Gelatin Methacryloyl (GelMA) Hydrogel Scaffolds: Predicting Physical Properties Using an Experimental Design Approach.

There is a growing interest for complex in vitro environments that closely mimic the extracellular matrix and allow cells to grow in microenvironments that are closer to the one in vivo. Protein-based matrices and especially hydrogels can answer this need, thanks to their similarity with the cell microenvironment and their ease of customization. In this study, an experimental design was conducted to study the influence of synthesis parameters on the physical properties of gelatin methacryloyl (GelMA). Temperature, ratio of methacrylic anhydride over gelatin, rate of addition, and stirring speed of the reaction were studied using a Doehlert matrix. Their impact on the following parameters was analyzed: degree of substitution, mass swelling ratio, storage modulus (log(G')), and compression modulus. This study highlights that the most impactful parameter was the ratio of methacrylic anhydride over gelatin. Although, temperature affected the degree of substitution, and methacrylic anhydride addition flow rate impacted the gel's physical properties, namely, its storage modulus and compression modulus. Moreover, this experimental design proposed a theoretical model that described the variation of GelMA's physical characteristics as a function of synthesis conditions.

Encapsulation of Salmon Peptides in Marine Liposomes: Physico-Chemical Properties, Antiradical Activities and Biocompatibility Assays.

Salmon byproducts (Salmo salar) generated by the food chain represent a source of long-chain polyunsaturated fatty acids (eicosapentaenoic acid (EPA): 20:5n-3; docosahexaenoic acid (DHA): 22:6n-3) and peptides that can be used as supplements in food for nutraceutical or health applications, such as in the prevention of certain pathologies (e.g., Alzheimer's and cardiovascular diseases). The extraction of polar lipids naturally rich in PUFAs by enzymatic processes without organic solvent (controlled by pH-Stat method), coupled with the production of 1 kDa salmon peptides by membrane filtration, allowed the formulation of nanocarriers. The physicochemical properties of the nanoliposomes (size ranging from 120 to 140 nm, PDI of 0.27, zeta potential between -32 and -46 mV and encapsulation efficiency) were measured, and the bioactivity of salmon hydrolysate peptides was assessed (antioxidant and antiradical activity: ABTS, ORAC, DPPH; iron metal chelation). Salmon peptides exhibited good angiotensin-conversion-enzyme (ACE) inhibition activity, with an IC50 value of 413.43 ± 13.12 µg/mL. Cytotoxicity, metabolic activity and proliferation experiments demonstrated the harmlessness of the nanostructures in these experimental conditions.

Investigating heartbeat-related in-plane motion and stress levels induced at the aortic root.

BACKGROUND: The axial motion of aortic root (AR) due to ventricular traction was previously suggested to contribute to ascending aorta (AA) dissection by increasing its longitudinal stress, but AR in-plane motion effects on stresses have never been studied. The objective is to investigate the contribution of AR in-plane motion to AA stress levels. METHODS: The AR in-plane motion was assessed on magnetic resonance imagining data from 25 healthy volunteers as the movement of the AA section centroid. The measured movement was prescribed to the proximal AA end of an aortic finite element model to investigate its influences on aortic stresses. The finite element model was developed from a patient-specific geometry using LS-DYNA solver and validated against the aortic distensibility. Fluid-structure interaction (FSI) approach was also used to simulate blood hydrodynamic effects on aortic dilation and stresses. RESULTS: The AR in-plane motion was 5.5 ± 1.7 mm with the components of 3.1 ± 1.5 mm along the direction of proximal descending aorta (PDA) to AA centroid and 3.0 ± 1.3 mm perpendicularly under the PDA reference system. The AR axial motion elevated the longitudinal stress of proximal AA by 40% while the corresponding increase due to in-plane motion was always below 5%. The stresses at proximal AA resulted approximately 7% less in FSI simulation with blood flow. CONCLUSIONS: The AR in-plane motion was comparable with the magnitude of axial motion. Neither axial nor in-plane motion could directly lead to AA dissection. It is necessary to consider the heterogeneous pressures related to blood hydrodynamics when studying aortic wall stress levels.

Neurotrophic Effect of Fish-Lecithin Based Nanoliposomes on Cortical Neurons.

