Rafael Contreras-Montoya

Bio: Rafael Contreras-Montoya is an academic researcher from University of Granada. The author has contributed to research in topics: Self-healing hydrogels & Protein crystallization. The author has an hindex of 8, co-authored 18 publications receiving 166 citations.

Iron nanoparticles-based supramolecular hydrogels to originate anisotropic hybrid materials with enhanced mechanical strength

Abstract: Here, we report the synthesis and structural characterization of novel iron nanoparticles (FeNPs)-based short-peptide supramolecular hydrogels. These hybrid hydrogels composed of Fmoc-diphenylalanine (Fmoc-FF) peptide and FeNPs were prepared through the self-assembly of Fmoc-FF in a suspension containing FeNPs in the presence or absence of an external magnetic field. Optical images of these hydrogels revealed the formation of column-like aggregates of FeNPs when the gels were formed in the presence of a magnetic field. Moreover, the intricate structure derived from the interwoven nature of the fiber peptides with these FeNP column-like aggregates resulted in anisotropic materials, more rigid under shear forces applied perpendicularly to the direction of the aggregates, presenting under these conditions values of G′ (storage modulus) about 7 times those of the native hydrogel. To the best of our knowledge, this is the first example in which the mechanical properties of peptide hydrogels were strongly enhanced due to the presence of FeNPs. A theoretical model trying to explain this phenomenon is presented. Quite interesting CD, FTIR and synchrotron X-ray diffraction analyses indicated that the anti-parallel β-sheet arrangement of Fmoc-FF peptide was highly conserved in the hydrogels containing FeNPs. Moreover, FLCS measurements showed that the diffusion of a small solute through the hydrogel network was improved in hydrogels containing FeNPs, probably caused by the formation of preferential channels for diffusion. Taken together, our results provide a new method for the synthesis of novel hybrid Fmoc-FF–FeNPs anisotropic hydrogels with enhanced mechanical strength and water-like diffusion behavior, thus easing their application in drug delivery and tissue engineering.

Bioorthogonal Uncaging of Cytotoxic Paclitaxel through Pd Nanosheet-Hydrogel Frameworks.

Abstract: The promising potential of bioorthogonal catalysis in biomedicine is inspiring incremental efforts to design strategies that regulate drug activity in living systems. To achieve this, it is not only essential to develop customized inactive prodrugs and biocompatible metal catalysts but also the right physical environment for them to interact and enable drug production under spatial and/or temporal control. Toward this goal, here, we report the first inactive precursor of the potent broad-spectrum anticancer drug paclitaxel (a.k.a. Taxol) that is stable in cell culture and labile to Pd catalysts. This new prodrug is effectively uncaged in cancer cell culture by Pd nanosheets captured within agarose and alginate hydrogels, providing a biodegradable catalytic framework to achieve controlled release of one of the most important chemotherapy drugs in medical practice. The compatibility of bioorthogonal catalysis and physical hydrogels opens up new opportunities to administer and modulate the mobility of transition metal catalysts in living environs.

Anisotropic magnetic hydrogels: design, structure and mechanical properties.

Abstract: Anisotropy is an intrinsic feature of most of the human tissues (e.g. muscle, skin or cartilage). Because of this, there has been an intense effort in the search of methods for the induction of per...

Catalytic and Electron Conducting Carbon Nanotube–Reinforced Lysozyme Crystals

Abstract: This study was supported by the projects BIO2016-74875-P and FIS201785954-R (Ministerio de Economia, Industria y Competitividad, MINECO, and Agencia Estatal de Investigacion, AEI, Spain, co-funded by Fondo Europeo de Desarrollo Regional, FEDER, European Union) and by the Junta de Andalucia (Spain) projects P12-FQM-2721 and P12-FQM-790. The authors also thank the “Unidad de Excelencia Quimica aplicada a Biomedicina y Medioambiente” (UGR) for funding. The authors are very grateful to the staff at Xaloc (ALBA) for support during data collection and CIC (Centro de Instrumentacion Cientifica) for the help during c-AFM measurements.

