Ana Alonso-Varona

Bioinspired antimicrobial and biocompatible bacterial cellulose membranes obtained by surface functionalization with aminoalkyl groups.

There has been a great deal of interest in the use of nanostructured bacterial cellulose membranes for biomedical applications, including tissue implants, wound healing, and drug delivery. However, as bacterial cellulose does not intrinsically present antimicrobial properties, in the present study, antimicrobial bacterial cellulose membranes were obtained by chemical grafting of aminoalkyl groups onto the surface of its nanofibrillar network. This approach intends to mimic intrinsic antimicrobial properties of chitosan. Interestingly, these novel grafted bacterial cellulose membranes (BC-NH2) are simultaneously lethal against S. aureus and E. coli and nontoxic to human adipose-derived mesenchymal stem cells (ADSCs) and thus may be useful for biomedical applications. In addition to these biological properties, the bioactive nanostructured BC-NH2 membranes also present improved mechanical and thermal properties.

Shape-Memory Bionanocomposites Based on Chitin Nanocrystals and Thermoplastic Polyurethane with a Highly Crystalline Soft Segment

Shape-memory bionanocomposites based on a naturally sourced segmented thermoplastic polyurethane and chitin nanocrystals were synthesized, and their mechanical properties and thermally activated shape-memory behavior were studied. The chitin nanocrystals were incorporated during the synthesis of the prepolymer made from a castor oil-based difunctional polyol and hexamethylene diisocyanate. The polymerization was completed by addition of propanediol, as a corn-sugar based chain extender, bringing the weight content of components from renewable resources to >60%. Thermal analysis of the bionanocomposites revealed a phase-separated morphology, which is composed of soft and hard domains, which bestow the material with two melting transitions at 60 and 125 °C, that are exploitable for a shape memory effect. The soft segment is responsible for temporary shape fixing, while the hard segment crystallites are responsible for the permanent shape. The introduction of small amounts (0.25-2 wt %) of chitin nanocrystals was found to increase the crystallinity of the hard segment by way of nucleation, which in turn improves the shape recovery considerably. The thermally activated shape-memory behavior of the synthesized bionancomposites is exploitable with a programming and release temperature of 60 °C. The materials display good in vitro cell response, as shown by short-term cytotoxicity assays, and therefore, the bionanocomposites appear to be potentially useful for biomedical applications.

Identification of a biomarker panel for colorectal cancer diagnosis

BackgroundMalignancies arising in the large bowel cause the second largest number of deaths from cancer in the Western World. Despite progresses made during the last decades, colorectal cancer remains one of the most frequent and deadly neoplasias in the western countries.MethodsA genomic study of human colorectal cancer has been carried out on a total of 31 tumoral samples, corresponding to different stages of the disease, and 33 non-tumoral samples. The study was carried out by hybridisation of the tumour samples against a reference pool of non-tumoral samples using Agilent Human 1A 60-mer oligo microarrays. The results obtained were validated by qRT-PCR. In the subsequent bioinformatics analysis, gene networks by means of Bayesian classifiers, variable selection and bootstrap resampling were built. The consensus among all the induced models produced a hierarchy of dependences and, thus, of variables.ResultsAfter an exhaustive process of pre-processing to ensure data quality--lost values imputation, probes quality, data smoothing and intraclass variability filtering--the final dataset comprised a total of 8, 104 probes. Next, a supervised classification approach and data analysis was carried out to obtain the most relevant genes. Two of them are directly involved in cancer progression and in particular in colorectal cancer. Finally, a supervised classifier was induced to classify new unseen samples.ConclusionsWe have developed a tentative model for the diagnosis of colorectal cancer based on a biomarker panel. Our results indicate that the gene profile described herein can discriminate between non-cancerous and cancerous samples with 94.45% accuracy using different supervised classifiers (AUC values in the range of 0.997 and 0.955).

