A non-invasive method of microplastics pollution quantification in green sea turtle Chelonia mydas of the Mexican Caribbean.

Due to the amply exposure of marine turtles to marine plastic pollution, this is a reason that the green sea turtle Chelonia mydas makes a good candidate species as a bioindicator for plastic pollution. Turtle feces were collected at Isla Blanca on the northeast Caribbean coast of the Yucatan Peninsula, Mexico. Microplastic extraction was done following Hidalgo-Ruz et al. (2012) and Masura et al. (2015) methods. After organic matter degradation of the feces samples, microplastics were identified and quantified by stereomicroscope. Their morphostructure was analyzed by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, while their composition was determined by Fourier transform infrared spectroscopy and Raman spectroscopy. Microplastics (MP) abundance ranged from 10 ± 2 MP·g-1 to 89 ± 3 MP·g-1. Kruskal Wallis test (KW = 70.31, p < 0.001) showed a significant difference between 22 green turtles analyzed. Most of the microplastics were fiber type. Blue, purple, and transparent fibers were the most abundant. The identified microplastics were nylon (polyamide), PVC, polypropylene, polyester, and viscose (cellulose). The non-invasive method used here allowed the detection of microplastic pollution and is promising for long-term microplastic pollution monitoring.

Macrophages morphology and cytokine reeducation by ex situ copper thiol complexes.

OBJECTIVE: To study the reeducation effect of copper thiol complexes on macrophage morphology and cytokine expression. METHODS: The effect of copper thiol complexes was assessed on murine macrophages by the cell morphology observed through optical microscopy, while the expression of cytokines by protein abundance after stimulation. A viability experiment was performed on PMBC to confirm that copper complexes do not affect other cells. RESULTS: The M1 shape was reported after treatment with copper thiol complexes at 1-200 µM, while M2 behavior was documented between 50 and 800 µM. Surprisingly, a thin elongate morphology was observed between 400-800 µM like the M2 shape. The expression of M1 cytokines was noted ranging from 1 to 100 µM, with the highest yield at 1 µM (2243 pg/µL) for the copper-penicillamine complex. M2 production behavior was observed at 1-800 µM, with the highest abundance close to 1150 pg/µL (200-400 µM) was quantified from the copper-cysteine complex. Finally, LCCu complexes did not induce a cytotoxic response on PBMC while exhibiting a high IL-4 and IL-10 production, similar to their gold analogs. CONCLUSIONS: The capacity of copper thiol complexes to reeducate M1 to M2 morphoexpression can be promising for cell protection by using copper thiol penicillamine or immuno-regeneration of tissues when using copper thiol cysteine.

Cell-free scaffold from jellyfish Cassiopea andromeda (Cnidaria; Scyphozoa) for skin tissue engineering.

Disruption of the continuous cutaneous membrane in the integumentary system is considered a health problem of high cost for any nation. Several attempts have been made for developing skin substitutes in order to restore injured tissue including autologous implants and the use of scaffolds based on synthetic and natural materials. Current biomaterials used for skin tissue repair include several scaffold matrices types, synthetic or natural, absorbable, degradable or non-degradable polymers, porous or dense scaffolds, and cells capsulated in hydrogels or spheroids systems so forth. These materials have advantages and disadvantages and its use will depend on the desired application. Recently, marine organisms such as jellyfish have attracted renewed interest, because both its composition and structure resemble the architecture of human dermic tissue. In this context, the present study aims to generate scaffolds from Cassiopea andromeda (C. andromeda), with application in skin tissue engineering, using a decellularization process. The obtained scaffold was studied by infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry analysis (DSC), and scanning electron microscopy (SEM). Crystal violet staining and DNA quantification assessed decellularization effectiveness while the biocompatibility of scaffold was determined with human dermic fibroblasts. Results indicated that the decellularization process reduce native cell population leading to 70% reduction in DNA content. In addition, SEM showed that the macro and microstructure of the collagen I-based scaffold were preserved allowing good adhesion and proliferation of human dermic fibroblasts. The C. andromeda scaffold mimics human skin and therefore represents great potential for skin tissue engineering.

