Ultraviolet-C inactivation and hydrophobicity of Bacillus subtilis and Bacillus velezensis spores isolated from extended shelf-life milk.

Bacterial spores are important in food processing due to their ubiquity, resistance to high temperature and chemical inactivation. This work aims to study the effect of ultraviolet C (UVC) on the spores of Bacillus subtilis and Bacillus velezensis at a molecular and individual level to guide in deciding on the right parameters that must be applied during the processing of liquid foods. The spores were treated with UVC using phosphate buffer saline (PBS) as a suspension medium and their lethality rate was determined for each sample. Purified spore samples of B. velezensis and B. subtilis were treated under one pass in a UVC reactor to inactivate the spores. The resistance pattern of the spores to UVC treatment was determined using dipicolinic acid (Ca-DPA) band of spectral analysis obtained from Raman spectroscopy. Flow cytometry analysis was also done to determine the effect of the UVC treatment on the spore samples at the molecular level. Samples were processed for SEM and the percentage spore surface hydrophobicity was also determined using the Microbial Adhesion to Hydrocarbon (MATH) assay to predict the adhesion strength to a stainless-steel surface. The result shows the maximum lethality rate to be 6.5 for B. subtilis strain SRCM103689 (B47) and highest percentage hydrophobicity was 54.9% from the sample B. velezensis strain LPL-K103 (B44). The difference in surface hydrophobicity for all isolates was statistically significant (P < 0.05). Flow cytometry analysis of UVC treated spore suspensions clarifies them further into sub-populations unaccounted for by plate counting on growth media. The Raman spectroscopy identified B4002 as the isolate possessing the highest concentration of Ca-DPA. The study justifies the critical role of Ca-DPA in spore resistance and the possible sub-populations after UVC treatment that may affect product shelf-life and safety. UVC shows a promising application in the inactivation of resistant spores though there is a need to understand the effects at the molecular level to design the best parameters during processing.

Blue-Light-Switchable Bacterial Cell-Cell Adhesions Enable the Control of Multicellular Bacterial Communities.

Although the fundamental importance and biotechnological potential of multibacterial communities, also called biofilms, are well-known, our ability to control them is limited. We present a new way of dynamically controlling bacteria-bacteria adhesions by using blue light and how these photoswitchable adhesions can be used to regulate multicellularity and associated bacterial behavior. To achieve this, the photoswitchable proteins nMagHigh and pMagHigh were expressed on bacterial surfaces as adhesins to allow multicellular clusters to assemble under blue light and reversibly disassemble in the dark. Regulation of the bacterial cell-cell adhesions with visible light provides unique advantages including high spatiotemporal control, tunability, and noninvasive remote regulation. Moreover, these photoswitchable adhesions make it possible to regulate collective bacterial functions including aggregation, quorum sensing, biofilm formation, and metabolic cross-feeding between auxotrophic bacteria with light. Overall, the photoregulation of bacteria-bacteria adhesions provides a new way of studying bacterial cell biology and will enable the design of biofilms for biotechnological applications.

Co infection of respiratory syncytial viruses (RSV) and streptococcus pneumonia modulates pathogenesis and dependent of serotype and phase variant.

Streptococcus pneumoniae (pneumococcus) is touted to be the generally found pathogen in patients with respiratory issues and there is an epidemiologic linkage present between Respiratory syncytial virus (RSV). This study aim at investigating the interaction between RSV and two serotypes of S. pneumoniae using a distinct animal model and a well-established colonizing pneumococcal strain. Phase variants phenotype of each strain was determined under oblique light. Co infection model was developed using BALB/c mice housed in a BSL-2 facility. Coinfection experiments were performed and number of bacterial colonies was quantified and phase determination was evaluated. RSV was detected in sample through real-time quantitative PCR. Adherence assays were performed to determine adherence of Spn strains and its knock out ΔNanA to nasopharyngeal carcinoma (NPC) epithelial CNE3 cell line. The biofilm viability was determined and phase composition was counted using plate count. Neuraminidase activity was measured in fluorometircassessed using 2'-(4-methylumbelliferyl)-α-D-N-acetylneuraminic acid (MUAN) as substrate as described in earlier literature. The GraphPad Software version 5.01 i.e., GraphPad Prism was used to conduct the statistical analysis. The extent of bacterial colonization was increased significantly (p < 0.05), when the mice were co infected. Nasal epithelium remained intact in mock sample with features of a thick mucociliary border. A small percentage of pneumococci exhibit phase variation between opaque phase and transparent phase. The percentage adherent of both phase were not found to be varying significantly within serotype but it was seen that nonpathogenic type 27 was more adherent. Biofilm formation was selectively more for transparent phase from a mixed-phase inoculum. Adherence of both phase variant of S. pneumoniae to nasopharyngeal epithelial cells 2 h post infection expressed as the percentage of adherent bacteria relative to the inoculum. In absence of viral infection, the nasal colonization of the opaque and the transparent variant was increased many folds, which was a significant differences. The extent of nasal colonization by the ΔNanA mutant strain were significantly reduced post-bacterial infection for both type of wild-type (P < 0.05). The findings explore insights into the interactions occurring between S. pneumoniae and RSV during respiratory infections and pneumococcal acquisition, indicate that pneumococcal serotypes have different ability to cause infection as well as co infections and potentially follow an unappreciated mechanism. Much more research work is needed to further understand the minutiae of this interaction within co-infection process.

