Effect of Ca+ on the photobactericidal efficacy of methylene blue and toluidine blue against gram-negative bacteria and the dye affinity for lipopolysaccharides

BACKGROUND AND OBJECTIVES: Methylene blue (MB) and toluidine blue (TB) form metachromatic complexes with lipopolysaccharides (LPS). The greater photobactericidal efficacy of TB may be explained by its affinity for LPS. This study aims to elucidate the difference in photobactericidal efficacies between the dyes using Ca(2+) as a competitor for dye-binding sites on the bacterial outer membrane. STUDY DESIGN/MATERIALS AND METHODS: Fixed dye concentration solutions with gram-negative bacteria and increasing concentrations of CaCl(2) were exposed to red laser light. Bacterial survival and spectrophotometry were used to describe the effect of Ca(2+) on dye interaction with bacteria and LPS. RESULTS: MB-mediated photokilling was inhibited more significantly than that of TB. CaCl(2) inhibited dye photobleaching and suppressed the metachromatic reaction between the dyes and LPS, in particular TB. CONCLUSIONS: CaCl(2) inhibits bacterial photokilling by binding with LPS, as well as other anionic polymers including outer membrane proteins. LPS is chiefly involved in TB-mediated photokilling, whereas outer membrane proteins probably are more involved in MB-mediated photokilling.     

Interaction of the photobactericides methylene blue and toluidine blue with a fluorophore in Pseudomonas aeruginosa cells

BACKGROUND AND OBJECTIVES: The difference in photobactericidal efficacy between methylene blue (MB) and toluidine blue (TB) may be explained by their involvement with proteins, lipopolysaccharides (LPS), and siderophores and siderophore-receptor protein complexes on the bacterial outer membrane. This study aims to determine if this is the case by using the fluorescence given off by a pseudomonal siderophore named pyoverdin. STUDY DESIGN/MATERIALS AND METHODS: Confocal laser scanning microscopy was used to observe the fluorescence of Pseudomonas aeruginosa cells excited at 488 nm in the presence of increasing dye concentrations. RESULTS: Cellular fluorescence at 522 nm progressively decreased with increasing dye concentrations. The Stern-Volmer constants for cellular fluorescence quenching with the dyes were compared to the association constants for dyes complexed with LPS. The quenching of cellular fluorescence was associated with the formation of a ground-state complex between the dyes and pyoverdin-FpvA protein system. MB readily complexed with this system, whereas TB complexed more strongly with LPS. CONCLUSION: The different affinities of the dyes for both pyoverdin-protein and LPS will affect the contributions of the dyes' interactions with these biopolymers to the overall bacterial photodamage.     

Photodynamic inactivation of Enterococcus faecalis in dental root canals in vitro

BACKGROUND AND OBJECTIVES: We previously reported the use of a flexible fiber optic that uniformly distributed light in the root canal space for targeting bacteria after their sensitization with methylene blue (MB). In the present study, we investigated the photodynamic effects of MB on Enterococcus faecalis species in experimentally infected root canals of extracted teeth after their sensitization with a concentration of MB that exhibits reduced dark toxicity. STUDY DESIGN/MATERIALS AND METHODS: In a model of root canal infection, 64 root canal specimens were prepared from extracted, single-rooted teeth and inoculated with E. faecalis (ATCC 29212). Three days later root canal infection was confirmed by scanning electron microscopy. The root canal systems were then incubated with 6.25 microg/ml MB for 5 minutes followed by exposure to light at 665 nm (60 J/cm(2)) that was delivered from a diode laser via a fiber optic with a diameter of 500 microm. Following photodynamic therapy (PDT) the canal content was sampled by flushing the root canals, serially diluted and cultured on blood agar. Survival fractions were calculated by counting colony-forming units. High-performance liquid chromatography (HPLC) was employed to determine the porphyrins content of E. faecalis. RESULTS: Scanning electron microscopy confirmed the presence of bacteria in the root canal system. PDT achieved 77.5% reduction of E. faecalis viability. MB alone and light alone reduced bacterial viability by 19.5% and 40.5%, respectively. HPLC did not reveal any porphyrin patterns expressed by E. faecalis. CONCLUSION: The results of this study support the need to determine the optimum MB concentration and light parameters to maximize bacterial killing in root canals.     