Lipids play multiple roles in preserving neuronal function and synaptic plasticity, and polyunsaturated fatty acids (PUFAs) have been of particular interest in optimizing synaptic membrane organization and function. We developed a green-based methodology to prepare nanoliposomes (NL) from lecithin that was extracted from fish head by-products. These NL range between 100-120 nm in diameter, with an n-3/n-6 fatty acid ratio of 8.88. The high content of n-3 PUFA (46.3% of total fatty acid content) and docosahexanoic acid (26%) in these NL represented a means for enrichment of neuronal membranes that are potentially beneficial for neuronal growth and synaptogenesis. To test this, the primary cultures of rat embryo cortical neurons were incubated with NL on day 3 post-culture for 24 h, followed by immunoblots or immunofluorescence to evaluate the NL effects on synaptogenesis, axonal growth, and dendrite formation. The results revealed that NL-treated cells displayed a level of neurite outgrowth and arborization on day 4 that was similar to those of untreated cells on day 5 and 6, suggesting accelerated synapse formation and neuronal development in the presence of NL. We propose that fish-derived NL, by virtue of their n-3 PUFA profile and neurotrophic effects, represent a new innovative bioactive vector for developing preventive or curative treatments for neurodegenerative diseases.

Preparation, Characterization, and Release Kinetics of Chitosan-Coated Nanoliposomes Encapsulating Curcumin in Simulated Environments.

Curcumin, a natural polyphenol, has many biological properties, such as anti-inflammatory, antioxidant, and anti-carcinogenic properties, yet, its sensitivity to light, oxygen, and heat, and its low solubility in water renders its preservation and bioavailability challenging. To increase its bioaccessibility, we fabricated nanoliposomes and chitosan-coated nanoliposomes encapsulating curcumin, and we evaluated the systems in terms of their physicochemical characteristics and release profiles in simulated gastrointestinal mediums. Chitosan-coating enhanced the stability of nanoliposomes and slowed the release of curcumin in the simulated gastrointestinal (GI) environment. This study demonstrates that nanoliposomes and chitosan-coated nanoliposomes are promising carriers for poorly soluble lipophilic compounds with low oral bioavailability, such as curcumin.

The Positive Role of Curcumin-Loaded Salmon Nanoliposomes on the Culture of Primary Cortical Neurons.

Curcumin (diferuloylmethane) is a natural bioactive compound with many health-promoting benefits. However, its poor water solubility and bioavailability has limited curcumin’s biomedical application. In the present study, we encapsulated curcumin into liposomes, formed from natural sources (salmon lecithin), and characterized its encapsulation efficiency and release profile. The proposed natural carriers increased the solubility and the bioavailability of curcumin. In addition, various physico-chemical properties of the developed soft nanocarriers with and without curcumin were studied. Nanoliposome-encapsulated curcumin increased the viability and network formation in the culture of primary cortical neurons and decreased the rate of apoptosis.

Bioactive Films Containing Alginate-Pectin Composite Microbeads with Lactococcus lactis subsp. lactis: Physicochemical Characterization and Antilisterial Activity.

Novel bioactive films were developed from the incorporation of Lactococcus lactis into polysaccharide films. Two different biopolymers were tested: cellulose derivative (hydroxylpropylmethylcellulose (HPMC)) and corn starch. Lactic acid bacteria (LAB) free or previously encapsulated in alginate-pectin composite hydrogel microbeads were added directly to the film forming solution and films were obtained by casting. In order to study the impact of the incorporation of the protective culture into the biopolymer matrix, the water vapour permeability, oxygen permeability, optical and mechanical properties of the dry films were evaluated. Furthermore, the antimicrobial effect of bioactive films against Listeria monocytogenes was studied in synthetic medium. Results showed that the addition of LAB or alginate-pectin microbeads modified slightly films optical properties. In comparison with HPMC films, starch matrix proves to be more sensitive to the addition of bacterial cells or beads. Indeed, mechanical resistance of corn starch films was lower but barrier properties were improved, certainly related to the possible establishment of interactions between alginate-pectin beads and starch. HPMC and starch films containing encapsulated bioactive culture showed a complete inhibition of listerial growth during the first five days of storage at 5 °C and a reduction of 5 logs after 12 days.

