Polymer Concentration Maximizes Encapsulation Efficiency in Electrohydrodynamic Mixing Nanoprecipitation

Encapsulation in self-assembled block copolymer (BCP) based nanoparticles (NPs) is a common approach to enhance hydrophobic drug solubility, and nanoprecipitation processes in particular can yield high encapsulation efficiency (EE). However, guiding principles for optimizing polymer, drug, and solvent selection are critically needed to facilitate rapid design of drug nanocarriers. Here, we evaluated the relationship between drug-polymer compatibility and concentration ratios on EE and nanocarrier size. Our studies employed a panel of four drugs with differing molecular structures (i.e., coumarin 6, dexamethasone, vorinostat/SAHA, and lutein) and two BCPs [poly(caprolactone)-b-poly(ethylene oxide) (PCL-b-PEO) and poly(styrene)-b-poly(ethylene oxide) (PS-b-PEO)] synthesized using three nanoprecipitation processes [i.e., batch sonication, continuous flow flash nanoprecipitation (FNP), and electrohydrodynamic mixing-mediated nanoprecipitation (EM-NP)]. Continuous FNP and EM-NP processes demonstrated up to 50% higher EE than batch sonication methods, particularly for aliphatic compounds. Drug-polymer compatibilities were assessed using Hansen solubility parameters, Hansen interaction spheres, and Flory Huggins interaction parameters, but few correlations were EE observed. Although some Hansen solubility (i.e., hydrogen bonding and total) and Flory Huggins interaction parameters were predictive of drug-polymer preferences, no parameter was predictive of EE trends among drugs. Next, the relationship between polymer: drug molar ratio and EE was assessed using coumarin 6 as a model drug. As polymer:drug ratio increased from <1 to 3–6, EE approached a maximum (i.e., ∼51% for PCL BCPs vs. ∼44% PS BCPs) with Langmuir adsorption behavior. Langmuir behavior likely reflects a formation mechanism in which drug aggregate growth is controlled by BCP adsorption. These data suggest polymer:drug ratio is a better predictor of EE than solubility parameters and should serve as a first point of optimization.

Influence of lactide vs glycolide composition of poly (lactic-co-glycolic acid) polymers on encapsulation of hydrophobic molecules: molecular dynamics and formulation studies

The work demonstrates the preparation of PLGA (PLGA 50:50, PLGA 75:25) nanoparticles, to encapsulate a hydrophobic molecule (coumarin-6), using the microreactor-based continuous process. The formulations were characterized using dynamic light scattering and transmission electron microscopy to determine their size, homogeneity, zeta potential, and surface morphology. The resulting nanoparticles were safe to the CHO cells (≈80% cell survival), at the concentration of ≤600 µg/mL and were successfully taken up by the cells, as demonstrated using confocal microscopy. Moreover, imaging flow cytometry confirmed that the nanoparticles were internalized in 73.96% of the cells. Furthermore, molecular dynamics simulation and docking studies were carried out to explore the effect of polymer chain length of PLGA and lactide vs glycolide (LA:GA) ratio on their compatibility with the coumarin-6 molecules and to study the coiling and flexibility of PLGA in the presence of coumarin-6 molecules. Flory–Huggins interaction parameter (χ) was calculated for polymer chains of varying lengths and LA:GA ratio, with respect to coumarin-6. χ parameter increased with increase in polymer chain length, which indicated superior interaction of coumarin-6 with the smaller chains. Amongst all the polymeric systems, PLGA55 exhibited the strongest interaction with coumarin-6, for all the chain lengths, possibly because of their homogeneous spatial arrangements and superior binding energy. PLGA27 showed better compatibility compared to PLGA72 and PGA, whereas PLA-based polymers exhibited the least compatibility. Analysis of the radius of gyration of the polymer chains in the polymer–coumarin-6 complexes, at the end of molecular dynamics run, exhibited that the polymer chains displayed varying coiling behavior and flexibility, depending upon the relative concentrations of the polymer and coumarin-6. Factors like intra-chain interactions, spatial arrangement, inter-chain binding energies, and polymer–coumarin-6 compatibility also influenced the coiling and flexibility of polymer chains.

