Silver and Antimicrobial Polymer Nanocomplexes to Enhance Biocidal Effects.

Antimicrobial resistance has become a major problem over the years and threatens to remain in the future, at least until a solution is found. Silver nanoparticles (Ag-NPs) and antimicrobial polymers (APs) are known for their antimicrobial properties and can be considered an alternative approach to fighting resistant microorganisms. Hence, the main goal of this research is to shed some light on the antimicrobial properties of Ag-NPs and APs (chitosan (CH), poly-L-lysine (PLL), ε-poly-L-lysine (ε-PLL), and dopamine (DA)) when used alone and complexed to explore the potential enhancement of the antimicrobial effect of the combination Ag-NPs + Aps. The resultant nanocomplexes were chemically and morphologically characterized by UV-visible spectra, zeta potential, transmission electron microscopy, and Fourier-transform infrared spectroscopy. Moreover, the Ag-NPs, APs, and Ag-NPs + APs nanocomplexes were tested against Gram-positive Staphylococcus aureus (S. aureus) and the Gram-negative Escherichia coli (E. coli) bacteria, as well as the fungi Candida albicans (C. albicans). Overall, the antimicrobial results showed potentiation of the activity of the nanocomplexes with a focus on C. albicans. For the biofilm eradication ability, Ag-NPs and Ag-NPs + DA were able to significantly remove S. aureus preformed biofilm, and Ag-NPs + CH were able to significantly destroy C. albicans biofilm, with both performing better than Ag-NPs alone. Overall, we have proven the successful conjugation of Ag-NPs and APs, with some of these formulations showing potential to be further investigated for the treatment of microbial infections.

Methyl Jasmonate and Nanoparticles Doped with Methyl Jasmonate affect the Cell Wall Composition of Monastrell Grape Skins.

The structural composition of the cell wall of grape skins is related to the cell wall integrity and subsequent extraction of the different compounds that are contained inside vacuoles and also the cell wall breakdown products. Different reports have established that methyl jasmonate (MeJ) produces changes in the composition of the grape skin cell wall. The use of elicitors to promote the production of secondary metabolites in grapes has been studied in several reports; however, its study linked to nanotechnology is less developed. These facts led us to study the effect of methyl jasmonate (MeJ) and nanoparticles doped with MeJ (nano-MeJ) on the cell walls of Monastrell grapes during three seasons. Both treatments tended to increase cell wall material (CWM) and caused changes in different components of the skin cell walls. In 2019 and 2021, proteins were enlarged in both MeJ and nano-MeJ-treated grapes. A general decrease in total phenolic compounds was detected with both treatments, in addition to an increment in uronic acids when the grapes were well ripened. MeJ and nano-MeJ produced a diminution in the amount of cellulose in contrast to an increase in hemicellulose. It should be noted that the effects with nano-MeJ treatment occurred at a dose 10 times lower than with MeJ treatment.

Effect of Methyl Jasmonate Doped Nanoparticles on Nitrogen Composition of Monastrell Grapes and Wines.

Nitrogen composition on grapevines has a direct effect on the quality of wines since it contributes to develop certain volatile compounds and assists in the correct kinetics of alcoholic fermentation. Several strategies can be used to ensure nitrogen content in grapes and one of them could be the use of elicitors such as methyl jasmonate. The use of this elicitor has been proven to be efficient in the production of secondary metabolites which increases the quality of wines, but its use also has some drawbacks such as its low water solubility, high volatility, and its expensive cost. This study observes the impact on the amino acid and ammonium composition of must and wine of Monastrell grapes that have been treated with methyl jasmonate (MeJ) and methyl jasmonate n-doped calcium phosphate nanoparticles (MeJ-ACP). The first objective of this study was to compare the effect of these treatments to determine if the nitrogenous composition of the berries and wines increased. The second aim was to determine if the nanoparticle treatments showed similar effects to conventional treatments so that the ones which are more efficient and sustainable from an agricultural point of view can be selected. The results showed how both treatments increased amino acid composition in grapes and wines during two consecutive seasons and as well as the use of MeJ-ACP showed better results compared to MeJ despite using less quantity (1 mM compared to 10 mM typically). So, this application form of MeJ could be used as an alternative in order to carry out a more efficient and sustainable agriculture.

Biomimetic Mineralization Promotes Viability and Differentiation of Human Mesenchymal Stem Cells in a Perfusion Bioreactor.