In situ polymerization and characterization of elastomeric polyurethane-cellulose nanocrystal nanocomposites. Cell response evaluation

Polyurethane/Cellulose nanocrystal (CNC) nanocomposites have been prepared by means of in situ polymerization using CNCs as precursors of polyurethane chains. Thermal, mechanical and morphological characterization has been analyzed to study the effect of CNC on the micro/nanostructure, which consisted of individualized nanocellulose crystallites covalently bonded to hard and soft segments of polyurethane. The incorporation of low CNC content led to a tough material whereas higher amount of CNC provoked an increase in soft and hard segments crystallization phenomenon. Moreover, from the viewpoint of polyurethane and polyurethane nanocomposites applications focused on biomedical devices, biocompatibility studies can be considered necessary to evaluate the influence of CNC on the biological behaviour. SEM micrographs obtained from cells seeded on top of the materials showed that L-929 fibroblasts massively colonized the materials surface giving rise to good substrates for cell adhesion and proliferation and useful as potential materials for biomedical applications.

Biocompatible Bacterial Cellulose-Poly(2-hydroxyethyl methacrylate) Nanocomposite Films

A series of bacterial cellulose-poly(2-hydroxyethyl methacrylate) nanocomposite films was prepared by in situ radical polymerization of 2-hydroxyethyl methacrylate (HEMA), using variable amounts of poly(ethylene glycol) diacrylate (PEGDA) as cross-linker. Thin films were obtained, and their physical, chemical, thermal, and mechanical properties were evaluated. The films showed improved translucency compared to BC and enhanced thermal stability and mechanical performance when compared to poly(2-hydroxyethyl methacrylate) (PHEMA). Finally, BC/PHEMA nanocomposites proved to be nontoxic to human adipose-derived mesenchymal stem cells (ADSCs) and thus are pointed as potential dry dressings for biomedical applications.

Crystallinity assessment and in vitro cytotoxicity of polylactide scaffolds for biomedical applications

Bioresorbable polylactides are one of the most important materials for tissue engineering applications. In this work we have prepared scaffolds based on the two optically pure stereoisomers: poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA). The crystalline structure and morphology were evaluated by DSC, AFM and X-ray diffraction. PLLA and PDLA crystallized in the α form and the equimolar PLLA/PDLA blend, crystallized in the stereocomplex form, were analyzed by a proliferation assay in contact with mouse L-929 and human fibroblasts and neonatal keratinocytes for in vitro cytotoxicity evaluation. SEM analysis was conducted to determine the cell morphology, spreading and adhesion when in contact with the different polymer surfaces. The preserved proliferation rate showed in MTT tests and the high colonization on the surface of polylactides observed by SEM denote that PLLA, PDLA and the equimolar PLLA/PDLA are useful biodegradable materials in which the crystalline characteristics can be tuned for specific biomedical applications.

Interleukin-2 increases intracellular glutathione levels and reverses the growth inhibiting effects of cyclophosphamide on B16 melanoma cells

Glutathione (GSH) plays an essential role in the metabolism of melanoma. As changes in intracellular GSH content can modify the processes of cell proliferation and detoxification, this could determine the therapeutic response to some cancer treatment strategies. The purpose of this study was to test the effects of treatment with interleukin-2 (IL-2), alone and in combination with cyclophosphamide (CY), on survival of mice bearing B16 melanoma liver metastases, and to determine the influence of these therapeutic agents on the GSH metabolism of B16 cells. In the in vivo test system, B16 melanoma liver metastases were induced in C57BL/6 mice which were subsequently treated with IL-2, CY and CY plus IL-2. Survival time was used to determine the response to treatment. In the in vitro system, we evaluated the effects of IL-2, acrolein (an active metabolite of CY responsible for GSH depletion) and acrolein plus IL-2 on GSH levels and proliferation of B16 melanoma cells. Results indicated that, in vivo, all treatments increased mouse survival times with respect to control mice. However, the addition of IL-2 to CY therapy decreased survival time compared with treatment with CY alone. In vitro, whereas acrolein produced a GSH depletion and inhibited B16 cell proliferation, IL-2 increased GSH content and cell proliferation rate compared with untreated cells. Moreover, addition of IL-2 to cells preincubated with acrolein increased GSH levels and proliferation with respect to acrolein alone. In summary, the data suggest that GSH plays a critical role in the growth-promoting effects of IL-2 on B16F10 melanoma cells and in the antagonistic effect of IL-2 on CY inhibitory activity on these tumor cells.

