1,720,968 research outputs found
Recent Strategies in Osteochondral Substitutes Design: Towards the Mimicking of a Multifaceted Anatomical Unit from the Nano to the Macro Level
No full textCorrection of MHS Viscosimetric Constants upon Numerical Simulation of Temperature Induced Degradation Kinetic of Chitosan Solutions
Full text linkThe Mark–Houwink–Sakurada (MHS) equation allows for estimation of rheological properties, if the molecular weight is known along with good understanding of the polymer conformation. The intrinsic viscosity of a polymer solution is related to the polymer molecular weight according to the MHS equation, where the value of the constants is related to the specific solvent and its concentration. However, MHS constants do not account for other characteristics of the polymeric solutions, i.e., Deacetilation Degree (DD) when the solute is chitosan. In this paper, the degradation of chitosan in different acidic environments by thermal treatment is addressed. In particular, two different solutions are investigated (used as solvent acetic or hydrochloric acid) with different concentrations used for the preparation of chitosan solutions. The samples were treated at different temperatures (4, 30, and 80 °C) and time points (3, 6 and 24 h). Rheological, Gel Permeation Chromatography (GPC), Fourier Transform Infrared Spectroscopy (FT-IR), Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analyses (TGA) were performed in order to assess the degradation rate of the polymer backbones. Measured values of molecular weight have been integrated in the simulation of the batch degradation of chitosan solutions for evaluating MHS coefficients to be compared with their corresponding experimental values. Evaluating the relationship between the different parameters used in the preparation of chitosan solutions (e.g., temperature, time, acid type and concentration), and their contribution to the degradation of chitosan backbone, it is important to have a mathematical frame that could account for phenomena involved in polymer degradation that go beyond the solvent-solute combination. Therefore, the goal of the present work is to propose an integration of MHS coefficients for chitosan solutions that contemplate a deacetylation degree for chitosan systems or a more general substitution degree for polymers in which viscosity depends not only on molecular weight and solvent combinations
Experimental Assessment of Gold Nanorods for Optoacoustic Imaging in a Tissue-mimicking Phantom
No full textMagnetically-coated silica nanospheres for dual-mode imaging at low ultrasound frequency
No full textTo experimentally investigate the acoustical behavior of different dual-mode nanosized contrast agents (NPCAs) for echographic medical imaging at low ultrasound (US) frequency
Supporto biomimetico per il trattamento personalizzato di patologie a carico del tessuto osteocondrale - Smart Cake
No full textAn Innovative Ultrasound Signal Processing Technique to Selectively Detect Nanosized Contrast Agents in Echographic Images
No full textThe aim of this paper was to optimize the employment of a novel algorithm for acquisition and processing of medical ultrasound (US) signals to facilitate its clinical translation. The implemented procedure is dedicated to selective enhancement of nanoparticle (NP) contrast agents in echographic images and is based on the differences in US signal backscatter between NP-containing targets and more homogeneous
objects. Previous preliminary studies verified the feasibility of this approach on silica nanospheres (SiNSs) dispersed at a constant volume concentration (0.7%) in agarose gel samples. The present extended these evaluations, addressing two issues of direct clinical interest: 1) safety: SiNSs were coated with a biocompatible layer made of polyethylene glycol (PEG) and the adopted NP volume concentration was reduced to 0.2%, which is in the nontoxic range and 2) reproducibility: a different phantom configuration was used, to verify the independence of algorithm performance from a specific target region shape. The obtained results demonstrated that the proposed method can be effectively
applied to enhance the presence of PEG-coated SiNSs in the diameter range 160–660 nm at a low and biocompatible volume concentration: the combined employment of a phantom with a different geometry and a lower concentration of PEG-coated NPs, in fact, caused only slight variations in the suppression patterns of noncontrast echoes, without affecting the final diagnostic effectiveness of the investigated contrast detection scheme. This approach also provides specific advantages with respect to the available measurement techniques dedicated to the enhancement of targeted US contrast agents for molecular imaging purposes
Multiparametric Evaluation of the Acoustic Behavior of Halloysite Nanotubes for Medical Echographic Image Enhancement