Effect of the rigid segment content on the properties of segmented polyurethanes conjugated with atorvastatin as chain extender.

Segmented polyurethanes were prepared with polycaprolactone diol as soft segment and various amounts of 4,4´-Methylenebis(cyclohexyl isocyanate) and atorvastatin, a statin used for lowering cholesterol, in order to obtain SPU with different content of rigid segments. Polyurethanes with 35% or 50% of rigid segment content were physicochemically characterized and their biocompatibility assessed with L929 fibroblasts. High concentrations of atorvastatin were incorporated by increasing the content of rigid segments as shown by FTIR, Raman, NMR, XPS and EDX. Thermal and mechanical characterization showed that polyurethanes containing atorvastatin and 35% of rigid segments were low modulus (13 MPa) semicrystalline polymers as they exhibited a glass transition temperature (Tg) at -38 °C, melting temperature (Tm) at 46 °C and crystallinity close to 35.9% as determined by DSC. In agreement with this, X-ray diffraction showed reflections at 21.3° and 23.6° for PCL without reflections for atorvastatin suggesting its presence in amorphous form with higher potential bioavailability. Low content of rigid segments led to highly degradable polymer in acidic, alkaline and oxidative media with an acceptable fibroblast cytotoxicity up to 7 days possibly due to low atorvastatin content.

Design of Silica-Oligourethane-Collagen Membranes for Inflammatory Response Modulation: Characterization and Polarization of a Macrophage Cell Line.

The polarization of macrophages M0 to M1 or M2 using molecules embedded in matrices and hydrogels is an active field of study. The design of biomaterials capable of promoting polarization has become a paramount need nowadays, since in the healing process macrophages M1 and M2 modulate the inflammatory response. In this work, several immunocytochemistry and ELISA tests strongly suggest the achievement of polarization using collagen-based membranes crosslinked with tri-functionalized oligourethanes and coated with silica. Measuring the amount of TGF-ß1 secreted to culture media by macrophages growth on these materials, and quantifying the macrophage morphology, it is proved that it is possible to stimulate the anti-inflammatory pathway toward M2, having measurements with p ≤ 0.05 of statistical significance between the control and the collagen-based membranes. Furthermore, some physicochemical characteristics of the hybrid materials are tested envisaging future applications: collagenase degradation resistance, water uptake, collagen fiber diameter, and deformation resistance are increased for all the crosslinked biomaterials. It is considered that the biological and physicochemical properties make the material suitable for the modulation of the inflammatory response in the chronic wounds and promising for in vivo studies.

Electrospun polycaprolactone/chitosan scaffolds for nerve tissue engineering: physicochemical characterization and Schwann cell biocompatibility.

Electrospun polycaprolactone (PCL)/chitosan (CH) blend scaffolds with different CH weight ratios were prepared to study the effect of scaffold composition on its physicochemical and biological properties. Scanning electron microscopy showed bead-free homogeneous randomly arranged nanofibers whose average diameter decreased from 240 to 110 nm with increasing CH content. The infrared spectra of the PCL/CH blends were very similar to the neat PCL scaffold. Energy-dispersive x-ray spectroscopy analysis confirmed the presence of carbon, oxygen and nitrogen in the scaffolds, although fluorine-from chemicals used as solvent-was also detected. The water contact angle decreased from 113° (for PCL) to 52° with increasing chitosan content. The biocompatibility was evaluated using fibroblasts and Schwann cell (SC) cultures. Cytotoxicity assays using fibroblasts demonstrated that electrospun scaffolds could be considered as non-cytotoxic material. Biocompatibility tests also revealed that the SCs adhered to scaffolds with different CH content, although the formulation containing CH at 5 wt% exhibited the highest proliferation on days 1 and 3. A better cell distribution was observed in the CH/PCL blends than in the neat PCL or CH scaffolds, where the cells were clustered. Immunochemistry analysis confirmed that SCs expressed the specific p75 cell marker on the scaffolds, suggesting that PCL/CH scaffolds would be good candidates for peripheral nerve tissue engineering.

