Fluorescence Emitted by Papanicolaou-Stained Urothelial Cells Improves Sensitivity of Urinary Conventional Cytology for Detection of Urothelial Tumors.

BACKGROUND: Urinary conventional cytology (UCCy) is easy to perform, but its low sensitivity, especially for low-grade urothelial neoplasms (LGUNs), limits its indications in the management of patients at risk of bladder cancer. The authors aim at obtaining a complementary test that would effectively increase the sensitivity of UCCy on voided urines by analyzing fluorescence of Papanicolaou-stained urothelial cells with no change of method in slide preparation. METHODS: In this retrospective study of 155 patients, 91 Papanicolaou-stained voided urines were considered satisfactory under fluorescence microscopy (FMi). The results of FMi were compared with UCCy (using transmission microscopy) and correlated to cystoscopy, histology and follow-up data. RESULTS: The results are given for all patients and for two groups of them according to the patients' main complaints (group 1: 33 patients followed up for a previously treated bladder tumor; group 2: 58 patients with persistent urinary symptoms). Overall negative predictive value (NPV) and sensitivity of FMi were 100% vs. 73.7% and 64.3% respectively for UCCy (P = 0.0001). Sensitivity of FMi for LGUN was unexpectedly high with a value of 100% vs. 46.2% for UCCy (P = 0.0002). FMi was significantly superior to UCCy for detecting urothelial tumors in every group of patients and would allow a better characterization of atypical urothelial cells (AUCs) defined by the Paris System for Reporting Urine Cytology (TPS). CONCLUSIONS: Because of its sensitivity and NPV of 100%, FMi could complement UCCy to screen voided urines allowing a better detection of primary urothelial tumors or early recurrences of previously treated urothelial carcinoma. Moreover, this "dual screening" would allow completing efficiently cystoscopy to detect flat dysplasia, carcinoma in situ (CIS) and extra bladder carcinoma.

Direct observation of the cell-wall remodeling in adhering Staphylococcus aureus 27217: An AFM study supported by SEM and TEM.

We took benefit from Atomic Force Microscopy (AFM) in the force spectroscopy mode to describe the time evolution - over 24 h - of the surface nanotopography and mechanical properties of the strain Staphylococcus aureus 27217 from bacterial adhesion to the first stage of biofilm genesis. In addition, Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) experiments allowed identifying two types of self-adhering subpopulations (the so-called "bald" and "hairy" cells) and revealed changes in their relative populations with the bacterial culture age and the protocol of preparation. We indeed observed a dramatic evanescing of the "hairy" subpopulation for samples that underwent centrifugation and resuspension processes. When examined by AFM, the "hairy" cell surface resembled to a herringbone structure characterized by upper structural units with lateral dimensions of ∼70 nm and a high Young modulus value (∼2.3 MPa), a mean depth of the trough between them of ∼15 nm and a resulting roughness of ∼5 nm. By contrast, the "bald" cells appeared much softer (∼0.35 MPa) with a roughness one order of magnitude lower. We observed too the gradual detachment of the herringbone patterns from the "hairy" bacterial envelope of cell harvested from a 16 h old culture and their progressive accumulation between the bacteria in the form of globular clusters. The secretion of a soft extracellular polymeric substance was also identified that, in addition to the globular clusters, may contribute to the initiation of the biofilm spatial organization.

Live intramacrophagic Staphylococcus aureus as a potential cause of antibiotic therapy failure: observations in an in vivo mouse model of prosthetic vascular material infections.

Objectives: To evaluate the significant role played by biofilms during prosthetic vascular material infections (PVMIs). Methods: We developed an in vivo mouse model of Staphylococcus aureus PVMI allowing its direct observation by confocal microscopy to describe: (i) the structure of biofilms developed on Dacron® vascular material; (ii) the localization and effect of antibiotics on these biostructures; and (iii) the interaction between bacteria and host tissues and cells during PVMI. Results: In this model we demonstrated that the biofilm structures are correlated to the activity of antibiotics. Furthermore, live S. aureus bacteria were visualized inside the macrophages present at the biofilm sites, which is significant as antibiotics do not penetrate these immune cells. Conclusions: This intracellular situation may explain the limited effect of antibiotics and also why PVMIs can relapse after antibiotic therapy.