Exploiting Mycosporines as Natural Molecular Sunscreens for the Fabrication of UV-Absorbing Green Materials

Ultraviolet radiations have many detrimental effects in living organisms that challenge the stability and function of cellular structures. UV exposure also alters the properties and durability of materials and affects their lifetime. It is becoming increasingly important to develop new biocompatible and environmentally friendly materials to address these issues. Inspired by the strategy developed by fish, algae, and microorganisms exposed to UV radiations in confined ecosystems, we have constructed novel UV-protective materials that exclusively consist of natural compounds. Chitosan was chosen as the matrix for grafting mycosporines and mycosporine-like amino acids as the functional components of the active materials. Here, we show that these materials are biocompatible, photoresistant, and thermoresistant, and exhibit a highly efficient absorption of both UV-A and UV-B radiations. Thus, they have the potential to provide an efficient protection against both types of UV radiations and overcome several shortfalls of the current UV-protective products. In practice, the same concept can be applied to other biopolymers than chitosan and used to produce multifunctional materials. Therefore, it has a great potential to be exploited in a broad range of applications in living organisms and nonliving systems.

Effects of all-trans retinoic acid on tumor recurrence and metastasis

OBJECTIVE All-trans-retinoic acid (ATRA) promotes cell differentiation. We have studied its effect on the local recurrence and metastatic spreading of an experimental rhabdomyosarcoma in rats. DESIGN syngenic rhabdomyosarcoma cells (S4MH) were inoculated s.c. in male WAG/RijCrl rats. After 25 days tumors were excised and a 40% hepatectomy was performed for all animals. Ten days later the rats were sacrificed and a thorough necropsy was performed. The animals were randomly allocated to receive daily doses of ATRA (5 mg/kg, i.p.) or its solvent (Clinoleic/ethanol 90/10), starting three days before surgery until the end of the experiment. RESULTS ATRA reduced the incidence of local recurrence from 70 to 33% (p < 0.05), but the tumor size was not altered (1.8 vs. 2.0 cc). Regarding inguinal metastasis, there was a six-fold decrease (0.2 vs. 1.2 cc; p < 0.05) in mean tumor volume, although the rate of this proliferation increased sharply (86 vs. 29%; p < 0.05) for treated animals. The volume of the retroperitoneal tumor masses also decreased with ATRA (0.7 vs. 5.1 cc; p < 0.05), but the difference in rate was not significant (71 vs. 67%). Lung metastases, which were present in 100% of control animals, were found in only 33% of treated rats, while the mean number of metastatic foci dropped from 26.7 to 5.7 (p < 0.05). CONCLUSION Protocols including retinoid administration prior to and following primary tumor excision could help in controlling both recurrence and metastatic progression in surgically treated rhabdomyosarcoma.

The role of reactive silicates on the structure/property relationships and cell response evaluation in polyurethane nanocomposites

Precursors of polyurethane chains have been reacted by means of in situ polymerization with organically modified montmorillonite clay to obtain polyurethane nanocomposites containing from 1 to 4 wt % of nanoreinforcement. The effective final dispersion of inorganic component at nanometric scale was investigated by X-ray diffraction, atomic force microscopy, and transmission electron microscopy. In addition, the effect of the nanoreinforcement incorporation on thermal and mechanical behavior of polyurethane nanocomposites was evaluated. Nanocomposites showed similar mechanical properties to polyurethanes containing high-hard segment contents with higher tensile modulus and a decrease in elastomeric properties of polyurethane materials. Finally, biocompatibility studies using L-929 fibroblast have been carried out to examine in vitro cell response and cytotoxicity of the matrix and their nanocomposite materials. Results suggested that the organic modifier in the clay is unsuitable for biomedical devices in spite of the fact that the matrix is a good candidate for cell adhesion and proliferation.