Red/Far-Red Light Switchable Cargo Attachment and Release in Bacteria-Driven Microswimmers.

In bacteria-driven microswimmers, i.e., bacteriabots, artificial cargos are attached to flagellated chemotactic bacteria for active delivery with potential applications in biomedical technology. Controlling when and where bacteria bind and release their cargo is a critical step for bacteriabot fabrication and efficient cargo delivery/deposition at the target site. Toward this goal, photoregulating the cargo integration and release in bacteriabots using red and far-red light, which are noninvasive stimuli with good tissue penetration and provide high spatiotemporal control, is proposed. In the bacteriabot design, the surfaces of E. coli and microsized model cargo particles with the proteins PhyB and PIF6, which bind to each other under red light and dissociate from each other under far-red light are functionalized. Consequently, the engineered bacteria adhere and transport the model cargo under red light and release it on-demand upon far-red light illumination due to the photoswitchable PhyB-PIF6 protein interaction. Overall, the proof-of-concept for red/far-red light switchable bacteriabots, which opens new possibilities in the photoregulation in biohybrid systems for bioengineering, targeted drug delivery, and lab-on-a-chip devices, is demonstrated.

Smart, Photothermally Activated, Antibacterial Surfaces with Thermally Triggered Bacteria-Releasing Properties.

The development of effective antibacterial surfaces to prevent the attachment of pathogenic bacteria and subsequent bacterial colonization and biofilm formation is critically important for medical devices and public hygiene products. In the work reported herein, a smart antibacterial hybrid film based on tannic acid/Fe3+ ion (TA/Fe) complex and poly(N-isopropylacrylamide) (PNIPAAm) is deposited on diverse substrates. This surface is shown to have bacteria-killing and bacteria-releasing properties based on, respectively, near-infrared photothermal activation and subsequent cooling. The TA/Fe complex has three roles in this system: (i) as a universal adhesive "anchor" for surface modification, (ii) as a high-efficiency photothermal agent for ablation of attached bacteria (including multidrug resistant bacteria), and (iii) as a robust linker for immobilization of NH2-terminated PNIPAAm via either Michael addition or Schiff base formation. Moreover, because of the thermoresponsive properties of the immobilized PNIPAAm, almost all of the killed bacteria and other debris can be removed from the surface simply by lowering the temperature. It is shown that this hybrid film can maintain good antibacterial performance after being used for multiple "kill-and-release" cycles and can be applied to various substrates regardless of surface chemistry or topography, thus providing a broadly applicable, simple, and reliable solution to the problems associated with surface-attached bacteria in various healthcare applications.

Effect of Er:YAG laser irradiation on deciduous enamel roughness and bacterial adhesion: An in vitro study.

