Roberto Pini

Photothermally-induced disordered patterns of corneal collagen revealed by SHG imaging.

The loss of organization of the corneal collagen lattice induced by photothermal effects was analyzed by using second-harmonic generation (SHG) imaging. Porcine cornea samples were treated with low-power laser irradiation in order to get localized areas of tissue disorganization. The disorder induced within the irradiated area of corneal stroma was quantified by means of Discrete Fourier Transform, auto-correlation and entropy analyses of the SHG images. Polarization modulated SHG measurements allowed to probe the changes in the structural anisotropy of sub-micron hierarchical levels of the stromal collagen. Our results emphasize the great potential of the SHG imaging to detect subtle modifications in the collagen assembly. The proposed analytical methods may be used to track several genetic, pathologic, accidental or surgical-induced disorder states of biological tissues.

Chitosan Films Doped with Gold Nanorods as Laser-Activatable Hybrid Bioadhesives

Chitosan is a linear chain polysaccharide comprising glucosamine and N -acetyl glucosamine residues joined together by β -1,4-glycosidic bonds. It is derived as an acids-soluble material by deacetylation of chitin, which is commonly found in the outer skeleton of crustaceans and in the cell walls of fungi. A variety of fundamental properties such as excellent biocompatibility and biodegradability make chitosan a very attractive material for biomedical applications including wound dressing, tissue engineering and drug delivery. [ 1 , 2 ] The peculiar tendency of chitosan to form films with high mechanical strength, good elasticity and rather slow biodegradation is among the principal reasons why this material is gaining a primary role in medical technology. [ 2–4 ] Examples of applications of chitosan films are the localized chemotherapy based on the local delivery and sustained release of antineoplastic agents after cancer removal [ 5 ] and the tissue repair by closing chronic, accidental, and surgical wounds. [ 4 , 6 ] In order to enable these applications, the chitosan films need to be secured to the target, which may be achieved by suturing. [ 7 ] However, in many cases, suturing may be hardly feasible such as for poorly accessible or delicate body regions (e.g., intracranial, myocardial, etc.). In addition metals and synthetic materials in use for implantation can interfere with the functional rehabilitation of the site due to foreign-body reactions, causing infl ammation and abnormal wound healing. [ 8 ]

Gold nanorods as new nanochromophores for photothermal therapies

Results and perspectives on the biomedical exploitation of gold nanorods with plasmon resonances in the near infrared window are reported. The authors describe experimental studies of laser-activated nanoparticles in the direct welding of connective tissues, which may become a valuable technology in biomedicine. In particular, colloidal gold nanorods excited by diode laser radiation at 810 nm were used to mediate functional photothermal effects and weld eyes lens capsules and arteries. The preparation of biopolymeric matrices including gold nanorods is also described, as well as preliminary tests for their application in the closure of wounds in vessels and tendons. Finally, the use of these nanoparticles for future applications in the diagnosis, imaging and therapy of cancer is discussed.

Photothermal effects in connective tissues mediated by laser-activated gold nanorods

We report a study on the application of laser-activated nanoparticles in the direct welding of connective tissues, which may become a valuable technology in biomedicine. We use colloidal gold nanorods as new near-infrared chromophores to mediate functional photothermal effects in the eye lens capsules. Samples obtained ex vivo from porcine eyes are treated to simulate heterotransplants with 810-nm diode laser radiation in association with a stain of gold nanorods of aspect ratio approximately 4. This stain is applied at the interface between a patch of capsule from a donor eye and the capsule of a recipient eye. Then, by administration of laser pulses of 40 msec and approximately 100-140 J/cm(2), we achieved the local denaturation of the endogenous collagen filaments, which reveals that the treated area reached temperatures above 50 degrees C. The thermal damage is confined within 50-70 mum in a radial distance from the irradiated area.

Cleaning processes of encrusted marbles by Nd:YAG lasers operating in free-running and Q-switching regimes.

The removal process of degraded superficial layers from marble samples by Nd:YAG lasers was studied while simulating operative conditions of stone artwork restoration. The effects of laser irradiation at 1064 nm with three different pulse durations of 6 ns, 20 micros, and 200 micros were investigated by time-resolved shadowgraphy and emission spectroscopy of the ejection plume to characterize the specific interaction regimes, with particular concern given to the occurrence of side effects, such as thermal and mechanical damages to the substrate, that could affect the laser cleaning procedure.

