Biomedical subjects

Robert W Redmond

Publications and source records attributed to Robert W Redmond.

8 recordsLinked to original sources

PubMed2005

Evaluation of photochemical tissue bonding for closure of skin incisions and excisions.

BACKGROUND AND OBJECTIVES: Photochemical tissue bonding (PTB) is a new non-thermal technique for tissue repair involving application of a photochemically active dye and irradiation with visible light. The objective was to compare PTB with standard sutures and the tissue adhesive, octyl cyanoacrylate, for closure of skin incisions and excisions. STUDY DESIGN/MATERIALS AND METHODS: Incisions and excisions made on the flanks of a Hanford mini-pig were secured with subcutaneous sutures. Superficial closure methods were 3-0 monofilament sutures, PTB (Rose Bengal and green light), tissue adhesive and the combination of tissue adhesive then PTB. Wounds were evaluated 2, 4, and 6 weeks postoperatively for cosmetic outcomes and histology. RESULTS: Cosmetic outcomes and histological scar width of incisions and excisions did not differ among the treatment groups at 2, 4, and 6 weeks. CONCLUSION: PTB is as effective as standard sutures for wound closure in porcine skin in terms of cosmetic outcomes and safety.

Animals↗

PubMed2005

Photochemical repair of Achilles tendon rupture in a rat model.

BACKGROUND: Photochemical tissue bonding (PTB) is an emerging technique for bonding or sealing tissue surfaces that requires light and a photoactive dye for its effect. The potential of PTB for tendon repair was assessed in a rat model. MATERIALS AND METHODS: The optical properties of bovine tendon were determined ex vivo to gauge the depth of light penetration as a function of wavelength and dosimetry parameters were established for PTB repair of ruptured tendon. PTB was then tested in vivo to repair transected tendons in Sprague-Dawley rats. Repair strengths were measured using a strain gauge up to 14 days post treatment. RESULTS: The effective penetration depth in tendon was estimated to be 0.68 mm at 514 nm. Following PTB treatment of mechanically ruptured tendon, significant bonding was dependent on the presence of both light and dye and attained a plateau strength at a fluence of 125 J/cm2. In a subsequent in vivo study to investigate PTB for repair of transected rat Achilles tendon, the ultimate stress required to break the repaired tendon was measured immediately after irradiation and at 7 and 14 days post-repair. Results showed that the difference in the ultimate stress between control and PTB treatment groups was statistically significant immediately after treatment and at 7 days (p = 0.04) but not 14 days (p = 0.75) post-repair. CONCLUSIONS: PTB provides a benefit to tendon repair at early stages in repair and is worthy of further investigation as a potential surgical adjunct for tendon repair in orthopedic surgeries.

Achilles Tendon↗

PubMed2004

Photochemical keratodesmos as an adjunct to sutures for bonding penetrating keratoplasty corneal incisions.

PURPOSE: To evaluate the benefit of photochemical keratodesmos (PKD) in acute wound closure of penetrating keratoplasty (PKP) corneal incisions in vivo. SETTING: Massachusetts General Hospital and Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, USA. METHODS: Penetrating keratoplasty incisions were performed in both eyes of 6 New Zealand white rabbits, followed by application of 1.5 mM rose bengal dye at the wound edges. The incision in 1 eye of each rabbit was irradiated with neodymium:YAG laser light at 532 nm and fluence of 40 J/cm2; the contralateral control eye was untreated. Intraocular pressure at which fluid leaked at the edges (IOPL) was determined immediately after surgery. RESULTS: The mean IOPL was 410 mm Hg +/- 70 (SD) in the PKD-treated eyes and 250 +/- 150 mm Hg in the unirradiated eyes. The difference was statistically significant by paired t test (P<.05). CONCLUSIONS: Photochemical keratodesmos may be a useful adjunct to sutures for approximating PKP corneal incisions in the immediate postoperative period. This process does not induce high temperature, and thus denaturation can be avoided and structural integrity restored.

Animals↗

PubMed2004

Photochemical keratodesmos for bonding corneal incisions.

PURPOSE: To evaluate the immediate and long-term effectiveness of a dye-plus-laser irradiation treatment (photochemical keratodesmos [PKD]) for sealing corneal incisions. METHODS: Incisions (3.5 mm) in rabbit corneas were treated on the incision walls with rose bengal dye followed by exposure to 514-nm laser radiation. PKD was evaluated in three groups (n = 3-6) using laser fluences of 115, 153, or 192 J/cm(2) (180-, 240-, and 300- second exposures, respectively) compared with an untreated group (n = 8). The intraocular pressure at which leakage occurred (IOP(L)) during infusion of saline into the anterior chamber was determined. In a long-term study, treated and control corneas were observed weekly for 10 weeks for the appearance of neovascularization, anterior chamber inflammation, iridocorneal adhesion, corneal melting, and scarring. RESULTS: Immediately after treatment, the IOP(L) increased with increasing laser fluence, producing IOPs of 230 +/- 90, 370 +/- 120, and more than 500 mm Hg at 115, 153, and 192 J/cm(2), respectively, compared with 40 +/- 20 mm Hg in control eyes (P < 0.005). No reduction in the IOP(L) was observed up to 14 days after surgery. Corneal melting in PKD-treated or control eyes was not observed in the 10-week healing study. Neovascularization, which peaked at 4 weeks but resolved by 8 weeks, was detected around the incision in both PKD-treated and control eyes. CONCLUSIONS: Immediate and lasting sealing of corneal incisions was obtained in eyes treated with PKD, using short irradiation times. These results suggest that PKD has potential for improved corneal tissue bonding.

Animals↗

PubMed2003

Secondary reactive oxygen species extend the range of photosensitization effects in cells: DNA damage produced via initial membrane photosensitization.