In bone tissue engineering, the design of 3D systems capable of recreating composition, architecture and micromechanical environment of the native extracellular matrix (ECM) is still a challenge. While perfusion bioreactors have been proposed as potential tool to apply biomechanical stimuli, its use has been limited to a low number of biomaterials. In this work, we propose the culture of human mesenchymal stem cells (hMSC) in biomimetic mineralized recombinant collagen scaffolds with a perfusion bioreactor to simultaneously provide biochemical and biophysical cues guiding stem cell fate. The scaffolds were fabricated by mineralization of recombinant collagen in the presence of magnesium (RCP.MgAp). The organic matrix was homogeneously mineralized with apatite nanocrystals, similar in composition to those found in bone. X-Ray microtomography images revealed isotropic porous structure with optimum porosity for cell ingrowth. In fact, an optimal cell repopulation through the entire scaffolds was obtained after 1 day of dynamic seeding in the bioreactor. Remarkably, RCP.MgAp scaffolds exhibited higher cell viability and a clear trend of up-regulation of osteogenic genes than control (non-mineralized) scaffolds. Results demonstrate the potential of the combination of biomimetic mineralization of recombinant collagen in presence of magnesium and dynamic culture of hMSC as a promising strategy to closely mimic bone ECM.

Fluoride-doped amorphous calcium phosphate nanoparticles as a promising biomimetic material for dental remineralization.

Demineralization of dental hard tissue is a widespread problem and the main responsible for dental caries and dentin hypersensitivity. The most promising strategies to induce the precipitation of new mineral phase are the application of materials releasing gradually Ca2+ and PO43- ions or mimicking the mineral phase of the host tissue. However, the design of formulations covering both processes is so far a challenge in preventive dentistry. In this work, we have synthesized innovative biomimetic amorphous calcium phosphate (ACP), which has been, for the first time, doped with fluoride ions (FACP) to obtain materials with enhanced anti-caries and remineralizing properties. Significantly, the doping with fluoride (F) did not vary the physico-chemical features of ACP but resulted in a faster conversion to the crystalline apatite phase in water, as observed by in-situ time-dependent Raman experiments. The efficacy of the as synthesized ACP and FACP samples to occlude dentinal tubules and induce enamel remineralization has been tested in vitro in human molar teeth. The samples showed good ability to partially occlude the tubules of acid-etched dentin and to restore demineralized enamel into its native structure. Results demonstrate that ACP and FACP are promising biomimetic materials in preventive dentistry to hinder demineralization of dental hard tissues.

Inhalation of peptide-loaded nanoparticles improves heart failure.

Peptides are highly selective and efficacious for the treatment of cardiovascular and other diseases. However, it is currently not possible to administer peptides for cardiac-targeting therapy via a noninvasive procedure, thus representing scientific and technological challenges. We demonstrate that inhalation of small (<50 nm in diameter) biocompatible and biodegradable calcium phosphate nanoparticles (CaPs) allows for rapid translocation of CaPs from the pulmonary tree to the bloodstream and to the myocardium, where their cargo is quickly released. Treatment of a rodent model of diabetic cardiomyopathy by inhalation of CaPs loaded with a therapeutic mimetic peptide that we previously demonstrated to improve myocardial contraction resulted in restoration of cardiac function. Translation to a porcine large animal model provides evidence that inhalation of a peptide-loaded CaP formulation is an effective method of targeted administration to the heart. Together, these results demonstrate that inhalation of biocompatible tailored peptide nanocarriers represents a pioneering approach for the pharmacological treatment of heart failure.

* Biomineralized Recombinant Collagen-Based Scaffold Mimicking Native Bone Enhances Mesenchymal Stem Cell Interaction and Differentiation.

