Anna Borriello

Conductive PANi/PEGDA Macroporous Hydrogels For Nerve Regeneration

Only recently polymers with intrinsic conductive properties have been studied in relation to their incorporation into bioactive scaffolds for use in tissue engineering. The reason for this interest is that such scaffolds could electrically stimulate cells and thus regulate specific cellular activities, and by this means influence the process of regeneration of those tissues that respond to electrical impulses. In our work, macroporous hydrogels are developed with controlled pore morphology and conductive properties to enable sufficient cell signaling to supply events inherent to nerve regeneration. A hybrid material has been prepared by in situ precipitation of polyaniline (PANi) in polyethyleneglycol diacrylate (PEGDA) solution, followed by crosslinking via UV irradiation. A porous architecture, characterized by macropores from 136 μm to 158 μm in size, has been achieved by sodium chloride particle leaching. In this work, we demonstrate that PANi synthesis and hydrogel crosslinking combine to enable the design of materials with suitable conductive behaviour. The presence of PANi evidently increased the electrical conductivity of the hybrid material from (1.1 ± 0.5) × 10(-3) mS/cm with a PANi content of 3wt%. The hydrophilic nature of PANi also enhanced water retention/proton conductivity by more than one order of magnitude. In vitro studies confirmed that 3 wt% PANi also improve the biological response of PC12 and hMSC cells. Hybrid PANi/PEGDA macroporous hydrogels supplement new functionalities in terms of morphological and conductive properties, both of which are essential prerequisites to drive nerve cells in regenerative processes.

Transition mode long period grating biosensor with functional multilayer coatings

We report our latest research results concerning the development of a platform for label-free biosensing based on overlayered Long Period Gratings (LPGs) working in transition mode. The main novelty of this work lies in a multilayer design that allows to decouple the problem of an efficient surface functionalization from that of the tuning in transition region of the cladding modes. An innovative solvent/nonsolvent strategy for the dip-coating technique was developed in order to deposit on the LPG multiple layers of transparent polymers. In particular, a primary coating of atactic polystyrene was used as high refractive index layer to tune the working point of the device in the so-called transition region. In this way, state-of-the-art-competitive sensitivity to surrounding medium refractive index changes was achieved. An extremely thin secondary functional layer of poly(methyl methacrylate-co-methacrylic acid) was deposited onto the primary coating by means of an original identification of selective solvents. This approach allowed to obtain desired functional groups (carboxyls) on the surface of the device for a stable covalent attachment of bioreceptors and minimal perturbation of the optical design. Standard 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide / N-hydrosuccinimide (EDC / NHS) coupling chemistry was used to link streptavidin on the surface of the coated LPG. Highly sensitive real-time monitoring of multiple affinity assays between streptavidin and biotinylated bovine serum albumin was performed by following the shift of the LPGs attenuation bands.

A protein-based biointerfacing route toward label-free immunoassays with long period gratings in transition mode

We present a fast and effective method for anchoring bioreceptors to optical waveguides exhibiting a poorly reactive polymer interface and that have to be minimally perturbed with respect to their design. The study originated from the need to biofunctionalize a fiber optic Long Period Grating (LPG) that is tuned in a highly sensitive working point, the so-called transition mode, through the deposition of a high refractive index overlay. In particular, a thin film of atactic polystyrene (PS) was dip-coated onto the LPG with a thickness suitable to optimize the LPG sensitivity to refractive index changes of the surrounding medium. Bovine serum albumin was selected as sacrificial layer for its well-known adhesion capabilities to PS surfaces, then glutaraldehyde was used to conjugate IgGs, serving as prototypical bioreceptor, on the device surface. The effectiveness of the immobilization method was assessed by studying the interaction between the immobilized IgG with a suitable anti-IgG. In a preliminary study performed by means of ELISA and surface plasmon resonance, optimal conditions for the biomolecular testing with the LPG were assessed. Four distinct interactions were thus monitored in real time following the shift of the LPG attenuation band. These experiments suggest a novel and interesting biofunctionalization approach of unreactive polymers with applications in immunosensing and basic life science research.