Synthesis and Characterization of Nanofunctionalized Gelatin Methacrylate Hydrogels.

Given the importance of the extracellular medium during tissue formation, it was wise to develop an artificial structure that mimics the extracellular matrix while having improved physico-chemical properties. That is why the choice was focused on gelatin methacryloyl (GelMA), an inexpensive biocompatible hydrogel. Physicochemical and mechanical properties were improved by the incorporation of nanoparticles developed from two innovative fabrication processes: High shear fluid and low frequencies/high frequencies ultrasounds. Both rapeseed nanoliposomes and nanodroplets were successfully incorporated in the GelMA networks during the photo polymerization process. The impact on polymer microstructure was investigated by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and enzymatic degradation investigations. Mechanical stability and viscoelastic tests were conducted to demonstrate the beneficial effect of the functionalization on GelMA hydrogels. Adding nanoparticles to GelMA improved the surface properties (porosity), tuned swelling, and degradability properties. In addition, we observed that nanoemulsion didn't change significantly the mechanical properties to shear and compression solicitations, whereas nanoliposome addition decreased Young's modulus under compression solicitations. Thus, these ways of functionalization allow controlling the design of the material by choosing the type of nanoparticle (nanoliposome or nanoemulsion) in function of the application.

Nanoliposomes Permeability in a Microfluidic Drug Delivery Platform across a 3D Hydrogel.

Nanoliposomes are nano-sized vesicles that can be used as drug delivery carriers with the ability to encapsulate both hydrophobic and hydrophilic compounds. Moreover, their lipid compositions facilitate their internalization by cells. However, the interaction between nanoliposomes and the membrane barrier of the human body is not well-known. If cellular tests and animal testing offer a solution, their lack of physiological relevance and ethical concerns make them unsuitable to properly mimic human body complexity. Microfluidics, which allows the environment of the human body to be imitated in a controlled way, can fulfil this role. However, existing models are missing the presence of something that would mimic a basal membrane, often consisting of a simple cell layer on a polymer membrane. In this study, we investigated the diffusion of nanoliposomes in a microfluidic system and found the optimal parameters to maximize their diffusion. Then, we incorporated a custom made GelMA with a controlled degree of substitution and studied the passage of fluorescently labeled nanoliposomes through this barrier. Our results show that highly substituted GelMA was more porous than lower substitution GelMA. Overall, our work lays the foundation for the incorporation of a hydrogel mimicking a basal membrane on a drug delivery microfluidic platform.

Impact of a Starch Hydrolysate on the Production of Exopolysaccharides in a Fermented Plant-Based Dessert Formulation.

Plant-based desserts are becoming increasingly popular with and appreciated by consumers. However, they are limited by the choice of ingredients, which are often expensive and unstable with a random texture. Therefore, the aim of the research is to propose a new product that offers an advantageous texture and flavour in a fermented dessert based on a flour mix supplemented with an enzymatic hydrolysate. This study involved the development of two processes: (i) an enzymatic hydrolysis of oat flour and (ii) a fermentation of a flour mixture (oat, chickpea, and coconut) by lactic acid bacteria (Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus). The result of the oat flour hydrolysate shows a significant decrease in starch after 60 min of reaction, followed by an increase in sugar content. During 23 days of storage at 4 °C, the formulations used showed post-acidification, water retention capacity decrease, and hardness increase related to the hydrolysate rate (p < 0.05). All formulations allowed the viability of lactic bacteria (over 5 log10 CFU/mL) and verified their ability to produce exopolysaccharides (0.23-0.73 g/100 g). The prototyping of such a product represents a key step in meeting the growing demand for plant-based alternatives, with qualitative sensory characteristics without additives.

Engineering of poly(caprolactone) and poly(glycerol sebacate) small-diameter vascular prosthesis with quercetin.

