Luciana S. A. de Melo

Random laser action from flexible biocellulose-based device

We demonstrate random lasing action in flexible bacterial cellulose (BC) membrane containing a laser-dye and either dielectric or metallic nanoparticles (NPs). The novel random laser system consists of BC nanofibers attached with Rhodamine 6G molecules and having incorporated either silica or silver NPs. The laser action was obtained by excitation of the samples with a 6 ns pulsed laser at 532 nm. Minimum laser threshold of ≈0.7 mJ/pulse was measured for the samples with silica NPs, whereas a laser threshold of 2.5 mJ/pulse for a system based on silver NPs was obtained. In both cases a linewidth narrowing from ≈50 to ≈4 nm was observed. Potential applications in biophotonics and life sciences are discussed for this proof-of-concept device.

Silk fibroin biopolymer films as efficient hosts for DFB laser operation

Biopolymer hosts can be successfully used for the fabrication of multifunctional photonic devices due to their good optical properties, biocompatibility, remarkable mechanical properties and a wealth of chemical functionalization. Particularly, the silk fibroin (SF) biopolymer presents a wide range of suitable properties for photonic applications that were not fully exploited. In the present work, we demonstrate the operation of a distributed feedback (DFB) laser based on SF films doped with Rhodamine 6G (Rh6G) dye and films containing Rh6G and silica or silver nanoparticles. The SF grating structures were fabricated using a commercial blank digital versatile disc (DVD) as the template. The addition of silica or silver nanoparticles to the SF film led to enhanced emission due to the multiple scattering of light by the silica nanoparticles and a reduction of the emission linewidth. The laser wavelength was centered between ≈560 and ≈575 nm corresponding to the fourth-order diffraction of a 750 nm period of the SF grating. The results show that regenerated SF films are promising matrices for DFB lasers because of the excellent optical quality and large potential for biomedicine regarding biocompatibility and benign processing conditions.

Photodynamic inactivation assisted by localized surface plasmon resonance of silver nanoparticles: In vitro evaluation on Escherichia coli and Streptococcus mutans

Localized surface plasmon resonance (LSPR) of gold nanoparticles has been reported to increase the antimicrobial effect of the photodynamic therapy. Although silver nanoparticles (AgNPs) are an efficient growth inhibitor of microorganisms, no studies exploring LSPR of AgNPs to enhance the photodynamic inactivation (PDI) have been related. In this work, we described the LSPR phenomenon of AgNP sand investigated its interaction with riboflavin, a natural photosensitizer. We evaluated the use of AgNPs coated with pectin (p-AgNP) in riboflavin (Rb)-mediated PDI of Escherichia coli (Gram- bacteria) and Streptococcus mutans (Gram + bacteria) using a blue light-emitting diode (λ = 455 ± 20 nm) of optical power 200 mW. Irradiance was 90 mW/cm2 and radiant exposure varied according to the time exposure. Uptake of Rb and p-AgNP by the cells was evaluated by measuring the supernatant absorption spectra of the samples. We observed that LSPR of p-AgNPs was able to enhance the riboflavin photodynamic action on S. mutans but not on E. coli, probably due to the lower uptake of Rb by E. coli. Taken together, our results provide insights to explore the use of the LPRS promoted by silver nanostructures to optimize antimicrobial PDI protocols.

Comparative analysis of gingival phenotype in animal and human experimental models using optical coherence tomography in a non-invasive approach

Imaging methods are widely used in diagnostic and among the diversity of modalities, optical coherence tomography (OCT) is nowadays commercially available and considered the most innovative technique used for imaging applications, in both medical and non-medical applications. In this study, we exploit the OCT technique in the oral cavity for identification and differentiation between free and attached gingiva, as well as determining the gingival phenotype, an important factor to determination of periodontal prognosis in patients. For the animal studies, five porcine jaws were analyzed using a Swept Source SS-OCT system operating at 1325nm and stereomicroscope, as gold pattern. The SSOCT at 1325nm was chosen due to the longer central wavelength, that allows to deeper penetration imaging, and the faster image acquisition, an essential factor for clinical setting. For the patient studies, a total of 30 males and female were examined using the SS-OCT at 1325nm and computer controlled periodontal probing. 2D and 3D images of tooth/gingiva interface were performed, and quantitative measurements of the gingival sulcus could be noninvasively obtained. Through the image analysis of the animals jaws, it was possible to quantify the free gingiva and the attached gingiva, the calculus deposition over teeth surface and also the subgingival calculus. For the patient’s studies, we demonstrated that the gingival phenotype could be measured without the periodontal probe introduction at the gingival sulcus, confirming that OCT can be potentially useful in clinic for direct observation and quantification of gingival phenotype in a non-invasive approach.

Optical coherence tomography as a method for quantitative skin evaluation in systemic sclerosis

Improved, non-invasive techniques for the diagnosis, classification and monitoring of patients with systemic sclerosis (SSc) are needed. One potential technique for quantifying the extent of cutaneous sclerosis in these patients is optical coherence tomography (OCT).1 ,2 Recently, Abignano et al 3 suggested the use of OCT as a feasible and reliable technique to evaluate skin fibrosis in SSc. Based on that initial work, the aim of this study was to evaluate OCT images and compare the findings with the modified Rodnan skin score (mRSS) in patients with SSc. Thirty-three Brazilian patients with SSc (28 women; mean age 46.1 years; range 19–71 years) were recruited and fulfilled criteria for SSc proposed by American College of Rheumatology (ACR), 19804 or ACR/European League Against Rheumatism, 2013.5 Patients were classified into limited SSc (n=18) and diffuse SSc (n=15) groups. The mean disease duration was 9.7 years (median 8 years, range 2–26 months). Thirty-five healthy control (HC) (28 women, …

Non-invasive diagnostic and monitoring of periodontal disease through optical coherence tomography: validation of the technique with animal model and patients

We propose the application of optical coherence tomography as an auxiliary tool for periodontal disease diagnostic, and demonstrated in three stages: animal modeling, healthy patients and follow up of disease regression upon treatment.

Monitoring the gingival regeneration after aesthetic surgery with optical coherence tomography

The aim of this study was to use the Optical Coherence Tomography (OCT) technique working in spectral domain (Swept Source OCT at 1325 nm, Thorlabs, New Jersey, USA) to monitor the tissue repair in patients undergoing periodontal plastic surgery. The evaluations were done over a period of 60 days. It was observed that 15 days after periodontal surgery the gum was still in different healing process as compared to the observation after 60 days. Thus it is clear that, despite some technical limitations, the OCT is an efficient method in the evaluation of regeneration gingival.

Optical coherence tomography investigations of ceramic lumineers

Lumineers are veneer laminates used as an alternative for aesthetic dental solutions of the highest quality, but the only current means of its performance assessment is visual inspection. The objective of this study was to use the Optical Coherence Tomography (OCT) technique working in spectral domain to analyze in vivo in a single patient, 14 lumineers 180 days after cementation. It was possible to observe images in various kinds of changes in the cementing line and the laminate. It was concluded that the OCT is an effective and promising method to clinical evaluation of the cementing line in lumineers.

Influence of Ag Nanoparticles Density on the Enhancement of Random Laser Emission from PMMA Thin Films Doped with Rh6g Dye

We study the dependence of random laser emission from thin polymer films doped with Rh6G using Ag nanoparticles in several concentrations. We demonstrate that a higher optical gain for lasing is obtained via surface-plasmon resonance.