Long period fiber grating nano-optrode for cancer biomarker detection

We report an innovative fiber optic nano-optrode based on Long Period Gratings (LPGs) working in reflection mode for the detection of human Thyroglobulin (TG), a protein marker of differentiated thyroid cancer. The reflection-type LPG (RT-LPG) biosensor, coated with a single layer of atactic polystyrene (aPS) onto which a specific, high affinity anti-Tg antibody was adsorbed, allowed the label-free detection of Tg in the needle washouts of fine-needle aspiration biopsies, at concentrations useful for pre- and post-operative assessment of the biomarker levels. Analyte recognition and capture were confirmed with a parallel on fiber ELISA-like assay using, in pilot tests, the biotinylated protein and HRP-labeled streptavidin for its detection. Dose-dependent experiments showed that the detection is linearly dependent on concentration within the range between 0 and 4 ng/mL, while antibody saturation occurs for higher protein levels. The system is characterized by a very high sensitivity and specificity allowing the ex-vivo detection of sub ng/ml concentrations of human Tg from needle washouts of fine-needle aspiration biopsies of thyroid nodule from different patients.

Electro-Active Polymers (EAPs): A Promising Route to Design Bio-Organic/Bioinspired Platforms with on Demand Functionalities

Through recent discoveries and new knowledge among correlations between molecular biology and materials science, it is a growing interest to design new biomaterials able to interact—i.e., to influence, to guide or to detect—with cells and their surrounding microenvironments, in order to better control biological phenomena. In this context, electro-active polymers (EAPs) are showing great promise as biomaterials acting as an interface between electronics and biology. This is ascribable to the highly tunability of chemical/physical properties which confer them different conductive properties for various applicative uses (i.e., molecular targeting, biosensors, biocompatible scaffolds). This review article is divided into three parts: the first one is an overview on EAPs to introduce basic conductivity mechanisms and their classification. The second one is focused on the description of most common processes used to manipulate EAPs in the form of two-dimensional (2D) and three-dimensional (3D) materials. The last part addresses their use in current applications in different biomedical research areas including tissue engineering, biosensors and molecular delivery.

Monolithic polymeric aerogels with VOCs sorbent nanoporous crystalline and water sorbent amorphous phases.

Monolithic syndiotactic polystyrene (s-PS) aerogels, formed by highly crystalline nanofibrils with a hydrophobic nanoporous-crystalline phase and a hydrophilic amorphous phase have been prepared and characterized. These aerogels, with a high degree of sulfonation of the amorphous phase and nearly negligible sulfonation of the crystalline phase, are obtained by treating physical gels exhibiting δ-clathrate form. With respect to unsulfonated nanoporous-crystalline polymeric aerogels, these new selectively sulfonated aerogels present the great advantage of a high water diffusivity and water uptake up to 600 wt %. This water uptake increases greatly the sorption kinetics of organic pollutants by the hydrophobic nanopores of the crystalline phase. For instance, for aerogels with a sulfonation of 10%, the diffusivity of a volatile organic compound (1,2-dichloroethane, DCE) from 10 ppm aqueous solution is more than 3 orders of magnitude higher than that for the unsulfonated aerogel and is very close to the DCE diffusivity in water.

Nanoscale TiO 2 -coated LPGs as radiation-tolerant humidity sensors for high-energy physics applications

