derivatives: A Systematic Review

Chitosan derivatives, and more specifically, glycosylated derivatives, are nowadays attracting much attention within the scientific community due to the fact that this set of engineered polysaccharides finds application in different sectors, spanning from food to the biomedical field. Overcoming chitosan (physical) limitations or grafting biological relevant molecules, to mention a few, represent two cardinal strategies to modify parent biopolymer; thereby, synthetizing high added value polysaccharides. The present review is focused on the introduction of oligosaccharide side chains on the backbone of chitosan. The synthetic aspects and the effect on physical-chemical properties of such modifications are discussed. Finally, examples of potential applications in biomaterials design and drug delivery of these novel modified chitosans are disclosed.

Long lasting mucoadhesive membrane based on alginate and chitosan for intravaginal drug delivery

The intravaginal route of administration can be exploited to treat local diseases and for systemic delivery. In this work, we developed an alginate/chitosan membrane sufficiently stable in a simulated vaginal fluid and able to dissolve over time at a very slow and linear rate. The membrane demonstrated good mechanical properties both in its swollen and dry form. As a study case, we evaluated the viability of this potential drug delivery system for the treatment of bacterial vaginosis, a common disease affecting women in their reproductive age. Metronidazole was effectively included in the alginate/chitosan membrane and its bactericide effect was demonstrated against Staphylococcus aureus and Gardnerella vaginalis, simultaneously showing good biocompatibility with a cervix epithelial cell line. Since this alginate/chitosan membrane is stable in a simulated vaginal environment, is easy to fabricate and can be used for the controlled release of a model drug, it represents a promising drug delivery system for local intravaginal applications.

Galectin-1 protein modified gold (III)-PEGylated complex-nanoparticles: Proof of concept of alternative probe in colorimetric glucose detection

Galectins (Gal) are a family of dimeric lectins, composed by two galactoside-binding sites implicated in the regulation of cancer progression and immune responses. In this study, we report for the first time the synthesis and the physical-chemical characterization of galectin-1-complex-gold COOH-terminated polyethlenglicole (PEG)-coated NPs (Gal-1 IN PEG-AuNPs) and their ability to recognize glucose in an aqueous solution with a concentration varying from 10 mM to 100 pM. The chemical protocol consistsof three steps: (i) complexation between galectin-1Gal-1 and tetrachloroauric acid (HAuCl₄) to form gold-protein grains; (ii) staking process of COOH-terminated polyethlenglicole molecules (PEG) onto Gal-1-Au complex and (iii) reduction of hybrid metal ions to obtain a colloidal stable solution. During the complexation, the spectral signatures related to the Gal-1 orientation on the gold surface have been found to change due to its protonation state. The effective glucose monitoring was detected by UV-vis, Raman spectroscopy and Transmission Electron Microscopy (TEM). Overall, we observed that the interaction is strongly dependent on the Gal-1 conformation at the surface of gold nanoparticles.

Development of hyaluronan-based membranes for the healing of intestinal surgical wounds: a preliminary study

Implantable membranes based on alginate and hyaluronic acid (HA) were manufactured to obtain a rapidly resorbing pliable mesh for the in situ administration of HA to intestinal tissue. Morphological analyses of this interpenetrated matrix pointed out a homogeneous polymeric texture while degradation studies demonstrated that the material is able to dissolve in physiological solutions within few days. Biological studies in vitro showed that the membrane is biocompatible towards human dermal fibroblasts and that liquid extracts from the HA-containing membrane can stimulate wound healing. A preliminary in vivo biocompatibility study on rats showed that the membranes in direct contact with the intestine did not elicit any acute adverse reaction or immune response, while only a mild inflammatory reaction was noticed at the mesenteric or serosal region. Overall, these results appear to support the application of these polysaccharide-based materials for intestinal wound healing.

