Enhanced stability of superparamagnetic iron oxide nanoparticles in biological media using a pH adjusted-BSA adsorption protocol

Superparamagnetic iron oxide nanoparticles (SPIONs) are widely used for biological applications due to their unique properties compared to their bulk counterparts, simplified SPIONs stabilization protocols applicable for a wide spectra of biological media remains a challenging issue. In this work, SPIONs with different surface coatings, tetramethylammonium hydroxide-coated SPIONs (T-SPIONs), and citrate-coated SPIONs (C-SPIONs) were synthesized by a facile, rapid and cost effective microwave-assisted method. C-SPIONs show robust stability in biological media of phosphate buffered saline and Roswell Park Memorial Institute Medium, while destabilize in DMEM. T-SPIONs were found to aggregate rapidly and significantly in all tested media. Then, a modified pH adjusted-BSA adsorption protocol and an addition of excess trisodium citrate dihydrate (Na3Cit) were used to enhance their stability in the media. The BSA adsorption protocol showed great efficiency in stabilizing the dispersed state of both SPIONs in the tested media, while the addition of excess Na3Cit showed limited effect, and it was only applicable for C-SPIONs. The formed BSA layer on SPIONs could be imaged by negative staining TEM, and revealed by Cryo-TEM, FTIR, DLS, and the zeta potential measurements. Results indicated that BSA forms a monolayer of a thickness of about 3 ± 1 nm and BSA interacts with C-SPIONs and T-SPIONs through their coating, rather than by replacing them. This synthetic method and stabilization protocol offer a general methodology to obtain SPIONs with a variety of surfactants, stable in different biological media in few minutes. © 2014 Springer Science+Business Media.Acknowledgments The research leading to these results has received funding from the People Program (Marie Curie Actions) of the European Union’s Seventh Framework Program (FP7/2007-2013) under REA grant agreement n8 303630 and cofounded by the European Social Fund. Authors acknowledge the funding from Spanish Ministry of Economy MAT 2012-35324, COST Action MP1202 and Ramon y Cajal grant RYC-2010-06082 (AL), China Scholarship Council fellowship (SMY, 201206150053).Peer Reviewe

Bacterial cellulose films: influence of bacterial strain and drying route on film properties

© 2014, Springer Science+Business Media Dordrecht. Structural properties of bacterial cellulose (BC) depend on the microstructure of the material, which in turn is influenced by the bacterial strain. This paper reports the production of BC thin films from two bacterial strains, gluconacetobacter xylinus (GX) and gluconacetobacter europaeus (GE), and three methods of drying the films; at room temperature, freeze drying and supercritical drying. The porosity, transparency, water absorption capacity (WAC) and mechanical properties of the obtained films are further investigated. We conclude that materials with different properties can be fabricated by selecting the bacterial strain or the drying method. Supercritical drying of films of GE achieved mechanically robust and extremely light films, 0.05 g/mL, with up to 96 % of porosity, and with a WAC up 110 times their dried weight. We determined that materials resulting from GE strain are not much affected by the drying method. On the other hand, GX produced BC films more sensitive to the drying method used. Films are denser, 0.6–0.2 g/mL, with tunable porosity from 60 to 90 % and their maximum WAC is 66 times their dried weight.The research leading to these results has received funding from the People Program (Marie Curie Actions) of the European Union’s Seventh Framework Program (FP7/2007-2013) under REA grant agreement no 303630 and cofounded by the European Social Fund. Authors acknowledge the funding from Spanish Ministry of Economy MAT 2012-35324, from the Generalitat de Catalunya 2014SGR213, COST Action MP1202, Ramon y Cajal grant RYC-2010-06082 (AL), and Chinese Scholarship Council fellowship (MZ). The group of Dr. Alex Peralvarez for their help in the bacterial culture, Dr. Josep PuigMartı´ and the group of Prof. David Amabilino for the use of the optical microscope, Prof. Elies Molins and Toni Pons for the use and training in the use of the freeze drier and Dr. Roberto L. Guzman de Villoria for his advices in the mechanical measurements.Peer Reviewe

Protective Effects of Bovine Serum Albumin on Superparamagnetic Iron Oxide Nanoparticles Evaluated in the Nematode Caenorhabditis elegans