This Letter deals with a feasibility analysis for the development of radiation-tolerant fiber-optic humidity sensors based on long-period grating (LPG) technology to be applied in high-energy physics (HEP) experiments currently running at the European Organization for Nuclear Research (CERN). In particular, here we propose a high-sensitivity LPG sensor coated with a finely tuned titanium dioxide (TiO₂) thin layer (~100 nm thick) through the solgel deposition method. Relative humidity (RH) monitoring in the range 0%-75% and at four different temperatures (in the range -10°C-25°C) was carried out to assess sensor performance in real operative conditions required in typical experiments running at CERN. Experimental results demonstrate the very high RH sensitivities of the proposed device (up to 1.4 nm/% RH in correspondence to very low humidity levels), which turned out to be from one to three orders of magnitude higher than those exhibited by fiber Bragg grating sensors coated with micrometer-thin polyimide overlays. The radiation tolerance capability of the TiO₂-coated LPG sensor is also investigated by comparing the sensing performance before and after its exposure to a 1 Mrad dose of γ-ionizing radiation. Overall, the results collected demonstrate the strong potential of the proposed technology with regard to its future exploitation in HEP applications as a robust and valid alternative to the commercial (polymer-based) hygrometers currently used.

Label-free fiber optic optrode for the detection of class C β-lactamases expressed by drug resistant bacteria

This paper reports the experimental assessment of an automated optical assay based on label free optical fiber optrodes for the fast detection of class C β-lactamases (AmpC BLs), actually considered as one of the most important sources of resistance to β-lactams antibiotics expressed by resistant bacteria. Reflection-type long period fiber gratings (RT-LPG) have been used as highly sensitive label free optrodes, while a higher affine boronic acid-based ligand was here selected to enhance the overall assay performances compared to those obtained in our first demonstration. In order to prove the feasibility analysis towards a fully automated optical assay, an engineered system was developed to simultaneously manipulate and interrogate multiple fiber optic optrodes in the different phases of the assay. The automated system tested in AmpC solutions at increasing concentrations demonstrated a limit of detection (LOD) of 6 nM, three times better when compared with the results obtained in our previous work. Moreover, the real effectiveness of the proposed optical assay has been also confirmed in complex matrices as the case of lysates of Escherichia coli overexpressing AmpC.

Cryogenic-temperature profiling of high-power superconducting lines using local and distributed optical-fiber sensors

This contribution presents distributed and multipoint fiber-optic monitoring of cryogenic temperatures along a superconducting power transmission line down to 30 K and over 20 m distance. Multipoint measurements were conducted using fiber Bragg gratings sensors coated with two different functional overlays (epoxy and poly methyl methacrylate (PMMA)) demonstrating cryogenic operation in the range 300-4.2 K. Distributed measurements exploited optical frequency-domain reflectometry to analyze the Rayleigh scattering along two concatenated fibers with different coatings (acrylate and polyimide). The integrated system has been placed along the 20 m long cryostat of a superconducting power transmission line, which is currently being tested at the European Organization for Nuclear Research (CERN). Cool-down events from 300-30 K have been successfully measured in space and time, confirming the viability of these approaches to the monitoring of cryogenic temperatures along a superconducting transmission line.

Self Assembling and Coordination of Water Nano-Layers On Polymer Coated Long Period Gratings: Toward New Perspectives for Cation Detection

In this work, polymeric coated Long Period Gratings (LPGs) working in transition mode have been used to monitor the coordination and self assembling of water nano-layers (typical thicknesses range in few tens of nanometers) providing new scenarios in chemical sensing applications. In particular, nano-scale layers (∼320 nm) of semicrystalline syndiotactic and amorphous atactic polystyrene (sPS and aPS), have been deposited by dip-coating onto LPGs to tune the devices at the transition point. Experimental results demonstrate the polymers capability to orient water molecules in proximity of their surfaces. The sPS and aPS interactions with water have been continuously monitored and then compared demonstrating the higher capability of the crystalline phase of sPS to orient water nano-layers. Moreover, the high sensitivity of the coated LPGs was used to monitor the effect of disorder induced on the interfacial water molecular arrangement by different cations (sodium, Na+, potassium, K+, and calcium, Ca2+, ions) depending on their size and electrical charge. Experimental results show for the first time that, thanks to the water-polymer interaction, sPS coated LPGs could be successfully employed as high sensitivity cation sensors. In fact, the monitoring of the disorder induced by cations on the coordinated water layer leads to high sensitivities, in terms of detected RI change for unitary variation of concentration (∼ for Na+ ions, ∼ for K+ ions, and ∼ for Ca2+ ions).