Chitosan Acetylation Degree Influences the Physical Properties of Polysaccharide Nanoparticles: Implication for the Innate Immune Cells Response

The aim of the present contribution is twofold as it reports (i) on the role played by chitosan acetylation degree for the stability of nanoparticles (NPs) formed with hyaluronan and (ii) on the effect of the interaction of such NPs with immune cells. Chitosans with similar viscosity-average molecular weight, [Formula: see text], (i.e., 200 000) and different fractions of acetylated units ( F_A) together with low-molecular-weight hyaluronan were chosen for developing a select library of formulations via electrostatic complex coacervation. The resulting NPs were analyzed in terms of size, polydispersity, surface charge, and stability in physiological-mimicked media by dynamic light scattering. Only medium acetylated chitosan ( F_A = 0.16) guaranteed the stability of NPs. To explore the effect of NPs interaction with immune cells, the release of proinflammatory cytokines and the reactive oxygen species production by human macrophages and neutrophils, respectively, were evaluated. Strikingly, a structure-function relationship emerged, showing that NPs made of chitosans with F_A = 0.02, 0.25, 0.46, and 0.63 manifested a proinflammatory activity, linked to the instability of the system. Conversely, NPs made of chitosan with F_A = 0.16 neither modified the functional response of macrophages nor that of neutrophils. Of note, such NPs were found to possess additional properties potentially advantageous in applications such as delivery of therapeutics to target inflamed sites: (i) they are devoid of cytotoxic effects, (ii) they avoid engulfment during the early stage of interaction with macrophages, and (iii) they are muco-adhesive, thereby providing for site-specificity and long-residence effects.

Three-Dimensional Bone Substitutes for Oral and Maxillofacial Surgery: Biological and Structural Characterization

Background: Bone substitutes, either from human (autografts and allografts) or animal (xenografts) sources, suffer from inherent drawbacks including limited availability or potential infectivity to name a few. In the last decade, synthetic biomaterials have emerged as a valid alternative for biomedical applications in the field of orthopedic and maxillofacial surgery. In particular, phosphate-based bone substitution materials have exhibited a high biocompatibility due to their chemical similitude with natural hydroxyapatite. Besides the nature of the biomaterial, its porous and interconnected architecture is essential for a correct osseointegration. This performance could be predicted with an extensive characterization of the biomaterial in vitro. Methods: In this study, we compared the biological, chemical, and structural features of four different commercially available bone substitutes derived from an animal or a synthetic source. To this end, µ-CT and SEM were used to describe the biomaterials structure. Both FTIR and EDS analyses were carried out to provide a chemical characterization. The results obtained by these techniques were correlated with cell adhesion and proliferation of the osteosarcoma MG-63 human cell line cultured in vitro. Results: The findings reported in this paper indicate a significant influence of both the nature and the structure of the biomaterials in cell adhesion and proliferation, which ultimately could affect the clinical performance of the biomaterials. Conclusions: The four commercially available bone substitutes investigated in this work significantly differed in terms of structural features, which ultimately influenced in vitro cell proliferation and may so affect the clinical performance of the biomaterials.

Lactose-Modified Chitosan Gold(III)-PEGylated Complex-Bioconjugates: From Synthesis to Interaction with Targeted Galectin-1 Protein

Galectins (Gal) are a family of glycan-binding proteins characterized by their affinity for β-galactosides. Galectin-1 (Gal-1), a dimeric lectin with two galactoside-binding sites, regulates cancer progression and immune responses. Coordination chemistry has been engaged to develop versatile multivalent neoglycoconjugates for binding Gal-1. In this study we report a fast and original method to synthesize hybrid gold nanoparticles in which a hydrochloride lactose-modified chitosan, named CTL, is mixed with dicarboxylic acid-terminated polyethylene glycol (PEG), leading to shell-like hybrid polymer-sugar-metal nanoparticles (CTL-PEG-AuNPs). The aim of this paper is to preliminarily study the interaction of the CTL-PEG-AuNPs with a target protein, namely, Gal-1, under specific conditions. The molecular interaction has been measured by Transmission Electron Microscopy (TEM), UV-vis, and Raman Spectroscopy on a large range of Gal-1 concentrations (from 0 to 10^-12 M). We observed that the interaction was strongly dependent on the Gal-1 concentration at the surface of the gold nanoparticles.