Impact of Bacterial Membrane Fatty Acid Composition on the Failure of Daptomycin To Kill Staphylococcus aureus.

Daptomycin is a last-resort membrane-targeting lipopeptide approved for the treatment of drug-resistant staphylococcal infections, such as bacteremia and implant-related infections. Although cases of resistance to this antibiotic are rare, increasing numbers of clinical, in vitro, and animal studies report treatment failure, notably against Staphylococcus aureus The aim of this study was to identify the features of daptomycin and its target bacteria that lead to daptomycin treatment failure. We show that daptomycin bactericidal activity against S. aureus varies significantly with the growth state and strain, according to the membrane fatty acid composition. Daptomycin efficacy as an antibiotic relies on its ability to oligomerize within membranes and form pores that subsequently lead to cell death. Our findings ascertain that daptomycin interacts with tolerant bacteria and reaches its membrane target, regardless of its bactericidal activity. However, the final step of pore formation does not occur in cells that are daptomycin tolerant, strongly suggesting that it is incapable of oligomerization. Importantly, membrane fatty acid contents correlated with poor daptomycin bactericidal activity, which could be manipulated by fatty acid addition. In conclusion, daptomycin failure to treat S. aureus is not due to a lack of antibiotic-target interaction, but is driven by its capacity to form pores, which depends on membrane composition. Manipulation of membrane fluidity to restore S. aureus daptomycin bactericidal activity in vivo could open the way to novel antibiotic treatment strategies.

Preclinical ex vivo evaluation of the diagnostic performance of a new device for in situ label-free fluorescence spectral analysis of breast masses.

OBJECTIVES: To assess the diagnostic performance of a new device for in situ label-free fluorescence spectral analysis of breast masses in freshly removed surgical specimens, in preparation for its clinical development. METHODS: Sixty-four breast masses from consenting patients who had undergone either a lumpectomy or a mastectomy were included. Label-free fluorescence spectral acquisitions were obtained with a 25G fibre-containing needle inserted into the mass. Data from benign and malignant masses were compared to establish the most discriminating thresholds and measurement algorithms. Accuracy was verified using the bootstrap method. RESULTS: The final histological examination revealed 44 invasive carcinomas and 20 benign lesions. The maximum intensity of fluorescence signal was discriminant between benign and malignant masses (p < .0001) whatever their sizes. Statistical analysis indicated that choosing five random measurements per mass was the best compromise to obtain high sensitivity and high negative predictive value with the fewest measurements. Thus, malignant tumours were identified with a mean sensitivity, specificity, negative and positive predictive value of 98.8%, 85.4%, 97.2% and 93.5%, respectively. CONCLUSION: This new in situ tissue autofluorescence evaluation device allows accurate discrimination between benign and malignant breast masses and deserves clinical development. KEY POINTS: • A new device allows in situ label-free fluorescence analysis of ex vivo breast masses • Maximum fluorescence intensity discriminates benign from malignant masses (p < .0001) • Five random measurements allow a high negative predictive value (97.2%).

How do fluorescence spectroscopy and multimodal fluorescence imaging help to dissect the enhanced efficiency of the vancomycin-rifampin combination against Staphylococcus aureus infections?

Staphylococcus aureus is one of the most frequent pathogens responsible for biofilm-associated infections. Among current clinical antibiotics, very few enable long-term successful treatment. Thus, it becomes necessary to better understand antibiotic failures and successes in treating infections in order to master the use of proper antibiotic therapies. In this context, we took benefit from a set of fluorescence spectroscopy and imaging methods, with the support of conventional microbiological tools to better understand the vancomycin-rifampin combination (in)efficiency against S. aureus biofilms. It was shown that both antibiotics interacted by forming a complex. This latter allowed a faster penetration of the drugs before dissociating from each other to interact with their respective biological targets. However, sufficiently high concentrations of free vancomycin should be maintained, either by increasing the vancomycin concentration or by applying repetitive doses of the two drugs, in order to eradicate rifampin-resistant mutants.

New Insight into Daptomycin Bioavailability and Localization in Staphylococcus aureus Biofilms by Dynamic Fluorescence Imaging.

