Evaluation of the Antibacterial Activity of New Dermaseptin Derivatives against Acinetobacter baumannii.

Nosocomial infections represent one of the biggest health problems nowadays. Acinetobacter baumannii is known as an opportunistic pathogen in humans, affecting people with compromised immune systems, and is becoming increasingly important as a hospital-derived infection. It is known that in recent years, more and more bacteria have become multidrug-resistant (MDR) and, for this reason, the development of new drugs is a priority. However, these products must not affect the human body, and therefore, cytotoxicity studies are mandatory. In this context, antimicrobial peptides with potential antibacterial proprieties could be an alternative. In this research, we describe the synthesis and the bioactivity of dermaseptins and their derivatives against Acinetobacter baumannii. The cytotoxicity of these compounds was investigated on the HEp-2 cell line by MTT cell viability assay. Thereafter, we studied the morphological alterations caused by the action of one of the active peptides on the bacterial membrane using atomic force microscopy (AFM). The cytotoxicity of dermaseptins was concentration-dependent at microgram concentrations. It was observed that all tested analogs exhibited antibacterial activity with Minimum Inhibitory Concentrations (MICs) ranging from 3.125 to 12.5 µg/mL and Minimum Bactericidal Concentrations (MBCs) ranging from 6.25 to 25 µg/mL. Microscopic images obtained by AFM revealed morphological changes on the surface of the treated bacteria caused by K4S4(1-16), as well as significant surface alterations. Overall, these findings demonstrate that dermaseptins might constitute new lead structures for the development of potent antibacterial agents against Acinetobacter baumannii infections.

Antibacterial and antifungal activity of curcumin and methylene blue associated with laser on bacterial and fungal strains

Objective:To analyze the effect of methylene blue and 10% curcumin in fungi and bacteria through an in vitrostudy using photodynamic therapy (PDT). Methods:Curcumin and methylene blue were photosensitized by a Photon Lase III laser applied for 90 s in a dark environment within a laminar flow chamber. Enterococcus faecalisand Candida albicans strains were cultured and standardized.Then, a minimum inhibitoryconcentration (MIC) assay was conducted for these photosensitizers, with concentration variations and incubation to evaluate their antimicrobial activity. Results:With PDT, Curcumin had significant antibacterial activity against E. faecalis (MIC = 250 µg/mL).In contrast, methylene blue had antibacterial activity against E. faecalis (MIC < 12.5 µg/mL with PDT) and antifungal activity against C. albicans (MIC <12.5 µg/mL with or without PDT).Both agents showed greater efficacy in the presence of the laser.The results suggest that curcumin and methylene blue associated with laser may effectively treat microbial infections. Conclusion:Further research is needed to evaluate the efficacy and safety of using these agents in animal and human models and theireffectiveness against different bacterial and fungal strains.

Natural cordiaquinones as strategies to inhibit the growth and biofilm formation of methicillin-sensitive and methicillin-resistant Staphylococcus spp.

AIMS: The aim of this study was to investigate the antibacterial and antibiofilm potential of cordiaquinones B, E, L, N, and O against different Staphylococci strains, in addition to analyzing in silico the observed effect. METHODS AND RESULTS: The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were determined according to CLSI guidelines. The inhibition of biofilm formation was investigated at sub-MICs. Atomic force microscopy (AFM) and density functional theory method were performed. The tested strains of Staphylococcus spp. were susceptible to cordiaquinones B, E, and L, among which cordiaquinone B exerted a bactericidal effect, confirmed by a bacterial growth curve study, against Staphylococcus saprophyticus. Cordiaquinones B and E showed lowest MBC values against S. saprophyticus. AFM revealed that cordiaquinone L reduced the mean cell size of S. saprophyticus. Cordiaquinones B and E inhibited the biofilm formation ability of S. aureus by ∼90%. The in silico analysis suggested that the antimicrobial activity of cordiaquinones is driven by their electron donation capability. CONCLUSIONS: Cordiaquinones inhibit the growth and biofilm formation (virulence factor) of both methicillin-sensitive and methicillin-resistant Staphylococci strains, indicating their antimicrobial potential.