The need of synthetic bone grafts that recreate from macro- to nanoscale level the biochemical and biophysical cues of bone extracellular matrix has been a major driving force for the development of new generation of biomaterials. In this study, synthetic bone substitutes have been synthesized via biomimetic mineralization of a recombinant collagen type I-derived peptide (RCP), enriched in tri-amino acid sequence arginine-glycine-aspartate (RGD). Three-dimensional (3D) isotropic porous scaffolds of three different compositions are developed by freeze-drying: non-mineralized (RCP, as a control), mineralized (Ap/RCP), and mineralized scaffolds in the presence of magnesium (MgAp/RCP) that closely imitate bone composition. The effect of mineral phase on scaffold pore size, porosity, and permeability, as well as on their in vitro kinetic degradation, is evaluated. The ultimate goal is to investigate how chemical (i.e., surface chemistry and ion release from scaffold) together with physical signals (i.e., surface nanotopography) conferred via biomimetic mineralization can persuade and guide mesenchymal stem cell (MSC) interaction and fate. The three scaffold compositions showed optimum pore size and porosity for osteoconduction, without significant differences between them. The degradation tests confirmed that MgAp/RCP scaffolds presented higher reactivity under physiological condition compared to Ap/RCP ones. The in vitro study revealed an enhanced cell growth and proliferation on MgAp/RCP scaffolds at day 7, 14, and 21. Furthermore, MgAp/RCP scaffolds potentially promoted cell migration through the inner areas reaching the bottom of the scaffold after 14 days. MSCs cultured on MgAp/RCP scaffolds displayed higher gene and protein expressions of osteogenic markers when comparing them with the results of those MSCs grown on RCP or Ap/RCP scaffolds. This work highlights that mineralization of recombinant collagen mimicking bone mineral composition and morphology is a versatile approach to design smart scaffold interface in a 3D model guiding MSC fate.

Biomimetic mineralization of recombinant collagen type I derived protein to obtain hybrid matrices for bone regeneration.

Understanding the mineralization mechanism of synthetic protein has recently aroused great interest especially in the development of advanced materials for bone regeneration. Herein, we propose the synthesis of composite materials through the mineralization of a recombinant collagen type I derived protein (RCP) enriched with RGD sequences in the presence of magnesium ions (Mg) to closer mimic bone composition. The role of both RCP and Mg ions in controlling the precipitation of the mineral phase is in depth evaluated. TEM and X-ray powder diffraction reveal the crystallization of nanocrystalline apatite (Ap) in all the evaluated conditions. However, Raman spectra point out also the precipitation of amorphous calcium phosphate (ACP). This amorphous phase is more evident when RCP and Mg are at work, indicating the synergistic role of both in stabilizing the amorphous precursor. In addition, hybrid matrices are prepared to tentatively address their effectiveness as scaffolds for bone tissue engineering. SEM and AFM imaging show an homogeneous mineral distribution on the RCP matrix mineralized in presence of Mg, which provides a surface roughness similar to that found in bone. Preliminary in vitro tests with pre-osteoblast cell line show good cell-material interaction on the matrices prepared in the presence of Mg. To the best of our knowledge this work represents the first attempt to mineralize recombinant collagen type I derived protein proving the simultaneous effect of the organic phase (RCP) and Mg on ACP stabilization. This study opens the possibility to engineer, through biomineralization process, advanced hybrid matrices for bone regeneration.

Bioinspired negatively charged calcium phosphate nanocarriers for cardiac delivery of MicroRNAs.

AIM: To develop biocompatible and bioresorbable negatively charged calcium phosphate nanoparticles (CaP-NPs) as an innovative therapeutic system for the delivery of bioactive molecules to the heart. MATERIALS & METHODS: CaP-NPs were synthesized via a straightforward one-pot biomineralization-inspired protocol employing citrate as a stabilizing agent and regulator of crystal growth. CaP-NPs were administered to cardiac cells in vitro and effects of treatments were assessed. CaP-NPs were administered in vivo and delivery of microRNAs was evaluated. RESULTS: CaP-NPs efficiently internalized into cardiomyocytes without promoting toxicity or interfering with any functional properties. CaP-NPs successfully encapsulated synthetic microRNAs, which were efficiently delivered into cardiac cells in vitro and in vivo. CONCLUSION: CaP-NPs are a safe and efficient drug-delivery system for potential therapeutic treatments of polarized cells such as cardiomyocytes.

pH-responsive collagen fibrillogenesis in confined droplets induced by vapour diffusion.

A novel methodology for the assembly of collagen fibrils in microliter drops is proposed. It consists in the gradual increase of pH by means of vapour diffusion coming from the decomposition of NH4HCO3 solutions. The pH increase rate as well as the final steady pH of solutions containing collagen can be adjusted by varying the concentration of NH4HCO3. Both parameters are of predominant importance in collagen fibrillogenesis. The effect of these parameters on the kinetic of the fibrillogenesis process and on the fibrils morphology was studied. We found that both the kinetic and the morphology are mainly driven by electrostatic interactions. A gradual increase of pH slows down the formation of collagen fibres and favours the lateral interaction between fibrils producing broader fibres. On the other hand, a rapid increase of pH reduces the lateral electrostatic interactions favouring the formation of thinner fibres. The formation of the D-band periodicity is also a pH-dependent process that occurs after fibrillogenesis when the most stable state of fibres formation has been reached.