Rodney Ian Trickett

Laser-activated solid protein bands for peripheral nerve repair: An in vivo study

Severed tibial nerves in rats were repaired using a novel technique, utilizing a semiconductor diode‐laser‐activated protein solder applied longitudinally across the join. Welding was produced by selective laser denaturation of solid solder bands containing the dye indocyanine green.

Sutureless microvascular anastomoses by a biodegradable laser-activated solid protein solder.

A new sutureless technique to successfully anastomose the abdominal aorta of rats (1.3 mm in diameter) by using a fully biodegradable, laser-activated protein solder is presented. A total of 90 rats were divided into two groups randomly. In group one, the anastomoses were performed by using conventional microsuturing technique, whereas in group two, the anastomoses were performed by using a new laser welding technique. In addition, each of the two groups were divided into five subgroups and evaluated at different follow-up periods (10 minutes, 1 hour, 1 day, 1 week, and 6 weeks). At these intervals, the anastomoses were evaluated for patency and tensile strength. Three anastomoses in each subgroup were processed for light and electron microscopy. All anastomoses were found to be patent. The mean clamp time of the anastomoses performed with conventional suturing was 20.6 minutes compared with 7.2 minutes for the laser-activated welded anastomoses (p < 0.001). The strain measurements showed a stronger mechanical bond of the sutured anastomoses in the initial phase. However, at 6 weeks the tensile strength of the laser-welded anastomoses was higher compared with the conventional suture technique. Histologic evaluations revealed a near complete resorption of the solder after 6 weeks. The junction site of the vessel ends cannot be determined on the luminal side of the artery. In conclusion, a resorbable protein used as a solder, activated by a diode laser, can provide a reliable, safe, and rapid arterial anastomosis, which could be performed by any microsurgeon faster than conventional suturing after a short learning curve.

4.7-W, 255-nm source based on second-harmonic generation of a copper-vapor laser in cesium lithium borate.

We have generated 4.7 W of UV (255-nm) radiation with wall plug efficiency of 0.12% by frequency doubling the green (511-nm) output of a kinetically enhanced medium-scale copper-vapor laser (CVL) in cesium lithium borate (CLBO). Frequency doubling in beta -barium borate produced 3.9 W of UV radiation with wall plug efficiency of 0.1%. We found that conversion was better with CLBO because of the reduced constraints on CVL beam quality, less UV absorption, and smaller UV walk-off.

Laser-activated protein bands for peripheral nerve repair

A 100 micrometer core optical fiber-coupled 75 mW diode laser operating at a wavelength of 800 nm has been used in conjunction with a protein solder to stripe weld severed rat tibial nerves, reducing the long operating time required for microsurgical nerve repair. Welding is produced by selective laser denaturation of the protein based solder which contains the dye indocyanine green. Operating time for laser soldering was 10 plus or minus 5 min. (n equals 24) compared to 23 plus or minus 9 min (n equals 13) for microsuturing. The laser solder technique resulted in patent welds with a tensile strength of 15 plus or minus 5 g, while microsutured nerves had a tensile strength of 40 plus or minus 10 g. Histopathology of the laser soldered nerves, conducted immediately after surgery, displayed solder adhesion to the outer membrane with minimal damage to the inner axons of the nerves. An in vivo study, with a total of fifty-seven adult male wistar rats, compared laser solder repaired tibial nerves to conventional microsuture repair. Twenty-four laser soldered nerves and thirteen sutured nerves were characterized at three months and showed successful regeneration with average compound muscle action potentials (CMAP) of 2.4 plus or minus 0.7 mV and 2.7 plus or minus 0.8 mV respectively. Histopathology of the in vivo study, confirmed the comparable regeneration of axons in laser and suture operated nerves. A faster, less damaging and long lasting laser based anastomotic technique is presented.

Laser welding of vas deferens in rodents : Initial experience with fluid solders

This study evaluates the use of sutureless laser welding for vasovasostomy. In 14 rodents, the left vas deferens underwent vasovasostomy using an albumin‐based solder applied to the adventitia of the vas deferens. The solder contained the dye, indocyanine green, to allow selective absorption and denaturation by a fiber‐coupled 800‐nm diode laser. The right vas deferens served as a control, receiving conventional layered microsurgical repair. We used a removable 4/0 nylon stent and microclamps to appose the vas deferens during repair, with no need for stay sutures. The mean time to perform laser solder repair (23.5 min) and conventional repair (23.3 min) were not significantly different (P = 0.91). However, examination after 8 weeks showed that granuloma formation (G) and patency (P) rates for the conventional suture technique (G, 14%; P, 93%) were significantly better than observed for the laser solder technique (G, 57%; P, 50%).

