Fluorescent labels, especially FRET probes, are promising tools for studying a number of bio-chemical processes. In this paper, we promoted 2 important applications of FRET probes (MUTMAC-R6G and FITC-R6G): i) the formation of micelles from surfactants of various natures and polymers (chitosan – fatty acid), as well as ii) monitoring of enzymatic activity with improved parameters (increased analytical signal and improved selectivity due to shift to the long-wavelength region). The formation of micelles is accompanied by the convergence of fluorophores in the hydrophobic micelle core by a distance closer than in the buffer solution, thus r/R0 (where R0 – Foerster radius) is chosen as an analytical signal of micelle formation, including critical micelle concentration (CMC) and critical pre-micelle concentration (CPMC). The CMC values calculated using FRET probes are in a good agreement with literature data. At the same time, the r/R0 function provides valuable information about the nature and mechanism of micelle formation. With the second analytical application of FRET probes, we considered the optimization of techniques for studying enzymatic activity. The enzyme catalyses the reaction with the release of a fluorescent product, the signal from which may not be enough for detection, or it may be quenched, for example, in the reverse micelles (AOT-octane). Here we have proposed a solution – a FRET probe containing a rhodamine 6G (R6G) acceptor, which allows us to monitor the enzymatic reaction selectively (in the red region, 550-600 nm), and obtain a significantly higher fluorescence yield (potentially from 10 to 250 times). Thus, we have demonstrated a high potential for the FRET probes application as indicators of micelle formation as well as for the study of the enzyme catalytic activity. In the future, the method developed has prospects for application in the visualization of the enzyme functioning in cells due to the shift of the fluorescence signal to the long-wavelength region with an increase in the signal selectivity to suppress autofluorescence.

In recent years, polyureas with dynamic hindered urea bonds (HUBs), as a class of promising biomedical polymers, have attracted attention as a benefit of their controlled hydrolytic property. The effect of the chemical structures on the properties of polyureas and their assemblies was rarely reported. In this study, four kinds of polyureas with different chemical groups have been synthesized, and the polyurea from cyclohexyl diisocyanate and tert-butyl diamine showed the fastest hydrolytic rate. The amphiphilic polyurea composed of hydrophobic cyclohexyl-tert-butyl polyurea and hydrophilic poly(ethylene glycol) was synthesized for controlled delivery of antitumor drug paclitaxel (PTX). The PTX-loaded PEGylated polyurea micelle more effectively entered into the murine breast cancer 4T1 cells and inhibited the corresponding tumor growth in vitro and in vivo. Therefore, the PEGylated polyurea with adjustable degradation might be a promising polymer matrix for drug delivery.

Abstract: Tumor-targeting and blood-brain barrier (BBB)-penetrating are highly desirable for the treatment of glioma. In this study, we developed Pep-1&borneol-bifunctionalized carmustin-loaded micelles (Pep-1/Bor/CMS-M) capable of targeting to IL-13 receptor-overexpressed glioma and penetrating the brain microvascular endothelial cells-associated physiologic barriers. Pep-1/Bor/CMS-M were nearly spherical particles with a dimeter of 32.6 ± 1.1 nm and zeta potential of -21.3 ± 3.1 mV. Carmustine (CMS) released from Pep-1/Bor/CMS-M in pH 7.4 was significantly faster than in acidic environments. In human glioma BT325 cellular studies, Pep-1/Bor/CMS-M remarkably increased the cytotoxicity, notably improved the internalization and effectively induced the cell apoptosis. Likewise, in human brain microvascular endothelial cells (HBMEC) cells, Pep-1/Bor/CMS-M obviously promoted the cellular uptake, rapidly decreased the transepithelial electrical resistance (TEER) and thereby of enhancing the ability of penetration. In orthotopic Luc-BT325 glioma tumor-bearing nude mouse models, the stronger fluorescence signal and longer retention were observed in brain tissues compared with other controls, after single administration of DiD-labelled Pep-1/Bor/M (DiD/Pep-1/Bor/M). Importantly, Pep-1/Bor/CMS-M displayed the strongest inhibition of tumor growth, the longest survival period and low systemic toxicity in treating orthotopic glioma tumor-bearing nude mice. Simultaneous functionalization of Pep-1 and borneol offers a novel strategy for designing CMS-based nanomedicine and precisely treating glioma.

Coarse-grained molecular dynamics simulations are employed to investigate the spatiotemporal evolution of vesicles (polymersomes) by the self-assembly of randomly distributed amphiphilic BAB triblock copolymers with hydrophilic A and hydrophobic B blocks in an aqueous solution. The vesiculation pathway consists of several intermediate structures, such as an interconnected network of copolymer aggregates, a cage of cylindrical micelles and a lamellar cage. The cage-to-vesicle transition occurs at a constant aggregation number and practically eliminates the hydrophobic interfacial area between the B block and solvent. Molecular reorganization under-lying the sequence of morphology transitions from a cage-like aggregate to a vesicle is nearly isentropic. The end-to-end distances of isolated copolymer chains in solution and those within a vesicular assembly follow log normal probability distributions. This is attributed to the pre-ponderance of folded chain configurations in which the two hydrophobic end groups of a given chain stay close to each other. However, the probability distribution of end-to-end distances is broader for chains within the vesicle as compared to that of a single chain. This is due to the swelling of the folded configurations within the hydrophobic bilayer. Increasing the hydropho-bicity of the B block reduces the vesiculation time without qualitatively altering the self-assembly pathway.