Staphylococcus aureus is one of the most frequent pathogens responsible for biofilm-associated infections (BAI), and the choice of antibiotics to treat these infections remains a challenge for the medical community. In particular, daptomycin has been reported to fail against implant-associated S. aureus infections in clinical practice, while its association with rifampin remains a good candidate for BAI treatment. To improve our understanding of such resistance/tolerance toward daptomycin, we took advantage of the dynamic fluorescence imaging tools (time-lapse imaging and fluorescence recovery after photobleaching [FRAP]) to locally and accurately assess the antibiotic diffusion reaction in methicillin-susceptible and methicillin-resistant S. aureus biofilms. To provide a realistic representation of daptomycin action, we optimized an in vitro model built on the basis of our recently published in vivo mouse model of prosthetic vascular graft infections. We demonstrated that at therapeutic concentrations, daptomycin was inefficient in eradicating biofilms, while the matrix was not a shield to antibiotic diffusion and to its interaction with its bacterial target. In the presence of rifampin, daptomycin was still present in the vicinity of the bacterial cells, allowing prevention of the emergence of rifampin-resistant mutants. Conclusions derived from this study strongly suggest that S. aureus biofilm resistance/tolerance toward daptomycin may be more likely to be related to a physiological change involving structural modifications of the membrane, which is a strain-dependent process.

Natural Rubber-Filler Interactions: What Are the Parameters?

Reinforcement of a polymer matrix through the incorporation of nanoparticles (fillers) is a common industrial practice that greatly enhances the mechanical properties of the composite material. The origin of such mechanical reinforcement has been linked to the interaction between the polymer and filler as well as the homogeneous dispersion of the filler within the polymer matrix. In natural rubber (NR) technology, knowledge of the conditions necessary to achieve more efficient NR-filler interactions is improving continuously. This study explores the important physicochemical parameters required to achieve NR-filler interactions under dilute aqueous conditions by varying both the properties of the filler (size, composition, surface activity, concentration) and the aqueous solution (ionic strength, ion valency). By combining fluorescence and electron microscopy methods, we show that NR and silica interact only in the presence of ions and that heteroaggregation is favored more than homoaggregation of silica-silica or NR-NR. The interaction kinetics increases with the ion valence, whereas the morphology of the heteroaggregates depends on the size of silica and the volume percent ratio (dry silica/dry NR). We observe dendritic structures using silica with a diameter (d) of 100 nm at a ∼20-50 vol % ratio, whereas we obtain raspberry-like structures using silica with d = 30 nm particles. We observe that in liquid the interaction is controlled by the hydrophilic bioshell, in contrast to dried conditions, where hydrophobic polymer dominates the interaction of NR with the fillers. A good correlation between the nanoscopic aggregation behavior and the macroscopic aggregation dynamics of the particles was observed. These results provide insight into improving the reinforcement of a polymer matrix using NR-filler films.

Analysis of autofluorescence in polymorphonuclear neutrophils: a new tool for early infection diagnosis.

Diagnosing bacterial infection (BI) remains a challenge for the attending physician. An ex vivo infection model based on human fixed polymorphonuclear neutrophils (PMNs) gives an autofluorescence signal that differs significantly between stimulated and unstimulated cells. We took advantage of this property for use in an in vivo pneumonia mouse model and in patients hospitalized with bacterial pneumonia. A 2-fold decrease was observed in autofluorescence intensity for cytospined PMNs from broncho-alveolar lavage (BAL) in the pneumonia mouse model and a 2.7-fold decrease was observed in patients with pneumonia when compared with control mice or patients without pneumonia, respectively. This optical method provided an autofluorescence mean intensity cut-off, allowing for easy diagnosis of BI. Originally set up on a confocal microscope, the assay was also effective using a standard epifluorescence microscope. Assessing the autofluorescence of PMNs provides a fast, simple, cheap and reliable method optimizing the efficiency and the time needed for early diagnosis of severe infections. Rationalized therapeutic decisions supported by the results from this method can improve the outcome of patients suspected of having an infection.

Patterned hydrophobic domains in the exopolymer matrix of Shewanella oneidensis MR-1 biofilms.