A New Flavonoid from Malaysian Dipterocarpus cornutus

Dipterocarpus cornutus Dyer is commonly known as ‘keruing’. It belongs to the family of Dipterocarpaceae, an important timber family in South East Asia. D. cornutus is listed as critically endangered on IUCN Red List. Since no comprehensive study has been documented on the chemical constituents of D. cornutus, there is an urgent need to study this plant comprehensively. Phytochemical study of the stem bark of D. cornutus afforded a new flavonoid (1) and nine known compounds, which consist of flavonoids (2, 3), oligostilbenoids (4, 5, 7, 8, 9, 10), and coumarin (6). The finding of the study contributes to the chemotaxonomic differentiation in the plants of the tribe Dipterocarpae.

Hyaluronic Acid Coating Reduces the Leakage of Melittin Encapsulated in Liposomes and Increases Targeted Delivery to Melanoma Cells

Melittin is a promising antitumor substance; however, it is a nonspecific cytolytic peptide, which limits its clinical application. In this study, melittin liposomes (Mel-Lip) and hyaluronic acid (HA)-modified Mel-Lip (Mel-HA-Lip) were designed to reduce the toxicity and increase the anti-tumor effects of melittin. The optimal preparation procedure was evaluated using a uniform design based on the single factor method, and the concentration of HA was determined based on the cellular uptake of coumarin 6 labeled HA-Lip. Liposomes and HA-modified liposomes were evaluated in vitro by assessing cytotoxicity, cellular uptake, and release behavior. Liposomes prepared in the optimum formulation improved stability, with a particle size of 132.7 ± 1.55 nm, zeta potential of −11.5 ± 1.51 mV, entrapment efficiency of 86.25 ± 1.28%, and drug-loading efficiency of 3.91 ± 0.49%. Cellular uptake tests revealed that the uptake of nanoparticles significantly increased with HA modification, suggesting that HA modification enhanced the internalization of liposomes within cells, which was consistent with the results of the cytotoxicity analysis. Furthermore, in vitro release experiments showed that Mel-HA-Lip possessed a stronger sustained-release effect compared with Mel-Lip. The results of this experiment provide insight into the potential tumor-targeting effects of melittin.

Fluorescently Labeled PLGA Nanoparticles for Visualization In Vitro and In Vivo: The Importance of Dye Properties

Fluorescently labeled nanoparticles are widely used for evaluating their distribution in the biological environment. However, dye leakage can lead to misinterpretations of the nanoparticles’ biodistribution. To better understand the interactions of dyes and nanoparticles and their biological environment, we explored PLGA nanoparticles labeled with four widely used dyes encapsulated (coumarin 6, rhodamine 123, DiI) or bound covalently to the polymer (Cy5.5.). The DiI label was stable in both aqueous and lipophilic environments, whereas the quick release of coumarin 6 was observed in model media containing albumin (42%) or liposomes (62%), which could be explained by the different affinity of these dyes to the polymer and lipophilic structures and which we also confirmed by computational modeling (log PDPPC/PLGA: DiI—2.3, Cou6—0.7). The importance of these factors was demonstrated by in vivo neuroimaging (ICON) of the rat retina using double-labeled Cy5.5/Cou6-nanoparticles: encapsulated Cou6 quickly leaked into the tissue, whereas the stably bound Cy.5.5 label remained associated with the vessels. This observation is a good example of the possible misinterpretation of imaging results because the coumarin 6 distribution creates the impression that nanoparticles effectively crossed the blood–retina barrier, whereas in fact no signal from the core material was found beyond the blood vessels.

Síntese de um Novo Derivado de Sulfonamida a Partir da Cumarina-6-Clorossulfonada