No full textHalloysite nanotubes (HNTs) are nanomaterials composed of double layered aluminosilicate minerals characterized by a wide range of medical applications. Nonetheless, systematic investigations of their imaging potential are still poorly documented. This paper shows a parametric assessment of the effectiveness of HNTs as scatterers for safe ultrasound (US)-based molecular imaging. Quantitative evaluation of average signal enhancement produced by HNTs with varying set up configuration was performed. The influence of different levels of power (20%, 50%, and 80%) of the signal emitted by clinical equipment was determined, to assess the efficacy of different HNT
concentrations (1.5, 3, and 5 mg/mL) at conventional ultrasonic frequencies (5.7–7 MHz), even in case of specific limitation regarding US mechanical interaction with target tissues. Different samples of HNT containing agarose gel were imaged through a commercially available echographic system and acquired data were processed through a dedicated prototypal platform to extract the average ultrasonic signal amplitude. The rate of signal enhancement achieved by different concentration values was quantified and the contribution of frequency increment was separately evaluated. Despite influencing the level of mechanical excitation on HNTs and tissues, our results demonstrated how increasing the power of the emitted signal negatively affected the measured backscatter
Automatic Image Detection of Halloysite Clay Nanotubes as a Future Ultrasound Theranostic Agent for Tumoral Cell Targeting and Treatment
Full text linkHalloysite clay Nanotubes (HNTs) are nanomaterials composed of double layered aluminosilicate minerals with a hollow tubular structure in the submicron range. They are characterized by a wide range of applications in anticancer therapy as agent delivery. In this work we aim to investigate the automatic detection features of HNTs through advanced quantitative ultrasound imaging employing different concentrations (3-5 mg/mL) at clinical conventional frequency, i.e. 7 MHz. Different tissue mimicking samples of HNT containing agarose gel were imaged through a commercially available echographic system, that was opportunely combined with ultrasound signal analysis research platform for extracting the raw ultrasound radiofrequency (RF) signals. Acquired data were stored and analyzed by means of an in-house developed algorithm based on wavelet decomposition, in order to identify the specific spectrum contribution of the HNTs and generate corresponding image mapping. Sensitivity and specificity of the HNT detection were quantified. Average specificity (94.36%) was very high with reduced dependency on HNT concentration, while sensitivity showed a proportional increase with concentration with an average of 46.78%. However, automatic detection performances are currently under investigation for further improvement taking into account image enhancement and biocompatibility issues
Epithelial cell biocompatibility of silica nanospheres for contrast-enhanced ultrasound molecular imaging
No full textNanosized particles are receiving increasing attention as future contrast agents (CAs) for ultrasound (US) molecular imaging, possibly decorated on its surface with biological recognition agents for targeted delivery and deposition of therapeutics. In particular, silica nanospheres (SiNSs) have been demonstrated to be feasible in terms of contrast enhancement on conventional US systems. In this work, we evaluated the cytotoxicity of SiNSs on breast cancer (MCF-7) and HeLa (cervical cancer) cells employing NSs with sizes ranging from 160 to 330 nm and concentration range of 1.5-5 mg/mL. Cell viability was evaluated in terms of size, dose and time dependence, performing the MTT reduction assay with coated and uncoated SiNSs. Whereas uncoated SiNSs caused a variable significant decrease in cell viability on both cell lines mainly depending on size and exposure time, PEGylated SiNSs (SiNSs-PEG) exhibit a high level of biocompatibility. In fact, after 72-h incubation, viability of both cell types was above the cutoff value of 70 % at concentration up to 5 mg/ mL. We also investigated the acoustical behavior of coated and uncoated SiNSs within conventional diagnostic US fields in order to determine a suitable configuration, in terms of particle size and concentration, for their employment as targetable CAs. Our results indicate that the employment of SiNSs with diameters around 240 nm assures the most effective contrast enhancement even at the lowest tested concentration, coupled with the possibility of targeting all tumor tissues, being the SiNSs still in a size range where reticuloendothelial system trapping effect is relatively low
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