Amino Acids as Raw Material for Biocompatible Surfactants

AAontology: An Ontology of Amino Acid Scales for Interpretable Machine Learning

Amino acid scales are crucial for protein prediction tasks, many of them being curated in the AAindex database. Despite various clustering attempts to organize them and to better understand their relationships, these approaches lack the fine-grained classification necessary for satisfactory interpretability in many protein prediction problems. To address this issue, we developed AAontology-a two-level classification for 586 amino acid scales (mainly from AAindex) together with an in-depth analysis of their relations-using bag-of-word-based classification, clustering, and manual refinement over multiple iterations. AAontology organizes physicochemical scales into 8 categories and 67 subcategories, enhancing the interpretability of scale-based machine learning methods in protein bioinformatics. Thereby it enables researchers to gain a deeper biological insight. We anticipate that AAontology will be a building block to link amino acid properties with protein function and dysfunctions as well as aid informed decision-making in mutation analysis or protein drug design.

Molecular simulation screening and sensory evaluation unearth a novel kokumi compound with bitter-masking effect: N-lauroyl-L-tryptophan

N-lauroyl-L-tryptophan (LT), which has the strongest potential flavor-presenting activity, was skillfully screened from numerous N-Lau-AAs docked to different taste receptors by molecular simulation techniques. Subsequently, LT was synthesized employing food-grade commercial enzymes and structurally characterized, the optimized yields of LT could reach 69.08%, 76.16%, and 50.40%, respectively. Sensory and E-tongue evaluations showed that LT at 1 mg/L significantly benefited the performance of different taste sensations and exhibited different bitter taste masking effects: L-Ile (68.42%), L-Trp (68.18%), D-salicylic acid (48.48%) and quinine (35.00%). The molecular docking results illustrated that LT had a high affinity for various taste receptors, dominated by hydrogen bonding and hydrophobic interactions. This work provided a rare systematic elucidation of the potential and mechanism of enzymatically synthesized LT in enhancing taste properties. It provides novel insights into the directions and strategies for the excavation and innovation of flavor enhancers and food flavors.

Self-healable, stimuli-responsive bio-ionic liquid and sodium alginate conjugated hydrogel with tunable Injectability and mechanical properties for the treatment of breast cancer

Designing stimuli-responsive drug delivery vehicles with higher drug loading capacity, sustained and targeted release of anti-cancer drugs and able to mitigate the shortcomings of traditional systems is need of hour. Herein, we designed stimuli-responsive, self-healable, and adhesive hydrogel through synergetic interaction between [Cho][Gly] (Choline-Glycine) and sodium alginate (SA). The hydrogel was formed as a result of non-covalent interaction between the components of the mixture forming the fibre kind morphology; confirmed through FTIR/computational analysis and SEM/AFM images. The hydrogel exhibited excellent mechanical strength, self-healing ability, adhesive character and most importantly; adjustable injectability. In vitro biocompatibility of the hydrogel was tested on HaCaT and MCF-7 cells, showing >92 % cell viability after 48 h. The hemolysis ratio (<4 %) of the hydrogel confirmed the blood compatibility of the hydrogel. When tested for drug-loading capacity, the hydrogel show 1500 times drug loading for the 5-fluorouracil (5-FU) against the SA based hydrogel. In vitro release data indicated that 5-FU have more preference towards the cancerous cell condition, i.e. acidic pH (>85 %), whereas the drug-loaded hydrogel successfully killed the MCF-7 and HeLa cell with a Collapse

Key Words

• Bio-ionic liquid
• Injectable-hydrogel
• Sodium alginate

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MESH Headings

• Alginates/chemistry
• Humans
• Breast Neoplasms/drug therapy
• Breast Neoplasms/pathology
• Hydrogels/chemistry
• MCF-7 Cells
• Female
• Drug Liberation
• Drug Carriers/chemistry
• Fluorouracil/pharmacology
• Fluorouracil/chemistry
• Cell Survival/drug effects
• Hemolysis/drug effects
• Drug Delivery Systems
• Antineoplastic Agents/pharmacology
• Antineoplastic Agents/chemistry

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Grants Collapse

Affiliation(s)

Raviraj Pansuriya Ionic Liquids Research Laboratory, Department of Chemistry, Sardar Vallabhbhai National Institute of Technology, Surat 395007, Gujarat, India
Tapas Patel Ionic Liquids Research Laboratory, Department of Chemistry, Sardar Vallabhbhai National Institute of Technology, Surat 395007, Gujarat, India
Kuldeep Singh Salt and Marine Chemicals Division, CSIR-Central Salt and Marine Chemicals Research Institute, Council of Scientific and Industrial Research, G. B. Marg, Bhavnagar 364002, India
Azza Al Ghamdi Department of Chemistry, College of Science, Imam Abdul Rahman Bin Faisal University, P.O. Box 1982, Dammam 31441, Saudi Arabia; Basic & Applied Scientific Research Center (BASRC), Water Treatment Unit, Imam Abdulrahman Bin Faisal University, P.O. Box 1982, Dammam 31441, Saudi Arabia
Naresh Kasoju Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum 695011, Kerala, India
Arvind Kumar Salt and Marine Chemicals Division, CSIR-Central Salt and Marine Chemicals Research Institute, Council of Scientific and Industrial Research, G. B. Marg, Bhavnagar 364002, India
Suresh Kumar Kailasa Ionic Liquids Research Laboratory, Department of Chemistry, Sardar Vallabhbhai National Institute of Technology, Surat 395007, Gujarat, India
Naved I Malek Ionic Liquids Research Laboratory, Department of Chemistry, Sardar Vallabhbhai National Institute of Technology, Surat 395007, Gujarat, India.