Antimicrobial photodynamic therapy—a promising treatment for prosthetic joint infections

Periprosthetic joint infection (PJI) is associated with high patient morbidity and a large financial cost. This study investigated Photodynamic Therapy (PDT) as a means of eradicating bacteria that cause PJI, using a laser with a 665-nm wavelength and methylene blue (MB) as the photosensitizer. The effectiveness of MB concentration on the growth inhibition of methicillin-sensitive Staphylococcus aureus (MSSA), methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus epidermidis, Pseudomonas aeruginosa and Acinetobacter baumannii was investigated. The effect of laser dose was also investigated and the optimized PDT method was used to investigate its bactericidal effect on species within planktonic culture and following the formation of a biofilm on polished titanium and hydroxyapatite coated titanium discs. Results showed that Staphylococci were eradicated at the lowest concentration of 0.1 mM methylene blue (MB). With P. aeruginosa and A. baumannii, increasing the MB concentration improved the bactericidal effect. When the laser dose was increased, results showed that the higher the power of the laser the more bacteria were eradicated with a laser power?≥?35 J/cm² and an irradiance of 35 mW/cm², eradicating all S. epidermidis. The optimized PDT method had a significant bactericidal effect against planktonic MRSA and S. epidermidis compared to MB alone, laser alone, or control (no treatment). When biofilms were formed, PDT treatment had a significantly higher bactericidal effect than MB alone and laser alone for all species of bacteria investigated on the polished disc surfaces. P. aeruginosa grown in a biofilm was shown to be less sensitive to PDT when compared to Staphylococci, and a HA-coated surface reduced the effectiveness of PDT. This study demonstrated that PDT is effective for killing bacteria that cause PJI.     

Methylene blue soldered microvascular anastomoses in vivo.

OBJECTIVES: solders containing chromophores and proteins enhance the strength of lasered anastomoses. Methylene blue (MB) solder anastomoses in vitro are strong but no in vivo work has been reported. We used an MB solder in vivo and studied the effects of two laser powers on patency and histological appearance. DESIGN, MATERIALS AND METHODS: two groups of 15 rabbits had unilateral end-to-end carotid anastomoses (1.5-2.0 mm) formed using three stay sutures and MB solder. Group 1 anastomoses were formed at 5.7 Wcm(-1) and Group 2 at 2.8 Wcm(-1). The vessels were examined at various points by necropsy for patency and gross macroscopic appearance, with subsequent histological examination. RESULTS: group 2 showed patency of 93.3% v 0% ( p<0.001) endothelialisation of 100% v 26.6% ( p<0.001), giant cell formation 0% v 40.0% ( p<0.01), but stenosis was not significantly different (0% v 13.3% p=0.06). Group 2 showed a higher rate of intimal hyperplasia (IH) (66.6% v 20.0% p<0.05) but neither group exhibited thermal injury or aneurysm formation. CONCLUSIONS: laser soldered microvascular anastomoses were formed in vessels of 1.5-2.0 mm with a high degree of patency. A relationship appears to exist between laser power and anastomotic patency. Methylene blue fading has the potential to act as a switch against over exposure and a visual indicator of solder activation.     

Bactericidal effects of different laser wavelengths on periodontopathic germs in photodynamic therapy