The fabrication of biodegradable, bioabsorbable, and biocompatible vascular scaffolds with enhanced mechanical and biological properties that are able to modulate local inflammation and induce endothelialization after surgical implant is still a challenge. In this work, a fibrous scaffold, made of poly(ε-caprolactone) and poly(glycerol sebacate), was fabricated to be potentially used as a small-diameter graft in vascular surgery. The novelty of this research is represented by the direct incorporation of quercetin, a well-known antioxidant compound with several biological properties, into a polymeric scaffold obtaining a vascular construct able to modulate two key factors involved in postsurgical inflammation, matrix metalloproteinase-9 and endothelial nitric oxide synthase. For its production, an electrospinning apparatus, a solution made of the two polymers (both 20% (w/v), mixed at the ratio 1:1 (v/v)), and free quercetin (0.05% (w/v)) were used. Scanning electron and atomic force microscopies were employed to investigate the morphological properties of the fabricated electrospun scaffolds. Furthermore, physicochemical properties, including Fourier-transform infrared spectroscopy, mass loss, fluid uptake, quercetin release, mechanical properties, and biological activity of the scaffolds were studied. The expression of matrix metalloproteinase-9, tissue inhibitor of metalloproteinase-1, and of endothelial nitric oxide synthase was evaluated when the quercetin-functionalized scaffold was exposed to  human endothelial cells treated with tumor necrosis factor-α. The results of this study confirmed the feasibility of incorporating free quercetin during the electrospinning process to impart biological properties to small-diameter vascular prostheses.

Pullulan films loading saffron extract encapsulated in nanoliposomes; preparation and characterization.

Nanoencapsulation of saffron extract (SE) components into the rapeseed lecithin nanoliposomes were performed by sonication of their aqueous dispersions as a green process. Dynamic light scattering (DLS) results exhibited that empty and SE loaded nanoliposomes (SENL) had average sizes in range of 118-138 nm, negative zeta potentials (-32.0 to -46.8 mV) and polydispersity index (PDI) less than 0.3 during storage for 28 days at 4 °C. Encapsulation efficiency of crocin was approximately 30%. The 70% of crocin released from SENLs within 5 h in PBS solution. Pullulan-based films were fabricated by incorporation of empty and SE loaded nanoliposomes into pullulan solution through casting method. The mechanical resistance and thermal stability of the films reduced by addition of nanoliposomes. FTIR and thermal characterizations indicated that SE was successfully encapsulated in the nanoliposomes and film matrix with high thermal stability. Incorporation of nanoliposomes enhanced the oxygen barrier properties of the films, while it didn't significantly affect the water vapor permeability (WVP) of the films. The obtained edible films or coatings can provide additional benefits due to unique flavor and color of saffron. In addition, the utilization of SE, can provide benefits for health-allegation from SE antioxidant capacity.

Nonlinear model for viscoelastic behavior of Achilles tendon.

Although the mechanical properties of ligament and tendon are well documented in research literature, very few unified mechanical formulations can describe a wide range of different loadings. The aim of this study was to propose a new model, which can describe tendon responses to various solicitations such as cycles of loading, unloading, and reloading or successive relaxations at different strain levels. In this work, experiments with cycles of loading and reloading at increasing strain level and sequences of relaxation were performed on white New Zealand rabbit Achilles tendons. We presented a local formulation of thermodynamic evolution outside equilibrium at a representative element volume scale to describe the tendon's macroscopic behavior based on the notion of relaxed stress. It was shown that the model corresponds quite well to the experimental data. This work concludes with the complexity of tendons' mechanical properties due to various microphysical mechanisms of deformation involved in loading such as the recruitment of collagen fibers, the rearrangement of the microstructure (i.e., collagens type I and III, proteoglycans, and water), and the evolution of relaxed stress linked to these mechanisms.

A novel bioreactor for ligament tissue engineering.

Bioreactors are defined as devices in which biological and/or biochemical processes develop under closely monitored and tightly controlled environmental and operating conditions (e.g. pH, temperature, mechanical conditions, nutrient supply and waste removal). In functional tissue engineering of musculoskeletal tissues, a bioreactor capable of controlling dynamic loading plays a determinant role. It has been shown that mechanical stretching promotes the expression of type I and III collagens, fibronectin, tenascin-C in cultured ligament fibroblasts (J.C.-H. Goh et al., Tissue Eng. 9 (2003), S31) and that human bone marrow mesenchymal stem cells (hBMMSC) - even in the absence of biochemical regulators - could be induced to differentiate into ligament-like fibroblast by the application of physiologically relevant cyclic strains (G. Vunjak-Novakovic et al., Ann. Rev. Biomed. Eng. 6 (2004), 131; H.A. Awad et al., Tissue Eng. 5 (1999), 267; R.G. Young et al., J. Orthop. Res. 16 (1998), 406). Different bioreactors are commercially available but they are too generic to be used for a given tissue, each tissue showing specific mechanical loading properties. In the case of ligament tissue engineering, the design of a bioreactor is still an open question. Our group proposes a bioreactor allowing cyclic traction-torsion on a scaffold seeded with stem cells.