Preparation and bioactive properties of nano bioactive glass and segmented polyurethane composites.

Composites of glutamine-based segmented polyurethanes with 5 to 25 wt.% bioactive glass nanoparticles were prepared, characterized, and their mineralization potential was evaluated in simulated body fluid. Biocompatibility with dental pulp stem cells was assessed by MTS to an extended range of compositions (1 to 25 wt.% of bioactive glass nanoparticles). Physicochemical characterization showed that composites retained many of the matrix properties, i.e. those corresponding to semicrystalline elastomeric polymers as they exhibited a glass transition temperature (Tg) between -41 and -36℃ and a melting temperature (Tm) between 46 and 49℃ in agreement with X-ray reflections at 23.6° and 21.3°. However, with bioactive glass nanoparticles addition, tensile strength and strain were reduced from 22.2 to 12.2 MPa and 667.2 to 457.8%, respectively with 25 wt.% of bioactive glass nanoparticles. Although Fourier transform infrared spectroscopy did not show evidence of mineralization after conditioning of these composites in simulated body fluid, X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray microanalysis showed the formation of an apatite layer on the surface which increased with higher bioactive glass concentrations and longer conditioning time. Dental pulp stem cells proliferation at day 5 was improved in bioactive glass nanoparticles composites containing lower amounts of the filler (1-2.5 wt.%) but it was compromised at day 9 in composites containing high contents of nBG (5, 15, 25 wt.%). However, Runx2 gene expression was particularly upregulated for the dental pulp stem cells cultured with composites loaded with 15 and 25 wt.% of bioactive glass nanoparticles. In conclusion, low content bioactive glass nanoparticles and segmented polyurethanes composites deserve further investigation for applications such as guided bone regeneration membranes, where osteoconductivity is desirable but not a demanding mechanical performance.

Human mesenchymal stem cell behavior on segmented polyurethanes prepared with biologically active chain extenders.

The development of elastomeric, bioresorbable and biocompatible segmented polyurethanes (SPUs) for use in tissue-engineering applications has attracted considerable interest because of the existing need of mechanically tunable scaffolds for regeneration of different tissues, but the incorporation of osteoinductive molecules into SPUs has been limited. In this study, SPUs were synthesized from poly (ε-caprolactone)diol, 4,4'-methylene bis(cyclohexyl isocyanate) using biologically active compounds such as ascorbic acid, L-glutamine, ß-glycerol phosphate, and dexamethasone as chain extenders. Fourier transform infrared spectroscopy (FTIR) revealed the formation of both urethanes and urea linkages while differential scanning calorimetry, dynamic mechanical analysis, X-ray diffraction and mechanical testing showed that these polyurethanes were semi-crystalline polymers exhibiting high deformations. Cytocompatibility studies showed that only SPUs containing ß-glycerol phosphate supported human mesenchymal stem cell adhesion, growth, and osteogenic differentiation, rendering them potentially suitable for bone tissue regeneration, whereas other SPUs failed to support either cell growth or osteogenic differentiation, or both. This study demonstrates that modification of SPUs with osteogenic compounds can lead to new cytocompatible polymers for regenerative medicine applications.

Towards optimization of the silanization process of hydroxyapatite for its use in bone cement formulations.