 This study was an attempt to clarify whether the bactericidal effects of photodynamic therapy (PDT) are wavelength or dose-dependent. We also attempted to create an optimised protocol for a light-based bactericidal modality to eliminate periodontal pathogens. Cultures of Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum, Porphromonas gingivalis, Prevotella intermedia, and Streptococcus sanguis, were exposed to a He-Ne laser (632.8 nm) with a 30 mW power output, a 100 mW diode laser at 665 nm, or a 100 mW diode laser at 830 nm, in the presence or absence of methylene blue (MB) as a photosensitiser. A control group was also used with exposure to MB alone without laser exposure. The cultures were analysed by viable counts. The results indicated that exposure to the 100 mW laser light could eliminate up to 40% of bacteria on average. In particular, the most effective killing occurred with exposure to laser light in combination with the MB photosensitiser. The results of kinetic studies indicated that the best PDT response rate was achieved with a 60 s (energy density 21.2 J/cm²) exposure to the 665 nm wavelength diode laser in the presence photosensitiser. In this condition, approximately 95% of A. actinomycetemcomitans and F. nucleatum, and 99–100% of the black-pigmented bacteria (P. gingivalis and P. intermedia) and S. sanguis were eliminated. These results showed that both wavelength and energy density are important factors, and that a low power laser of optimal wavelength and dosage, in combination with an appropriate photosensitiser, is a practical bactericidal modality. We concluded that using a diode laser of proper power and wavelength to deliver 60 s of irradiation could be a useful adjunct with mechanical debridement in the prevention of the re-colonisation of subgingival lesions by pathogenic microorganisms. Received: 29 November 2001 / Accepted: 18 June 2002     

The effect of low-power laser light at different doses on gastric mucosa sensitized with methylene blue, haematoporphyrin derivative or toluidine blue

Helicobacter pylori has been associated with peptic ulcers, gastric cancer and various other gastroduodenal pathologies. Conventional antibiotic treatment is not entirely satisfactory, whereas photodynamic therapy (PDT) is a possible alternative. Although PDT has been shown to be effective in killing helicobacter on native gastric mucosa, the success of the technique will depend upon the mucosa underlying the bacteria remaining unharmed. This study examined the effect of increasing doses of low-power laser light on rat gastric mucosa, sensitized with either methylene blue (MB), haematoporphyrin derivative (HpD) or toluidine blue (TBO). No damage was detectable with any of the photosensitizers when a light dose of 250 Jcm^-2 was used. Mucosal damage was seen consistently with TBO (1 mg ml^-1) and a light dose of 500 J cm^-2. The same light dose of 500 J cm^-2 using MB caused inconsistent damage to the mucosa, whereas HpD had no effect even with the highest dose of laser light (500 J cm^-2). As the energy doses required to kill bacteria (50 and 200 Jcm^-2 for MB and TBO, respectively) are well below the levels shown to damage normal gastric mucosa, PDT forH. pylori should not be harmful to the underlying epithelium.     

Oral bacteria in multi-species biofilms can be killed by red light in the presence of toluidine blue

BACKGROUND AND OBJECTIVES: Oral bacteria can be killed by light in the presence of a suitable photosensitizer, and this could be used in the treatment of oral infections. In these diseases, however, bacteria are present as biofilms, which are refractive to antimicrobial agents. The purpose of this study was to determine whether oral bacterial biofilms were susceptible to lethal photosensitization. STUDY DESIGN/MATERIALS AND METHODS: Multi-species biofilms of oral bacteria were irradiated with light from a helium/neon laser in the presence of toluidine blue O (TBO) and the survivors enumerated. Controls examining the effects of light and TBO alone were also included. The biofilms were also examined by confocal scanning laser microscopy (CSLM). RESULTS: CSLM revealed that the biofilms had structures similar to those of dental plaque. Although, the biofilms consisted of extremely large numbers of bacteria ( approximately 9 x 10(9)), 97.4% were killed following irradiation with 31.5 J of laser light in the presence of 25 microg/ml TBO. CONCLUSIONS: Substantial numbers of oral bacteria in multi-species biofilms can be killed by light in the presence of TBO. This may be useful in the treatment of dental plaque-related diseases.     