Complex Coacervates between a Lactose-Modified Chitosan and Hyaluronic Acid as Radical-Scavenging Drug Carriers

Complex coacervation of two oppositely charged polysaccharides, namely a lactose-modified chitosan (CTL) and hyaluronan (HA), was investigated in this study. Coacervates of the two polysaccharides were prepared by drop-by-drop injection of HA into CTL. Transmittance and dynamic light scattering (DLS) measurements in combination with TEM analyses demonstrated the formation of spheroidal colloids in the nano-/microsize range showing good homogeneity. Strikingly, the presence of 150 mM supporting NaCl did not hamper the colloid formation. Stability studies on selected formulations demonstrated that HA/CTL coacervates were stable up to 3 weeks at 37 °C and behaved as pH-responsive colloids since transition from entangled to disentangled chains was attained for a proper pH range. The possibility of freeze-drying the coacervates for storage purposes and the ability of encapsulating selected payloads were investigated as well, for two values of the fraction of the lactitol side-chain substitution (F_L). Finally, biological tests using human neutrophils were undertaken at acidic pH value (pH = 6.0): under such experimental conditions, akin to those frequently occurring in the inflammatory microenvironment, coacervates scavenged reactive oxygen species (ROS) generated by these cells in basal conditions. Given the well documented bioactivity of CTL with respect to chitosan toward cartilage regeneration, these findings point to a possible application of HA/CTL-based colloids as scavenging and bioactive carriers for the delivery of therapeutic molecules at confined inflamed sites such as knee joints.

Concepts for Developing Physical Gels of Chitosan and of Chitosan Derivatives

Chitosan macro- and micro/nano-gels have gained increasing attention in recent years, especially in the biomedical field, given the well-documented low toxicity, degradability, and non-immunogenicity of this unique biopolymer. In this review we aim at recapitulating the recent gelling concepts for developing chitosan-based physical gels. Specifically, we describe how nowadays it is relatively simple to prepare networks endowed with different sizes and shapes simply by exploiting physical interactions, namely (i) hydrophobic effects and hydrogen bonds-mostly governed by chitosan chemical composition-and (ii) electrostatic interactions, mainly ensured by physical/chemical chitosan features, such as the degree of acetylation and molecular weight, and external parameters, such as pH and ionic strength. Particular emphasis is dedicated to potential applications of this set of materials, especially in tissue engineering and drug delivery sectors. Lastly, we report on chitosan derivatives and their ability to form gels. Additionally, we discuss the recent findings on a lactose-modified chitosan named Chitlac, which has proved to form attractive gels both at the macro- and at the nano-scale.

Exploiting natural polysaccharides to enhance in vitro bio-constructs of primary neurons and progenitor cells

Current strategies in Central Nervous System (CNS) repair focus on the engineering of artificial scaffolds for guiding and promoting neuronal tissue regrowth. Ideally, one should combine such synthetic structures with stem cell therapies, encapsulating progenitor cells and instructing their differentiation and growth. We used developments in the design, synthesis, and characterization of polysaccharide-based bioactive polymeric materials for testing the ideal composite supporting neuronal network growth, synapse formation and stem cell differentiation into neurons and motor neurons. Moreover, we investigated the feasibility of combining these approaches with engineered mesenchymal stem cells able to release neurotrophic factors. We show here that composite bio-constructs made of Chitlac, a Chitosan derivative, favor hippocampal neuronal growth, synapse formation and the differentiation of progenitors into the proper neuronal lineage, that can be improved by local and continuous delivery of neurotrophins.

STATEMENT OF SIGNIFICANCE

In our work, we characterized polysaccharide-based bioactive platforms as biocompatible materials for nerve tissue engineering. We show that Chitlac-thick substrates are able to promote neuronal growth, differentiation, maturation and formation of active synapses. These observations support this new material as a promising candidate for the development of complex bio-constructs promoting central nervous system regeneration. Our novel findings sustain the exploitation of polysaccharide-based scaffolds able to favour neuronal network reconstruction. Our study shows that Chitlac-thick may be an ideal candidate for the design of biomaterial scaffolds enriched with stem cell therapies as an innovative approach for central nervous system repair.

Molecular mechanisms driving Streptococcus mitis entry into human gingival fibroblasts in presence of chitlac-nAg and saliva

The molecular mechanisms leading to Streptococcus mitis capability of entering oral cells were investigated in a co-culture of S. mitis and Human Gingival Fibroblasts (HGFs) in the presence of saliva. An innovative colloidal solution based on silver nanoparticles (Chitlac-nAg), a promising device for daily oral care, was added to the experimental system in order to study the effects of silver on the bacterial overgrowth and ability to enter non-phagocytic eukaryotic cells. The entry of bacteria into the eukaryotic cells is mediated by a signalling pathway involving FAK, integrin β1, and the two cytoskeleton proteins vinculin and F-actin, and down-regulated by the presence of saliva both at 3 and 48 h of culture, whereas Chitlac-n Ag exposure seems to influence, by incrementing it, the number of bacteria entering the fibroblasts only at 48 h. The formation of fibrillary extrusion from HGFs and the co-localization of bacteria and silver nanoparticles within the fibroblast vacuoles were also recorded. After longer experimental times (72 and 96 h), the number of S. mitis chains inside gingival cells is reduced, mainly in presence of saliva. The results suggest an escape of bacteria from fibroblasts to restore the microbial balance of the oral cavity.