The aim of this work was to provide some fundamental information for optimization of silanization of hydroxyapatite intended for bone cement formulations. The effect of 3-(trimethoxysilyl) propyl methacrylate (MPS) concentration and solvent system (acetone/water or methanol/water mixtures) during HA silanization was monitored by X-ray diffraction (XRD), FTIR spectroscopy and EDX analysis. The effect of silanized HA on the mechanical properties of acrylic bone cements is also reported. It was found that the silanization process rendered hydroxyapatite with lower crystallinity compared to untreated HA. Through EDX, it was observed that the silicon concentration in the HA particles was higher for acetone-water than that obtained for methanol-water system, although the mechanical performance of cements prepared with these particles exhibited the opposite behavior. Taking all these results together, it is concluded that methanol-water system containing MPS at 3wt.% provides the better results during silanization process of HA.

Synthesis and characterization of protected oligourethanes as crosslinkers of collagen-based scaffolds.

This paper describes the preparation and characterization of water-soluble urethane oligomers bearing protected isocyanate groups. It also points out its ability to crosslink decellularized pericardium, as a model collagen scaffold, and to adjust their structural characteristics. A library of oligourethanes was synthesized by varying the molecular weight (Mw 400, 600, 1000 or 2000 g mol-1) of the poly(ethylene glycol) and the type of aliphatic diisocyanate (isophorone diisocyanate/IPDI or hexamethylene diisocyanate/HDI). 1H and 13C NMR, FTIR and mass spectrometry demonstrated that the crosslinkers are composed of chains with carbamoylsulfonate end groups that have trimeric and pentameric oligourethanes, and monomeric diisocyanate. The degree of crosslinking and hence the in vitro degradation susceptibility of the decellularized pericardium were inversely related to the Mw of the oligourethanes. The toxicity of the extractable products from oligourethane-collagen materials toward fibroblasts and macrophages was found to be lower for the crosslinker derived from IPDI than for those derived from HDI. On the other hand, the resistance to collagenase or oxidative degradation of the bovine pericardium crosslinked with HDI/oligourethane was higher than the one prepared with IPDI/oligourethane. As the Mw of the oligomers regulates the degree of crosslinking while the chemical composition influences the cytocompatibility and biodegradation of decellularized pericardium, these urethane oligomers can be used as safer crosslinkers for other protein-based biomaterials.

Stability and mechanical evaluation of bovine pericardium cross-linked with polyurethane prepolymer in aqueous medium.

The present study investigates the potential use of non-catalyzed water-soluble blocked polyurethane prepolymer (PUP) as a bifunctional cross-linker for collagenous scaffolds. The effect of concentration (5, 10, 15 and 20%), time (4, 6, 12 and 24 h), medium volume (50, 100, 200 and 300%) and pH (7.4, 8.2, 9 and 10) over stability, microstructure and tensile mechanical behavior of acellular pericardial matrix was studied. The cross-linking index increased up to 81% while the denaturation temperature increased up to 12 °C after PUP crosslinking. PUP-treated scaffold resisted the collagenase degradation (0.167±0.14 mmol/g of liberated amine groups vs. 598±60 mmol/g for non-cross-linked matrix). The collagen fiber network was coated with PUP while viscoelastic properties were altered after cross-linking. The treatment of the pericardial scaffold with PUP allows (i) different densities of cross-linking depending of the process parameters and (ii) tensile properties similar to glutaraldehyde method.

Comparative study on the mechanical and fracture properties of acrylic bone cements prepared with monomers containing amine groups.

In this work, the effect of the incorporation of comonomers containing amine groups on the mechanical and fracture properties of acrylic bone cements was studied. Cements were prepared with either diethyl amino ethyl acrylate (DEAEA), dimethyl amino ethyl methacrylate (DMAEM) or diethyl amino ethyl methacrylate (DEAEM) as comonomer in the liquid phase. It was found that strength and modulus decreased with increasing comonomer content in the bending and compressive tests. It was also observed that fracture toughness (K(IC)) and the critical strain energy release rate (G(IC)) increase with increasing comonomer concentration and are significantly higher compared to the control formulation. The mechanical and fracture properties of cements were also evaluated after soaking the specimens in Simulated Body Fluid (SBF) for 3 and 6 months. It was found that the mechanical properties of cements decreased when the samples were stored in SBF, although the impact strength increased in the first 3 months and then decreased. SEM micrographs were in agreement with the results obtained during mechanical characterization as the increase in toughness was confirmed by the appearance of ductile tearing pattern which is associated with plastic deformation.