Methylene blue in the evaluation of gastrointestinal tract integrity: potential limitations

INTRODUCTION: The integrity of the gastrointestinal tract can be evaluated by oral or rectal application of methylene blue. In the presence of anastomotic leaks or fistulas, methylene blue can be recovered in adjacent drains. However, parts of the dye can biochemically be reduced by intestinal bacteria to its colorless form leucomethylene blue, limiting the prediction of the test. MATERIALS AND METHODS: Diluted methylene blue was added to different concentrations of bacterial suspensions of Escherichia coli and Enterococcus faecalis. The time for discoloration of the suspension was measured. RESULTS: Reduction of methylene blue to leucomethylene blue was observed in both types of bacterial suspension. A 10(8) bacterial concentration discolorated the dye within 1 h in the E. faecalis suspension, respectively 2.5 h in the E. coli suspension. Longer bacterial interaction with methylene blue reduced the bacterial concentration required to achieve complete discoloration. DISCUSSION: Methylene blue can reliably be used as routine diagnostic test for the assessment of upper gastrointestinal integrity, where bacterial load is low. In the lower gastrointestinal tract, where bacterial load is generally higher, the dye can indicate leaks, only if extended intestinal passage after oral ingestion is avoided. In all other cases, the examiner has to be aware of false-negative results by bacterial discoloration of methylene blue.     

Methylene blue dye--a safe and effective alternative for sentinel lymph node localization

Abstract:  Sentinel lymph node (SLN) biopsy has emerged as an effective diagnostic tool in axillary staging in breast cancer. The commonly used technique employs isosulfan blue/patent blue V combined with radioactive colloid tracer. Methylene blue (MB) is a less expensive and readily available alternative dye. The study evaluated the safety and efficacy of MB in SLN localization. A retrospective study of 329 patients with early breast cancer who had SLN localization as part of an ethically approved prospective evaluation study of SLN localization technique was carried out. Lymph node positive, tumors >2 cm on clinical and radiological evaluation, those with previous breast and axillary surgery, neo-adjuvant chemotherapy were excluded from the study. One hundred seventy three patients underwent SLN localization using 1 mL of 1% MB, and a combined MB-radio colloid tracer technique was used in the other 156 patients. Allocation to the groups was by simple randomization. Injection of the dye and radioisotope was into the subdermal plane in the sub-areolar region. Patients underwent breast conservation surgery or mastectomy with SLN directed four node axillary sampling ± axillary clearance. The lymph node was examined by standard microscopy. There were no reported complications with the use of MB aside from temporary tattooing. The technique failed in eight patients giving an identification rate of 97.6%. Ten of the 258 (3.9%) patients had false-negative SLN, with negative predictive value of 96.1%, sensitivity of predicting further axillary disease of 73%, specificity of 87.3%, and overall accuracy of 85.7%. Reported adverse reaction to isosulfan blue/patent blue V varied from minor to severe anaphylactic reactions (1–3%) requiring vigorous resuscitation. Subdermal sub-areolar injection of MB is safe and effective readily available dye for SLN localization in axillary staging of breast cancer with no major adverse reaction.     

Dye-mediated bactericidal effect of He-Ne laser irradiation on oral microorganisms.

Little attention has been given to the bactericidal effect of laser irradiation, particularly using low-power energy lasers. It has been demonstrated that He-Ne laser light has an inhibitory action on dental plaque. The purpose of this study was to investigate the bactericidal effect of He-Ne laser irradiation on cariogenic microorganisms. The bactericidal effect was determined by the formation of a growth-inhibitory zone or by the counting of viable bacterial colonies. Streptococcus sobrinus AHT that is a Gram-positive microorganism was sensitive to He-Ne laser light, but Escherichia coli, a Gram-negative microorganism, was resistant. The effect of several dyes necessary to instigate a bactericidal action was also examined. A growth-inhibitory zone was observed using 10 kinds of blue, purple, or green dyes, which were mainly phenylmethane dyes. The leakage of potassium from S. sobrinus AHT following laser irradiation was determined using an atomic absorption spectrophotometer. The leakage began to increase following irradiation for 2 min, and reached a plateau following irradiation for 30-60 min. Moreover, to examine some changes in the dye itself following laser irradiation in the absence of bacteria, ultraviolet-visible absorption spectra and 1H NMR spectra were recorded. In this study, it was indicated that the bactericidal effect on cariogenic bacteria by He-Ne laser irradiation was efficient only in the presence of specific dyes. It is suggested that this laser may be suitable for clinical applications in preventive dentistry.     