Alginate membranes loaded with hyaluronic acid and silver nanoparticles to foster tissue healing and to control bacterial contamination of non-healing wounds

Chronic non-healing wounds are a clinically important problem in terms of number of patients and costs. Wound dressings such as hydrogels, hydrocolloids, polyurethane films and foams are commonly used to manage these wounds since they tend to maintain a moist environment which is shown to accelerate re-epithelialization. The use of antibacterial compounds is important in the management of wound infections. A novel wound-dressing material based on a blended matrix of the polysaccharides alginate, hyaluronic acid and Chitlac-silver nanoparticles is here proposed and its application for wound healing is examined. The manufacturing approach to obtain membranes is based on gelling, foaming and freeze-casting of alginate, hyaluronic acid and Chitlac-silver nanoparticles mixtures using calcium ions as the cross-linking agent. Comprehensive evaluations of the morphology, swelling kinetics, permeability, mechanical characteristics, cytotoxicity, capability to inhibit metalloproteinases and of antibacterial property were conducted. Biological in vitro studies demonstrated that hyaluronic acid released by the membrane is able to stimulate the wound healing meanwhile the metal silver exploits an efficient antibacterial activity against both planktonic bacteria and biofilms. Overall, the experimental data evidence that the studied material could be used as antibacterial wound dressing for wound healing promotion.

Alginate/Hydroxyapatite-Based Nanocomposite Scaffolds for Bone Tissue Engineering Improve Dental Pulp Biomineralization and Differentiation

Tissue engineering is widely recognized as a promising approach for bone repair and reconstruction. Several attempts have been made to achieve materials that must be compatible, osteoconductive, and osteointegrative and have mechanical strength to provide a structural support. Composite scaffolds consisting in biodegradable natural polymers are very promising constructs. Hydroxyapatite (HAp) can support alginate as inorganic reinforcement and osteoconductive component of alginate/HAp composite scaffolds. Therefore, HAp-strengthened polymer biocomposites offer a solid system to engineer synthetic bone substitutes. In the present work, HAp was incorporated into an alginate solution and internal gelling was induced by addition of slowly acid-hydrolyzing D-gluconic acid delta-lactone for the direct release of calcium ions from HAp. It has been previously demonstrated that alginate-based composites efficiently support adhesion of cancer bone cell lines. Human dental pulp stem cells (DPSCs) identified in human dental pulp are clonogenic cells capable of differentiating in multiple lineage. Thus, this study is aimed at verifying the mineralization and differentiation potential of human DPSCs seeded onto scaffolds based on alginate and nano-hydroxyapatite. For this purpose, gene expression profile of early and late mineralization-related markers, extracellular matrix components, viability parameters, and oxidative stress occurrence were evaluated and analyzed. In summary, our data show that DPSCs express osteogenic differentiation-related markers and promote calcium deposition and biomineralization when growing onto Alg/HAp scaffolds. These findings confirm the use of Alg/HAp scaffolds as feasible composite materials in tissue engineering, being capable of promoting a specific and successful tissue regeneration as well as mineralized matrix deposition and sustaining natural bone regeneration.

Boric Acid Induced Transient Cross-Links in Lactose-Modified Chitosan (Chitlac)

The present paper explores the effect of boric acid on Chitlac, a lactose-modified chitosan which had previously shown interesting biological and physical-chemical features. The herewith-reported experimental evidences demonstrated that boric acid binds to Chitlac, producing conformational and association effects on the chitosan derivative. The thermodynamics of boric acid binding to Chitlac was explored by means of ¹¹B NMR, circular dichroism (CD), and UV-vis spectroscopy, while macromolecular effects were investigated by means of viscometry and dynamic light scattering (DLS). The experimental results revealed a chain-chain association when limited amounts of boric acid were added to Chitlac. However, upon exceeding a critical boric acid limit dependent on the polysaccharide concentration, the soluble aggregates disentangle. The rheological behavior of Chitlac upon treatment with boric acid was explored showing a dilatant behavior in conditions of steady flow. An uncommonly high dependence in the scaling law between the zero-shear viscosity and the concentration of Chitlac was found, i.e., η₀ ∝ C_CTL^5.8, pointing to interesting potential implications of the present system in biomaterials development.