Nanomaterials give rise to unique biological reactivity that needs to be thoroughly investigated. The quest for enhanced magnetic nanomaterials of different shapes, magnetic properties, or surface coatings continues for applications in drug delivery, targeting therapies, biosensing, and magnetic separation. In this context, the use of simple in vivo models, such as Caenorhabditis elegans, to biologically evaluate nanoparticles is currently in increasing demand as it offers low-cost and information-rich experiments. In this work, we evaluated how surface modification (citrate- and protein-coated) of superparamagnetic iron oxide nanoparticles (C-SPIONs and BSA-SPIONs, respectively) induces changes in their toxicological profile and biodistribution using the animal model C. elegans and combining techniques from materials science and biochemistry. The acute toxicity and nanoparticle distribution were assessed in two populations of worms (adults and larvae) treated with both types of SPIONs. After 24 h treatment, nanoparticles were localized in the alimentary system of C. elegans; acute toxicity was stronger in adults and larvae exposed to C-SPIONs rather than BSA-SPIONs. Adult uptake was similar for both SPION types, whereas uptake in larvae was dependent on the surface coating, being higher for BSA-SPIONs. Nanoparticle size was evaluated upon excretion, and a slight size decrease was found. Interestingly, all results indicate the protective effects of the BSA to prevent degradation of the nanoparticles and decrease acute toxicity to the worms, especially at high concentrations. We argue that this relevant information on the chemistry and toxicity of SPIONs in vivo could not be gathered using more classical in vitro approaches such as cell culture assays, thus endorsing the potential of C. elegans to assess nanomaterials at early stages of their synthetic formulations.C. elegans N2 and E. coli OP50 were provided by the CGC, which is funded by NIH Office of Research Infrastructure Programs (P40 OD010440). The research leading to these results has received funding from the People Program (Marie Curie Actions) of the European Union’s Seventh Framework Program (FP7/2007-2013) under REA grant agreement nº 303630 and cofounded by the European Social Fund. Authors acknowledge the funding from Spanish Ministry of Economy MAT 2012-35324 and FEDER funds, the Generalitat de Catalunya 2014SGR213, the COST Action MP1202, Ramon y Cajal grant RYC-2010-06082 (AL), China Scholarship Council fellowship (SMY, 201206150053), and FPU fellowship FPU12/05549 (LGM).Peer Reviewe

Shifts in the Distribution of Mass Densities Is a Signature of Caloric Restriction in Caenorhabditis elegans

Although the starvation response of the model multicellular organism Caenorhabditis elegans is a subject of much research, there is no convenient phenotypic readout of caloric restriction that can be applicable to large numbers of worms. This paper describes the distribution of mass densities of populations of C. elegans, from larval stages up to day one of adulthood, using isopycnic centrifugation, and finds that density is a convenient, if complex, phenotypic readout in C. elegans. The density of worms in synchronized populations of wildtype N2 C. elegans grown under standard solid-phase culture conditions was normally distributed, with distributions peaked sharply at a mean of 1.091 g/cm3 for L1, L2 and L3 larvae, 1.087 g/cm3 for L4 larvae, 1.081 g/cm3 for newly molted adults, and 1.074 g/cm3 at 24 hours of adulthood. The density of adult worms under starvation stress fell well outside this range, falling to a mean value of 1.054 g/cm3 after eight hours of starvation. This decrease in density correlated with the consumption of stored glycogen in the food-deprived worms. The density of the worms increased when deprived of food for longer durations, corresponding to a shift in the response of the worms: worms sacrifice their bodies by retaining larvae, which consume the adults from within. Density-based screens with the drug Ivermectin on worms cultured on single plates resulted in a clear bimodal (double-peaked) distribution of densities corresponding to drug exposed and non-exposed worms. Thus, measurements of changes in density could be used to conduct screens on the effects of drugs on several populations of worms cultured on single plates

Limbal Stem Cells on Bacterial Nanocellulose Carriers for Ocular Surface Regeneration

Limbal stem cells (LSCs) are already used in cell-based treatments for ocular surface disorders. Clinical translation of LSCs-based therapies critically depends on the successful delivery, survival, and retention of these therapeutic cells to the desired region. Such a major bottleneck could be overcome by using an appropriate carrier to provide anchoring sites and structural support to LSC culture and transplantation. Bacterial nanocellulose (BNC) is an appealing, yet unexplored, candidate for this application because of its biocompatibility, animal-free origin and mechanical stability. Here, BNC as a vehicle for human embryonic stem cells-derived LSC (hESC-LSC) are investigated. To enhance cell-biomaterial interactions, a plasma activation followed by a Collagen IV and Laminin coating of the BNC substrates is implemented. This surface functionalization with human extracellular matrix proteins greatly improved the attachment and survival of hESC-LSC without compromising the flexible, robust and semi-transparent nature of the BNC. The surface characteristics of the BNC substrates are described and a preliminary ex vivo test in simulated transplantation scenarios is provided. Importantly, it is shown that hESC-LSC retain their self-renewal and stemness characteristics up to 21 days on BNC substrates. These results open the door for future research on hESC-LSC/BNC constructs to treat severe ocular surface pathologies.acceptedVersionPeer reviewe

Enhancing Localized Pesticide Action through Plant Foliage by Silver-Cellulose Hybrid Patches