Laser irradiation has been proposed as a preventive method against dental caries since it is capable to inhibit enamel demineralization by reducing carbonate and modifying organic matter, yet it can produce significant morphological changes. The purpose of this study was to evaluate the influence of Er:YAG laser irradiation on superficial roughness of deciduous dental enamel and bacterial adhesion. Fifty-four samples of deciduous enamel were divided into three groups (n = 18 each). G1_control (nonirradiated); G2_100 (7.5 J/cm2 ) and G3_100 (12.7 J/cm2 ) were irradiated with Er:YAG laser at 7.5 and 12.7 J/cm2 , respectively, under water irrigation. Surface roughness was measured before and after irradiation using a profilometer. Afterwards, six samples per group were used to measure bacterial growth by XTT cell viability assay. Adhered bacteria were observed using confocal laser scanning microscopy (CLSM) and a scanning electron microscopy (SEM). Paired t-, one-way analysis of variance (ANOVA), Kruskal-Wallis and pairwise Mann-Whitney U tests were performed to analyze statistical differences (p < .05). Before treatment, samples showed homogenous surface roughness, and after Er:YAG laser irradiation, the surfaces showed a significant increase in roughness values (p < .05). G3_100 (12.7 J/cm2 ) showed the highest amount of Streptococcus mutans adhered (p < .05). The increase in the roughness of the tooth enamel surfaces was proportional to the energy density used; the increase in surface roughness caused by laser irradiation did not augment the adhesion of Streptococcus sanguinis; only the use of the energy density of 12.7 J/cm2 favored significantly the adhesion of S. mutans.

Bacterial viability after antimicrobial photodynamic therapy with curcumin on multiresistant Staphylococcus aureus.

Staphylococcus aureus are multiresistant pathogens that causes superficial and systemic infections. Antimicrobial photodynamic therapy (APDT) is an alternative in the treatment of diseases caused by these bacteria. Aim: In this study the APDT response on growth, viability, formation of reactive oxygen species and adhesion of methicillin-sensitive strains of Staphylococcus aureus, strains of methicillin-resistant S. aureus and American-type culture collection (ATCC) of S. aureus were evaluated in vitro, after incubation with curcumin for 20 min, and irradiated with LED. Materials & methods: Bacterial growth was assessed by the number of colony-forming units, viability and adhesion were evaluated by confocal microscopy and ROS quantification was performed by fluorimetry. Results: Was observed increase in the production of ROS in APDT groups, besides a decrease in the 4 log growth and loss of the bacterial adhesion. Conclusion: APDT with Curcumin may be an interesting therapeutic alternative, due to its in vitro response, in the control multiresistant clinical S. aureus strains.

A Photoswitchable Trivalent Cluster Mannoside to Probe the Effects of Ligand Orientation in Bacterial Adhesion.

We have recently demonstrated, by employing azobenzene glycosides, that bacterial adhesion to surfaces can be switched through reversible reorientation of the carbohydrate ligands. To investigate this phenomenon further, we have turned here to more complex-that is, multivalent-azobenzene glycoclusters. We report on the synthesis of a photosensitive trivalent cluster mannoside conjugated to an azobenzene hinge at the focal point. Molecular dynamics studies suggested that this cluster mannoside, despite the conformational flexibility of the azobenzene-glycocluster linkage, offers the potential for reversibly changing the glycocluster's orientation on a surface. Next, the photoswitchable glycocluster was attached to human cells, and adhesion assays with type 1 fimbriated Escherichia coli bacteria were performed. They showed marked differences in bacterial adhesion, dependent on the light-induced reorientation of the glycocluster moiety. These results further underline the importance of orientational effects in carbohydrate recognition and likewise the value of photoswitchable glycoconjugates for their study.

Efficacy of UV-TiO2 photocatalysis technology for inactivation of Escherichia coli K12 on the surface of blueberries and a model agar matrix and the influence of surface characteristics.

Surface disinfection of fresh blueberries is an important food safety challenge due to the delicate texture and short shelf life of these small fruits. A newly designed water-assisted photocatalytic reactor was developed for disinfection of fruits with a delicate texture and complex surface characteristics. Efficacy of UV-TiO2 photocatalysis was evaluated in comparison with UV alone for inactivation of Escherichia coli K12 (as a surrogate for Escherichia coli O157:H7) inoculated onto the surface of the blueberry skin, calyx, and an experimentally prepared agar matrix that was used as a model matrix. Influence of surface characteristics such as surface hydrophobicity and surface free energy on bacterial adhesion were also investigated. The initial bacterial population on all surfaces was approximately 7.0 log CFU/g. UV-TiO2 photocatalysis (4.5 mW/cm2) for 30 s achieved comparatively higher bacterial reductions of 5.3 log and 4.6 log CFU/g on blueberry skin and agar matrix surfaces, respectively, than 4.5 log and 3.4 log CFU/g reductions for UV alone (6.0 mW/cm2). Total phenolic and total anthocyanin contents of fruits were significantly increased after both UV-TiO2 and UV treatments, compared with water washed control fruits. UV-TiO2 photocatalysis technology is a non-chemical and residue-free method with reduced water usage for surface disinfection of fresh blueberries.