Decellularization of pericardial tissue and its impact on tensile viscoelasticity and glycosaminoglycan content.

Bovine pericardium is a collagenous tissue commonly used as a natural biomaterial in the fabrication of cardiovascular devices. For tissue engineering purposes, this xenogeneic biomaterial must be decellularized to remove cellular antigens. With this in mind, three decellularization protocols were compared in terms of their effectiveness to extract cellular materials, their effect on glycosaminoglycan (GAG) content and, finally, their effect on tensile biomechanical behavior. The tissue decellularization was achieved by treatment with t-octyl phenoxy polyethoxy ethanol (Triton X-100), tridecyl polyethoxy ethanol (ATE) and alkaline treatment and subsequent treatment with nucleases (DNase/RNase). The quantified residual DNA content (3.0±0.4%, 4.4±0.6% and 5.6±0.7% for Triton X-100, ATE and alkaline treatment, respectively) and the absence of nuclear structures (hematoxylin and eosin staining) were indicators of effective cell removal. In the same way, it was found that the native tissue GAG content decreased to 61.6±0.6%, 62.7±1.1% and 88.6±0.2% for Triton X-100, ATE and alkaline treatment, respectively. In addition, an alteration in the tissue stress relaxation characteristics was observed after alkaline treatment. We can conclude that the three decellularization agents preserved the collagen structural network, anisotropy and the tensile modulus, tensile strength and maximum strain at failure of native tissue.

Combined influence of barium sulfate content and co-monomer concentration on properties of PMMA bone cements for vertebroplasty.

In this work, the combined influence of barium sulfate content and co-monomer concentration on the properties of acrylic bone cement for percutaneous vertebroplasty (PVP) was investigated using a response surface methodology. Cements were prepared with methyl methacrylate (MMA) and either diethyl amino ethyl methacrylate (DEAEM) or dimethyl amino ethyl methacrylate (DMAEM) as co-monomer in the liquid phase, while variable amounts of barium sulfate were incorporated to the solid phase in order to improve the radiopacity of cements. It was found that various properties such as peak temperature, setting time, residual monomer content, mechanical properties and injectability, had an effect on the occurrence of interactions (combined effect) between the barium sulfate and DEAEM in bone cements formulations when independent variables were at their maximum.

Sensing and tactile artificial muscles from reactive materials.

Films of conducting polymers can be oxidized and reduced in a reversible way. Any intermediate oxidation state determines an electrochemical equilibrium. Chemical or physical variables acting on the film may modify the equilibrium potential, so that the film acts as a sensor of the variable. The working potential of polypyrrole/DBSA (Dodecylbenzenesulfonic acid) films, oxidized or reduced under constant currents, changes as a function of the working conditions: electrolyte concentration, temperature or mechanical stress. During oxidation, the reactive material is a sensor of the ambient, the consumed electrical energy being the sensing magnitude. Devices based on any of the electrochemical properties of conducting polymers must act simultaneously as sensors of the working conditions. Artificial muscles, as electrochemical actuators constituted by reactive materials, respond to the ambient conditions during actuation. In this way, they can be used as actuators, sensing the surrounding conditions during actuation. Actuating and sensing signals are simultaneously included by the same two connecting wires.

The effect of surfactants, crosslinking agents and L-cysteine on the stabilization and mechanical properties of bovine pericardium.