Efficacy and efficiency of pesticide application in the field through the foliage still face many challenges. There exists a mismatch between the hydrophobic character of the leaf and the active molecule, low dispersion of the pesticides on the leaves' surface, runoff loss, and rolling down of the active molecules to the field, decreasing their efficacy and increasing their accumulation to the soil. We produced bacterial cellulose-silver nanoparticles (BC-AgNPs) hybrid patches by in situ thermal reduction under microwave irradiation in a scalable manner and obtaining AgNPs strongly anchored to the BC. Those hybrids increase the interaction of the pesticide (AgNPs) with the foliage and avoids runoff loss and rolling down of the nanoparticles. The positive antibacterial and antifungal properties were assessed in vitro against the bacteria Escherichia coli and two agro-economically relevant pathogens: the bacterium Pseudomonas syringae and the fungus Botrytis cinerea. We showed in vivo inhibition of the infection in Nicotiana benthamiana and tomato leaves, as proven by the suppression of the expression of defense molecular markers and reactive oxygen species production. The hydrogel-like character of the bacterial cellulose matrix increases the adherence to the foliage of the patches

Highly Aligned Bacterial Nanocellulose Films Obtained During Static Biosynthesis in a Reproducible and Straightforward Approach

Bacterial nanocellulose (BNC) is usually produced as randomly-organized highly pure cellulose nanofibers films. Its high water-holding capacity, porosity, mechanical strength, and biocompatibility make it unique. Ordered structures are found in nature and the properties appearing upon aligning polymers fibers inspire everyone to achieve highly aligned BNC (A-BNC) films. This work takes advantage of natural bacteria biosynthesis in a reproducible and straightforward approach. Bacteria confined and statically incubated biosynthesized BNC nanofibers in a single direction without entanglement. The obtained film is highly oriented within the total volume confirmed by polarization-resolved second-harmonic generation signal and Small Angle X-ray Scattering. The biosynthesis approach is improved by reusing the bacterial substrates to obtain A-BNC reproducibly and repeatedly. The suitability of A-BNC as cell carriers is confirmed by adhering to and growing fibroblasts in the substrate. Finally, the thermal conductivity is evaluated by two independent approaches, i.e., using the well-known 3 ω -method and a recently developed contactless thermoreflectance approach, confirming a thermal conductivity of 1.63 W mK −1 in the direction of the aligned fibers versus 0.3 W mK −1 perpendicularly. The fivefold increase in thermal conductivity of BNC in the alignment direction forecasts the potential of BNC-based devices outperforming some other natural polymer and synthetic materials. Bacteria confined and statically incubated for a few days biosynthesized bacterial nanocellulose (BNC) nanofibers in a single direction without entanglement. The obtained film is highly oriented within the total volume of the film, and it shows a five-fold increase in thermal conductivity in the parallel direction forecasting the potential of BNC-based devices outperforming some other natural polymer and synthetic materials

Measuring Markers of Liver Function Using a Micropatterned Paper Device Designed for Blood from a Fingerstick

This paper describes a paper-based microfluidic device that measures two enzymatic markers of liver function (alkaline phosphatase, ALP, and aspartate aminotransferase, AST) and total serum protein. A device consists of four components: (i) a top plastic sheet, (ii) a filter membrane, (iii) a patterned paper chip containing the reagents necessary for analysis, and (iv) a bottom plastic sheet. The device performs both the sample preparation (separating blood plasma from erythrocytes) and the assays; it also enables both qualitative and quantitative analysis of data. The data obtained from the paper-microfluidic devices show standard deviations in calibration runs and “spiked” standards that are acceptable for routine clinical use. This device illustrates a type of test useable for a range of assays in resource-poor settings.Chemistry and Chemical Biolog

A Microfluidic Device for Whole-Animal Drug Screening Using Electrophysiological Measures in the Nematode C. Elegans

This paper describes the fabrication and use of a microfluidic device for performing whole-animal chemical screens using non-invasive electrophysiological readouts of neuromuscular function in the nematode worm, C. elegans. The device consists of an array of microchannels to which electrodes are attached to form recording modules capable of detecting the electrical activity of the pharynx, a heart-like neuromuscular organ involved in feeding. The array is coupled to a tree-like arrangement of distribution channels that automatically delivers one nematode to each recording module. The same channels are then used to perfuse the recording modules with test solutions while recording the electropharyngeogram (EPG) from each worm with sufficient sensitivity to detect each pharyngeal contraction. The device accurately reported the acute effects of known anthelmintics (anti-nematode drugs) and also correctly distinguished a specific drug-resistant mutant strain of C. elegans from wild type. The approach described here is readily adaptable to parasitic species for the identification of novel anthelmintics. It is also applicable in toxicology and drug discovery programs for human metabolic and degenerative diseases for which C. elegans is used as a model.Chemistry and Chemical Biolog

Enzymically attaching oligosaccharide-linked ‘cargoes’ to cellulose and other commercial polysaccharides via stable covalent bonds

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