A review on recent advances in polymer and peptide hydrogels

Abstract: In this review, we focus on the very recent developments on the use of the stimuli responsive properties of polymer hydrogels for targeted drug delivery, tissue engineering, and biosensing utilizing their different optoelectronic properties. Besides, the stimuli-responsive hydrogels, the conducting polymer hydrogels are discussed, with specific attention to the energy generation and storage behavior of the xerogel derived from the hydrogel. The electronic and ionic conducting gels have been discussed that have applications in various electronic devices, e.g., organic field effect transistors, soft robotics, ionic skins, and sensors. The properties of polymer hybrid gels containing carbon nanomaterials have been exemplified here giving attention to applications in supercapacitors, dye sensitized solar cells, photocurrent switching, etc. Recent trends in the properties and applications of some natural polymer gels to produce thermal and acoustic insulating materials, drug delivery vehicles, self-healing material, tissue engineering, etc., are discussed. Besides the polymer gels, peptide gels of different dipeptides, tripeptides, oligopeptides, polypeptides, cyclic peptides, etc., are discussed, giving attention mainly to biosensing, bioimaging, and drug delivery applications. The properties of peptide-based hybrid hydrogels with polymers, nanoparticles, nucleotides, fullerene, etc., are discussed, giving specific attention to drug delivery, cell culture, bio-sensing, and bioimaging properties. Thus, the present review delineates, in short, the preparation, properties, and applications of different polymer and peptide hydrogels prepared in the past few years.

Anisotropic and self-healing hydrogels with multi-responsive actuating capability.

Abstract: Inspired by smart biological tissues, artificial muscle-like actuators offer fascinating prospects due to their distinctive shape transformation and self-healing function under external stimuli. However, further practical application is hindered by the lack of simple and general routes to fabricate ingenious soft materials with anisotropic responsiveness. Here, we describe a general in situ polymerization strategy for the fabrication of anisotropic hydrogels composed of highly-ordered lamellar network crosslinked by the metal nanostructure assemblies, accompanied with remarkably anisotropic performances on mechanical, optical, de-swelling and swelling behaviors. Owing to the dynamic thiolate-metal coordination as healing motifs, the composites exhibit rapid and efficient multi-responsive self-healing performance under NIR irradiation and low pH condition. Dependent on well-defined anisotropic structures, the hydrogel presents controllable solvent-responsive mechanical actuating performance. Impressively, the integrated device through a healing-induced assembly way can deliver more complicated, elaborate forms of actuation, demonstrating its great potentials as superior soft actuators like smart robots.

Peptide-Based Molecular Hydrogels as Supramolecular Protein Mimics.

Abstract: This Minireview concerns recent advances in the design, synthesis, and application of low molecular-weight peptidic hydrogelators. The sequence-specific combinations of amino acid side chain functionalities combined with hydrogen bonding of amide backbones and hydrophobic (aromatic) capping groups give these peptidic molecules the intrinsic tendency to self-assemble. The most prevalent designs include N-capped amino acid residues, bolamphiphilic peptides, and amphipathic peptides. Factors such as hydrophobic effects, the Hofmeister effect, and tunable ionization influence their aggregation properties. The self-assembly of simple bio-inspired building blocks into higher organized structures allows comparisons to be drawn with proteins and their complex functionalities, providing preliminary insights into complex biological functions and also enabling their application in a wide range of fields including catalysis, biomedical applications, and mimicry of natural dissipative systems. The Minireview is concluded by a short summary and outlook, highlighting the advances and steps required to bridge the gaps in the understanding of such systems.

Metal-Catalyzed β-Functionalization of Michael Acceptors through Reductive Radical Addition Reactions.

Abstract: Transition-metal-catalyzed radical reactions are becoming increasingly important in modern organic chemistry. They offer fascinating and unconventional ways for connecting molecular fragments that are often complementary to traditional methods. In particular, reductive radical additions to α,β-unsaturated compounds have recently gained substantial attention as a result of their broad applicability in organic synthesis. This Minireview critically discusses the recent landmark achievements in this field in context with earlier reports that laid the foundation for today's developments.

Self-Assembling Peptides and Their Application in the Treatment of Diseases.

Abstract: Self-assembling peptides are biomedical materials with unique structures that are formed in response to various environmental conditions. Governed by their physicochemical characteristics, the peptides can form a variety of structures with greater reactivity than conventional non-biological materials. The structural divergence of self-assembling peptides allows for various functional possibilities; when assembled, they can be used as scaffolds for cell and tissue regeneration, and vehicles for drug delivery, conferring controlled release, stability, and targeting, and avoiding side effects of drugs. These peptides can also be used as drugs themselves. In this review, we describe the basic structure and characteristics of self-assembling peptides and the various factors that affect the formation of peptide-based structures. We also summarize the applications of self-assembling peptides in the treatment of various diseases, including cancer. Furthermore, the in-cell self-assembly of peptides, termed reverse self-assembly, is discussed as a novel paradigm for self-assembling peptide-based nanovehicles and nanomedicines.