Characterization of Pseudomonas aeruginosa Films on Different Inorganic Surfaces before and after UV Light Exposure.

The changes of the surface properties of Au, GaN, and SiO x after UV light irradiation were used to actively influence the process of formation of Pseudomonas aeruginosa films. The interfacial properties of the substrates were characterized by X-ray photoelectron spectroscopy and atomic force microscopy. The changes in the P. aeruginosa film properties were accessed by analyzing adhesion force maps and quantifying the intracellular Ca2+ concentration. The collected analysis indicates that the alteration of the inorganic materials' surface chemistry can lead to differences in biofilm formation and variable response from P. aeruginosa cells.

Th17 activation by dendritic cells stimulated with gamma-irradiated Streptococcus pneumoniae.

Dendritic cells (DCs) play an important role in antigen presentation, which is an essential step for the induction of antigen-specific adaptive immunity. Inactivated bacterial whole cell vaccines have been widely used to prevent many bacterial infections because they elicit good immunogenicity due to the presence of various antigens and are relatively inexpensive and easy to manufacture. Recently, gamma-irradiated whole cells of nonencapsulated Streptococcus pneumoniae were developed as a broad-spectrum and serotype-independent multivalent vaccine. In the present study, we generated gamma-irradiated S. pneumoniae (r-SP) and investigated its capacity to stimulate mouse bone marrow-derived DCs (BM-DCs) in comparison with heat-inactivated and formalin-inactivated S. pneumoniae (h-SP and f-SP, respectively). r-SP showed an attenuated binding and internalization level to BM-DCs when compared to h-SP or f-SP. r-SP weakly induced the expression of CD80, CD83, CD86, MHC class I, and PD-L2 compared with h-SP or f-SP. Furthermore, r-SP less potently induced IL-6, TNF-α, and IL-23 expression than h-SP or f-SP but more potently induced IL-1ß expression than h-SP or f-SP in BM-DCs. Since Th17-mediated immune responses are known to be important for the protection against pneumococcal infections, r-SP-primed DCs were co-cultured with splenocytes or splenic CD4+ T cells. Interestingly, r-SP-sensitized BM-DCs markedly induced IL-17A+ CD4+ T cells whereas h-SP- or f-SP-sensitized BM-DCs weakly induced them. Collectively, these results suggest that r-SP could be an effective pneumococcal vaccine candidate eliciting Th17-mediated immune responses by stimulation of DCs.

Biofilm Lithography enables high-resolution cell patterning via optogenetic adhesin expression.

Bacterial biofilms represent a promising opportunity for engineering of microbial communities. However, our ability to control spatial structure in biofilms remains limited. Here we engineer Escherichia coli with a light-activated transcriptional promoter (pDawn) to optically regulate expression of an adhesin gene (Ag43). When illuminated with patterned blue light, long-term viable biofilms with spatial resolution down to 25 µm can be formed on a variety of substrates and inside enclosed culture chambers without the need for surface pretreatment. A biophysical model suggests that the patterning mechanism involves stimulation of transiently surface-adsorbed cells, lending evidence to a previously proposed role of adhesin expression during natural biofilm maturation. Overall, this tool-termed "Biofilm Lithography"-has distinct advantages over existing cell-depositing/patterning methods and provides the ability to grow structured biofilms, with applications toward an improved understanding of natural biofilm communities, as well as the engineering of living biomaterials and bottom-up approaches to microbial consortia design.

Surface roughness and bacterial adhesion on root dentin treated with diode laser and conventional desensitizing agents.