Butyrate-Loaded Chitosan/Hyaluronan Nanoparticles: A Suitable Tool for Sustained Inhibition of ROS Release by Activated Neutrophils

Tissue damage caused by excessive amounts of neutrophil-derived reactive oxygen species (ROS) occurs in many inflammatory diseases. Butyrate is a short-chain fatty acid (SCFA) with known anti-inflammatory properties, able to modulate several neutrophil functions. Evidence is provided here that butyrate inhibits neutrophil ROS release in a dose and time-dependent fashion. Given the short half-life of butyrate, chitosan/hyaluronan nanoparticles are next designed and developed as controlled release carriers able to provide cells with a long-lasting supply of this SCFA. Notably, while the inhibition of neutrophil ROS production by free butyrate declines over time, that of butyrate-loaded chitosan/hyaluronan nanoparticles (B-NPs) is sustained. Additional valuable features of these nanoparticles are inherent ROS scavenger activity, resistance to cell internalization, and mucoadhesiveness. B-NPs appear as promising tools to limit ROS-dependent tissue injury during inflammation. Particularly, by virtue of their mucoadhesiveness, B-NPs administered by enema can be effective in the treatment of inflammatory bowel diseases.

Mimicking mechanical response of natural tissues. Strain hardening induced by transient reticulation in lactose-modified chitosan (chitlac)

The effect of transient cross-links has been explored on a lactose-modified chitosan, which previously had shown interesting biological features. The presence of galactose side chains and of the polyol spacer resulted particularly appealing for the reticulation by borate ions. The interaction between chitlac and borax was investigated by means of ¹¹B NMR while rheology pointed to a marked non-linear behavior depending on the amount of borax added to the system. The presence of limited amount of cross-linking ion led to dilatant behavior when the steady flow curve was measured. In addition, strain stiffening was noticed on elastic response upon exceeding a critical stress, indicating a transient nature in the formation of the cross-links. The non-linear response of chitlac in the presence of borax compared surprisingly well with the one showed by proteins composing the natural ECM pointing at a possible role of mechanotransduction in the biological significance of the modified chitosan.

Highly monodisperse colloidal coacervates based on a bioactive lactose-modified chitosan: From synthesis to characterization

The present contribution aims at describing the fabrication of coacervates in the nano-size range starting from a 1-deoxylactit-1-yl chitosan (in this manuscript termed as CTL60) and the multivalent anion tripolyphosphate (TPP). Colloidal coacervates have been obtained for precise values of the molar ratio of TPP to CTL60 repeating unit. Coacervation is ensured only at pH 4.5 and not at 7.4, thus demonstrating the key role of electrostatic interactions in the stabilization of the coacervates. At a variance with chitosan, CTL60 favors the formation of highly homogeneous coacervates with very low values of the polydispersity index (PDI). Moreover, CTL60 coacervates can be freeze-dried without any cryoprotectant, they can host a model molecule and are stable up to three weeks at 4°C. Conversely, such coacervates dissolve upon increasing pH and ionic strength. By considering the bioactive polycation CTL60, the present system can be suggested as a first step in the development of innovative biologically-active nano-carriers to be used as drug delivery systems.

Antibacterial-nanocomposite bone filler based on silver nanoparticles and polysaccharides