The Er:YAG laser in endodontics: results of an in vitro study

BACKGROUND AND OBJECTIVE: Until recently, the main field of Er:YAG laser application was the removal of dental hard substances within the scope of cavity preparation. Nowadays, several new delivery-systems are available, permitting the application of the Er:YAG laser in endodontics. The aim of the present study was to assess the effects of Er:YAG laser irradiation on root canals in vitro. STUDY DESIGN/MATERIALS AND METHODS: For this purpose, 220 extracted human teeth were endodontically processed and subsequently irradiated at different settings using an Er:YAG laser imitating in vivo irradiation procedures. The teeth were then subdivided into three groups and subjected to bacteriological evaluations, scanning electron microscopy, and temperature measurements. RESULTS: The bacteriological evaluation revealed a decisive bactericidal effect of the Er:YAG laser in the root canal. The bactericidal effect was dependent on the applied output power and specific for the different species of bacteria investigated. Scanning electron microscopy showed discrete removal of dentine from the root canal walls. The temperature rise during irradiation was moderate when standardized power settings were used. CONCLUSION: The investigations indicate that the Er:YAG laser is a suitable tool for the elimination of bacteria in root canals under in vitro conditions.     

Our approach to pediatric dermatologic laser surgery

BACKGROUND AND OBJECTIVES: Many pediatric dermatological conditions may be successfully treated with laser surgery. STUDY DESIGN/MATERIALS AND METHODS: The clinical approach to various pediatric dermatological conditions utilizing laser treatment options is discussed. RESULTS: Clinical uses of various modalities such as pulsed dye laser, KTP laser, Nd-YAG laser, Q-switched ruby laser, erbium-YAG laser, diode laser, non-coherent blue light sources, and fractional resurfacing are presented with successful parameters, developed over 22 years, utilized on a daily basis in a laser surgery clinic. CONCLUSION: Laser surgery can make a significant improvement in many pediatric skin lesions, thanks to the unique properties of pediatric skin and a vast array of laser technologies.     

Comparison of the photodynamic fungicidal efficacy of methylene blue, toluidine blue, malachite green and low-power laser irradiation alone against Candida albicans

This study was to evaluate specific effects of photodynamic therapy (energy density 15.8 J/cm², 26.3 J/cm² and 39.5 J/cm²) using methylene blue, toluidine blue and malachite green as photosensitizers and low-power laser irradiation on the viability of Candida albicans. Suspensions of C. albicans containing 10⁶ cells/ml were standardized in a spectrophotometer. For each dye, 120 assays, divided into four groups according to the following experimental conditions, were carried out: laser irradiation in the presence of the photosensitizer; laser irradiation only; treatment with the photosensitizer only; no exposure to laser light or photosensitizer. Next, serial dilutions were prepared and seeded onto Sabouraud dextrose agar for the determination of the number of colony-forming units per milliliter (CFU/ml). The results were subjected to analysis of variance and the Tukey test (P < 0.05). Photodynamic therapy using the photosensitizers tested was effective in reducing the number of C. albicans.. The number of CFU/ml was reduced by between 0.54 log₁₀ and 3.07 log₁₀ and depended on the laser energy density used. Toluidine blue, methylene blue and malachite green were effective photosensitizers in antimicrobial photodynamic therapy against C. albicans, as was low-power laser irradiation alone.     