The treatments for dentin hypersensitivity (DH) may change the surface roughness of the root dentin, which can lead to biofilm accumulation, increasing the risk of root caries. The aim was to compare the surface roughness of root dentin after different treatments of DH and the biofilm formation on those surfaces. After initial surface roughness (Sa) assessment, 50 bovine root fragments received the following treatments (n = 10): G 1-no treatment; G2-5% sodium fluoride varnish; G3-professional application of a desensitizing dentifrice; G4-toothbrushing with a desensitizing dentifrice; and G5-diode laser application (908 nm; 1.5 W, 20 s). The Sa was reevaluated after treatments. Afterward, all samples were incubated in a suspension of Streptococcus mutans at 37 °C for 24 h. The colony-forming units (CFU) were counted using a stereoscope, and the results were expressed in CFU/mL. The one-way ANOVA and the Tukey's tests compared the roughness data and the results obtained on the bacterial adhesion test (α = 5%). G2 (2.3 ± 1.67%) showed similar Sa variation than G1 (0.25 ± 0.41%) and G5 (5.69 ± 0.99%), but different from group G3 (9.05 ± 2.39%). Group 4 showed the highest Sa variation (30.02 ± 3.83%; p < 0.05). Bacterial adhesion was higher in G4 (2208 ± 211.9), suggesting that bacterial growth is greater on rougher surfaces. The diode laser and the conventional treatments for DH may change the surface roughness of the root dentin, but only brushing with desensitizing dentifrice induced a higher bacteria accumulation on root dentin surface.

Blue Light Switchable Bacterial Adhesion as a Key Step toward the Design of Biofilms.

The control of where and when bacteria adhere to a substrate is a key step toward controlling the formation and organization in biofilms. This study shows how we engineer bacteria to adhere specifically to substrates with high spatial and temporal control under blue light, but not in the dark, by using photoswitchable interaction between nMag and pMag proteins. For this, we express pMag proteins on the surface of E. coli so that the bacteria can adhere to substrates with immobilized nMag protein under blue light. These adhesions are reversible in the dark and can be repeatedly turned on and off. Further, the number of bacteria that can adhere to the substrate as well as the attachment and detachment dynamics are adjustable by using different point mutants of pMag and altering light intensity. Overall, the blue light switchable bacteria adhesions offer reversible, tunable and bioorthogonal control with exceptional spatial and temporal resolution. This enables us to pattern bacteria on substrates with great flexibility.

In Vitro Laser Treatment Platform Construction with Dental Implant Thread Surface on Bacterial Adhesion for Peri-Implantitis.

This study constructs a standard in vitro laser treatment platform with dental implant thread surface on bacterial adhesion for peri-implantitis at different tooth positions. The standard clinical adult tooth jaw model was scanned to construct the digital model with 6 mm bone loss depth on behalf of serious peri-implantitis at the incisor, first premolar, and first molar. A cylindrical suite connected to the implant and each tooth root in the jaw model was designed as one experimental unit set to allow the suite to be replaced for individual bacterial adhesion. The digital peri-implantitis and suite models were exported to fulfill the physical model using ABS material in a 3D printer. A 3 mm diameter specimen implant on bacterial adhesion against Escherichia coli was performed for gram-negative bacteria. An Er:YAG laser, working with a chisel type glass tip, was moved from the buccal across the implant thread to the lingual for about 30 seconds per sample to verify the in vitro laser treatment platform. The result showed that the sterilization rate can reach 99.3% and the jaw model was not damaged after laser irradiation testing. This study concluded that using integrated image processing, reverse engineering, CAD system, and a 3D printer to construct a peri-implantitis model replacing the implant on bacterial adhesion and acceptable sterilization rate proved the feasibility of the proposed laser treatment platform.

Effect of ultraviolet treatment on bacterial attachment and osteogenic activity to alkali-treated titanium with nanonetwork structures.

PURPOSE: Alkali-treated titanium with nanonetwork structures (TNS) possesses good osteogenic activity; however, the resistance of this material to bacterial contamination remains inadequate. As such, TNS implants are prone to postoperative infection. In this work, we attempted to alter the biological properties of TNS by treatment with short-duration high-intensity ultraviolet (UV) irradiation. METHODS: TNS discs were treated with UV light (wavelength =254 nm, strength =100 mW/cm2) for 15 minutes using a UV-irradiation machine. We carried out a surface characterization and evaluated the discs for bacterial film formation, protein adsorption, and osteogenic features. RESULTS: The superhydrophilicity and surface hydrocarbon elimination exhibited by the treated material (UV-treated titanium with a nanonetwork structure [UV-TNS]) revealed that this treatment effectively changed the surface characteristics of TNS. Notably, UV-TNS also showed reduced colonization by Actinomyces oris during an initial attachment period and inhibition of biofilm formation for up to 6 hours. Moreover, compared to conventional TNS, UV-TNS showed superior osteogenic activity as indicated by increased levels of adhesion, proliferation, alkaline phosphatase activity, osteogenic factor production, and osteogenesis-related gene expression by rat bone marrow mesenchymal stem cells (rBMMSCs). This inverse relationship between bacterial attachment and cell adhesion could be due to the presence of electron-hole pairs induced by high-intensity UV treatment. CONCLUSION: We suggest that simple UV treatment has great clinical potential for TNS implants, as it promotes the osseointegration of the TNS while reducing bacterial contamination, and can be conducted chair-side immediately prior to implantation.