Injectable bone fillers represent an attractive strategy for the treatment of bone defects. These injectable materials should be biocompatible, capable of supporting cell growth and possibly able to exert antibacterial effects. In this work, nanocomposite microbeads based on alginate, chitlac, hydroxyapatite and silver nanoparticles were prepared and characterized. The dried microbeads displayed a rapid swelling in contact with simulated body fluid and maintained their integrity for more than 30 days. The evaluation of silver leakage from the microbeads showed that the antibacterial metal is slowly released in saline solution, with less than 6% of silver released after 1 week. Antibacterial tests proved that the microbeads displayed bactericidal effects toward Staphylococcus aureus, Pseudomonas aeruginosa and Staphylococcus epidermidis, and were also able to damage pre-formed bacterial biofilms. On the other hand, the microbeads did not exert any cytotoxic effect towards osteoblast-like cells. After characterization of the microbeads bioactivity, a possible means to embed them in a fluid medium was explored in order to obtain an injectable paste. Upon suspension of the particles in alginate solution or alginate/hyaluronic acid mixtures, a homogenous and time-stable paste was obtained. Mechanical tests enabled to quantify the extrusion forces from surgical syringes, pointing out the proper injectability of the material. This novel antibacterial bone filler appears as a promising material for the treatment of bone defects, in particular when possible infections could compromise the bone-healing process. Copyright © 2016 John Wiley & Sons, Ltd.

Adhesive coatings based on melanin-like nanoparticles for surgical membranes

Adhesive coatings for implantable biomaterials can be designed to prevent material displacement from the site of implant. In this paper, a strategy based on the use of melanin-like nanoparticles (MNPs) for the development of adhesive coatings for polysaccharidic membranes was devised. MNPs were synthesized in vitro and characterized in terms of dimensions and surface potential, as a function of pH and ionic strength. The in vitro biocompatibility of MNPs was investigated on fibroblast cells, while the antimicrobial properties of MNPs in suspension were evaluated on E. coli and S. aureus cultures. The manufacturing of the adhesive coatings was carried out by spreading MNPs over the surface of polysaccharidic membranes; the adhesive properties of the nano-engineered coating to the target tissue (intestinal serosa) were studied in simulated physiological conditions. Overall, this study opens for novel approaches in the design of naturally inspired nanostructured adhesive systems.

Comparison of three different application routes of butyrate to improve colonic anastomotic strength in rats

INTRODUCTION

Despite extensive research, anastomotic leakage (AL) remains one of the most dreaded complications after colorectal surgery. Since butyrate enemas are known to enhance anastomotic healing, several administration routes have been explored in this study.

METHODS

Three intraluminal approaches involving butyrate were investigated: (1) butyrin-elucidating patch, (2) a single injection of hyaluronan-butyrate (HA-But) prior to construction of the proximal anastomosis and (3) rectal hyaluronan-butyrate (HA-But) enemas designed for distal anastomoses. The main outcome was AL and secondary outcomes were bursting pressure, histological analysis of the anastomosis, zymography to detect MMP activity and qPCR for gene expression of MMP2, MMP9, MUC2 and TFF3.

RESULTS

Neither the patches nor the injections led to a reduction of AL in experiments 1 and 2. In experiment 3, a significant reduction of AL was accomplished with the (HA-But) enema compared to the control group together with a higher bursting pressure. Histological analysis detected only an increased inflammation in experiment 2 in the hyaluronan injection group compared to the control group. No other differences were found regarding wound healing. Zymography identified a decreased proenzyme of MMP9 when HA-But was administered as a rectal enema. qPCR did not show any significant differences between groups in any experiment.

CONCLUSION

Butyrate enemas are effective in the enhancement of colonic anastomosis. Enhanced butyrate-based approaches designed to reduce AL in animal models for both proximal and distal anastomoses were not more effective than were butyrate enemas alone. Further research should focus on how exogenous butyrate can improve anastomotic healing after gastrointestinal surgery.

Enhanced bioadhesivity of dopamine-functionalized polysaccharidic membranes for general surgery applications

An emerging strategy to improve adhesiveness of biomaterials in wet conditions takes inspiration from the adhesive features of marine mussel, which reside in the chemical reactivity of catechols. In this work, a catechol-bearing molecule (dopamine) was chemically grafted onto alginate to develop a polysaccharide-based membrane with improved adhesive properties. The dopamine-modified alginates were characterized by NMR, UV spectroscopy and in vitro biocompatibility. Mechanical tests and in vitro adhesion studies pointed out the effects of the grafted dopamine within the membranes. The release of HA from these resorbable membranes was shown to stimulate fibroblasts activities (in vitro). Finally, a preliminary in vivo test was performed to evaluate the adhesiveness of the membrane on porcine intestine (serosa). Overall, this functionalized membrane was shown to be biocompatible and to possess considerable adhesive properties owing to the presence of dopamine residues grafted on the alginate backbone.