The interaction of lipopolysaccharides with phenothiazine dyes

BACKGROUND AND OBJECTIVES: The difference in the photobactericidal efficacy of methylene blue and toluidine blue against gram-negative bacteria may result from their primary reaction with lipopolysaccharides (LPS) of the outer bacterial membrane. The aim of the present study was to compare the reactivity of these dyes with LPS extracted from different gram-negative bacteria. STUDY DESIGN/MATERIALS AND METHODS: The interactions of methylene blue and toluidine blue with LPS from Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa), Klebsiella pneumoniae (K. pneumoniae), and Serratia marcescens (S. marcescens) were studied spectrophotometrically in 0.45% saline. The dyes were used at the concentration of 10 microM. The concentrations of LPS ranged from 5-100 microg/ml. RESULTS: Methylene blue and toluidine blue enter into a metachromatic reaction with the LPS resulting the in generation of dimers of methylene blue and higher aggregates of toluidine blue. The more significant hypochromic and hypsochromic effects in the reaction of the latter with LPS indicate a greater metachromatic efficacy of toluidine blue than methylene blue. The equilibrium constants of the metachromatic complex between toluidine blue and different LPS were calculated. The spectrophotometric titration of LPS with the dyes was used to estimate the equivalent weight of LPS. CONCLUSIONS: Toluidine blue interacts with LPS more significantly than methylene blue in vitro. This may be one of the main factors determining its greater photobactericidal efficacy against gram-negative bacteria.     

Toluidine blue-mediated photoinactivation of periodontal pathogens from supragingival plaques

This study aimed to assess the effect of toluidine blue (TB)-mediated photodynamic inactivation of periodontal pathogens (PP) from periodontopathic patients. Photodynamic therapy (PDT) was carried out using TB and 635 nm laser light irradiation. The bactericidal effect was evaluated, and important PDT parameters including light intensity, energy dose, and TB concentration were determined. Our findings suggest that TB-mediated lethal photosensitization of PP in vivo is possible. However, to obtain ideal bactericidal effect, higher doses of light and photosensitizer should be required in treatment in vivo than their planktonic counterparts. The best therapeutic effect was observed in treatment by 1 mg/ml TB combined with 12 J/cm² at 159 mW/cm² light irradiation. Moreover, because of the considerable interindividual differences of bacterial populations, TB-mediated PDT might not be equally effective among periodontopathic patients, and further studies on improvement of this therapeutic modality is needed.     

Sentinel node and operable breast cancer: utilization of blue dye injection. Pilot study

STUDY AIM: Sentinel node detection in breast cancer can be realized with colorimetric and isotopic procedures often associated. The aim of this study was to report results obtained with blue dye injection only. PATIENTS AND METHOD: From September 1998 to July 1999, blue dye injection was performed in 73 consecutive patients (mean age: 51 years, range: 36-71 years); 51/70 70% were post-menopausal and half of them were under substitute hormonal treatment; 70% of cancers were discovered through routine mammography. There were 12 bilateral cancers, six of them synchronous, and 84% of cancers were located in the external quadrants. Individualization of sentinel node was performed through blue dye injection into the tumor in case of preoperative diagnosis or in the tumoral site in case of discovery of the cancer through extemporaneous histological examination. RESULTS: 71 out of 73 cancers were classified pT1 and 70% measured 10 mm and over. Individualization of sentinel node failed in two obese patients. Sentinel node invasion concerned one node (n = 7), two nodes (n = 1) and three nodes (n = 1). Conservative treatment was performed in 72 patients out of 73; in case of sentinel node invasion, axillary irradiation was performed without reoperation. CONCLUSION: Blue dye injection for sentinel node individualization is an accurate technique in selected patients in case of small tumors. Reoperation can be avoided and replaced by axillary irradiation in case of N+ tumors. Duration of hospitalization was 48 hours or under in 70/73 patients. Nevertheless isotopic procedure must be recommended as a routine technique in learning centers and for most surgical teams.     