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Protein Classes Predicted by Molecular Surface Chemical Features: Machine Learning-Assisted Classification of Cytosol and Secreted Proteins

Chemical structures of protein surfaces govern intermolecular interaction, and protein functions include specific molecular recognition, transport, self-assembly, etc. Therefore, the relationship between the chemical structure and protein functions provides insights into the understanding of the mechanism underlying protein functions and developments of new biomaterials. In this study, we analyze protein surface features, including surface amino acid populations and secondary structure ratios, instead of entire sequences as input for the classifier, intending to provide deeper insights into the determination of protein classes (cytosol or secreted). We employed a random forest-based classifier for the prediction of protein locations. Our training and testing data sets consisting of secreted and cytosol proteins were constructed using filtered information from UniProt and 3D structures from AlphaFold. The classifier achieved a testing accuracy of 93.9% with a feature importance ranking and quantitative boundary values for the top three features. We discuss the significance of these features quantitatively and the hidden rules to determine the protein classes (cytosol or secreted).

Critical Aggregation Concentration Can be a Predictor of Doxorubicin Delivery Performance of Self-Assembling Amphiphilic Peptides with Different Hydrophobic Tails

Amphiphilic peptides hold great potential as drug delivery systems. A popular peptide design approach has been to place amino acids in the peptide sequence based on their known properties. On the other hand, the directed discovery approach aims to screen a sequence space for a desired property. However, screening amphiphilic peptides for desirable drug delivery properties is not possible without a quantity that is predictive of these properties. We studied the predictive power of critical aggregation concentration (CAC) values on the drug delivery performance of a series of amphiphilic peptides with different hydrophobic tails and close CAC values. The CAC values were predicted by our previously developed model and doxorubicin was used as a model hydrophobic drug. All peptides showed close drug loading, entrapment efficiency, and release profile. They also formed similar spherical particles by assembling in reverse β-sheet arrangements regardless of drug presence. Moreover, the assembled particles were able to accumulate doxorubicin inside ordinary as well as drug-resistant breast cancer cells and enhance its toxicity up to 39 and 17 folds, respectively. It can be concluded that similar drug delivery properties displayed by the peptides can be attributed to their similar hydrophilic-lipophilic balance as reflected in their close CAC values.

Enantioselective organocatalytic strategies to access noncanonical α-amino acids

Organocatalytic asymmetric synthesis has evolved over the years and continues to attract the interest of many researchers worldwide. Enantiopure noncanonical amino acids (ncAAs) are valuable building blocks in organic synthesis, medicinal chemistry, and chemical biology. They are employed in the elaboration of peptides and proteins with enhanced activities and/or improved properties compared to their natural counterparts, as chiral catalysts, in chiral ligand design, and as chiral building blocks for asymmetric syntheses of complex molecules, including natural products. The linkage of ncAA synthesis and enantioselective organocatalysis, the subject of this perspective, tries to imitate the natural biosynthetic process. Herein, we present contemporary and earlier developments in the field of organocatalytic activation of simple feedstock materials, providing potential ncAAs with diverse side chains, unique three-dimensional structures, and a high degree of functionality. These asymmetric organocatalytic strategies, useful for forging a wide range of C-C, C-H, and C-N bonds and/or combinations thereof, vary from classical name reactions, such as Ugi, Strecker, and Mannich reactions, to the most advanced concepts such as deracemisation, transamination, and carbene N-H insertion. Concurrently, we present some interesting mechanistic studies/models, providing information on the chirality transfer process. Finally, this perspective highlights, through the diversity of the amino acids (AAs) not selected by nature for protein incorporation, the most generic modes of activation, induction, and reactivity commonly used, such as chiral enamine, hydrogen bonding, Brønsted acids/bases, and phase-transfer organocatalysis, reflecting their increasingly important role in organic and applied chemistry.

New Trends in Biosurfactants: From Renewable Origin to Green Enhanced Oil Recovery Applications

Enhanced oil recovery (EOR) processes are technologies used in the oil and gas industry to maximize the extraction of residual oil from reservoirs after primary and secondary recovery methods have been carried out. The injection into the reservoir of surface-active substances capable of reducing the surface tension between oil and the rock surface should favor its extraction with significant economic repercussions. However, the most commonly used surfactants in EOR are derived from petroleum, and their use can have negative environmental impacts, such as toxicity and persistence in the environment. Biosurfactants on the other hand, are derived from renewable resources and are biodegradable, making them potentially more sustainable and environmentally friendly. The present review intends to offer an updated overview of the most significant results available in scientific literature on the potential application of biosurfactants in the context of EOR processes. Aspects such as production strategies, techniques for characterizing the mechanisms of action and the pros and cons of the application of biosurfactants as a principal method for EOR will be illustrated and discussed in detail. Optimized concepts such as the HLD in biosurfactant choice and design for EOR are also discussed. The scientific findings that are illustrated and reviewed in this paper show why general emphasis needs to be placed on the development and adoption of biosurfactants in EOR as a substantial contribution to a more sustainable and environmentally friendly oil and gas industry.

Biodegradable Cationic and Ionizable Cationic Lipids: A Roadmap for Safer Pharmaceutical Excipients

Cationic and ionizable cationic lipids are broadly applied as auxiliary agents, but their use is associated with adverse effects. If these excipients are rapidly degraded to endogenously occurring metabolites such as amino acids and fatty acids, their toxic potential can be minimized. So far, synthesized and evaluated biodegradable cationic and ionizable cationic lipids already showed promising results in terms of functionality and safety. Within this review, an overview about the different types of such biodegradable lipids, the available building blocks, their synthesis and cleavage by endogenous enzymes is provided. Moreover, the relationship between the structure of the lipids and their toxicity is described. Their application in drug delivery systems is critically discussed and placed in context with the lead compounds used in mRNA vaccines. Moreover, their use as preservatives is reviewed, guidance for their design is provided, and an outlook on future developments is given.

Evaluation of synthesized biosurfactants as promising corrosion inhibitors and alternative antibacterial and antidermatophytes agents

This study investigated different amino acid-based surfactants (AASs), also known as biosurfactants, including sodium N-dodecyl asparagine (AS), sodium N-dodecyl tryptophan (TS), and sodium N-dodecyl histidine (HS) for their potential anticorrosion, antibacterial, and antidermatophyte properties. The chemical and electrochemical techniques were employed to examine the copper corrosion inhibition efficacy in H₂SO₄ (1.0 M) solution at 298 K. The results indicated their promising corrosion inhibition efficiencies (% IEs), which varied with the biosurfactant structures and concentrations, and the concentrations of corrosive medium. Higher % IEs values were attributed to the surfactant adsorption on the copper surface and the production of a protective film. The adsorption was in agreement with Langmuir adsorption isotherm. The kinetics and mechanisms of copper corrosion and its inhibition by the examined AASs were illuminated. The surfactants behaved as mixed-kind inhibitors with minor anodic priority. The values of % IEs gained from weight loss technique at a 500 ppm of the tested surfactants were set to be 81, 83 and 88 for AS, HS and TS, respectively. The values of % IEs acquired from all the applied techniques were almost consistent which were increased in the order: TS > HS ≥ AS, establishing the validity of this study. These surfactants also exhibited strong broad-spectrum activities against pathogenic Gram-negative and Gram-positive bacteria and dermatophytes. HS exhibited the highest antimicrobial activity followed by TS, and AS. The sensitivity of pathogenic bacteria varied against tested AASs. Shigella dysenteriae and Trichophyton mantigrophytes were found to be the most sensitive pathogens. HS exhibited the highest antibacterial activity against Shigella dysenteriae, Bacillus cereus, E. coli, K. pneumoniae, and S. aureus through the formation of clear zones of 70, 50, 40, 39, and 35 mm diameters, respectively. AASs also exhibited strong antifungal activity against all the tested dermatophyte molds and fungi. HS caused the inhibition zones of 62, 57, 56, 48, and 36 mm diameters against Trichophyton mantigrophytes, Trichophyton rubrum, Candida albicans, Trichosporon cataneum, and Cryptococcus neoformans, respectively. AASs minimal lethal concentrations ranged between 16 to 128 µg/ml. HS presented the lowest value (16 µg/ml) against tested pathogens followed by TS (64 µg/ml), and AS (128 µg/ml). Therefore, AASs, especially HS, could serve as an effective alternative antimicrobial agent against food-borne pathogenic bacteria and skin infections-associated dermatophyte fungi.

Study on the synthesis and performance of sodium 2-laurylamido isobutyrate

In the present work, sodium 2-laurylamido isobutyrate was synthesized from 2-aminoisobutyric acid, NaOH and lauroyl chloride by the Schotten-Baumann condensation. Fourier transform infrared spectroscopy, mass spectroscopy and nuclear magnetic resonance spectroscopy were used to characterize the products, and confirming the successful synthesis of sodium 2-laurylamido isobutyrate. The influence of temperature on the surface tension of sodium 2-laurylamido isobutyrate was studied, comparing the chemical properties of the surface with those of sodium N-lauroyl sarcosinate. The results indicate that both surfactants have a similar pC 20, while the critical micelle concentration (CMC) and the surface tension at the critical micelle concentration (γ CMC) of sodium 2-laurylamido isobutyrate are higher than those of sodium N-lauroyl sarcosinate. Further studies on the thermodynamic parameters of sodium 2-laurylamido isobutyrate and sodium N-lauroyl sarcosinate indicate that the formation of micelles is a spontaneous exothermic process mainly driven by entropy. According to the dynamic surface tension of sodium 2-laurylamido isobutyrate and sodium N-lauroyl sarcosinate, the molecular adsorption of the two components mixture change from the initial diffusion controlled adsorption to the later mixed dynamic controlled adsorption.

Microcystins can be extracted from Microcystis aeruginosa using amino acid-derived biosurfactants

Microcystin, a cyanotoxin produced by Microcystis aeruginosa growing in eutrophic waters, can promote liver tumors in people ingesting contaminated water. To date, water treatment systems have not been effective in removing or degrading these cyanotoxins. In this work, we investigated the inhibitory activity of surfactants on the growth of M. aeruginosa and their application to extract the intracellular produced cyanotoxins. The experiments involving growth inhibition and extraction of cyanotoxins were carried out using the non-biodegradable surfactant cetyl trimethyl ammonium bromide (CTAB) in addition to other biodegradable surfactants. These were Tween 80 and surfactants derived from amino acids and peptides, respectively, from arginine, SDA, and hydrolyzed peptone, SDP. We demonstrated that the tested surfactants could be used to inhibit the growth of M. aeruginosa. At this point, CTAB and SDA proved to be the most competent surfactants in reducing cyanobacterial growth. Moreover, microcystins have been successfully removed from the water employing a cloud point extraction protocol based on the use of these surfactants and ammonium sulfate.

Cationic gemini surfactant properties, its potential as a promising bioapplication candidate, and strategies for improving its biocompatibility: A review

Gemini surfactants consist of two cationic monomers of a surfactant linked together with a spacer. The specific structure of a cationic gemini surfactant is the reason for both its high surface activity and its ability to decrease the surface tension of water. The high surface activity and unique structure of gemini surfactants result in outstanding properties, including antibacterial and antifungal activity, anticorrosion properties, unique aggregation behaviour, the ability to form various structures reversibly in response to environmental conditions, and interactions with biomacromolecules such as DNA and proteins. These properties can be tailored by selecting the optimal structure of a gemini surfactant in terms of the nature and length of its alkyl substituents, spacer, and head group. Additionally, regarding their properties, comparison with their monomeric counterparts demonstrates that gemini surfactants have higher performance efficacy at lower concentrations. Hence, less material is needed, and the toxicity is lower. However, there are some limitations regarding their biocompatibility that have led researchers to develop amino acid-based and sugar-based gemini surfactants. Owing to their remarkable properties, cationic gemini surfactants are promising candidates for bioapplications such as drug delivery systems, gene carriers, and biomaterial surface modification.

Heads or tails? The synthesis, self-assembly, properties and uses of betaine and betaine-like surfactants

Betaines are a key class of zwitterionic surfactant that exhibit particularly favorable properties, making them indispensable in modern formulation. Due to their composition, betaines are readily biodegradable, mild on the skin and exhibit some antimicrobial activity. Vital to their function, these surfactants self-assemble into diverse micellar geometries, some of which contribute to increased solution viscosity, and their surface activity results in strong detergency and foaming. As such, their behavior has been exploited in various applications from personal care (including shampoos and liquid soaps) to specific industrial fields (such as enhanced oil recovery). This review aims to inform the reader of the diverse range of different betaine and betaine-like surfactants that have been actively researched over the past three decades. Synthesis as well as both chemical and physical characterization of betaine surfactants are discussed, including small-angle scattering studies that indicate self-assembly structures and rheological data that demonstrates texture and flow. Stimulus responsive systems and exotic betaine analogs with enhanced functionality are also covered. Crucially, the connection between surfactant molecular architecture and function are highlighted, exemplifying precisely why zwitterionic betaine and related surfactants are so uniquely functional.

Impact of Processing Conditions on Rheology, Tribology and Wet Lubrication Performance of a Novel Amino Lipid Hair Conditioner

The objective of this work was to carry out a comprehensive evaluation of the performance of a novel cationic amino lipid surfactant, Brassicyl Valinate Esylate (BVE), in contrast to conventional alkyl quaternary ammonium surfactants (quats), through a study of the effects of process mixing speed on its overall rheological, tribological and wet lubrication performance in comparison to BTAC and CTAC, two cationic surfactants widely used in cosmetics. The major cosmetic application of cationic surfactants is in the preparation of hair conditioners. Hence, this analysis was done firstly by conducting tensile combing tests to evaluate reduction in wet lubrication which translates to conditioning performance. The combing results serve as a testing metric that adequately corresponds to consumer perception of conditioned hair. To correlate this technically, yield stress measurements were conducted to establish rheologic profiles of the conditioner formulations, and in vitro tribological testing of the emulsion systems between two steel surfaces were done to technically simulate the spreading and rubbing of conditioner on the hair. The effect of processing conditions on the formulations was then evaluated. BVE was found to be an effective conditioning surfactant suitable as an eco-friendly replacement for BTAC and CTAC in hair conditioner formulations. The results showed that higher shear mixing rates during formulation lead to poorer performance effects evident through decreased yield stress values, lower percentage reduction in combing force and a higher coefficient of friction.

Formation of catanionic vesicles by threonine-derived surfactants and gemini surfactants based on conventional or serine-derived headgroups: designing versatile and cytocompatible nanocarriers

In this work, we explore the ability of newly synthesized threonine-derived surfactants to form robust, versatile and cytocompatible catanionic vesicles when mixed with gemini surfactants, as potential effective nanocarriers for biomolecules. The threonine surfactants consist of single-tailed amphiphiles with carboxylate headgroups and varying alkyl tail length, CnThr, where n is the (even) number of tail C atoms, varying from 8 to 16. After an initial characterization of the micellization behavior of the neat CnThr surfactants (at pH = 7 and 12), the dodecyl derivative, C12Thr, was selected as the optimal surfactant to investigate regions of formation of spontaneous catanionic vesicles. Phase behavior studies and microstructural characterization of mixtures involving both conventional bis-quat n-s-n gemini (where n and s are the tail and spacer number of C atoms) and biocompatible serine-derived gemini surfactants were carried out. Light and electron microscopy, dynamic light scattering and zeta potential measurements show spontaneous vesicles indeed form and exhibit versatile features in terms of average size, morphology, polydispersity, surface charge and pH. The toxicological profile of the neat surfactants and C12Thr/gemini vesicles based on MTT assays with a L929 cell line was also evaluated, showing good levels of in vitro cytocompatibility. Overall, the assortment of developed catanionic vesicles offers very attractive physicochemical and biological features to be explored for delivery purposes.

Micro-structural investigations on oppositely charged mixed surfactant gels with potential dermal applications

Dicarboxylic amino acid-based surfactants (N-dodecyl derivatives of -aminomalonate, -aspartate, and -glutamate) in combination with hexadecyltrimethylammonium bromide (HTAB) form a variety of aggregates. Composition and concentration-dependent mixtures exhibit liquid crystal, gel, precipitate, and clear isotropic phases. Liquid crystalline patterns, formed by surfactant mixtures, were identified by polarizing optical microscopy. FE-SEM studies reveal the existence of surface morphologies of different mixed aggregates. Phase transition and associated weight loss were found to depend on the composition where thermotropic behaviours were revealed through combined differential scanning calorimetry and thermogravimetric studies. Systems comprising more than 60 mol% HTAB demonstrate shear-thinning behaviour. Gels cause insignificant toxicity to human peripheral lymphocytes and irritation to bare mouse skin; they do not display the symptoms of cutaneous irritation, neutrophilic invasion, and inflammation (erythema, edema, and skin thinning) as evidenced by cumulative irritancy index score. Gels also exhibit substantial antibacterial effects on Staphylococcus aureus, a potent causative agent of skin and soft tissue infections, suggesting its possible application as a vehicle for topical dermatological drug delivery.

Interaction of cationic surfactants with DPPC membranes: effect of a novel Nα-benzoylated arginine-based compound

Cationic amino acid-based surfactants are known to interact with the lipid bilayer of microorganism resulting in cell death through a disruption of the membrane topology. To elucidate the interaction of a cationic surfactant synthesized in our lab, investigations involving N^α-benzoyl-arginine decyl amide (Bz-Arg-NHC₁₀), and model membranes composed by 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) were done. Bz-Arg-NHC₁₀was able to penetrate into DPPC monolayers up to a critical pressure of 59.6 mN m^-1. Differential scanning calorimetry revealed that as the concentration of Bz-Arg-NHC₁₀ increased, the main transition temperature of DPPC slightly decreased. Atomic force microscopy (AFM) in situ experiments performed on supported DPPC bilayers on mica allowed monitoring the changes induced by Bz-Arg-NHC₁₀. DPPC bilayer patches were partially removed, mainly in borders and bilayer defects for 50 µM Bz-Arg-NHC₁₀ solution. Increasing the concentration to 100 µM resulted in a complete depletion of the supported bilayers. Surface plasmon resonance (SPR) experiments, carried out with fully DPPC bilayers covered chips, showed a net increase of the SPR signal, which can be explained by Bz-Arg-NHC₁₀ adsorption. When patchy DPPC bilayers were formed on the substrate, a SPR signal net decrease was obtained, which is consistent with the phospholipids' removal observed in the AFM images. The results obtained suggest that the presence of the benzoyl group attached to the polar head of our compound would be the responsible of the increased antimicrobial activity against gram-negative bacteria when compared with other arginine-based surfactants.

Design of a New Gemini Lipoaminoacid with Immobilized Lipases Based on an Eco-Friendly Biosynthetic Process

Lipoaminoacids (LAA) are an important group of biosurfactants, formed by a polar hydrophilic part (amino acid) and a hydrophobic tail (lipid). The gemini LAA structures allow the formation of a supramolecular complex with bioactive molecules, like DNA, which provides them with good transfection efficiency. Since lipases are naturally involved in lipid and protein metabolism, they are an alternative to the chemical production of LAA, offering an eco-friendly biosynthetic process option. This work aimed to design the production of novel cystine derived gemini through a bioconversion system using immobilized lipases. Three lipases were used: porcine pancreatic lipase (PPL); lipase from Thermomyces lanuginosus (TLL); and lipase from Rizhomucor miehei (RML). PPL was immobilized in sol-gel lenses. L-cystine dihydrochloride and dodecylamine were used as substrates for the bioreaction. The production of LAA was evaluated by thin layer chromatography (TLC), and colorimetric reaction with eosin. The identification and quantification was carried out by High Performance Liquid Chromatographer-Mass Spectrometry (HPLC-MS/MS). The optimization of media design included co-solvent (methanol, dimethylsulfoxide), biphasic (n-hexane and 2-propanol) or solvent-free media, in order to improve the biocatalytic reaction rates and yields. Moreover, a new medium was tested where dodecylamine was melted and added to the cystine and to the biocatalyst, building a system of mainly undissolved substrates, leading to 5 mg/mL of LAA. Most of the volume turned into foam, which indicated the production of the biosurfactant. For the first time, the gemini derived cystine lipoaminoacid was produced, identified, and quantified in both co-solvent and solvent-free media, with the lipases PPL, RML, and TLL.

Radical-Based Synthesis and Modification of Amino Acids

Amino acids (AAs) are key structural motifs with widespread applications in organic synthesis, biochemistry, and material sciences. Recently, with the development of milder and more versatile radical-based procedures, the use of strategies relying on radical chemistry for the synthesis and modification of AAs has gained increased attention, as they allow rapid access to libraries of novel unnatural AAs containing a wide range of structural motifs. In this Minireview, we provide a broad overview of the advancements made in this field during the last decade, focusing on methods for the de novo synthesis of α-, β-, and γ-AAs, as well as for the selective derivatisation of canonical and non-canonical α-AAs.

Antioxidant, Antidiabetic and Anticancer Activities of L-Phenylalanine and L-Tyrosine Ester Surfactants: In Vitro and In Silico Studies of their Interactions with Macromolecules as Plausible Mode of Action for their Biological Properties

Background:

Aromatic amino acid-based surfactants have been found to have interesting biological properties such as antibacterial and hemolytic activities. Recently, we have reported the antibacterial activity of a range of ester hydrochloride surfactants derived from L-Phenylalanine and LTyrosine. This study aims at assessing the antioxidant, α-glycosidase inhibitory and cytotoxic activities of a series of L-Phenylalanine and L-Tyrosine ester hydrochlorides. Molecular docking and BSA binding studies were also carried out in order to investigate their potential therapeutic targets.

Methods:

L-Phenylalanine and L-Tyrosine surfactants were tested as potential lipophilic antioxidants using the DPPH and ABTS assays. These surfactants were also tested for their α-glycosidase inhibitory activity using 4-nitrophenyl α -D-glucopyranoside (pNPG) as substrate. Their cytotoxicity effects were screened using HeLa and KB cell lines. Glide version 5.7 as implemented in Schrödinger suite 2013-1, was used for performing docking studies of L-Phenylalanine and L-Tyrosine dodecyl esters. The interaction of the ester hydrochlorides of L-Phenylalanine and L-Tyrosine with bovine serum albumin (BSA) was investigated using fluorometric titration.

Results:

The presence of the phenolic moiety in L-Tyrosine-based surfactants was found to enhance the antioxidant and α-glucosidase inhibitory activities compared to the L-Phenylalanine derivatives. The α- glucosidase and anticancer activities of the phenylalanine surfactants were found to increase with chain length up to C12 above which the activities exhibited a downward trend. In the case of the tyrosine series, an increase in chain length from C8 to C14 was found to decrease the α-glucosidase inhibitory activity and increase the anticancer activity of the surfactants. Binding studies with bovine serum albumin showed that the tyrosine surfactants displayed greater affinity for the serum albumin, owing to the presence of the phenolic group which altered the orientation of the surfactant molecule within the hydrophobic core of BSA.

Conclusion:

L-Tyrosine esters having a phenolic moiety were found to possess enhanced biological activity in terms of both the antioxidant and antidiabetic activities as well as also bind more strongly to Bovine serum albumin. Molecular docking studies of the phenylalanine and tyrosine surfactants of similar chain length with target proteins showed direct correlation with their anticancer and antidiabetic activity. Therefore, the findings show that these aromatic based surfactants derived from L-Tyrosine can act as promising antioxidant, antidiabetic and anticancer agents, and they can also be efficiently transported and eliminated in the body, making them useful candidates for drug designs.

Lipoaminoacids Enzyme-Based Production and Application as Gene Delivery Vectors

Biosurfactant compounds have been studied in many applications, including biomedical, food, cosmetic, agriculture, and bioremediation areas, mainly due to their low toxicity, high biodegradability, and multifunctionality. Among biosurfactants, the lipoplexes of lipoaminoacids play a key role in medical and pharmaceutical fields. Lipoaminoacids (LAAs) are amino acid-based surfactants that are obtained from the condensation reaction of natural origin amino acids with fatty acids or fatty acid derivatives. LAA can be produced by biocatalysis as an alternative to chemical synthesis and thus become very attractive from both the biomedical and the environmental perspectives. Gemini LAAs, which are made of two hydrophobic chains and two amino acid head groups per molecule and linked by a spacer at the level of the amino acid residues, are promising candidates as both drug and gene delivery and protein disassembly agents. Gemini LAA usually show lower critical micelle concentration, interact more efficiently with proteins, and are better solubilising agents for hydrophobic drugs when compared to their monomeric counterparts due to their dimeric structure. A clinically relevant human gene therapy vector must overcome or avoid detect and silence foreign or misplaced DNA whilst delivering sustained levels of therapeutic gene product. Many non-viral DNA vectors trigger these defence mechanisms, being subsequently destroyed or rendered silent. The development of safe and persistently expressing DNA vectors is a crucial prerequisite for a successful clinical application, and it one of the main strategic tasks of non-viral gene therapy research.

Dynamic Imine Chemistry at Complex Double Emulsion Interfaces

Interfacial chemistry provides an opportunity to control dynamic materials. By harnessing the dynamic covalent nature of imine bonds, emulsions are generated in situ, predictably manipulated, and ultimately destroyed along liquid-liquid and emulsion-solid interfaces through simple perturbation of the imine equilibria. We report the rapid production of surfactants and double emulsions through spontaneous in situ imine formation at the liquid-liquid interface of oil/water. Complex double emulsions with imine surfactants are stable to neutral and basic conditions and display dynamic behavior with acid-catalyzed hydrolysis and imine exchange. We demonstrate the potential of in situ imine surfactant formation to generate complex surfactants with biomolecules (i.e., antibodies) for biosensing applications. Furthermore, imine formation at the emulsion-solid interface offers a triggered payload release mechanism. Our results illustrate how simple, dynamic interfacial imine formation can translate changes in bonding to macroscopic outputs.

Water-mediated catalyst-free synthesis of lysine-based ampholytic amphiphiles for multipurpose applications: Characterization and pH-responsive emulsifying properties

A novel series of lysine-based ampholytic amphiphiles, with alkylsuccinic anhydrides of varying chain lengths as hydrophobic acylating agents, were synthesized in medium to high yield (50.23-90.15%) based on a facile, catalyst-free method in water medium; and structurally confirmed by mass spectrometry (MS), Fourier transform infra-red (FTIR) spectroscopy, and ¹H/¹³C nuclear magnetic resonances (NMR) analysis. The resulting compounds were subjected to pH-dependent amphiphilic property, ferrous ion chelating, DPPH antioxidant capacity, and cytotoxicity analyses. Results showed that CMC values decrease, γ value increase, and emulsion stability increase with the increase of medium pH, suggesting that the surface activity of synthetic compounds at air/water and oil/water interface under neutral and alkaline conditions was remarkably higher than that under acidic condition. Lauryl O-acylated malic lysine (compound 4b) presented excellent foaming ability close to commercial detergent sodium dodecyl sulphate; dodecyl succinic lysine (compound 4a) afforded highly stable o/w nanoemulsion. Moreover, compound 4b displayed comparable ferrous ion chelating property to lysine and 2,2-diphenyl-1-picrylhydrazyl (DPPH) antioxidative capacity similar to a commercial food ingredient, diacetyl tartaric acid esters of mono- and di-glycerides (DATEM), indicating its multi-faceted functionalities. A cytotoxicity study of compounds 3b &4b showed that they were non-toxic. Thus, these novel ampholytic amphiphiles may find multi-purpose applications in food, detergent, pharmaceutical, and cosmetic industry.

Purification, characterization, and gene cloning of a novel aminoacylase from Burkholderia sp. strain LP5_18B that efficiently catalyzes the synthesis of N-lauroyl-l-amino acids

An N-lauroyl-l-phenylalanine-producing bacterium, identified as Burkholderia sp. strain LP5_18B, was isolated from a soil sample. The enzyme was purified from the cell-free extract of the strain and shown to catalyze degradation and synthesis activities toward various N-acyl-amino acids. N-lauroyl-l-phenylalanine and N-lauroyl-l-arginine were obtained with especially high yields (51% and 89%, respectively) from lauric acid and l-phenylalanine or l-arginine by the purified enzyme in an aqueous system. The gene encoding the novel aminoacylase was cloned from Burkholderia sp. strain LP5_18B and expressed in Escherichia coli. The gene contains an open reading frame of 1,323 nucleotides. The deduced protein sequence encoded by the gene has approximately 80% amino acid identity to several hydratase of Burkholderia. The addition of zinc sulfate increased the aminoacylase activity of the recombinant E. coli strain.

Arginine-based cationic surfactants: Biodegradable auxiliary agents for the formation of hydrophobic ion pairs with hydrophilic macromolecular drugs

WORKING HYPOTHESIS

It was the hypothesis of this study that esters of arginine (Arg) with medium and long chain aliphatic alcohols are biodegradable and less cytotoxic than well-established cationic surfactants being used for hydrophobic ion pairing (HIP) with hydrophilic macromolecular drugs.

EXPERIMENTS

Arg was linked to nonan-1-ol and hexadecan-1-ol (C₉ and C₁₆) via an ester linkage. The newly formed Arg-nonyl ester (ANE) and Arg-hexadecanoyl ester (AHE) surfactants were evaluated regarding critical micelle concentration (CMC) using pyrene fluorescent method, cytotoxicity on human colorectal adenocarcinoma-derived cells (Caco-2) and biodegradability at the concentrations of 2.5 and 5 mg/mL using 2500 N_α-benzoyl-l-arginine ethyl ester hydrochloride (BAEE) units/mL of trypsin. Furthermore, in order to evaluate their potential for HIP, heparin and daptomycin were used as model polysaccharide and peptide drugs, respectively.

FINDINGS

Chemical structures of ANE and AHE surfactants were confirmed by FTIR, ¹H NMR, and LC-MS. CMC of ANE was 7.5 mM and CMC of AHE was 2 mM. Arg-surfactants were not cytotoxic below their CMC. At CMC and above CMC, ANE was significantly (P < 0.05) more cytotoxic than AHE. ANE in both concentrations was degraded ˃98% within 48 h. The degradation of AHE at lower concentration was ˃97% and about 50% at higher concentration. Arg-surfactants were able to efficiently precipitate heparin and daptomycin from corresponding aqueous solutions.

CONCLUSION

Arg-surfactants being biodegradable and less toxic seems to be a promising alternative to well-established cationic surfactants for the formation of hydrophobic ion pairs (HIPs) with hydrophilic macromolecular drugs.

Multi-targeted approach by 2-benzimidazolylquinoxalines-loaded cationic arginine liposomes against сervical cancer cells in vitro

Multi-targeted approaches for inhibition of сervical cancer cells in vitro were developed by implementing two different strategies and drug combination for creation of new therapeutic target agents and for nanotechnological-enhancement of intracellular delivery. New 2-benzimidazolylquinoxalines derivatives were synthesized and characterized by combining two different pharmacophores - benzimidazole and quinoxaline rings directly bonded in their structures. Spectrophotometric technique for determination of content of compounds in various media was developed to evaluate their solubility in water and micellar solutions of surfactants. The bioavailability of poorly water-soluble 2-benzimidazolylquinoxalines was improved by PEGylated liposomes as antitumor drug delivery carriers. 2-benzimidazolylquinoxalines-loaded PEGylated liposomes, with size close to 100 nm and negative zeta potential ranging from -13 mV to -27 mV, were time-stable at room temperature. The design of liposomal formulations for improving cellular uptake and in vitro antitumor efficacy was performed by modification of liposome surface with the new arginine surfactant. The cell viability of 2-benzimidazolylquinoxalines-loaded arginine liposomes on human cancer M-Hela cells was 16% at the concentration 0.15 mg/ml. Moreover, these liposomes showed a lower toxicity (40%) against normal human Gang liver cells both at the lowest and highest tested concentrations.

Self-Assembly of Unconventional Low-Molecular-Mass Amphiphiles Containing a PEG Chain

The design and synthesis of biocompatible surfactants are important for a wide range of applications in cosmetics, personal care products, and nanomedicine. This feature article summarizes our studies over the past 8 years on the design, synthesis, surface activity, and self-assembly of a series of unconventional low-molecular-mass amphiphiles containing a poly(ethylene glycol) (PEG) tail or spacer and different ionic or zwitterionic headgroups, including carboxylate, sulfonate, and quaternary ammonium salts. Despite having a so-called polar PEG chain as a tail or spacer, these ionic amphiphiles are found to have a tendency to adsorb at the air/water interface and self-assemble in pH 7.0 buffers at 298 K in the same way that conventional hydrocarbon tail surfactants do. However, they are observed to be relatively less surface-active compared to hydrocarbon tail surfactants. Although these amphiphilic molecules have less surface activity, they do self-assemble in aqueous buffer at 298 K, producing a range of microstructures, including spherical micelles, disclike micelles, and vesicles. In fact, our group is the first to report the self-assembly of PEG-tailed ionic amphiphiles in water at room temperature. Some of these molecules are also found to gel various organic liquids on heat-cool treatment or by ultrasound irradiation. We think that the present article will arouse general interest among researchers working toward the development of new biocompatible amphiphiles and soft materials.

Cationic surfactants as antifungal agents

Fungi-in being responsible for causing diseases in animals and humans as well as environmental contaminations in health and storage facilities-represent a serious concern to health security. Surfactants are a group of chemical compounds used in a broad spectrum of applications. The recently considered potential employment of cationic surfactants as antifungal or fungistatic agents has become a prominent issue in the development of antifungal strategies, especially if such surface-active agents can be synthesized in an eco-friendly manner. In this review, we describe the antifungal effect and the reported mechanisms of action of several types of cationic surfactants and also include a discussion of the contribution of these surfactants to the inhibition of yeast-based-biofilm formation. Furthermore, the putative mechanism of arginine-based tensioactive compounds as antifungal agents and their applications are also analyzed.