Evaluation of Surface Roughness and Bacterial Adhesion on Tooth Enamel Irradiated With High Intensity Lasers.

The aim was to evaluate the surface roughness and bacterial adhesion on enamel irradiated with high intensity lasers, associated or not to a fluoride varnish. Eighty fragments of bovine enamel were equally divided in 8 groups (n=10). Group 1 was not treated and Group 2 received only a 5% fluoride varnish application. The other groups were irradiated with an Er:Cr:YSGG (8.92 J/cm2), an Nd:YAG (84.9 J/cm2) and a diode laser (199.04 J/cm2), associated or not to a 5% fluoride varnish. The surface roughness was measured before and after treatments. Afterward, all samples were incubated in a suspension of S. mutans at 37 °C for 24 h. The colony-forming units (CFU) were counted by a stereoscope and the results were expressed in CFU/mm2. One-way ANOVA and the Tukey´s test compared the roughness data and the Student´s test compared the results obtained in the bacterial adhesion test (a=5%). The results showed that the irradiated samples without varnish presented the same roughness and the same bacterial adhesion that the non-irradiated samples. However, samples irradiated in the presence of fluoride varnish showed higher surface roughness and higher bacterial adhesion than the non-irradiated samples and those irradiated without varnish. Presence of pigments in the varnish increased the lasers' action on the enamel surface, which produced ablation in this hard tissue and significantly increased its surface roughness. For this reason, the enamel's susceptibility to bacterial adhesion was higher when the irradiation of the samples was made in presence of fluoride varnish.

Evaluation of Surface Roughness and Bacterial Adhesion on Tooth Enamel Irradiated With High Intensity Lasers

Abstract The aim was to evaluate the surface roughness and bacterial adhesion on enamel irradiated with high intensity lasers, associated or not to a fluoride varnish. Eighty fragments of bovine enamel were equally divided in 8 groups (n=10). Group 1 was not treated and Group 2 received only a 5% fluoride varnish application. The other groups were irradiated with an Er:Cr:YSGG (8.92 J/cm2), an Nd:YAG (84.9 J/cm2) and a diode laser (199.04 J/cm2), associated or not to a 5% fluoride varnish. The surface roughness was measured before and after treatments. Afterward, all samples were incubated in a suspension of S. mutans at 37 °C for 24 h. The colony-forming units (CFU) were counted by a stereoscope and the results were expressed in CFU/mm2. One-way ANOVA and the Tukey´s test compared the roughness data and the Student´s test compared the results obtained in the bacterial adhesion test (a=5%). The results showed that the irradiated samples without varnish presented the same roughness and the same bacterial adhesion that the non-irradiated samples. However, samples irradiated in the presence of fluoride varnish showed higher surface roughness and higher bacterial adhesion than the non-irradiated samples and those irradiated without varnish. Presence of pigments in the varnish increased the lasers’ action on the enamel surface, which produced ablation in this hard tissue and significantly increased its surface roughness. For this reason, the enamel’s susceptibility to bacterial adhesion was higher when the irradiation of the samples was made in presence of fluoride varnish.