Cytotoxic and Antileishmanial Effects of the Monoterpene ß-Ocimene.

Leishmaniasis is a group of infectious-parasitic diseases with high mortality rates, and endemic in many regions of the globe. The currently available drugs present serious problems such as high toxicity, costs, and the emergence of drug resistance. This has stimulated research into new antileishmania drugs based on natural products and their derivatives. ß-Ocimene is a monoterpene found naturally in the essential oils of many plant species which presents antileishmanial activity, and which has not yet been evaluated for its potential to inhibit the etiological agent of leishmaniasis. The aim of this work was to evaluate the activity of ß-ocimene against Leishmania amazonensis, its cytotoxicity, and potential mechanisms of action. ß-Ocimene presented direct activity against the parasite, with excellent growth inhibition of promastigotes (IC50 = 2.78 µM) and axenic amastigotes (EC50 = 1.12 µM) at concentrations non-toxic to RAW 264.7 macrophages (CC50 = 114.5 µM). The effect is related to changes in membrane permeability and resulting abnormalities in the parasitic cell shape. These were, respectively, observed in membrane integrity and atomic force microscopy assays. ß-Ocimene was also shown to act indirectly, with greater activity against intra-macrophagic amastigotes (EC50 = 0.89 µM), increasing TNF-α, nitric oxide (NO), and reactive oxygen species (ROS), with lysosomal effects, as well as promoting decreases in IL-10 and IL-6. Against intra-macrophagic amastigote forms the selectivity index was higher than the reference drugs, being 469.52 times more selective than meglumine antimoniate, and 42.88 times more selective than amphotericin B. Our results suggest that ß-ocimene possesses promising in vitro antileishmania activity and is a potential candidate for investigation in in vivo assays.

DOPE/CHEMS-Based EGFR-Targeted Immunoliposomes for Docetaxel Delivery: Formulation Development, Physicochemical Characterization and Biological Evaluation on Prostate Cancer Cells.

Docetaxel (DTX) is a non-selective antineoplastic agent with low solubility and a series of side effects. The technology of pH-sensitive and anti-epidermal growth factor receptor (anti-EGFR) immunoliposomes aims to increase the selective delivery of the drug in the acidic tumor environment to cells with EFGR overexpression. Thus, the study aimed to develop pH-sensitive liposomes based on DOPE (dioleoylphosphatidylethanolamine) and CHEMS (cholesteryl hemisuccinate), using a Box-Behnken factorial design. Furthermore, we aimed to conjugate the monoclonal antibody cetuximab onto liposomal surface, as well as to thoroughly characterize the nanosystems and evaluate them on prostate cancer cells. The liposomes prepared by hydration of the lipid film and optimized by the Box-Behnken factorial design showed a particle size of 107.2 ± 2.9 nm, a PDI of 0.213 ± 0.005, zeta potential of -21.9 ± 1.8 mV and an encapsulation efficiency of 88.65 ± 20.3%. Together, FTIR, DSC and DRX characterization demonstrated that the drug was properly encapsulated, with reduced drug crystallinity. Drug release was higher in acidic pH. The liposome conjugation with the anti-EGFR antibody cetuximab preserved the physicochemical characteristics and was successful. The liposome containing DTX reached an IC50 at a concentration of 65.74 nM in the PC3 cell line and 28.28 nM in the DU145 cell line. Immunoliposome, in turn, for PC3 cells reached an IC50 of 152.1 nM, and for the DU145 cell line, 12.60 nM, a considerable enhancement of cytotoxicity for the EGFR-positive cell line. Finally, the immunoliposome internalization was faster and greater than that of liposome in the DU145 cell line, with a higher EGFR overexpression. Thus, based on these results, it was possible to obtain a formulation with adequate characteristics of nanometric size, a high encapsulation of DTX and liposomes and particularly immunoliposomes containing DTX, which caused, as expected, a reduction in the viability of prostate cells, with high cellular internalization in EGFR overexpressing cells.

Lemon gum: Non-toxic arabinogalactan isolated from Citrus × latifolia with antiproliferative property against human prostate adenocarcinoma cells.

Lemon gum (LG) obtained from Citrus × latifolia in Brazil was isolated and characterized. In addition, gum biocompatibility was evaluated in vitro and in vivo by Galleria mellonella and mice model. The cytotoxicity against tumor cells was also evaluated. The ratio of arabinose:galactose: rhamnose:4-OMe-glucuronic acid was 1:0.65:0.06:0.15. Small traces of protein were detected, emphasizing the isolate purity. Molar mass was 8.08 × 105 g/mol, with three different degradation events. LG showed antiproliferative activity against human prostate adenocarcinoma cancer cells, with percentage superior to 50 %. In vivo toxicity models demonstrated that LG is biocompatible polymer, with little difference in the parameters compared to control group. These results demonstrate advance in the study of LG composition and toxicity, indicating a potential for several biomedical and biotechnological future applications.

Nanoemulsion of cashew gum and clove essential oil (Ocimum gratissimum Linn) potentiating antioxidant and antimicrobial activity.

In this study, nanoemulsions of essential oil from Ocimumgratissimum (Linn) (EO) were produced using low and high energy techniques using cashew gum (CG) as a co-surfactant. The main constituents of the EO were determined by Gas Chromatography coupled with Mass Spectrometry (GC-MS), and their presence in the EO and in the formulations verified by Fourier Transform Infrared Spectroscopy (FTIR) and UV-visible spectrophotometry was observed the encapsulation efficiency (EE%), with colloidal stability. Nuclear magnetic resonance (NMR) was used to study cashew gum. Dynamic light scattering analysis (DLS) determined the nanoemulsion Z means, polydispersity index and the Zeta potential value, nanoparticle tracking analysis (NTA) were determined. The nanostructured EO showed better antibacterial action against the pathogenic gastroenteritis species Staphylococcus aureus, Escherichia coli and Salmonella enterica when compared to free EO. Atomic Force Microscopy (AFM) was used for morphological analysis of the nanoparticle and study of the action of the nanoemulsion through images of the cellular morphology of S. enterica. The antioxidant activity was evaluated against the ABTS radical (2,2'-azino-bis diazonium salt (3-ethylbenzothiazoline-6-sulfonic acid)). The encapsulation of EO in a nanostructured system improved its antibacterial and antioxidant activity, the low energy synthesis showed greater storage stability, remaining stable for 37 days.

Curzerene antileishmania activity: Effects on Leishmania amazonensis and possible action mechanisms.

Leishmaniasis is a set of infectious diseases with high rates of morbidity and mortality, it affects millions of people around the world. Treatment, mainly with pentavalent antimonials, presents significant toxicity and many cases of resistance. In previous works we have demonstrated the effective and selective antileishmanial activity of Eugenia uniflora L. essential oil, being constituted (47.3%) by the sesquiterpene curzerene. Considering the high rate of parasite inhibition demonstrated for E. uniflora essential oil, and the significant presence of curzerene in the oil, this study aimed to evaluate its antileishmania activity and possible mechanisms of action. Curzerene was effective in inhibiting the growth of promastigotes (IC50 3.09 ± 0.14 µM) and axenic amastigotes (EC50 2.56 ± 0.12 µM), with low cytotoxicity to RAW 264.7 macrophages (CC50 83.87 ± 4.63 µM). It was observed that curzerene has direct effects on the parasite, inducing cell death by apoptosis with secondary necrotic effects (producing pores in the plasma membrane). Curzerene proved to be even more effective against intra-macrophage amastigote forms, with an EC50 of 0.46 ± 0.02 µM. The selectivity index demonstrated by curzerene on these parasite forms was 182.32, being respectively 44.15 and 8.47 times more selective than meglumine antimoniate and amphotericin B. The antiamastigote activity of curzerene was associated with immunomodulatory activity, as it increased TNF-α, IL-12, and NO levels, and lysosomal activity, and decreased IL-10 and IL-6 cytokine levels detected in macrophages infected and treated. In conclusion, our results demonstrate that curzerene is an effective and selective antileishmanial agent, a candidate for in vivo investigation in models of antileishmanial activity.

Acetylated cashew gum and fucan for incorporation of lycopene rich extract from red guava (Psidium guajava L.) in nanostructured systems: Antioxidant and antitumor capacity.

Industrial application of lycopene is limited due to its chemical instability and low bioavailability. This study proposes the development of fucan-coated acetylated cashew gum nanoparticles (NFGa) and acetylated cashew gum nanoparticles (NGa) for incorporation of the lycopene-rich extract from red guava (LEG). Size, polydispersity, zeta potential, nanoparticles concentration, encapsulation efficiency, transmission electron microscopy (TEM) and atomic force microscopy (AFM) were used to characterize nanoparticles. The antioxidant activity was determinated and cell viability was evaluated in the human breast cancer cells (MCF-7) and human keratinocytes (HaCaT) by MTT assay. The toxic effect was evaluated by hemolysis test and by Galleria mellonella model. NFGa showed higher stability than NGa, having a size of 162.10 ± 3.21 nm, polydispersity of 0.348 ± 0.019, zeta potential -30.70 ± 0.53 mV, concentration of 6.4 × 109 nanoparticles/mL and 60% LEG encapsulation. Microscopic analysis revealed a spherical and smooth shape of NFGa. NFGa showed antioxidant capacity by ABTS method and ORAC assay. The NFGa presented significant cytotoxicity against MCF-7 from the lowest concentration tested (6.25-200 µg/mL) and did not affect the cell viability of the HaCaT. NFGa showed non-toxic effect in the in vitro and in vivo models. Therefore, NFGa may have a promising application in LEG stabilization for antioxidant and antitumor purposes.

Human Mesenchymal Stem Cells Seeded on the Natural Membrane to Neurospheres for Cholinergic-like Neurons.

This study aimed to differentiate human mesenchymal stem cells (hMSCs) from the human umbilical cord in cholinergic-like neurons using a natural membrane. The isolation of hMSCs from Wharton's jelly (WJ) was carried out using "explant" and mononuclear cells by the density gradient from umbilical blood and characterized by flow cytometry. hMSCs were seeded in a natural functional biopolymer membrane to produce neurospheres. RT-PCR was performed on hMSCs and neurospheres derived from the umbilical cord. Neural precursor cells were subjected to a standard cholinergic-like neuron differentiation protocol. Dissociated neurospheres, neural precursor cells, and cholinergic-like neurons were characterized by immunocytochemistry. hMSCs were CD73+, CD90+, CD105+, CD34- and CD45- and demonstrated the trilineage differentiation. Neurospheres and their isolated cells were nestin-positive and expressed NESTIN, MAP2, ßIII-TUBULIN, GFAP genes. Neural precursor cells that were differentiated in cholinergic-like neurons expressed ßIII-TUBULIN protein and choline acetyltransferase enzyme. hMSCs seeded on the natural membrane can differentiate into neurospheres, obtaining neural precursor cells without growth factors or gene transfection before cholinergic phenotype differentiation.

Antimicrobial, modulatory, and antibiofilm activity of tt-farnesol on bacterial and fungal strains of importance to human health.

In this study, we analyzed the antimicrobial, antibiofilm, and modulatory activities of trans-trans-farnesol (tt-farnesol). The minimum inhibitory concentration (MIC) of this sesquiterpene was evaluated against 31 Gram-positive and Gram-negative bacterial strains and 4 species of the genus Candida. Furthermore, we examined its inhibitory action on biofilm production as well as antibiotic modulation. Only Gram-positive species presented susceptibility to tt-farnesol (MIC ranging from 8 µg/mL to 128 µg/mL). No synergistic or antagonistic effects were observed between tt-farnesol (1/4 and 1/8 of MIC) and first-choice antibiotics against multidrug resistant strains. However, the modulatory action of tt-farnesol (1/2 and 1/4 of the MIC) decreased 8 × MIC of non-inhibitory ß-lactam antibiotic against a Methicillin-resistant strain. In the antibiofilm assay, tt-farnesol inhibited biofilm formation, especially in Methicillin-resistant Staphylococcus aureus (MRSA) strains, at concentrations ranging from 2 µg/mL to 128 µg/mL. Additionally, in the molecular docking study, the tt-farnesol molecule demonstrated a remarkable binding affinity with important proteins involved in the biofilm production, such as IcaA and Srt proteins. The antimicrobial action of tt-farnesol on Streptococcus pyogenes and Streptococcus agalactiae strains was evaluated for the first time, presenting an MIC of 16 µg/mL for both strains. Our findings reveal the antibacterial, antibiofilm, and modulatory potential of tt-farnesol to aid in the fight against infectious processes.

Alendronate sodium-polymeric nanoparticles display low toxicity in gastric mucosal of rats and Ofcol II cells.

The use of bisphosphonates constitutes the gold-standard therapy for the control and treatment of bone diseases. However, its long-term use may lead to gastric problems, which limits the treatment. Thus, this study aimed to formulate a nanostructured system with biodegradable polymers for the controlled release of alendronate sodium. The nanoparticles were characterized, and its gastric toxicity was investigated in rats. The synthesis process proved to be effective for encapsulating alendronate sodium, exhibiting nanoparticles with an average size of 51.02 nm and 98.5% of alendronate sodium incorporation. The release tests demonstrated a controlled release of the drug in 420 min, while the morphological analyzes showed spherical shapes and no apparent roughness. The biological tests demonstrated that the alendronate sodium nanoformulation reversed the gastric lesions, maintaining the normal levels of malondialdehyde and myeloperoxidase. Also, the encapsulated alendronate sodium showed no toxicity in murine osteoblastic cells, even at high concentrations.

Antileishmanial activity of cordiaquinone E towards Leishmania (Leishmania) amazonensis.

Leishmaniasis is caused by several protozoan species of Leishmania, and being endemically present in 98 countries around the world, it is also a severe public-health problem. The available antileishmanial drugs are toxic and yet present risks of recurrent infection. Efforts to find new, effective, and safe oral agents for the treatment of leishmaniasis are continuing throughout the world. This work aimed to evaluate the antileishmania activity of cordiaquinone E (CORe), isolated from the roots of Cordia polycephala (Lam.) I. M. Johnston. Cytotoxicity, and possible mechanisms of action against promastigote and amastigote forms of Leishmania amazonensis were examined. CORe was effective in inhibiting promastigote (IC50 4.5 ± 0.3 µM) and axenic amastigote (IC50 2.89 ± 0.11 µM) growth in concentrations found non-toxic for the host cell (CC50 246.81 ± 14.5 µM). Our results revealed that CORe presents direct activity against the parasite, inducing cell death by apoptosis. CORe present greater activity against intracellular amastigotes (EC50 1.92 ± 0.2 µM), yet with much higher selectivity indexes than the reference drugs, being respectively more benign towards RAW 264.7 macrophages than meglumine antimoniate and amphotericin B, (respectively by 4.68 and 42.84 fold). The antiamastigote activity was associated with increased TNF-α, IL-12, NO, and ROS levels, as well as decreased IL-10 levels. These results encourage the progression of studies on this compound for the development of new leishmanicidal agents.

Antimicrobial and antibiofilm activity of the benzoquinone oncocalyxone A.

Resistance to antimicrobials is a challenging issue that complicates the treatment of infections caused by bacteria and fungi, thus requiring new therapeutic options. Oncocalyxone A, a benzoquinone obtained from Auxemma oncocalyx (Allem) Taub has several biological effects; however, there is no data on its antimicrobial action. In this study, its antimicrobial and antibiofilm activities were evaluated against bacteria and fungi of clinical interest. Strains of Gram-positive and Gram-negative bacteria, and filamentous fungi and yeasts were selected to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of oncocalyxone A. The antibacterial effect of oncocalyxone A was studied using survival curves, atomic force microscopy (AFM), and the involvement of oxidative stress. We examined the inhibitory action of the molecule on biofilm formation and its hemolytic activity against human erythrocytes. Our results showed that among the strains tested, Staphylococcus epidermidis was highly sensitive to the action of oncocalyxone A, with an MIC of 9.43 µg/mL. In most bacterial strains analyzed, a bacteriostatic effect was observed, though the molecule showed no antifungal activity. Antibiofilm activity was observed against the methicillin-resistant S. aureus bacteria. Additionally, results from atomic force microscopy imaging showed that oncocalyxone A significantly altered bacterial morphology. Further, oncocalyxone A showed no hemolytic activity at concentrations ≥151 µg/mL. Together, our results demonstrate the antibacterial and antibiofilm potential of oncocalyxone A, indicating its therapeutic potential against bacterial resistance.

Structural characterization, antifungal and cytotoxic profiles of quaternized heteropolysaccharide from Anadenanthera colubrina.

In the present work, we investigated the minimal inhibitory concentration (MIC) against fungal strains (Fonsecaea pedrosoi, Microsporum canis, Candida albicans, Cryptococcus neoformans), and cytotoxicity to normal cell lines for modified red angico gum (AG) with eterifying agent N-chloride (3-chloro-2-hydroxypropyl) trimethylammonium (CHPTAC). Quaternized ammonium groups were linked to AG backbone using N-(3-chloro-2-hydroxypropyl) trimethylammonium chloride. The chemical features of the quaternized gum derivatives (QAG) were analyzed by: FTIR, elemental analysis, Zeta potential and gel permeation chromatography. The angico quaternizated gum presented a degree of substitution (DS) of 0.22 and Zeta potential of +36.43. For the antifungal test, it was observed that unmodified gum did not inhibit fungal growth. While, QAG inhibited the growth of most fungi used in this study. By AFM technique QAG interacted with the fungal surface, altering wall roughness significantly. The probable affinity of fragments of the QAG structure for the fungal enzyme 5I33 (Adenylosuccinate synthetase) has been shown by molecular docking. Low cytotoxicity was observed for polymers (unmodified gum and QAG). The results demonstrate that the quaternized polymer of AG presented in this study is a quite promising biomaterial for biotechnological applications.

Mechanisms of action of antimicrobial peptides ToAP2 and NDBP-5.7 against Candida albicans planktonic and biofilm cells.

Candida albicans is a major cause of human infections, ranging from relatively simple to treat skin and mucosal diseases to systemic life-threatening invasive candidiasis. Fungal infections treatment faces three major challenges: the limited number of therapeutic options, the toxicity of the available drugs, and the rise of antifungal resistance. In this study, we demonstrate the antifungal activity and mechanism of action of peptides ToAP2 and NDBP-5.7 against planktonic cells and biofilms of C. albicans. Both peptides were active against C. albicans cells; however, ToAP2 was more active and produced more pronounced effects on fungal cells. Both peptides affected C. albicans membrane permeability and produced changes in fungal cell morphology, such as deformations in the cell wall and disruption of ultracellular organization. Both peptides showed synergism with amphotericin B, while ToAP2 also presents a synergic effect with fluconazole. Besides, ToAP2 (6.25 µM.) was able to inhibit filamentation after 24 h of treatment and was active against both the early phase and mature biofilms of C. albicans. Finally, ToAP2 was protective in a Galleria mellonella model of infection. Altogether these results point to the therapeutic potential of ToAP2 and other antimicrobial peptides in the development of new therapies for C. albicans infections.