Structural Behavior of Highly Concentrated Hyaluronan

When investigated under high concentration conditions, hyaluronan (HA) solutions in physiological saline are shown to generate stable superstructures. An abrupt change in the rheological properties observed on increasing the temperature suggests the breaking of certain cooperative bonds. The thermal disruption of the HA superstructure is accompanied by a sharp transition from a long- to a restricted-connectivity water structuring, which is interpreted as a concurrent transition from a stable to a temporary polymer network. The intermolecular associations are considered to be originated by hydrophobic interactions between the nonpolar groups of the polymer backbones.

Tests of laser cleaning on archeological metal artefacts

Abstract Previously reported experiences on laser cleaning of metal surfaces of artworks such as statues and decorations altered by atmospheric pollution demonstrated the potential advantages of this technique. Here we present a study on the use of laser cleaning on excavated metal objects that typically show alterations and corrosion processes quite different with respect to exposed metal artefacts. Tests were performed on a selection of archaeological samples, such as coins, plates, clamps and ornaments collected from Italian sites. Metals considered in this study are bronze, copper, silver and lead. Different laser systems and different irradiation conditions were employed and compared. The results, evaluated by metallurgic diagnostics and objective observations, indicated that the laser cleaning process was selective and highly precise, allowing the preservation of fine surface details.

Experimental and model analysis on the temperature dynamics during diode laser welding of the cornea

Corneal laser welding is a technique used clinically to induce the immediate sealing of corneal wounds. We present an experimental and model analysis of the temperature dynamics during diode laser-induced corneal welding, which is aimed at characterizing the mechanism of tissue fusion. Ex vivo tests were performed on porcine eyes in the typical irradiation conditions used for laser-induced suturing in cornea transplant. Three laser power densities (12.5 W/cm(2), 16.7 W/cm(2), 20.8 W/cm(2)) were tested. The superficial temperature of the cornea was measured by means of an infrared thermocamera. Experimental data were compared with the results of a three-dimensional (3D) model of a laser-welding process in the cornea, solved by the use of the Finite Element Method (FEM). The model solution and experimental results showed good agreement. The model was thus used to estimate the temperature enhancement inside the corneal wound and to calculate the thermal damage inside the tissue. The results indicated a selective, spatially confined heating effect that occurred at operative temperatures (59 to 66 degrees C) close to intermediate denaturation points of the stromal collagen, before its complete disorganization. No significant heat damage to the region of the laser-treated wound was evidenced in the operative irradiation conditions of corneal welding.

Laser-assisted corneal welding in cataract surgery: Retrospective study

PURPOSE: To evaluate the efficacy of laser welding to close corneal wounds in cataract surgery. SETTING: Department of Ophthalmology, Hospital of Misericordia e Dolce, Prato, Italy. METHODS: This retrospective nonrandomized interventional case series included 20 eyes of 20 patients. All eyes had cataract with visual acuity worse than 20/200. Ten patients had phacoemulsification surgery, and 10 had extracapsular cataract extraction (ECCE). Surgeries were followed by laser‐assisted closure of the corneal wounds by diode laser welding of the stroma using a technique established in animal models. Preoperative and postoperative (1, 3, 7, 30, and 90 days) astigmatism, level of inflammation, Seidel testing, and endothelial cell counts were obtained. RESULTS: There were minor differences in preoperative and postoperative astigmatism except in 1 eye in the ECCE group. The Seidel test showed no wound leakage during the follow‐up examinations, and endothelial cell loss was similar to that published for standard surgical cataract procedures. No collateral effects of the laser welding were detected, nor was postoperative inflammation. CONCLUSIONS: Astigmatism was slightly affected by the use of laser welding for corneal wound closure after phacoemulsification and ECCE. The laser‐assisted corneal sealing procedure was rapid and safe and could serve as an alternative to corneal suturing, with significant potential applications for the closure of longer incisions, such as those used in penetrating keratoplasty.

Determination of damage thresholds to prevent side effects in laser cleaning of pliocene sandstone of Siena

Abstract The present work reports a basic investigation aimed at optimizing laser cleaning interventions on pliocene sandstone of Siena. Irradiation trials were performed with a short free running Nd:YAG laser, on quarry samples and on samples from Palazzo Spannocchi presenting black crust. The physical parameterization associated with a detailed petrographic and mineralogic diagnostics of the induced effects, allowed the irradiation thresholds for damage phenomena to be derived and their nature understood. The experimental results reported here allow the definition of the best irradiation conditions and the laser parameter ranges for a safe and controlled black crust removal from pliocene sandstone.