Resumo O objetivo foi avaliar a rugosidade superficial e adesão bacteriana no esmalte dental irradiado com lasers de alta intensidade, associados ou não a um verniz fluoretado. Oitenta fragmentos de esmalte foram igualmente divididos em 8 grupos (n= 10). O grupo 1 não recebeu tratamento e o grupo 2 recebeu aplicação de verniz fluoretado a 5%. Os outros grupos foram irradiados com os lasers Er,Cr:YSGG (8,92 J/cm2), Nd:YAG (84,9 J/cm2) e um laser de diodo (199,04 J/cm2), associados ou não ao verniz fluoretado. A rugosidade superficial foi medida antes e após os tratamentos. Depois, todas as amostras foram imersas em suspensão de S. mutans a 37 °C durante 24 h. As unidades formadoras de colônia (UFC) foram contadas utilizando uma lupa estereoscópica, e os resultados foram expressos em UFC/mm2. Os resultados de rugosidade foram analisados por ANOVA e pelo teste de Tukey, e a adesão bacteriana foi analisada pelo teste de Student (a=5%). As amostras irradiadas sem verniz apresentaram a mesma rugosidade superficial e a mesma adesão bacteriana que as amostras não irradiadas. No entanto, as amostras irradiadas na presença do verniz fluoretado apresentaram maior rugosidade superficial e aderência bacteriana do que as amostras não irradiadas e daquelas irradiadas sem o verniz. A presença de pigmentos no verniz aumentou a ação dos lasers na superfície do esmalte, promovendo a ablação do tecido duro e aumentando significativamente a sua rugosidade superficial. Por isso, a adesão bacteriana no esmalte foi maior quando a irradiação foi realizada na presença do verniz fluoretado.

Impact of combined CO2 laser irradiation and fluoride on enamel and dentin biofilm-induced mineral loss.

OBJECTIVES: The caries-protective effects of CO2 laser irradiation on dental enamel have been demonstrated using chemical demineralization models. We compared the effect of CO2 laser irradiation, sodium fluoride, or both on biofilm-induced mineral loss (∆Z) and Streptococcus mutans adhesion to enamel and dentin in vitro. MATERIALS AND METHODS: Ground, polished bovine enamel, and dentin samples were allocated to four groups (n = 12/group): no treatment (C); single 22,600-ppm fluoride (F) varnish (5 % NaF) application; single CO2 laser treatment (L) with short pulses (5 µs/λ = 10.6 µm); and laser and subsequent fluoride treatment (LF). Samples were sterilized and submitted to an automated mono-species S. mutans biofilm model. Brain heart infusion plus 5 % sucrose medium was provided eight times daily, followed by rinses with artificial saliva. After 10 days, bacterial numbers in biofilms were enumerated as colony-forming units/ml (CFU/ml) (n = 7/group). ∆Z was assessed using transversal microradiography (n = 12/group). Univariate ANOVA with post hoc Tukey honestly-significant-difference test was used for statistical analysis. RESULTS: Bacterial numbers were significantly higher on dentin than enamel (p < 0.01/ANOVA). On dentin, LF yielded significantly lower CFUs than other groups (p = 0.03/Tukey), while no differences between groups were found for enamel. The lowest ∆Z in enamel was observed for L (mean/SD 2036/1353 vol%×µm), which was not only significantly lower than C (9642/2452 vol%×µm) and F (7713/1489 vol%×µm) (p < 0.05) but also not significantly different from LF (3135/2628 vol%×µm) (p > 0.05). In dentin, only LF (163/227) significantly reduced ∆Z (p < 0.05). CONCLUSION/CLINICAL RELEVANCE: CO2 laser irradiation did not increase adhesion of S. mutans in vitro. Laser treatment alone protected enamel against biofilm-induced demineralization, while a combined laser-fluoride application was required to protect dentin.

Fabricating upconversion fluorescent nanoparticles modified substrate for dynamical control of cancer cells and pathogenic bacteria.

Lanthanide-doped upconversion nanoparticles (UCNPs) have attracted widespread interests in the field of biomedicine because of their unique upconverting capability by converting near infrared (NIR) excitation to visible or ultraviolet (UV) emission. Here, we developed a novel UCNP-based substrate for dynamic capture and release of cancer cells and pathogenic bacteria under NIR-control. The UCNPs harvest NIR light and convert it to ultraviolet light, which subsequently result in the cleavage of photoresponsive linker (PR linker) from the substrate, and on demand allows the release of a captured cell. The results show that after seeding cells for 5 h, the cells were efficiently captured on the surface of the substrate and ˜89.4% of the originally captured S. aureus was released from the surface after exposure to 2 W/cm2 NIR light for 30 min, and ˜92.1% of HepG2 cells. These findings provide a unique platform for exploring an entirely new application field for this promising luminescent nanomaterial.