Anti-proliferative profile of Anacardium occidentale polysaccharide and characterization by AFM.

This paper explores the application of cashew gum (CG) as an in vitro antiproliferative, firstly by isolating and characterizing the gum using elemental analysis, gel-permeation chromatography, nuclear magnetic resonance (NMR) and atomic force microscopy (AFM). The molar mass of isolated CG was in the order of 103-104 g/mol, with small protein traces present. Polymer characterization by NMR identified key signals correlating to galactose, glucose, rhamnose and acid-related groups. Three distinct conformational stages were observed by AFM. The impact of CG on cell morphology and viability with both tumor and non-tumor cell lines was studied by AFM and 3-(4,5-dimethyl-2-thiazole)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay respectively. Antiproliferative activity was confirmed for HCT116 (colorectal carcinoma), B16F10 (melanoma) and HL60 (promyelocytic leukemia) cancer cell lines. A change in cell morphology was demonstrated as an increased surface roughness for HL60. Considering that a CG does not exhibit cytotoxicity to non-tumor lines, it can be seen that the CG shows selectivity for tumor cells and can be a promising biomaterial for future studies.

Photodynamic Therapy With Propolis: Antibacterial Effects on Staphylococcus aureus, Streptococcus mutans and Escherichia coli Analysed by Atomic Force Microscopy.

Introduction: Photodynamic therapy (PDT) is a process that uses a light source (e.g. laser), oxygen molecules and a photosensitizing agent. PDT aims to act against pathogens, including those resistant to antimicrobials. The association of PDT with natural drugs, such as Propolis, has not been widely studied. Methods: Therefore, this study aimed to evaluate the antimicrobial effect of PDT in vitro by using Propolis as a photosensitizing agent. For this purpose, the dry Propolis extract was used as a photosensitizer and a low-power laser (Photon Laser III model) was irradiated onto the microwells for 90 seconds. Gram-positive and Gram-negative bacterial strains were used in the tests at a concentration of 5 × 105 CFU/mL. Initially, the antibacterial activity of the photosensitizers without laser action was determined by using a serial microdilution method before the experiment with a laser. After the incubation of the plates in a bacteriological oven, resazurin (0.1%) was added and the minimum inhibitory concentration (MIC) was determined. Alterations in the morphology of the bacteria were analysed by using atomic force microscopy (AFM). Results: Bacteria were sensitive to Propolis with MICs ranging from 13.75 to 0.85 mg/mL, but no susceptibility was observed for methylene blue without laser application. A change was observed for MIC values of Propolis against Staphylococcus aureus after irradiation, which decreased from 1.71 mg/mL to 0.85 mg/mL. However, this behaviour was not observed in Escherichia coli, the only gram-negative strain used. In addition, AFM images revealed alterations in the size of one of the bacteria tested. Conclusion: The Propolis is more active against gram-positive bacteria and PDT improved its activity against one of the strains tested.

Development of amphotericin B-loaded propionate Sterculia striata polysaccharide nanocarrier.

This work was aimed at the production and characterization of a new nanocarrier based on a Sterculia striata polysaccharide (SSP) modified via acylation reaction with propionic anhydride. Nanocapsules of propionated SSP (PSSP) were produced via spontaneous nanoemulsification process and tested as a potential amphotericin B (AMB) nanocarrier. Stable nanoparticles with a very low polydispersity index (0.08-0.29) and high zeta potential (ζ -42.7 to -53.8 mV) were obtained. Particle size was dependent on the degree of substitution and ranged from 205 to 286 nm. A nanocapsule with a degree of substitution (DS) of 2.53 (NCP 2.53) was selected for encapsulation, biocompatibility, and antifungal evaluation against Candida albicans strains. A maximum of 98.3% AMB encapsulation was achieved. Encapsulated AMB was in its monomeric form and showed good biocompatibility and antifungal activity against four C. albicans strains. Data indicate that PSSP has potential as a nanocarrier system for AMB.