STATEMENT OF SIGNIFICANCE

This article describes the development of a mussels-inspired strategy for the development of an adhesive polysaccharide-based membrane for wound healing applications. Bioadhesion was achieved by grafting dopamine moieties on the structural component on the membrane (alginate): this novel biomaterial showed improved adhesiveness to the intestinal tissue, which was demonstrated by both in vitro and in vivo studies. Overall, this study points out how this nature-inspired strategy may be successfully exploited for the development of novel engineered biomaterials with enhanced bioadhesion, thus opening for novel applications in the field of general surgery.

Bioactive glass surface for fiber reinforced composite implants via surface etching by Excimer laser

Biostable fiber-reinforced composites (FRC) prepared from bisphenol-A-glycidyldimethacrylate (BisGMA)-based thermosets reinforced with E-glass fibers are promising alternatives to metallic implants due to the excellent fatigue resistance and the mechanical properties matching those of bone. Bioactive glass (BG) granules can be incorporated within the polymer matrix to improve the osteointegration of the FRC implants. However, the creation of a viable surface layer using BG granules is technically challenging. In this study, we investigated the potential of Excimer laser ablation to achieve the selective removal of the matrix to expose the surface of BG granules. A UV-vis spectroscopic study was carried out to investigate the differences in the penetration of light in the thermoset matrix and BG. Thereafter, optimal Excimer laser ablation parameters were established. The formation of a calcium phosphate (CaP) layer on the surface of the laser-ablated specimens was verified in simulated body fluid (SBF). In addition, the proliferation of MG63 cells on the surfaces of the laser-ablated specimens was investigated. For the laser-ablated specimens, the pattern of proliferation of MG63 cells was comparable to that in the positive control group (Ti6Al4V). We concluded that Excimer laser ablation has potential for the creation of a bioactive surface on FRC-implants.

Adhesion of human gingival fibroblasts/Streptococcus mitis co-culture on the nanocomposite system Chitlac-nAg

Composite materials are increasingly used as dental restoration. In the field of biomaterials, infections remain the main reason of dental devices failure. Silver, in the form of nanoparticles (AgNPs), ions and salt, well known for its antimicrobial properties, is used in several medical applications in order to avoid bacterial infection. To reduce both bacterial adhesion to dental devices and cytotoxicity against eukaryotic cells, we coated BisGMA/TEGDMA methacrylic thermosets with a new material, Chitlac-nAg, formed by stabilized AgNPs with a polyelectrolyte solution containing Chitlac. Here we analyzed the proliferative and adhesive ability of human gingival fibroblasts (HGFs) on BisGMA/TEGDMA thermosets uncoated and coated with AgNPs in a coculture model system with Streptococcus mitis. After 48 h, HGFs well adhered onto both surfaces, while S. mitis cytotoxic response was higher in the presence of AgNPs coated thermosets. After 24 h thermosets coated with Chitlac as well as those coated with Chitlac-nAg exerted a minimal cytotoxic effect on HGFs, while after 48 h LDH release raised up to 20 %. Moreover the presence of S. mitis reduced this release mainly when HGFs adhered to Chitlac-nAg coated thermosets. The reduced secretion of collagen type I was significant in the presence of both surfaces with the co-culture system even more when saliva is added. Integrin β1 localized closely to cell membranes onto Chitlac-nAg thermosets and PKCα translocated into nuclei. These data confirm that Chitlac-nAg have a promising utilization in the field of restorative dentistry exerting their antimicrobial activity due to AgNPs without cytotoxicity for eukaryotic cells.

A silver complex of hyaluronan-lipoate (SHLS12): Synthesis, characterization and biological properties

In this study we present a novel silver complex of hyaluronan-lipoate (SHLS12) in a gel-state form. NMR analysis, conductometry and elemental analysis demonstrated stable non-covalent interactions between silver ions and the polysaccharide-lipoate backbone, whereas rheological investigations confirmed its gel-like physical-chemical behavior. Biological studies showed the ability of SHLS12 to exert a straightforward activity against different bacterial strains grown in sessile/planktonic state. The biocompatibility was also proved toward two eukaryotic cell lines. By considering both its ability to preserve antibacterial properties when exposed to the serum protein BSA and its low susceptibility to be degraded by hyaluronidase enzyme, this novel complex may be considered as a promising biomaterial for future in vivo applications.