Water-dispersible amphiphilic surface-engineered quantum dots (QDs) were found to be strongly accumulated within discrete zones of the exopolymer network of Shewanella oneidensis MR-1 biofilms, but not on the cell surfaces. These microdomains showed a patterned distribution in the exopolymer matrix, which led to a restricted diffusion of the amphiphilic nanoparticles.

Competition of bovine serum albumin adsorption and bacterial adhesion onto surface-grafted ODT: in situ study by vibrational SFG and fluorescence confocal microscopy.

The interaction of hydrophilic and hydrophobic ovococcoid bacteria and bovine serum albumin (BSA) proteins with a well ordered surface of octadecanethiol (ODT) self assembled monolayer (SAM) has been studied in different situations where proteins were either preadsorbed on ODT or adsorbed simultaneously with bacterial adhesion as in life conditions. The two situations lead to very different antimicrobial behavior. Bacterial adhesion on preadsorbed BSA is very limited, while the simultaneous exposure of ODT SAM to proteins and bacteria lead to a markedly weaker antimicrobial effect. The combination of sum frequency generation spectroscopy and fluorescence confocal microscopy experiments allow one to draw conclusions on the factors that govern the ODT SAM or BSA film interaction with bacteria at the molecular level. On the hydrophobic ODT surface, interaction with hydrophobic or hydrophilic biomolecules results in opposite effects on the SAM, namely, a flattening or a raise of the terminal methyl groups of ODT. On an amphiphilic BSA layer, the bacterial adhesion strength is weakened by the negative charges carried by both BSA and bacteria. Surprisingly, preadsorbed BSA that cover part of the bacteria cell walls increase the adhesion strength to the BSA film and reduce hydrophobic interactions with the ODT SAM. Finally, bacterial adhesion on a BSA film is shown to modify the BSA proteins in some way that change their interaction with the ODT SAM. The antimicrobial effect is much stronger in the case of a preadsorbed BSA layer than when BSA and bacteria are in competition to colonize the ODT SAM surface.

A fluorescence-based assay for monitoring clinical drug resistance.

BACKGROUND AND AIMS: Multidrug resistance (MDR) limits effectiveness in treating malignancy by modifying internalisation and/or externalisation of drugs through cancer cell membranes. In this study we describe an assay to monitor patients' responses to chemotherapy. METHODS: The assay is based on the fluorescent properties of doxorubicin alone as well as in combination with methotrexate, vinblastine, doxorubicin and cisplatin (MVAC). The slide-based cell imaging technique was first optimised using a panel of breast and urothelial cancer cell lines and then extended to fine needle breast aspiration biopsy and urine cytology. RESULTS: The drug fluorescence behaviour observed on smears of clinical specimens is identical to that obtained using fixed cultured cells. The fluorescence of sensitive cells to chemotherapy is mainly localised in the nucleus, whereas resistant cells show a weak fluorescence signal localised in the cytoplasm. The difference in terms of fluorescence intensity is also highlighted through fluorescence spectra. CONCLUSIONS: The results suggest that the assay provides clinically valuable information in predicting responses to doxorubicin and/or MVAC therapy. Originally set up on a confocal microscope, the assay was also effective using a standard epifluorescence microscope; as such it is technically simple, reliable and inexpensive.

Surface-engineered quantum dots for the labeling of hydrophobic microdomains in bacterial biofilms.

Quantum dots (QDs) nanoprobes are emerging as alternatives to small-molecule fluorescent probes in biomedical technology. This paper reports an efficient and rapid method of producing highly dispersed and stable CdSe-core QDs with a hydrophobic gradient. Amphiphilic core/shell CdSe/ZnS QDs were prepared by ligand exchange at the surface of lipophilic CdSe/ZnS QDs using the dihydrolipoic acid (DHLA) dithiol ligand linked to leucine or phenylalanine amino acids. Contact angle relaxations on a hydrophobic surface and surface tension measurements indicated that aqueous dispersions of CdSe/ZnS@DHLA-Leu or CdSe/ZnS@DHLA-Phe QDs exhibit increased hydrophobicity compared to CdSe-core QDs capped by the hydrophilic 3-mercaptopropionic acid (MPA) ligand. We found that the surface functional groups and the ligand density at the periphery of these QDs significantly dictated their interactions with a complex biological matrix called biofilm. Using fluorescence confocal microscopy and an autocorrelation function (semi-variogram), we demonstrated that MPA-capped QDs were homogeneously associated to the biopolymers, while amphiphilic CdSe/ZnS@DHLA-Leu or CdSe/ZnS@DHLA-Phe QDs were specifically confined allowing identification of hydrophobic microdomains of the biofilms. Results obtained clearly point out that the final destination of QDs in biofilms can properly be controlled by an appropriate design of surface ligands.

