Saldatura laser della pelle: stato dell’arte e prospettive future

Da diversi anni ormai la tecnologia laser svolge un ruolo importante nell’ambito di numerose applicazioni biomedicali. Il principale vantaggio prospettato dalle tecniche laser è quello di ridurre notevolmente il trauma chirurgico riducendo il tempo di guarigione e il rischio di complicazioni post-operatorie con netto miglioramento della qualità della vita dei pazienti. Una tra le applicazioni più promettenti del laser in campo medico-chirurgico è la saldatura dei tessuti biologici (“laser tissue welding”). La giunzione di lembi di tessuto tramite luce laser è stata conseguita per la prima volta con successo alla fine degli anni settanta, impiegando un laser a neodimio:ittrio-alluminio-garnet (Nd:YAG) per l’anastomosi microvascolare della carotide e delle arterie femorali di topo. Successivamente, la saldatura laser-assistita è stata sperimentata su numerosi modelli come vasi sanguiferi, pelle, cornea, nervi, intestino, tendini, tratto urinario, tessuto biliare e così via [1, 2]. Tale tecnica, grazie alle sue caratteristiche minimamente invasive, ha assunto progressivamente rilevanza a livello clinico dove appare oggi come valida alternativa all’approccio chirurgico tradizionale. Attualmente sono sempre più numerose le applicazioni di saldatura laser che stanno ricevendo il consenso della comunità scientifica

Notes on the mechanism of low-temperature laser tissue welding

In this report we propose an hypothesis on the mechanism of low-temperature laser welding of a model connective tissue (cornea), based on the reorganization of the proteoglycans of the extracellular matrix

Analysis of second harmonic generation polarization profiles: an attempt to devise a complete three-dimensional model

We report the first attempt to build a three dimensional model of the polarization modulated second harmonic generation and emission dynamics from collagen fibrils under realistic conditions. Our analytical model is constructed by integration of previous knowledge on the stimulation of a second harmonic polarization in a non-centrosymmetric cylindrical target, and on the propagation of a resultant second harmonic disturbance. The application of our paradigm to actual biological targets allows one to retrieve their spatial orientation, mutual organization and inner configuration, which holds great potential to develop biological investigations and theragnostic applications

Emerging concepts of laser-activated nanoparticles for tissue bonding

We report recent achievements and future perspectives of minimally invasive bonding of biological tissues triggered by laser light. In particular, we review new advancements in the biomedical exploitation of near-infrared absorbing gold nanoparticles as an original solution for the photothermal closure of surgical incisions. Advanced concepts of laser tissue bonding involving the application of hybrid nanocomposites obtained by inclusion of nanochromophores into biopolymer scaffolds are also introduced. The perspectives of tissue bonding are discussed in the following aspects: (1) tissue bonding with highly-stabilized nanochromophores, (2) enhanced tissue bonding with patterned nanocomposites, (3) real-time monitoring of temperature distributions, (4) tracking of tissue regeneration based on the optical resonances of gold nanoparticles

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

In vivo carotid artery closure by laser activation of hyaluronan-embedded gold nanorods.

We prove the first application of near-infrared-absorbing gold nanorods (GNRs) for in vivo laser closure of a rabbit carotid artery. GNRs are first functionalized with a biopolymeric shell and then embedded in hyaluronan, which gives a stabilized and handy laser-activable formulation. Four rabbits undergo closure of a 3-mm longitudinal incision performed on the carotid artery by means of a 810-nm diode laser in conjunction with the topical application of the GNRs composite. An effective surgery is obtained by using a 40-W/cm(2) laser power density. The histological and electron microscopy evaluation after a 30-day follow-up demonstrates complete healing of the treated arteries with full re-endothelization at the site of GNRs application. The absence of microgranuloma formation and/or dystrophic calcification is evidence that no host reaction to nanoparticles interspersed through the vascular tissue occurred. The observation of a reshaping and associated blue shift of the NIR absorption band of GNRs after laser treatment supports the occurrence of a self-terminating process, and thus of additional safety of the minimally invasive laser procedure. This study underlines the feasibility of using GNRs for in vivo laser soldering applications, which represents a step forward toward the introduction of nanotechnology-based therapies in minimally invasive clinical practices

Three-dimensional mapping of the orientation of collagen corneal lamellae in healthy and keratoconic human corneas using SHG microscopy

SHG image acquired with sagittal optical sectioning (A) of a healthy cornea and (B) of a keratoconic cornea. Scale bars: 30 μm. Keratoconus is an eye disorder that causes the cornea to take an abnormal conical shape, thus impairing its refractive functions and causing blindness. The late diagnosis of keratoconus is among the principal reasons for corneal surgical transplantation. This pathology is characterized by a reduced corneal stiffness in the region immediately below Bowman's membrane, probably due to a different lamellar organization, as suggested by previous studies. Here, the lamellar organization in this corneal region is characterized in three dimensions by means of second-harmonic generation (SHG) microscopy. In particular, a method based on a three-dimensional correlation analysis allows to probe the orientation of sutural lamellae close to the Bowman's membrane, finding statistical differences between healthy and keratoconic samples. This method is demonstrated also in combination with an epi-detection scheme, paving the way for a potential clinical ophthalmic application of SHG microscopy for the early diagnosis of keratoconus

Organosilicon phantom for photoacoustic imaging

Photoacoustic imaging is an emerging technique. Although commercially available photoacoustic imaging systems currently exist, the technology is still in its infancy. Therefore, the design of stable phantoms is essential to achieve semiquantitative evaluation of the performance of a photoacoustic system and can help optimize the properties of contrast agents. We designed and developed a polydimethylsiloxane (PDMS) phantom with exceptionally fine geometry; the phantom was tested using photoacoustic experiments loaded with the standard indocyanine green dye and compared to an agar phantom pattern through polyethylene glycol-gold nanorods. The linearity of the photoacoustic signal with the nanoparticle number was assessed. The signal-to-noise ratio and contrast were employed as image quality parameters, and enhancements of up to 50 and up to 300%, respectively, were measured with the PDMS phantom with respect to the agar one. A tissue-mimicking (TM)-PDMS was prepared by adding TiO2 and India ink; photoacoustic tests were performed in order to compare the signal generated by the TM-PDMS and the biological tissue. The PDMS phantom can become a particularly promising tool in the field of photoacoustics for the evaluation of the performance of a PA system and as a model of the structure of vascularized soft tissues. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE