Rhamnolipids elicit the same cytotoxic sensitivity between cancer cell and normal cell by reducing surface tension of culture medium

Targeting Pseudomonas aeruginosa quorum sensing with sodium salicylate modulates immune responses in vitro and in vivo

Introduction

Chronic infections are a major clinical challenge in hard-to-heal wounds and implanted devices. Pseudomonas aeruginosa is a common causative pathogen that produces numerous virulence factors. Due to the increasing problem of antibiotic resistance, new alternative treatment strategies are needed. Quorum sensing (QS) is a bacterial communication system that regulates virulence and dampens inflammation, promoting bacterial survival. QS inhibition is a potent strategy to reduce bacterial virulence and alleviate the negative impact on host immune response.

Aim

This study investigates how secreted factors from P. aeruginosa PAO1, cultured in the presence or absence of the QS inhibitor sodium salicylate (NaSa), influence host immune response.

Material and methods

In vitro, THP-1 macrophages and neutrophil-like HL-60 cells were used. In vivo, discs of titanium were implanted in a subcutaneous rat model with local administration of P. aeruginosa culture supernatants. The host immune response to virulence factors contained in culture supernatants (+/-NaSa) was characterized through cell viability, migration, phagocytosis, gene expression, cytokine secretion, and histology.

Results

In vitro, P. aeruginosa supernatants from NaSa-containing cultures significantly increased THP-1 phagocytosis and HL-60 cell migration compared with untreated supernatants (-NaSa). Stimulation with NaSa-treated supernatants in vivo resulted in: (i) significantly increased immune cell infiltration and cell attachment to titanium discs; (ii) increased gene expression of IL-8, IL-10, ARG1, and iNOS, and (iii) increased GRO-α protein secretion and decreased IL-1β, IL-6, and IL-1α secretion, as compared with untreated supernatants.

Conclusion

In conclusion, treating P. aeruginosa with NaSa reduces the production of virulence factors and modulates major immune events, such as promoting phagocytosis and cell migration, and decreasing the secretion of several pro-inflammatory cytokines.

Green Surfactants (Biosurfactants): A Petroleum-Free Substitute for Sustainability-Comparison, Applications, Market, and Future Prospects

Surfactants are a group of amphiphilic molecules (i.e., having both hydrophobic and hydrophilic domains) that are a vital part of nearly every contemporary industrial process such as in agriculture, medicine, personal care, food, and petroleum. In general surfactants can be derived from (i) petroleum-based sources or (ii) microbial/plant origins. Petroleum-based surfactants are obvious results from petroleum products, which lead to petroleum pollution and thus pose severe problems to the environment leading to various ecological damages. Thus, newer techniques have been suggested for deriving surfactant molecules and maintaining environmental sustainability. Biosurfactants are surfactants of microbial or plant origins and offer much added advantages such as high biodegradability, lesser toxicity, ease of raw material availability, and easy applicability. Thus, they are also termed "green surfactants". In this regard, this review focused on the advantages of biosurfactants over the synthetic surfactants produced from petroleum-based products along with their potential applications in different industries. We also provided their market aspects and future directions that can be considered with selections of biosurfactants. This would open up new avenues for surfactant research by overcoming the existing bottlenecks in this field.

Perfusion culture of endothelial cells under shear stress on microporous membrane in a pressure-driven microphysiological system

This paper reports perfusion culture of human umbilical vein endothelial cells (HUVECs) on a microporous membrane in a pressure-driven microphysiological system (PD-MPS), which we developed previously as a multi-throughput perfusion culture platform. We designed fluidic culture unit with microporous membrane to culture HUVECs under fluidic shear stress and constructed a perfusion culture model in the PD-MPS platform. Four fluidic culture units were arranged in the microplate-sized device, which enables four-throughput assay for characterization of HUVECs under flow. Medium flow was generated above and below the membrane by sequential pneumatic pressure to apply physiological shear stress to HUVECs. HUVECs exhibited aligned morphology to the direction of the flow with shear stress of 11.5-17.7 dyn/cm² under the flow condition, while they randomly aligned under static culture condition in a 6 well plate. We also observed 3.3- and 5.0-fold increase in the expression levels of the thrombomodulin and endothelial nitric oxide synthase mRNAs, respectively, under the flow condition in the PD-MPS compared to the static culture in 6 well plate. We also observed actin filament aligned to the direction of flow in HUVECs cultured under the flow condition.

Mono-Rhamnolipid Biosurfactants Synthesized by Pseudomonas aeruginosa Detrimentally Affect Colorectal Cancer Cells

Over the past 15 years, glycolipid-type biosurfactant compounds have been postulated as novel, naturally synthesized anticancer agents. This study utilized a recombinant strain of Pseudomonas aeruginosa to biosynthesize a preparation of mono-rhamnolipids that were purified via both liquid and solid-phase extraction, characterized by HPLC-MS, and utilized to treat two colorectal cancer cell lines (HCT-116 and Caco2) and a healthy colonic epithelial cell line CCD-841-CoN. Additionally, the anticancer activity of these mono-rhamnolipids was compared to an alternative naturally derived anticancer agent, Piceatannol. XTT cell viability assays showed that treatment with mono-rhamnolipid significantly reduced the viability of both colorectal cancer cell lines whilst having little effect on the healthy colonic epithelial cell line. At the concentrations tested mono-rhamnolipids were also shown to be more cytotoxic to the colorectal cancer cells than Piceatannol. Staining of mono-rhamnolipid-treated cells with propidium iodine and acridine orange appeared to show that these compounds induced necrosis in both colorectal cancer cell lines. These data provide an early in vitro proof-of-principle for utilizing these compounds either as active pharmaceutical ingredient for the treatment of colorectal cancer or incorporations into nutraceutical formulations to potentially prevent gastrointestinal tract cancer.

Characterization and Cytotoxicity of Pseudomonas Mediated Rhamnolipids Against Breast Cancer MDA-MB-231 Cell Line

A biosurfactant producing bacterium was identified as Pseudomonas aeruginosa DNM50 based on molecular characterization (NCBI accession no. MK351591). Structural characterization using MALDI-TOF revealed the presence of 12 different congeners of rhamnolipid such as Rha-C8-C8:1, Rha-C10-C8:1, Rha-C10-C10, Rha-C10-C12:1, Rha-C16:1, Rha-C16, Rha-C17:1, Rha-Rha-C10:1-C10:1, Rha-Rha-C10-C12, Rha-Rha-C10-C8, Rha-Rha-C10-C8:1, and Rha-Rha-C8-C8. The radical scavenging activity of rhamnolipid (DNM50RL) was determined by 2, 3-diphenyl-1-picrylhydrazyl (DPPH) assay which showed an IC₅₀ value of 101.8 μg/ ml. The cytotoxic activity was investigated against MDA-MB-231 breast cancer cell line by MTT (4,5-dimethylthiazol-2-yl-2,5-diphenyl tetrazolium bromide) assay which showed a very low IC50 of 0.05 μg/ ml at 72 h of treatment. Further, its activity was confirmed by resazurin and trypan blue assay with IC₅₀ values of 0.01 μg/ml and 0.64 μg/ ml at 72 h of treatment, respectively. Thus, the DNM50RL would play a vital role in the treatment of breast cancer targeting inhibition of p38MAPK.

Antimicrobial Properties of Chitosan and Chitosan Derivatives in the Treatment of Enteric Infections

Antibiotics played an important role in controlling the development of enteric infection. However, the emergence of antibiotic resistance and gut dysbiosis led to a growing interest in the use of natural antimicrobial agents as alternatives for therapy and disinfection. Chitosan is a nontoxic natural antimicrobial polymer and is approved by GRAS (Generally Recognized as Safe by the United States Food and Drug Administration). Chitosan and chitosan derivatives can kill microbes by neutralizing negative charges on the microbial surface. Besides, chemical modifications give chitosan derivatives better water solubility and antimicrobial property. This review gives an overview of the preparation of chitosan, its derivatives, and the conjugates with other polymers and nanoparticles with better antimicrobial properties, explains the direct and indirect mechanisms of action of chitosan, and summarizes current treatment for enteric infections as well as the role of chitosan and chitosan derivatives in the antimicrobial agents in enteric infections. Finally, we suggested future directions for further research to improve the treatment of enteric infections and to develop more useful chitosan derivatives and conjugates.

Rhamnolipid Biosurfactants—Possible Natural Anticancer Agents and Autophagy Inhibitors

Background/Aim: A number of biologically active substances were proved as an alternative to conventional anticancer medicines. The aim of the study is in vitro investigation of the anticancer activity of mono- and di-Rhamnolipids (RL-1 and RL-2) against human breast cancer. Additionally, the combination with Cisplatin was analyzed. Materials and Methods: Breast cell lines (MCF-10A, MCF-7 and MDA-MB-231) were treated with RLs and in combination with Cisplatin. The viability was analyzed using MTT assay, and investigation of autophagy was performed via acridine orange staining. Results: In contrast to the healthy cells, both tested cancer lines exhibited sensitivity to RLs treatment. This effect was accompanied by an influence on the autophagy-related acidic formation process. Only for the triple-negative breast cancer cell line (MDA-MB-231) the synergistic effect of the combined treatment (10 µM Cisplatin and 1 µg/mL RL-2) was observed. Conclusion: Based on studies on the reorganization of membrane models in the presence of RL and the data about a higher amount of lipid rafts in cancer cell membranes than in non-tumorigenic, we suggest a possible mechanism of membrane remodelling by formation of endosomes. Shortly, in order to have a synergistic effect, it is necessary to have Cisplatin andRL-2 as RL2 is a molecule inducingpositive membrane curvature.

Rhamnolipids Nano-Micelles as a Potential Hand Sanitizer

COVID-19 is a pandemic disease caused by the SARS-CoV-2, which continues to cause global health and economic problems since emerging in China in late 2019. Until now, there are no standard antiviral treatments. Thus, several strategies were adopted to minimize virus transmission, such as social distancing, face covering protection and hand hygiene. Rhamnolipids are glycolipids produced formally by Pseudomonas aeruginosa and as biosurfactants, they were shown to have broad antimicrobial activity. In this study, we investigated the antimicrobial activity of rhamnolipids against selected multidrug resistant bacteria and SARS-CoV-2. Rhamnolipids were produced by growing Pseudomonas aeruginosa strain LeS3 in a new medium formulated from chicken carcass soup. The isolated rhamnolipids were characterized for their molecular composition, formulated into nano-micelles, and the antibacterial activity of the nano-micelles was demonstrated in vitro against both Gram-negative and Gram-positive drug resistant bacteria. In silico studies docking rhamnolipids to structural and non-structural proteins of SARS-CoV-2 was also performed. We demonstrated the efficient and specific interaction of rhamnolipids with the active sites of these proteins. Additionally, the computational studies suggested that rhamnolipids have membrane permeability activity. Thus, the obtained results indicate that SARS-CoV-2 could be another target of rhamnolipids and could find utility in the fight against COVID-19, a future perspective to be considered.

Total synthesis, isolation, surfactant properties, and biological evaluation of ananatosides and related macrodilactone-containing rhamnolipids

Rhamnolipids are a specific class of microbial surfactants, which hold great biotechnological and therapeutic potential. However, their exploitation at the industrial level is hampered because they are mainly produced by the opportunistic pathogen Pseudomonas aeruginosa. The non-human pathogenic bacterium Pantoea ananatis is an alternative producer of rhamnolipid-like metabolites containing glucose instead of rhamnose residues. Herein, we present the isolation, structural characterization, and total synthesis of ananatoside A, a 15-membered macrodilactone-containing glucolipid, and ananatoside B, its open-chain congener, from organic extracts of P. ananatis. Ananatoside A was synthesized through three alternative pathways involving either an intramolecular glycosylation, a chemical macrolactonization or a direct enzymatic transformation from ananatoside B. A series of diasteroisomerically pure (1→2), (1→3), and (1→4)-macrolactonized rhamnolipids were also synthesized through intramolecular glycosylation and their anomeric configurations as well as ring conformations were solved using molecular modeling in tandem with NMR studies. We show that ananatoside B is a more potent surfactant than its macrolide counterpart. We present evidence that macrolactonization of rhamnolipids enhances their cytotoxic and hemolytic potential, pointing towards a mechanism involving the formation of pores into the lipidic cell membrane. Lastly, we demonstrate that ananatoside A and ananatoside B as well as synthetic macrolactonized rhamnolipids can be perceived by the plant immune system, and that this sensing is more pronounced for a macrolide featuring a rhamnose moiety in its native 1 C 4 conformation. Altogether our results suggest that macrolactonization of glycolipids can dramatically interfere with their surfactant properties and biological activity.

Rhamnolipid-Based Liposomes as Promising Nano-Carriers for Enhancing the Antibacterial Activity of Peptides Derived from Bacterial Toxin-Antitoxin Systems

Background

Antimicrobial resistance poses substantial risks to human health. Thus, there is an urgent need for novel antimicrobial agents, including alternative compounds, such as peptides derived from bacterial toxin-antitoxin (TA) systems. ParELC3 is a synthetic peptide derived from the ParE toxin reported to be a good inhibitor of bacterial topoisomerases and is therefore a potential antibacterial agent. However, ParELC3 is inactive against bacteria due to its inability to cross the bacterial membranes. To circumvent this limitation we prepared and used rhamnolipid-based liposomes to carry and facilitate the passage of ParELC3 through the bacterial membrane to reach its intracellular target - the topoisomerases.

Methods and Results

Small unilamellar liposome vesicles were prepared by sonication from three formulations that included 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and cholesterol. ParELC3 was loaded with high efficiency into the liposomes. Characterization by DLS and TEM revealed the appropriate size, zeta potential, polydispersity index, and morphology. In vitro microbiological experiments showed that ParELC3 loaded-liposomes are more efficient (29 to 11 µmol·L⁻¹) compared to the free peptide (>100 µmol·L⁻¹) at inhibiting the growth of standard E. coli and S. aureus strains. RL liposomes showed high hemolytic activity but when prepared with POPC and Chol this activity had a significant reduction. Independently of the formulation, the vesicles had no detectable cytotoxicity to HepG2 cells, even at the highest concentrations tested (1.3 mmol·L⁻¹ and 50 µmol·L⁻¹ for rhamnolipid and ParELC3, respectively).

Conclusion

The present findings suggest the potential use of rhamnolipid-based liposomes as nanocarrier systems to enhance the bioactivity of peptides.

Exploring the potential of chitosan-based particles as delivery-carriers for promising antimicrobial glycolipid biosurfactants

Driven by the need to find alternatives to control Staphylococcus aureus infections, this work describes the development of chitosan-based particulate systems as carriers for antimicrobial glycolipids. By using a simple ionic gelation method stable nanoparticles were obtained showing an encapsulation efficiency of 41.1 ± 8.8 % and 74.2 ± 1.3 % and an average size of 210.0 ± 15.7 nm and 329.6 ± 8.0 nm for sophorolipids and rhamnolipids chitosan-nanoparticles, respectively. Glycolipids incorporation and particle size was correspondingly corroborated by FTIR-ATR and TEM analysis. Rhamnolipids chitosan nanoparticles (RLs-CS_p) presented the highest antimicrobial effect towards S. aureus (ATCC 25923) exhibiting a minimal inhibitory concentration of 130 μg/mL and a biofilm inhibition ability of 99 %. Additionally, RLs-CS_p did not interfere with human dermal fibroblasts (AG22719) viability and proliferation under the tested conditions. The results revealed that the RLs-CS_p were able to inhibit bacterial growth showing adequate cytocompatibility and might become, after additional studies, a valuable approach to prevent S. aureus related infections.

Cells with Higher Cortical Membrane Tension Are More Sensitive to Lysis by Biosurfactant Di-rhamnolipids

Tissue and cellular stiffening is associated with pathologies including fibrosis and cancer. Healthy cells also exhibit a wide range of membrane cortical tensions, which have been studied in the field of mechanobiology. Here, we quantify the mechanosensitivity of the lysis agent the di-rhamnolipid (RHA), which is a bacterially produced biosurfactant. RHA exhibited selective lysis correlated strongly with cortical membrane tension in osteoblasts, smooth muscle cells, fibroblasts, epithelial cells, and erythrocytes. Reducing cortical membrane tension by cytoskeleton inhibitors (cytochalasin D and nocodazole) or osmotic regulators (sucrose, polyethylene glycol, and nonionic surfactants) attenuated the RHA toxicity. The selective toxicity of RHA toward human chronic myeloid leukemia K562 cells over healthy blood cells suggests a potential therapy for blood cancer. Targeted killing of myofibroblasts transformed from either fibroblasts or epithelial cells indicates its antifibrotic effect. Combined, these studies showed the potential for specific targeting of cells with differential mechanical properties rather than chemical or biological pathways.

High Di-rhamnolipid Production Using Pseudomonas aeruginosa KT1115, Separation of Mono/Di-rhamnolipids, and Evaluation of Their Properties

Rhamnolipids (RLs) are important bioproducts that are regarded as promising biosurfactant for applications in oil exploitation, cosmetics, and food industry. In this study, the newly isolated Pseudomonas aeruginosa KT1115 showed high production of di-RLs. The highest yield of RLs by P. aeruginosa KT1115, reaching 44.39 g/L after 8 days of fermentation in a 5 L bioreactor, was obtained from rapeseed oil-nitrate medium after process optimization. Furthermore, we established a new separation process that achieved up to 91.82% RLs recovery with a purity of 89% and further obtained mono/di-rhamnolipids. Finally, ESI-MS analysis showed that the RLs produced by strain KT1115 have a high proportion of di-RLs (mono-RLs: di-RLs = 11.47: 88.53), which have a lower critical micelle-forming concentration (8 mN/m) and better emulsification ability with kerosene (52.1% EI₂₄) than mono-RLs (167 mN/m and 41.4% EI₂₄, respectively). These results demonstrated that P. aeruginosa KT1115 is a potential industrial producer of di-RLs, which have improved applicability and offer significant commercial benefits.

Bioavailability of microplastic-bound pollutants in vitro: The role of adsorbate lipophilicity and surfactants

The potential role of microplastic particles (MPs) as vectors for lipophilic organic pollutants enhancing their uptake by organisms has repeatedly been discussed in the scientific community. Likewise, several studies indicate an important role of surfactants in pollutant-transfer from MP to organisms. Employing polyethylene particles, the bioavailability of three MP-bound inducers of 7-ethoxyresorufin-O-deethylase (EROD) with variable lipophilicity was quantitatively compared via EROD activity in RTL-W1 cells. In addition, non-cytotoxic surfactant concentrations of Pluronic F-127, rhamnolipids, sodium deoxycholate and sodium dodecyl sulfate (SDS) supplemented to the medium were tested for their effects on pollutant desorption from MPs as well as on cellular EROD induction. Bioavailability of MP-bound pollutants was negatively correlated with lipophilicity, and all surfactants were found to modulate the cellular response towards inducers by unidentified mechanisms. After experimental correction for effects on the cellular response, all surfactants except SDS moderately increased desorption of inducer from MPs. Results on the impact of lipophilicity agree with previously published thermodynamic models, indicating that appreciable pollutant desorption from MPs may only occur for substances with comparatively low lipophilicity, the accumulation of which on MPs is negligible in the environment. However, the role of surfactants should be considered further with respect to potential effects on sorption of pollutants to and from MPs.

Cytotoxic effects of mono- and di-rhamnolipids from Pseudomonas aeruginosa MR01 on MCF-7 human breast cancer cells

Rhamnolipids produced by P. aeruginosa MR01 were fractionated into mono- and di-rhamnolipids, and their dominant congeners, Rha-C₁₀-C₁₀ and Rha-Rha-C₁₀-C₁₀, were shown by mass spectrometry. Minimum surface tensions and critical micelle concentrations (CMC) were determined as "≃34 mN/m; ≃26.17 mg/l;" and "≃29 mN/m; ≃29.63 mg/l" for mono- and di-rhamnolipids, respectively. Spectrophotometry measurements provided a close approximation of CMC. Contact angle and diameter of wet area were determined for rhamnolipid-containing drops on hydrophobic paper to display their capability for alteration of surface wettability. Wet area measurement is a simple, reliable method not requiring a Drop Shape Analyzer. Cell viabilities determined by MTT assay showed a decline in a dose-dependent manner and estimated IC₅₀ values were 25.87 μg/ml and 31.00 μg/ml for mono- and di-rhamnolipids treating MCF-7 cells for 48 h. Morphological observations using the inverted phase-contrast microscopy and fluorescence microscopy via Hoechst staining revealed the apoptotic characteristics in treated MCF-7 cells. The semi-quantitative RT-PCR method demonstrated that expression of the p53 gene in mRNA levels significantly (P < 0.05) increased when treated with 30 μg/ml of each rhamnolipid compound for 12 h. It can be concluded that rhamnolipids derived from MR01 show significant anticancer potential against MCF-7 cell line and should be further investigated as natural, therapeutic anti-tumor agents.

Chemical synthesis and cytotoxicity of neo-glycolipids; rare sugar-glycerol-lipid compounds

Rare sugars are defined as monosaccharides and their derivatives, which rarely exist in nature and have various beneficial effects on organisms, biomaterials and foods. Glycolipids are composed of sugars and lipids and have been intensively studied in various fields such as environmental engineering, nanotechnology and molecular biology. Here, we synthesise new types of glycolipids composed of rare sugars, glycerol and lipids (RSGLs), using 6 different types of rare sugars by combining the modified Fischer and lipase reverse reactions. We confirm the production of RSGLs by thin layer chromatography (TLC), Fourier-transform infrared (FT-IR) spectroscopy and matrix assisted laser desorption/ionisation time of flight mass spectroscopy (MALDI-TOF-MS) and investigate the cytotoxicity of RSGLs by lactate dehydrogenase (LDH) and alamar blue assays. We successfully synthesise novel RSGLs; i.e., D-ribose-glycorol-lipid, D-allose-glycorol-lipid, L-rhamnose-glycorol-lipid, L-lyxorse-glycorol-lipid, L-gulose-glycorol-lipid and L-fucose-glycorol-lipid. We finally clarify the effect of the concentration of those RSGLs on cytotoxicity, which is of great importance considering the utilisation of RSGLs particularly in the field of biomedicine.

Characterization of Rhamnolipids Produced by an Arctic Marine Bacterium from the Pseudomonas fluorescence Group

The marine environment is a rich source of biodiversity, including microorganisms that have proven to be prolific producers of bioactive secondary metabolites. Arctic seas are less explored than warmer, more accessible areas, providing a promising starting point to search for novel bioactive compounds. In the present work, an Arctic marine Pseudomonas sp. belonging to the Pseudomonas (P.) fluorescence group was cultivated in four different media in an attempt to activate biosynthetic pathways leading to the production of antibacterial and anticancer compounds. Culture extracts were pre-fractionated and screened for antibacterial and anticancer activities. One fraction from three of the four growth conditions showed inhibitory activity towards bacteria and cancer cells. The active fractions were dereplicated using molecular networking based on MS/MS fragmentation data, indicating the presence of a cluster of related rhamnolipids. Six compounds were isolated using HPLC and mass-guided fractionation, and by interpreting data from NMR and high-resolution MS/MS analysis; the structures of the compounds were determined to be five mono-rhamnolipids and the lipid moiety of one of the rhamnolipids. Molecular networking proved to be a valuable tool for dereplication of these related compounds, and for the first time, five mono-rhamnolipids from a bacterium within the P. fluorescence group were characterized, including one new mono-rhamnolipid.

Anti-biofilm Properties of Bacterial Di-Rhamnolipids and Their Semi-Synthetic Amide Derivatives

A new strain, namely Lysinibacillus sp. BV152.1 was isolated from the rhizosphere of ground ivy (Glechoma hederacea L.) producing metabolites with potent ability to inhibit biofilm formation of an important human pathogens Pseudomonas aeruginosa PAO1, Staphylococcus aureus, and Serratia marcescens. Structural characterization revealed di-rhamnolipids mixture containing rhamnose (Rha)-Rha-C10-C10, Rha-Rha-C8-C10, and Rha-Rha-C10-C12 in the ratio 7:2:1 as the active principle. Purified di-rhamnolipids, as well as commercially available di-rhamnolipids (Rha-Rha-C10-C10, 93%) were used as the substrate for the chemical derivatization for the first time, yielding three semi-synthetic amide derivatives, benzyl-, piperidine-, and morpholine. A comparative study of the anti-biofilm, antibacterial and cytotoxic properties revealed that di-Rha from Lysinibacillus sp. BV152.1 were more potent in biofilm inhibition, both cell adhesion and biofilm maturation, than commercial di-rhamnolipids inhibiting 50% of P. aeruginosa PAO1 biofilm formation at 50 μg mL^-1 and 75 μg mL^-1, respectively. None of the di-rhamnolipids exhibited antimicrobial properties at concentrations of up to 500 μg mL^-1. Amide derivatization improved inhibition of biofilm formation and dispersion activities of di-rhamnolipids from both sources, with morpholine derivative being the most active causing more than 80% biofilm inhibition at concentrations 100 μg mL^-1. Semi-synthetic amide derivatives showed increased antibacterial activity against S. aureus, and also showed higher cytotoxicity. Therefore, described di-rhamnolipids are potent anti-biofilm agents and the described approach can be seen as viable approach in reaching new rhamnolipid based derivatives with tailored biological properties.

Amphiphilic glycoconjugates as potential anti-cancer chemotherapeutics

Amphiphilicity is one of the desirable features in the process of drug development which improves the biological as well as the pharmacokinetics profile of bioactive molecule. Carbohydrate moieties present in anti-cancer natural products and synthetic molecules influence the amphiphilicity and hence their bioactivity. This review focuses on natural and synthetic amphiphilic anti-cancer glycoconjugates. Different classes of molecules with varying degree of amphiphilicity are covered with discussions on their structure-activity relationship and mechanism of action.

Potential applications of biosurfactant rhamnolipids in agriculture and biomedicine

Rhamnolipids have recently emerged as promising bioactive molecules due to their novel structures, diverse and versatile biological functions, lower toxicity, higher biodegradability, as well as production from renewable resources. The advantages of rhamnolipids make them attractive targets for research in a wide variety of applications. Especially rhamnolipids are likely to possess potential applications of the future in areas such as biomedicine, therapeutics, and agriculture. The purpose of this mini review is to provide a comprehensive prospective of biosurfactant rhamnolipids as potential antimicrobials, immune modulators, and virulence factors, and anticancer agents in the field of biomedicine and agriculture that may meet the ever-increasing future pharmacological treatment and food safety needs in human health.

Rhamnolipids as epithelial permeability enhancers for macromolecular therapeutics

The use of surfactants as drug permeability enhancers across epithelial barriers remains a challenge. Although many studies have been performed in this field using synthetic surfactants, the possibility of employing surfactants produced by bacteria (the so called biosurfactants") has not been completely explored. Among them, one of the most well characterized class of biosurfactants are rhamnolipids. The aim of the study was to investigate the effect of rhamnolipids on the epithelial permeability of fluorescein isothiocyanate-labelled dextrans 4kDa and 10kDa (named FD4 and FD10, respectively) as model for macromolecular drugs, across Caco-2 and Calu-3monolayers. These cell lines were selected as an in vitro model for the oral and respiratory administration of drugs. Before performing permeability studies, rhamnolipids mixture was analysed in terms of chemical composition and quantification through mass analysis and HPLC. Cytotoxicity and transepithelial electrical resistance (TEER) studies were also conducted using Caco-2 and Calu-3 cell lines. A dose-dependent effect of rhamnolipids on TEER and FD4 or FD10 permeability across both cell lines was observed at relatively safe concentrations. Overall, results suggest the possibility of using rhamnolipids as absorption enhancers for macromolecular drugs through a reversible tight junction opening (paracellular route), despite more investigations are required to confirm their mechanism of action in term of permeability.

Rhamnolipids form drug-loaded nanoparticles for dermal drug delivery

Bacterial biosurfactants are nature's strategy to solubilize and ingest hydrophobic molecules and nutrients using a fully biodegradable transport system. Eight structurally defined rhamnolipids were selected and investigated as potential drug carrier systems. Depending on the molecular structures defining their packing parameters, the rhamnolipids were found to form spherical nanoparticles with precisely defined average sizes between 5 and 100nm, low polydispersity, and stability over a broad concentration range as revealed from dynamic light scattering and electron microscopy. As rhamnolipids were tolerated well by the human skin, rhamnolipid nanoparticles were considered for dermal drug delivery and thus loaded with hydrophobic drug molecules. Using the drug model, Nile red, dexamethasone, and tacrolimus nanoparticles charged with up to 30% drug loading (w/w) were obtained. Nanoparticles loaded with Nile red were investigated for dermal drug delivery in a Franz cell using human skin. Fluoresence microscopy of skin slices indicated the efficient penetration of the model drug into human skin, both into the stratum corneum and although to a lesser extent into the lower epidermis. Rhamnolipid nanocarriers were found to be non-toxic to primary human fibroblasts in a proliferation assay and thus are considered candidates for the dermal delivery of drugs.

Targeted killing of myofibroblasts by biosurfactant di-rhamnolipid suggests a therapy against scar formation

Pathological myofibroblasts are often involved in skin scarring via generating contractile force and over-expressing collagen fibers, but no compound has been found to inhibit the myofibroblasts without showing severe toxicity to surrounding physiological cells. Here we report that di-rhamnolipid, a biosurfactant secreted by Pseudomonas aeruginosa, showed potent effects on scar therapy via a unique mechanism of targeted killing the myofibroblasts. In cell culture, the fibroblasts-derived myofibroblasts were more sensitive to di-rhamnolipid toxicity than fibroblasts at a concentration-dependent manner, and could be completely inhibited of their specific functions including α-SMA expression and collagen secretion/contraction. The anti-fibrotic function of di-rhamnolipid was further verified in rabbit ear hypertrophic scar models by presenting the significant reduction of scar elevation index, type I collagen fibers and α-SMA expression. In this regard, di-rhamnolipid treatment could be suggested as a therapy against skin scarring.

Current status in biotechnological production and applications of glycolipid biosurfactants

Biosurfactants are natural compounds with surface activity and emulsifying properties produced by several types of microorganisms and have been considered an interesting alternative to synthetic surfactants. Glycolipids are promising biosurfactants, due to low toxicity, biodegradability, and chemical stability in different conditions and also because they have many biological activities, allowing wide applications in different fields. In this review, we addressed general information about families of glycolipids, rhamnolipids, sophorolipids, mannosylerythritol lipids, and trehalose lipids, describing their chemical and surface characteristics, recent studies using alternative substrates, and new strategies to improve of production, beyond their specificities. We focus in providing recent developments and trends in biotechnological process and medical and industrial applications.

Rhamnolipids functionalized AgNPs-induced oxidative stress and modulation of toxicity pathway genes in cultured MCF-7 cells

Rhamnolipids extracted from Pseudomonas aeruginosa strain JS-11 were utilized for synthesis of stable silver nanoparticles (Rh-AgNPs). The Rh-AgNPs (23 nm) were characterized by Fourier transform infra-red (FTIR) spectroscopy, atomic force microscopy (AFM) and transmission electron microscopy (TEM). The cytotoxicity assays suggested significant decrease in viability of Rh-AgNPs treated human breast adenocarcinoma (MCF-7) cells, compared with normal human peripheral blood mononuclear (PBMN) cells. Flow cytometry data revealed 1.25-fold (p<0.05) increase in the fluorescence of 2',7'-dichlorofluorescein (DCF) at 0.25 μg/mL. However, at Rh-AgNPs concentrations of 0.5 and 1.0 μg/mL, much lesser fluorescence was noticed, which is attributed to cell death. Results with the fluorescent probe Rh123 demonstrated change in inner mitochondrial membrane and dissipation of membrane potential. The cell cycle analysis suggested 19.9% (p<0.05) increase in sub-G1 peak with concomitant reduction in G1 phase at 1 μg/mL of Rh-AgNPs, compared to 2.7% in untreated control. The real-time RT(2) Profiler™ PCR array data elucidated the overexpression of seven oxidative stress and DNA damage pathways genes viz. BAX, BCl2, Cyclin D1, DNAJA1, E2F transcription factor 1, GPX1 and HSPA4, associated with apoptosis signaling, proliferation and carcinogenesis, pro inflammatory and heat shock responses in Rh-AgNPs treated cells. Thus, the increased ROS production, mitochondrial damage and appearance of sub-G1 (apoptotic) population suggested the anti-proliferative activity, and role of oxidative stress pathway genes in Rh-AgNPs induced death of MCF-7 cancer cells.