Ultrasound-Stimulated PVA Microbubbles for Adhesive Removal from Cellulose-Based Materials: A Groundbreaking Low-Impact Methodology

Polymeric materials for ultrasound imaging and therapy

Ultrasound (US) is routinely used for diagnostic imaging and increasingly employed for therapeutic applications. Materials that act as cavitation nuclei can improve the resolution of US imaging, and facilitate therapeutic US procedures by promoting local drug delivery or allowing temporary biological barrier opening at moderate acoustic powers. Polymeric materials offer a high degree of control over physicochemical features concerning responsiveness to US, e.g. via tuning chain composition, length and rigidity. This level of control cannot be achieved by materials made of lipids or proteins. In this perspective, we present key engineered polymeric materials that respond to US, including microbubbles, gas-stabilizing nanocups, microcapsules and gas-releasing nanoparticles, and discuss their formulation aspects as well as their principles of US responsiveness. Focusing on microbubbles as the most common US-responsive polymeric materials, we further evaluate the available chemical toolbox to engineer polymer shell properties and enhance their performance in US imaging and US-mediated drug delivery. Additionally, we summarize emerging applications of polymeric microbubbles in molecular imaging, sonopermeation, and gas and drug delivery, based on refinement of MB shell properties. Altogether, this manuscript provides new perspectives on US-responsive polymeric designs, envisaging their current and future applications in US imaging and therapy.

Ultrasound-Stimulated PVA Microbubbles as a Green and Handy Tool for the Cleaning of Cellulose-Based Materials

One of the main issues in the cultural heritage field of restoration chemistry is the identification of greener and more effective methods for the wet cleaning of paper artefacts, which serve as witnesses to human history and custodians of cultural values. In this context, we propose a biocompatible method to perform wet cleaning on paper based on the use of 1 MHz ultrasound in combination with water-dispersed polyvinyl alcohol microbubbles (PVAMBs), followed by dabbing with PVA-based hydrogel. This method can be applied to both old and new papers. FTIR spectroscopy, X-ray diffraction, HPLC analysis, pH measurements and tensile tests were performed on paper samples, to assess the efficacy of the cleaning system. According to the results, ultrasound-activated PVAMB application allows for an efficient interaction with rough and porous cellulose paper profiles, promoting the removal of cellulose degradation byproducts, while the following hydrogel dabbing treatment guarantees the removal of cleaning materials residues. Moreover, the results also pointed out that after the treatment no thermal or mechanical damages had affected the paper. In conclusion, the readability of these kinds of artifacts can be improved without causing an alteration of their structural properties, while mitigating the risk of ink diffusion.

Toward a theranostic device for gliomas

BACKGROUND

In the surgical management of glioblastoma, a highly aggressive and incurable type of brain cancer, identification and treatment of residual tissue is the most common site of disease recurrence. Monitoring and localized treatment are achieved with engineered microbubbles (MBs) by combining ultrasound and fluorescence imaging with actively targeted temozolomide (TMZ) delivery.

METHODS

The MBs were conjugated with a near-infrared fluorescence probe CF790, cyclic pentapeptide bearing the RGD sequence and a carboxyl-temozolomide, TMZA. The efficiency of adhesion to HUVEC cells was assessed in vitro in realistic physiological conditions of shear rate and vascular dimensions. Cytotoxicity of TMZA-loaded MBs on U87 MG cells and IC50 were assessed by MTT tests.

RESULTS

We report on the design of injectable poly(vinyl alcohol) echogenic MBs designed as a platform with active targeting ability to tumor tissues, by tethering on the surface a ligand having the tripeptide sequence, RGD. The biorecognition of RGD-MBs onto HUVEC cells is quantitatively proved. Efficient NIR emission from the CF790-decorated MBs was successfully detected. The conjugation on the MBs surface of a specific drug as TMZ is achieved. The pharmacological activity of the coupled-to-surface drug is preserved by controlling the reaction conditions.

CONCLUSIONS

We present an improved formulation of PVA-MBs to achieve a multifunctional device with adhesion ability, cytotoxicity on glioblastoma cells and supporting imaging.