Deciphering biofilm structure and reactivity by multiscale time-resolved fluorescence analysis.

In natural, industrial and medical environments, microorganisms mainly live as structured and organised matrix-encased communities known as biofilms. In these communities, microorganisms demonstrate coordinated behaviour and are able to perform specific functions such as dramatic resistance to antimicrobials, which potentially lead to major public health and industrial problems. It is now recognised that the appearance of such specific biofilm functions is intimately related to the three-dimensional organisation of the biological edifice, and results from multifactorial processes. During the last decade, the emergence of innovative optical microscopy techniques such as confocal laser scanning microscopy in combination with fluorescent labelling has radically transformed imaging in biofilm research, giving the possibility to investigate non-invasively the dynamic mechanisms of formation and reactivity of these biostructures. In this chapter, we discuss the contribution of fluorescence analysis and imaging to the study at different timescales of various processes: biofilm development (hours to days), antimicrobial reactivity within the three-dimensional structure (minutes to hours) or molecular diffusion/reaction phenomena (pico- to milliseconds).

Non-invasive vibrational SFG spectroscopy reveals that bacterial adhesion can alter the conformation of grafted "brush" chains on SAM.

Understanding bacterial adhesion on a surface is a crucial step to design new materials with improved properties or to control biofilm formation and eradication. Sum Frequency Generation (SFG) vibrational spectroscopy has been employed to study in situ the conformational response of a self-assembled monolayer (SAM) of octadecanethiol (ODT) on a gold film to the adhesion of hydrophilic and hydrophobic ovococcoid model bacteria. The present work highlights vibrational SFG spectroscopy as a powerful and unique non-invasive biophysical technique to probe and control bacteria interaction with ordered surfaces. Indeed, the SFG vibrational spectral changes reveal different ODT SAM conformations in air and upon exposure to aqueous solution or bacterial adhesion. Furthermore, this effect depends on the bacterial cell surface properties. The SFG spectral modeling demonstrates that hydrophobic bacteria flatten the ODT SAM alkyl chain terminal part, whereas the hydrophilic ones raise this ODT SAM terminal part. Microorganism-induced alteration of grafted chains can thus affect the desired interfacial functionality, a result that should be considered for the design of new reactive materials.

Diffusion of nanoparticles in biofilms is altered by bacterial cell wall hydrophobicity.

Diffusion of entities inside biofilm triggers most mechanisms involved in biofilm-specific phenotypes. Using genetically engineered hydrophilic and hydrophobic cells of Lactococcus lactis yielding similar biofilm architectures, we demonstrated by fluorescence correlation spectroscopy that bacterial surface properties affect diffusion of nanoparticles through the biofilm matrix.

Optimizing photodynamic therapy by liposomal formulation of the photosensitizer pyropheophorbide-a methyl ester: in vitro and ex vivo comparative biophysical investigations in a colon carcinoma cell line.

Photodynamic therapy (PDT), induced by a photosensitizer (PS) encapsulated in a nanostructure, has emerged as an appropriate treatment to cure a multitude of oncological and non-oncological diseases. Pyropheophorbide-a methyl ester (PPME) is a second-generation PS tested in PDT, and is a potential candidate for future clinical applications. The present study, carried out in a human colon carcinoma cell line (HCT-116), evaluates the improvement resulting from a liposomal formulation of PPME versus free-PPME. Absorption and fluorescence spectroscopies, fluorescence lifetime measurements, subcellular imaging and co-localization analysis have been performed in order to analyze the properties of PPME for each delivery mode. The benefit of drug encapsulation in DMPC-liposomes is clear from our experiments, with a 5-fold higher intracellular drug delivery than that observed with free-PPME at similar concentrations. The reactive oxygen species (ROSs) produced after PPME-mediated photosensitization have been identified and quantified by using electron spin resonance spectroscopy. Our results demonstrate that PPME-PDT-mediated ROSs are composed of singlet oxygen and a hydroxyl radical. The small amounts of PPME inside mitochondria, as revealed by fluorescence co-localization analysis, could maybe explain the very low apoptotic cell death measured in HCT-116 cells.