Sulfonamida é uma classe de compostos de interesse para obtenção de novos medicamentos por apresentar propriedades químicas e biológicas como antitumoral, antimicrobiana, antifúngica, anti-inflamatória, antiobesidade, diurético, hipoglicêmico, anti-neuropática, entre outras. Mais de trinta medicamentos contendo esse grupo funcional estão em uso clínico, incluindo antibacterianos, diuréticos, anticonvulsivantes, hipoglicêmicos e inibidores de protease do vírus da imunodeficiência humana (HIV). Aproximadamente, 150 diferentes sulfonamidas são comercializadas como agentes bactericidas, contendo variações estruturais para potencializar a eficiência e solubilidade em sistemas biológicos. É importante estabelecer métodos rápidos e simples para a síntese de novas sulfonamidas com rendimento satisfatório. Nesse trabalho foi relatado um método sintético eficiente e fácil para obter sulfonamidas à partir da cumarina-6-clorossulfonada e as aminas primárias, tercbutilamina (CSNtert), isobutilamina (CSNiso) e isopropilamina (CSNisop) com rendimento de 71%. Essas novas sulfonamidas à base de cumarina foram caracterizadas por análise elementar, espectroscopia ultravioleta, espectroscopia no infravermelho por refletância total atenuada (ATR) e Ressonância Magnética Nuclear de 1H e 13C. Além disso, foram realizados testes de condutividade e ponto de fusão. A caracterização espectroscópica e química confirmou a formação de novos compostos e foi possível propor sua estrutura. Estudos da citotoxicidade da CSNtert, CSNiso e CSNisop em células epiteliais normais mostrou que estes compostos apresentam menor citotoxicidade que a cumarina-6-clorossulfonada. Palavras-chave: Cumarina. Sulfonamida. Síntese Abstract Sulfonamide is an important class of compounds that play an important role in the discovery of new medicines due to its broad chemical and biological activities such as antitumoral, antimicrobial, antifungic, anti-inflammatory, anti-obesity, diuretic, hypoglycemic, anti-neuropathic pain activities, among others. More than 30 drugs containing this functional group are in clinical use, including, antibacterial, diuretics, anticonvulsants, hypoglycemic and human immunodeficient virus (HIV) protease inhibitors. Approximately 150 different sulfonamides have been sold as bactericidal agents, and structural variations seems to increase their efficiency, potency and solubility in biological systems. Fast and simple synthetic methods for the construction of new sulfonamides with satisfactory yielding are important to be stablished. In this work an efficient and easy synthetic method was reported to obtain sulfonamides from coumarin-6-sulfonyl chloride and primary amines, tert-butyl amine (CSNtert), isobutylamine (CSNiso) and isopropylamine (CSNisop) with excellent yield, (71%). These new coumarin-based sulfonamides were characterized by elementary analysis, spectroscopy UV, Infrared by Attenuated Total Reflectance (ATR) and Nuclear Magnetic Resonance of 1H and 13C. In addition, conductivity tests were performed and melting point determined. The spectroscopic and chemical characterization confirmed the structures of the new compounds and could be possible to propose the structure. Studying their cytotoxicity against normal epithelial cells shows that the new compounds have lower cytotoxicity than coumarin-6-sulfonyl chloride. Keywords: Coumarin. Sulfonamide. Synthesis

Signal transmission encryption based on dye-doped chiral liquid crystal via tunable and efficient circularly polarized luminescence

Multi-channel adjustable chiral liquid crystal materials with outstanding circularly polarized luminescence (CPL) have aroused lots of interest. Here, we demonstrate a coumarin 6 (C6) doped chiral liquid crystal, exhibiting crosstalk-free...

EGFP-EGF1-conjugated poly (lactic-co-glycolic acid) nanoparticles as a carrier for the delivery of CCR2− shRNA to atherosclerotic macrophage in vitro

Reducing macrophage recruitment by silencing chemokine (C–C motif) receptor 2 (CCR2) expression is a promising therapeutic approach against atherosclerosis. However the transfection of macrophages with siRNA is often technically challenging. EGFP-EGF1-conjugated poly (lactic-co-glycolic acid) (PLGA) nanoparticles (ENPs) have a specific affinity to tissue factor (TF). In this study, the feasibility of ENPs as a carrier for target delivery of CCR2-shRNA to atherosclerotic cellular models of macrophages was investigated. Coumarin-6 loaded ENPs were synthesized using a double-emulsion method. Fluorescence microscopy and flow cytometry assay were taken to examine the uptake of Coumarin-6 loaded ENPs in the cellular model. Then a sequence of shRNA specific to CCR2 mRNA was constructed and encapsulated into ENPs. Target delivery of CCR2-shRNA to atherosclerotic cellular models of macrophages in vitro were evaluated. Results showed more uptake of ENPs by the cellular model than common PLGA nanoparticles. CCR2-shRNA loaded ENPs effectively silenced CCR2 gene in the atherosclerotic macrophages and exhibited a favorable cytotoxic profile to cultured cells. With their low cytotoxicity and efficient drug delivery, ENP could be a useful carrier for target delivery of CCR2-shRNA to inflammatory monocytes/macrophages for the therapy against atherosclerosis.