Laura Blasi

In Situ Formation and Size Control of Gold Nanoparticles into Chitosan for Nanocomposite Surfaces with Tailored Wettability

The in situ formation of gold nanoparticles into the natural polymer chitosan is described upon pulsed laser irradiation. In particular, hydrogel-type films of chitosan get loaded with the gold precursor, chloroauric acid salt (HAuCl(4)), by immersion in its aqueous solution. After the irradiation of this system with increasing number of ultraviolet laser pulses, we observe the formation of gold nanoparticles with increasing density and decreasing size. Analytical studies using absorption measurements, atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy of the nanocomposite samples throughout the irradiation procedure reveal that under the specific irradiation conditions there are two competing mechanisms responsible for the nanoparticles production: the photoreduction of the precursor responsible for the rising growth of gold particles with increasing size and the subsequent photofragmentation of these particles into smaller ones. The described method allows the localized formation of gold nanoparticles into specific areas of the polymeric films, expanding its potential applications due to its patterning capability. The size and density control of the gold nanoparticles, obtained by the accurate increase of the laser irradiation time, is accompanied by the simultaneously controlled increase of the wettability of the obtained gold nanocomposite surfaces. The capability of tailoring the hydrophilicity of nanocomposite materials based on natural polymer and biocompatible gold nanoparticles provides new potentialities in microfluidics or lab on chip devices for blood analysis or drugs transport, as well as in scaffold development for preferential cells growth.

Smart surfaces for pH controlled cell staining

In this work, novel smart surfaces for in situcell staining were realized by covalent attachment of pH-responsive microgels on platforms dedicated to microfluidics for lab-on-chip. The poly(methacrylic acid) microgels were firstly synthesized in solution and then covalently immobilized on a glass surface. As they preserve their pH-sensitive nature after the covalent immobilization, microgels were loaded with an oligothiophene-conjugated anti-human CD4 monoclonal antibody, and finally incubated with a Jurkat T-cell suspension. The physiological pH of the extracellular environment induced the pH-triggered release of the labeled antiCD4 antibodies and the selective staining of the CD4-positive subpopulations within the Jurkat cell suspension. The realization of this type of smart surface for the encapsulation of specific monoclonal antibodies and their release in an on-demand way should have an enormous potential in developing fully integrated platforms for cell analysis.

pH controlled staining of CD4+ and CD19+ cells within functionalized microfluidic channel

Herein proposed is a simple system to realize hands-free labeling and simultaneous detection of two human cell lines within a microfluidic device. This system was realized by novel covalent immobilization of pH-responsive poly(methacrylic acid) microgels onto the inner glass surface of an assembled polydimethylsiloxane/glass microfluidic channel. Afterwards, selected thiophene labeled monoclonal antibodies, specific for recognition of CD4 antigens on T helper/inducer cells and CD19 antigens on B lymphocytes cell lines, were encapsulated in their active state by the immobilized microgels. When the lymphocytes suspension, containing the two target subpopulations, was flowed through the microchannel, the physiological pH of the cellular suspension induced the release of the labeled antibodies from the microgels and thus the selective cellular staining. The selective pH-triggered staining of the CD4- and CD19-positive cells was investigated in this preliminary experimental study by laser scanning confocal microscopy. This approach represents an interesting and versatile tool to realize cellular staining in a defined module of lab-on-a-chip devices for subsequent detection and counting.

Poly(lactide-co-glycolide) nanoparticles embedded in a micropatterned collagen scaffold for neuronal tissue regeneration

ABSTRACT Micropatterned collagen scaffold with axially oriented pores embedded with poly(lactide-co-glycolide) nanoparticles (PLGA NPs) was synthesized and characterized. Two different concentrations of PLGA nanoparticles have been tested and the experimental results indicate that the concentration affects the release kinetic, whereas the stiffness, the crosslink density, and the degradation rate of the collagen matrix are comparable to bare scaffold. Further, the proposed crosslinking procedure provides a resistance to thermal and enzymatic degradation, thereby promoting the persistence of scaffold for a period of time compatible with nerve regeneration. GRAPHICAL ABSTRACT

New biocompatible polymeric micelles designed for efficient intracellular uptake and delivery

New amphiphilic block copolymers are easily synthesised by post-polymerisation modifications of poly(glycidyl methacrylate) chain derivatives. The obtained material, upon dispersion in water, is capable of self-assembling into robust micelles. These nanoparticles, which are also characterised by adaptable stability, were loaded with different thiophene based fluorophores. The photoluminescent micelles were administered to cultured cells revealing a high and rapid internalisation of structurally different fluorescent molecules by the same internalisation pathway. Appropriate pairs of chromophores were selected and loaded into the micelles to induce Förster resonance energy transfer (FRET). The disappearing of the FRET phenomenon, after cell uptaking, demonstrated the intracellular release of the nanoparticle contents. The studied nanomaterial and the loaded chromophores have also shown to be biocompatible and non toxic towards the tested cells.

Enzyme-responsive multifunctional surfaces for controlled uptake/release of (bio)molecules.

The current trend in the development of biomaterials is towards bioactive and biodegradable systems. In particular, enzyme-responsive structures are useful tools to realize biodegradable surfaces for the controlled delivery of biomolecules/drugs through a triggered surface erosion process. Up to now, enzyme-responsive structures have been designed by covalent linkage between synthetic polymers and biodegradable functionalities that are responsive to chemical and biological cues (i.e. proteases or pH) [1-4]. Here, we present a novel approach to achieve enzyme-responsive surface-attached networks by exploiting the non-covalent interaction between streptavidin and biotin. The functional component of this three-dimensional (3D) structure is a layer of biotinylated peptides that are degraded by the action of specific proteases. The system was stable under typical physiological conditions; however, it was efficiently degraded upon enzyme exposure. Further, the controlled release of biomolecules and drugs--previously entrapped into the surface-attached network--was demonstrated to occur as a consequence of the enzymatic cleavage. This versatile approach does not require complex chemical procedures. Interestingly, it can be easily adapted to different enzyme-peptide partners and therefore is very attractive for tissue replacement, drug delivery and biosensing.

Retracted article: Laser-induced gold/chitosan nanocomposites with tailored wettability applied to multi-irradiated microfluidic channels

We, the named authors, hereby wholly retract this RSC Advances article. Signed: Fabrizio Spano, Alessandro Massaro, Laura Blasi, Roberto Cingolani and Athanassia Athanassiou, Italy, October 2012. Retraction endorsed by Sarah Ruthven, Managing Editor, RSC Advances. Retraction published 2nd October 2012.