Coarse-grained molecular dynamics simulations are employed to investigate spatiotemporal evolution of vesicles (polymersomes) via self-assembly of randomly distributed amphiphilic diblock copolymers in water. Vesiculation pathway consists of several intermediate structures such as spherical/rodlike aggregates, wormlike micelles, lamellae, and cavities. Lamella to vesicle transition occurs at a constant aggregation number and is accompanied by a reduction in the solvent accessible surface area. Simulation predictions are in qualitative agreement with the mechanism of vesicle formation in which the unfavorable hydrophobic interactions between water molecules and polymer segments along the edge of the lamella are eliminated at the expense of gaining curvature energy. However, rod-lamella-vesicle transition is accompanied by an increase in copolymer packing density. Hence, the change in the surface area accompanying vesiculation predicted by the simulations is significantly lower than theoretical estimates. Changes in information entropy, quantified by the expectation of the logarithm of the probability distribution function of the segmental stretch parameter s, defined as the difference between the maximum and instantaneous segmental extension, are statistically insignificant along the vesiculation pathway. For rods, lamellae and polymersomes, s follows a log normal distribution. This is explained based on the configurational dynamics of a single diblock chain in water.

In the current scenario of changing climatic conditions and rising global population, there is always a need to explore novel, efficient, and economical natural products for the benefit of human kind. Biosurfactant is one of the latest explored microbial biomolecules that have been used in numerous fields, including agriculture, pharmaceuticals, cosmetics, food processing, and environment-cleaning industries as raw material, lubrication, wetting, foaming softening, making emulsions, and stabilizing dispersions. The amphiphilic nature of biosurfactant biomolecules showed great advantage, distributing themselves into two immiscible surfaces by reducing interfacial surface tension and increasing the solubility of hydrophobic compounds. Furthermore, their eco-friendly nature, low or even no toxic nature, durability at higher temperatures, and wide range of pH fluctuations making the microbial surfactants preferable compared to their chemical counterparts. Additionally, the biosurfactants can obviate the oxidation flow by eliciting the antioxidant property, antimicrobial, anticancer activity, and drug delivery system, further broadening their applicability in the food, pharmaceutical, and pharma industries. Nowadays, biosurfactant has been broadly utilized to improve the soil quality by improving the concentration of trace elements and mixed with pesticides or applied singly on the plant surfaces for plant disease management. In the present review, we summarise the latest aspect of microbial synthesized biosurfactant compounds, limiting factors of biosurfactant production, and their application in improving soil quality, plant disease management.

Systems Chemistry has been a key component of origin of life research, invoking models of life’s inception based on evolving molecular networks. One such model is the Graded Autocatalysis Replication Domain (GARD) formalism embodied in a Lipid World scenario, which offers rigorous computer simulation based on defined chemical kinetics equations. GARD suggests that the first pre-RNA life-like entities could have been homeostatically-growing assemblies of amphiphiles, undergoing compositional replication and mutations, as well as rudimentary selection and evolution. Recent progress in Molecular Dynamics has provided an experimental tool to study complex biological phenomena such as protein folding, ligand-receptor interactions and micellar formation, growth and fission. The detailed molecular definition of GARD and its inter-molecular catalytic interactions make it highly compatible with Molecular Dynamics analyses. We present a roadmap for simulating GARD’s kinetic and thermodynamic behavior using various Molecular Dynamics methodologies. We review different approaches for testing the validity of the GARD model, by following micellar accretion and fission events and examining compositional changes over time. Near future computational advances could provide empirical delineation for further system complexification, from simple compositional non-covalent assemblies towards more life-like protocellular entities with covalent chemistry that underlies metabolism and genetic encoding.

Poly(2-methoxyethyl acrylate) (PMEA) and poly(ethylene oxide) (PEO) have protein-antifouling properties and blood compatibility. ABA triblock copolymers (PMEAn-PEO11340-PMEAn (MEOMn)) were prepared using single-electron transfer-living radical polymerization (SET-LRP) using a bi-functional PEO macroinitiator. Two types of MEOMn composed of PMEA blocks with a degree of polymerization (DP = n) of 85 and 777 were prepared using the same PEO macroinitiator. MEOMn formed flower micelles with a hydrophobic PMEA (A) core and hydrophilic PEO (B) loop shells in diluted water with a similar appearance to petals. The hydrodynamic radii of MEOM85 and MEOM777 were 151 and 108 nm, respectively. The PMEA block with a large DP formed a tightly packed core. The aggregation number (Nagg) of the PMEA block in a single flower micelle for MEOM85 and MEOM777 was 156 and 164, respectively, which were estimated using a light scat-tering technique. The critical micelle concentrations (CMCs) for MEOM85 and MEOM777 were 0.01 and 0.002 g/L, respectively, as determined by the light scattering intensity and fluorescence probe techniques. The size, Nagg, and CMC for MEOM85 and MEOM777 were almost the same inde-pendent of hydrophobic DP of the PMEA block.