The type-II photosensitization process is mediated by the formation of singlet oxygen (O2[1deltag]). The short lifetime of this species dictates that chemical reactions with biological substrates can only occur when O2(1deltag) is in very close proximity to the photosensitizer itself. In this study, deuteroporphyrin, a type-II, membrane-localized photosensitizer, was used to generate O2(1deltag) in human lymphoblast WTK-1 cells, and the range of influence was determined by a variety of biological assays. Surprisingly, the initial membrane-confined events were shown, by comet assay, to induce DNA damage in these cells. DNA damage was inhibited both by membrane-localized (alpha-tocopherol acetate) and by cytoplasmic (trolox) free radical scavengers. Comet formation also was inhibited by treatment at low temperature. DNA fragmentation was not influenced by treatment with the pan-caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone, showing that apoptosis was not responsible for fragmentation. Taken together, these results show that primary photosensitization reactions involving O2(1deltag), even when tightly confined in extranuclear locations, leads to the production of secondary reactive oxygen species, probably as a result of lipid peroxidation, that can act at greater distances from the photosensitizer itself. These experiments were carried out under conditions where cell survival was significant and raise questions regarding DNA damage and mutagenesis pathways, even when extranuclear O2(1deltag)-generating compounds are used.

Cell Membrane↗

PubMed2002

Singlet-singlet annihilation in ultraviolet matrix-assisted laser desorption/ionization studied by fluorescence spectroscopy.

Laser-induced fluorescence spectroscopy was carried out on microcrystalline samples of three typical matrices under conditions of matrix-assisted laser desorption/ionization (MALDI). The emitted fluorescence intensity was determined as a function of incident laser fluence and a sublinear increase of the fluorescence intensity with laser fluence was found. A very good fit was obtained when the experimental fluorescence vs. fluence data were compared with a numerical model assuming that under typical MALDI fluence conditions a large fraction of molecules in the excited singlet state undergoes singlet-singlet annihilation. Throughout the fluence range relevant for MALDI, however, the experimental data could not be fit well to a model assuming resonant two-photon absorption as the process depopulating the singlet state. In a separate set of experiments, the singlet lifetimes of several typical crystalline MALDI matrices were determined and found to be considerably shorter than previously reported. While both singlet-singlet annihilation and resonant two-photon absorption have been discussed in the literature as candidates for pathways to primary matrix ion generation in MALDI, the data presented here suggest that singlet-singlet annihilation is the dominant mechanism for depopulating the singlet state in a matrix crystal excited at typical MALDI fluences.

Electrons↗

PubMed2002

Enhancement of porcine skin graft adherence using a light-activated process.

BACKGROUND: Skin grafts are widely used in plastic surgery, and burn and ulcer wound management. Rapid and sustained adherence, the ability to resist shear stress, and a void-free surface-to-surface contact are critical to the success of graft survival. Mechanical and adhesive fixation aids are currently used to achieve graft adherence and they are not free of problems. Photochemical tissue bonding (PTB) is an emerging laser technique with numerous applications in surgical specialties. In the current study, PTB was investigated as a means to bond and enhance the adherence of skin grafts. METHODS: In this study, ex vivo porcine skin grafts treated with a photosensitizing dye, rose bengal (RB), were approximated dermis-to-dermis and irradiated with visible light from an argon laser at 514 nm. The adherence of the skin grafts was measured immediately after irradiation. Dose-response relationships between the light and the dye with adherence of the grafts were established. The surface temperature of the skin under irradiation was monitored and the viability of the skin cells in the grafts was also measured. RESULTS: Results showed that the skin graft adherence was RB dose-dependent in a statistically significant manner with the concentration of RB reaching a plateau value of 0.1% (w/v) of RB. Graft adhesion also increased with laser fluence up to 504 J/cm(2) in the presence of 0.1% RB. No fluence dependence was observed in the absence of RB. Thermogram results showed that the maximal surface temperature during irradiation was less than 40 degrees C. Histological investigation and trypan blue exclusion assays demonstrated that skin grafts retained cell viability and collagen organization after PTB. CONCLUSIONS: This ex vivo study demonstrates that PTB using argon laser irradiation and RB enhances skin graft adherence by forming dermal-dermal bonding. The increase in adherence is a function of the concentration of RB and the laser fluence. The results also suggest that the PTB is a potentially safe procedure because it is nonthermal in nature and does not significantly affect the skin cell viability.

Animals↗

PubMedDate not supplied

Spatially resolved cellular responses to singlet oxygen.

Singlet oxygen (1O2) is unique amongst reactive oxygen species formed in cells in that it is an excited state molecule with an inherent upper lifetime of 4 micros in water. Whether the lifetime of 1O2 in cells is shortened by reactions with cellular molecules or reaches the inherent maximum value is still unclear. However, even with the maximum lifetime, the diffusion radius is only approximately 220 nm during three lifetimes (approximately 5% 1O2 remaining), much shorter than cellular dimensions indicating that the primary reactions of 1O2 will be subcellularly localized near the site of 1O2 formation. This fact has raised the question of whether spatially resolved cellular responses to 1O2 occur, i.e. whether responses can be initiated by generation and reaction of 1O2 at a particular subcellular location that would not have been produced by 1O2 generation at other subcellular sites. In this paper, we discuss examples of spatially resolved responses initiated by 1O2 as a function of distance from the site of generation of 1O2. Three levels are recognized, namely, a molecular level where the primary oxidation product directly modifies the behavior of a cell, an organelle level where the initial photo-oxidation products initiate mechanisms that are unique to the organelle and the cellular level where mediators diffuse from their site of formation to the target molecules that initiate the response. These examples indicate that, indeed, spatially resolved responses to 'O2 occur in cells.

Humans↗