AIM: Bovine pericardium (BP) is a collagenous tissue commonly used in cardiovascular applications. However, it suffers from thrombus formation and calcification, the latter generally being related to cell debris and the use of glutaraldehyde (GA). With this in mind, BP was decellularized, crosslinked and grafted with L-cysteine in order to improve its stabilization and mechanical properties. METHODS: BP was decellularized with ionic and non-ionic surfactants such as sodium dodecyl sulfate (SDS), cetyl trimethyl ammonium chloride (CTMA) or t-octyl phenoxy polyethoxy ethanol (Triton X-100). It was then crosslinked with 1-(3-dimethyl amino propyl)-3-ethyl carbodiimide hydrochloride (EDAC) or GA. Finally, residual aldehyde groups on GA only or EDAC-GA crosslinked pericardium were left to react with L-cysteine (Cys). RESULTS: It was found that the treatment with GA led to a biomaterial with a lower amino-group content than the treatment with EDAC (15 vs. 50 micro;mol/g). The increase in denaturation temperature from 71.2 plusmn; 0.5 to 86.3 plusmn; 0.8 deg;C confirmed that GA was a more effective crosslinking agent than EDAC. In a similar manner, crosslinking with GA increased the percentage of deformation while decreasing their tensile strength. CONCLUSION: The amount of grafted Cys varied from 3 to 9 micro;mol/g thiol-groups and depended on the concentration of this amino acid and method of crosslinking, but did not modify its physicochemical and mechanical properties.

Surface characterisation of various bone cements prepared with functionalised methacrylates/bioactive ceramics in relation to HOB behaviour.

This study reports the relationship between the biocompatibility and surface properties of experimental bone cements. The effect of hydroxyapatite (HA) or alpha-tri-calcium phosphate (alpha-TCP) incorporated into bone cements prepared with methyl methacrylate as base monomer and either methacrylic acid or diethyl amino ethyl methacrylate (DEAEMA) as comonomers was investigated. The in vitro biocompatibility of these composite cements was assessed in terms of the interaction of primary human osteoblasts grown on the materials over a period of 5 days and compared with a control surface. These results were related to the surface properties investigated through a number of techniques, namely Fourier transform infrared, contact angle measurements, X-ray photoelectron spectroscopy and energy dispersive analysis of X-rays. Complementary techniques of thermal analysis and ion chromatography were also performed. Biocompatibility results showed that the addition of alpha-TCP improves biocompatibility regardless of comonomer type. This is in contrast to HA-based cements where cell proliferation was significantly lower. Surface characterisations showed that structural integrity of the materials was maintained in the presence of the acid and base comonomers, and water contact angles were reduced particularly in DEAEMA containing materials. Furthermore, ion chromatography confirmed higher Ca2+ and PO4(3-) ion release by both types of ceramics, particularly for those containing DEAEMA. In conclusion, the incorporation of acidic and basic comonomers to either HA or alpha-TCP ceramics containing bone cements can have differential effects upon the attachment and proliferation of bone cells in vitro. Moreover, those cements consisting of alpha-TCP and containing DEAEMA comonomer indicated the most favourable biocompatibility.

Physicochemical, mechanical, and biological properties of bone cements prepared with functionalized methacrylates.

Bone cements prepared with methyl methacrylate (MMA) as a base monomer and either methacrylic acid (MAA) or diethyl amino ethyl methacrylate (DEAEMA) as comonomers were characterized in terms of curing behavior, mechanical properties, and their in vitro biocompatibility. The curing time and setting temperature were found to be composition dependent while the residual monomer was not greatly affected by the presence of either acidic or alkaline comonomers in the bone cements. For samples with MAA comonomer, a faster curing time and higher setting temperature were observed when compared to the cement with DEAEMA comonomer. In terms of mechanical properties, the highest compressive strength was exhibited by formulations containing MAA, while the highest impact strength was shown by the formulations prepared with DEAEMA. There were no differences observed between the two formulations for tensile, shear, and bending strength values. Similarly, fatigue crack propagation studies did not reveal differences with the addition of either DEAEMA or MAA.No differences were observed in the initial number of attached primary rat femur osteoblasts on the different bone cements and positive controls. However, after 48 h there was a reduced proliferation in the cells grown on bone cements containing MAA.