Laser-activated protein solder for peripheral nerve repair

A 100 micrometers core optical fiber-coupled 75 mW diode laser operating at a wavelength of 800 nm has been used in conjunction with a protein solder to stripe weld severed rat tibial nerves, reducing the long operating time required for microsurgical nerve repair. Welding is produced by selective laser denaturation of the albumin based solder which contains the dye indocyanine green. Operating time for laser soldering was 10 +/- 5 min. (n equals 20) compared to 23 +/- 9 min. (n equals 10) for microsuturing. The laser solder technique resulted in patent welds with a tensile strength of 15 +/- 5 g, while microsutured nerves had a tensile strength of 40 +/- 10 g. Histopathology of the laser soldered nerves, conducted immediately after surgery, displayed solder adhesion to the outer membrane with minimal damage to the inner axons of the nerves. An in vivo study is under way comparing laser solder repaired tibial nerves to conventional microsuture repair. At the time of submission 15 laser soldered nerves and 7 sutured nerves were characterized at 3 months and showed successful regeneration with compound muscle action potentials of 27 +/- 8 mV and 29 +/- 8 mW respectively. A faster, less damaging and long lasting laser based anastomotic technique is presented.

Assessment of nerve ultrastructure by fibre-optic confocal microscopy

Fibre‐optic technology combined with confocality produces a microscope capable of optical thin sectioning. In this original study, tibial nerves have been stained in a rat model with a vital dye, 4‐(4‐diethylaminostyryl)‐N‐methylpyridinium iodide, and analysed by fibre‐optic confocal microscopy to produce detailed images of nerve ultrastructure. Schwann cells, nodes of Ranvier and longitudinal myelinated sheaths enclosing axons were clearly visible. Single axons appeared as brightly staining longitudinal structures. This allowed easy tracing of multiple signal axons within the nerve tissue. An accurate measurement of internodal lengths was easily accomplished. This technique is comparable to current histological techniques, but does not require biopsy, thin sectioning or tissue fixing. This study offers a standard for further in vivo microscopy, including the possibility of monitoring the progression of nerve regeneration following microsurgical neurorraphy.

Diode Laser Activated Protein Solder for Sutureless Microsurgical Repair of Blood Vessels

In the past decade laser photorefractive keratectomy (PRX, surgery of cornea using-193 nm excimer lasers) ha; become a very popular clinical procedure for changing the refractlvitv of the human eve. However. PRK occaaionallv produces p0;toperative compiications .&h-is ~ i i g h ; i i & n problems,decreased contrast sensitivity halos redness photophobia. glare, etc. Some of these bomp1ic;tions weLe related to corneal irregularity which appears due to evaporation of tissue in course of laser irradiation via thermomechanical mechanism. Possible photochemical consequences Of PRK have been neglected, though some of PRK-induced corneal alterations, e.g. epithelian haze, can be of a photochemical nature. The human Cornea consists of collagen to the extent of 6 4 8 . Collagen is the most abundant protein in mammals constituting a quarter of their total weight. The basic struCtu;al unit Of collagen consists of three polypeptide chains. In polypeptide chain of Collagen every third amino acid residue is glycine (Gly). Proline (Pro), alanine (Ala) and 4-hydroxyproline (Hyp) are also Present in a much greater extent than other amino acid residues. Neither the photochemistry of aliphatic amino acids nor the photochemistry of collagen itself were investigated until now. The goal of the present work is to establish the photolysis and quantm yield values for some model objects related to collagen photochemistry. The aliphatic amino acid residues (Gly. Pro, Ala, Hyp) and dipeptides (Gly-Pro and Pro-Gly) were irradiated in neutral agueous solution using 1 9 3 3 nm A r F laser light and the photolysis products were Studied b; HPLC analysis. Comparing the efficiency of photodecomposition of these model compounds, we have determined that the peptide bond is likely to be the main target in collagen and its scission could be the most important photochemical reaction taking place during 1 9 3 . 3 nm laser shaping of the human cornea. Future photochemical experiments with more complex collagen components will allow us to evaluate more Precisely the mechanism of ArF laser light action on corneal collagen PRK with minimal PostoperaCive complioations, Yielding the optimal procedure for 18.15 CThU

Laser-activated solder weld repair of the inferior alveolar nerve in rats

A new laser activated solder weld technique is described for the microsurgical repair of the inferior alveolar nerve in rats. The laser weld technique used an albumin based solder, containing indocyanine cardiogreen, plus an infrared diode laser. Seven animals had inferior alveolar nerve repairs performed using the laser weld technique and these were compared against corresponding unoperated controls plus three cases of nerve section without repair. Histochemical analysis was performed utilizing neuron counts and horseradish peroxidase tracer (HRP) uptake in the trigeminal ganglion following sacrifice and staining of frozen sections with cresyl violet and diaminobenzidene. The results of this analysis showed comparable mean neuron counts and mean HRP uptake by neurons for the unoperated control and laser weld groups with considerable reduction of mean values in cases of nerve section with no repair. Sections of the repaired inferior alveolar nerves, stained with Massons trichrome, showed no adverse reactions by axons or epineurium to the coagulative repair with the solder and demonstrated regeneration of myelinated axons at the time of sacrifice. In summary a new technique of laser weld repair of the inferior alveolar nerve is described which, on initial analysis, appears to be a reliable alternative to traditional techniques.