Diffusion measurements inside biofilms by image-based fluorescence recovery after photobleaching (FRAP) analysis with a commercial confocal laser scanning microscope.

Research about the reactional and structural dynamics of biofilms at the molecular level has made great strides, owing to efficient fluorescence imaging methods in terms of spatial resolution and fast acquisition time but also to noninvasive conditions of observation consistent with in situ biofilm studies. In addition to conventional fluorescence intensity imaging, the fluorescence recovery after photobleaching (FRAP) module can now be routinely implemented on commercial confocal laser scanning microscopes (CLSMs). This method allows measuring of local diffusion coefficients in biofilms and could become an alternative to fluorescence correlation spectroscopy (FCS). We present here an image-based FRAP protocol to improve the accuracy of FRAP measurements inside "live" biofilms and the corresponding analysis. An original kymogram representation allows control of the absence of perturbing bacterial movement during image acquisition. FRAP data analysis takes into account molecular diffusion during the bleach phase and uses the image information to extract molecular diffusion coefficients. The fluorescence spatial intensity profile analysis used here for the first time with biofilms is supported both by our own mathematical model and by a previously published one. This approach was validated to FRAP experiments on fluorescent-dextran diffusion inside Lactococcus lactis and Stenotrophomonas maltophilia biofilms, and the results were compared to previously published FCS measurements.

Tracking the photosensitizing antibacterial activity of mono(acridyl)bis(arginyl)porphyrin (MABAP) by time-resolved spectroscopy.

Photodynamic inactivation (PDI) is currently receiving interest for its potential as an antimicrobial treatment. Although photosensitizing agents and light have been used for medical purposes for a very long time, only a little information is available about the mechanism of PDI for bacteria. Pseudomonas aeruginosa is a gram negative bacteria involved in chronic infections in cystic fibrosis patients and also one of the commonest agents of hospital acquired infections. In the present study the sensitivity of Pseudomonas aeruginosa to the phototoxic effects of the mono(acridyl)bis(arginyl)porphyrin (MABAP) has been investigated as well as the photophysical and photochemical properties of this cationic porphyrin complexed to [poly(dG-dC)](2) to investigate the mechanisms that lead to bacteria inactivation. Both picosecond time-resolved fluorescence and femtosecond to nanosecond transient absorption measurements give evidence that while MABAP can react through its triplet state and/or an ultrafast electron transfer with guanine, its intercalation between GC base pairs is not the main target of MABAP photoactivity. The analysis of both fluorescence emission and excitation spectra reveals the occurrence of an energy transfer through the DNA double helix between the acridine and porphyrin chromophores of MABAP, as previously observed for the stacked free molecule in solution. This efficient process may lead to the excitation of twice more porphyrin chromophores in MABAP by comparison to other cationic porphyrins.

Towards an optical biopsy for the diagnosis of breast cancer in vivo by endogenous fluorescence spectroscopy.

The techniques of medical imaging allow the detection of suspect lesions in the breast, but they do not always evidence the malignant nature of these lesions. Breast biopsies and histological analyses are therefore implemented to establish a diagnosis. In order to reduce the number of these invasive procedures, a portable clinical system was designed based upon the excitation of Endogenous Fluorescence in vivo at 405 nm via a fiber-optics probe included in a disposable needle of small diameter (<1 mm). From the fluorescence signal, the authors are able to discriminate between diseased and healthy areas of human breast biopsies. Stronger fluorescence intensity and systematic spectral red shift of the tumor areas were observed. These results are confirmed by confocal microscopy. This new instrument is promising for the minimally invasive diagnosis of breast tumors in vivo with an appreciable limitation of patient trauma and of operational and financial cost.