Multimodal confocal microscopy for diagnosing nonmelanoma skin cancers

BACKGROUND AND SIGNIFICANCE: The standard diagnostic procedure for skin cancers is invasive biopsy followed by histopathological evaluation. The biopsy may result in scarring and infection. A reliable way to noninvasively image suspicious lesions with high resolution and contrast would be valuable. In this study, the suitability of dye-enhanced multimodal confocal microscopy for the detection of nonmelanoma skin cancers was evaluated. MATERIALS AND METHODS: For the experiments we used fresh tumor material stained using 0.2 mg/ml or 0.05 mg/ml aqueous solutions of methylene blue (MB) or toluidine blue (TB), respectively. Reflectance, fluorescence, and fluorescence polarization images of skin specimens stained with MB and TB were excited by 656 nm and 633 nm light, respectively. Fluorescence emission and anisotropy were registered between 690 nm and 710 nm. In addition, reference reflectance images at 830 nm were acquired. In total we imaged, analyzed, and compared to histology at least 10 samples of each tumor-type including nodular basal cell carcinoma (BCC), infiltrative basal cell carcinoma, and squamous cell carcinoma (SCC). RESULTS AND CONCLUSION: The morphological features and appearance of skin structures in the fluorescence images correlate well with corresponding histology for all investigated tumor-types. Multi-spectral reflectance images provide information on the tissue spectral responses and are complimentary to the fluorescence images. The differences detected by fluorescence polarization in cancerous and normal structures may be used for cancerous tissue discrimination. Our results indicate the feasibility of using multimodal confocal microscopy as real-time tool for detecting skin pathology.     

Methylene blue based protein solder for vascular anastomoses: an in vitro burst pressure study

BACKGROUND AND OBJECTIVE: Attempts at sutureless anastomoses have used protein-based solders containing chromophores [Oz et al., J Vasc Surg 1990;11:718; Poppas et al., J Urol 1998150:1052] to enhance the strength of laser anastomoses. Reports have described the use of indocyanine green [Oz et al., Surg Forum 1989;316.], fuschin, and fluorescein isothiocyanate as chromophores [Chuck et al. , Lasers Surg Med 1989;9:471; Vance et al., Lasers Med Sci 1988;3:219]. Methylene blue (MB) is a chromophore with absorption peaks in the 600-700 nm region whose use has not been reported in laser-assisted vascular anastomoses. Therefore, we set out to produce and characterise a MB-containing protein solder. The absorption and burst pressure characteristics have been investigated and described as well as a brief review of the chemical and biological properties of MB. STUDY DESIGN/MATERIALS AND METHODS: The MB and porcine serum albumin (PSA)-based solder was produced and used to form end-to-end anastomoses in porcine splenic arteries. The solder was activated using a laser diode emitting at 670 nm. The burst pressures of the anastomoses were tested, and the results analysed as a function of MB concentration and absorption. In addition, the relationship between MB concentration and absorption was examined. RESULTS: A dose-response relationship was found between the measured absorption of the solder and the burst pressure of the anastomoses formed. Burst pressures exceeding physiological levels were found. Changes in MB concentration revealed a marked negative deviation from Beer's law at 670 nm, owing to the monomer-dimer-trimer equilibria. CONCLUSION: PSA with MB solder is able to form high-quality end-to-end anastomoses, with immediate burst pressure profiles similar to those previously described for sutured [Quigley et al., Microsurgery 1985;6:229], lasered [Quigley et al., Microsurgery 1985;6:229], and soldered anastomoses [Small et al., J Clin Laser Med Surg 1997;15:205]. The relationship between burst pressure strength and chromophore absorption is discussed.     

美蓝和专利蓝在乳癌前哨淋巴结活检中作用的研究

目的 探讨美蓝及专利蓝两种蓝染剂鉴别前哨淋巴结（SLN）的成功率及预测乳癌淋巴结转移的准确性。方法 从1999年10月－2001年4月我科收治的乳癌病例中选取94例实施了前哨淋巴结活检（SNB）,其中于术中在乳腺肿块周围腺体内注射1％美蓝32例（美蓝组）、注射1％专利蓝62例（专利蓝组）、以鉴别定位SLN。全部病例都实施了腋淋巴结清扫术。结果 SLN鉴别的成功率美蓝组和专利蓝组分别为65．6％（21／32）和88．7％（55／62）（P＜0．01）;预测腋淋巴结转移状态准确性分别为90．5％（19／21）和98．2％（54／55）（P＞0．05）。结论 与美蓝比,专利蓝是较理想的乳癌SNB的生物活性染料示踪剂。