Mechanical properties evolution of a PLGA-PLCL composite scaffold for ligament tissue engineering under static and cyclic traction-torsion in vitro culture conditions.

This study aims to investigate the in vitro degradation of a poly(L-lactic-co-glycolic acid)-poly(L-lactic-co-ϵ-caprolactone) (PLGA-PLCL) composite scaffold's mechanical properties under static culture condition and 2 h period per day of traction-torsion cyclic culture conditions of simultaneous 10% uniaxial strain and 90° of torsion cycles at 0.33 Hz. Scaffolds were cultured in static conditions, during 28 days, with or without cell seeded or under dynamic conditions during 14 days in a bioreactor. Scaffolds' biocompatibility and proliferation were investigated with Alamar Blue tests and cell nuclei staining. Scaffolds' mechanical properties were tested during degradation by uniaxial traction test. The PLGA-PLCL composite scaffold showed a good cytocompatibility and a high degree of colonization in static conditions. Mechanical tests showed a competition between two process of degradation which have been associated to hydrolytic and enzymatic degradation for the reinforce yarn in poly(L-lactic-co-glycolic acid) (PLGA). The enzymatic degradation led to a decrease effect on mechanical properties of cell-seeded scaffolds during the 21st days, but the hydrolytic degradation was preponderant at day 28. In conclusion, the structure of this scaffold is adapted to culture in terms of biocompatibility and cell orientation (microfiber) but must be improved by delaying the degradation of it reinforce structure in PLGA.

Structural and mechanical multi-scale characterization of white New-Zealand rabbit Achilles tendon.

Multi-scale characterization of structures and mechanical behavior of biological tissues are of huge importance in order to evaluate the quality of a biological tissue and/or to provide bio-inspired scaffold for functional tissue engineering. Indeed, the more information on main biological tissue structures we get, the more relevant we will be to design new functional prostheses for regenerative medicine or to accurately evaluate tissues. From this perspective, we have investigated the structures and their mechanical properties from nanoscopic to macroscopic scale of fresh ex-vivo white New-Zealand rabbit Achilles tendon using second harmonic generation (SHG) microscopy, atomic force microscopy (AFM) and tensile tests to provide a "simple" model whose parameters are relevant of its micro or nano structure. Thus, collagen fiber's crimping was identified then measured from SHG images as a plane sine wave with 28.4 ± 5.8 µm of amplitude and 141 ± 41 µm of wavelength. Young's moduli of fibrils (3.0 GPa) and amorphous phases (223 MPa) were obtained using TH-AFM. From these investigations, a non-linear Zener model linking a statistical Weibull's distribution of taut fibers under traction to crimp fibers were developed. This model showed that for small strain (<0.1), the amorphous inter-fibrils phase in collagen fibers is more solicited than collagen fibrils themselves. The results open the way to modeled macroscopic mechanical behavior of aligned-crimped collagen soft tissues using multi-scale tendon observations under static or dynamic solicitations.

Elaboration and characterization of nanoliposome made of soya; rapeseed and salmon lecithins: application to cell culture.

Health benefits of unsaturated fatty acids have been demonstrated over the last decades. Nanotechnology provided new process to produce particles such as liposomes and nanoliposomes made of pure phospholipids. These techniques are already used in pharmaceutics to augment the bioavailability and the bioefficiency of drugs. The aim of this paper is to characterize and evaluate the potential of nanoliposomes made of three lecithins (soya, rapeseed and salmon) on cell culture in order to use them in the future as drug delivery systems for tissue engineering. We began to measure, with zetasizer, the radius size of liposomes particles which are 125.5, 136.7 and 130.3 nm respectively for rapeseed, soya and salmon lecithin. Simultaneously, solutions observed by TEM demonstrated the particles were made much of liposomes than droplet (emulsion). Finally, we found that the solutions of lecithins were enough stable over 5 days at 37 °C to be used in culture medium. We investigated the effect of soya, rapeseed and salmon lecithin liposome from 2mg/mL to 5.2 µg/mL on metabolic activity and cell proliferation on rat bone marrow stem cells (rBMSC) during 14 days. The results showed that the three lecithins (soya, rapeseed and salmon) improve cell proliferation at different concentration.

A poly(lactic-co-glycolic acid) knitted scaffold for tendon tissue engineering: an in vitro and in vivo study.

We have designed a composite scaffold for potential use in tendon or ligament tissue engineering. The composite scaffold was made of a cellularized alginate gel that encapsulated a knitted structure. Our hypothesis was that the alginate would act as a cell carrier and deliver cells to the injury site while the knitted structure would provide mechanical strength to the composite construct. The mechanical behaviour and the degradation profile of the poly(lactic-co-glycolic acid) knitted scaffolds were evaluated. We found that our scaffolds had an elastic modulus of 750 MPa and that they lost their physical integrity within 7 weeks of in vitro incubation. Autologous rabbit mesenchymal stem cell seeded composite scaffolds were implanted in a 1-cm-long defect created in the rabbit tendon, and the biomechanical properties and the morphology of the regenerated tissues were evaluated after 13 weeks. The regenerated tendons presented higher normalized elastic modulus of (60%) when compared with naturally healed tendons (40%). The histological study showed a higher cell density and vascularization in the regenerated tendons.

Effect of uniaxial stretching on rat bone mesenchymal stem cell: orientation and expressions of collagen types I and III and tenascin-C.

Bone marrow mesenchymal stem cells (BMSC) have the potential to differentiate into a variety of cell types like osteoblasts, chondroblasts, adipocytes, etc. It is well known that mechanical forces regulate the biological function of cells. The aim of this study was to investigate the effect of uniaxial stretching on the orientation and biological functions of BMSC. Rat BMSCs were harvested from femoral and tibial bone marrow by density gradient centrifugation. Cells from passages 1-6 were characterized by flow cytometry using monoclonal antibodies. The recovered cells were stably positive for the markers CD90 and CD44 and negative for CD34 and CD45. A cyclic 10% uniaxial stretching at 1Hz was applied on rat BMSC for different time-courses. The length, width, and orientation of the cells were subsequently determined. Expression of collagen types I and III and tenascin-C mRNAs was measured by real-time RT-PCR, and the synthesis of these receptors was determined by radioimmunoassay. Results showed that uniaxial stretching lengthened and rearranged the cells. Compared with control groups, expression of collagen types I and III mRNAs was up-regulated after 12-h of stretching, while significant increase in synthesis of the two collagen protein types was not observed until after 24-h stretching. The expression of tenascin-C mRNA was significantly increased after a 24-h stretching. These data suggest that cyclic stretching promotes the synthesis of collagen types I and III and tenascin-C by the rat BMSC.

Time-related changes in expression of collagen types I and III and of tenascin-C in rat bone mesenchymal stem cells under co-culture with ligament fibroblasts or uniaxial stretching.

Adult bone-marrow-derived mesenchymal stroma cells (BMSC) seem to be a potential cell source for tissue engineering of the ligament. The objective of this work was to study the time-related changes in mRNA expression and protein levels of collagen types I and III and of tenascin-C in BMSC under co-culture with fibroblasts or under a uniaxial cyclic condition. Rat BMSC harvested from the femur and tibial bone marrow were co-cultured with ligament fibroblasts or stimulated by cyclic 10% uniaxial stretching at 1 Hz. Image analysis showed significant cell loss in stretched BMSC, particularly in the directions close to the stretching direction. However, these BMSC displayed an equivalent growth rate to that of non-stretched cells. Real-time reverse transcription/polymerase chain reaction revealed that the mRNA expression of collagen types I and III and of tenascin-C by BMSC was significantly up-regulated by co-culture and cyclic stretching. Radioimmunoassay results confirmed the effects of these stimulations, showing increases in the level of these proteins. Thus, BMSC might be useful as a cell source for the tissue engineering of ligament.