Orthogonal analysis reveals inconsistencies in cargo loading of extracellular vesicles

Since extracellular vesicles (EVs) have emerged as a promising drug delivery system, diverse methods have been used to load them with active pharmaceutical ingredients (API) in preclinical and clinical studies. However, there is yet to be an engineered EV formulation approved for human use, a barrier driven in part by the intrinsic heterogeneity of EVs. API loading is rarely assessed in the context of single vesicle measurements of physicochemical properties but is likely administered in a heterogeneous fashion to the detriment of a consistent product. Here, we applied a suite of single-particle resolution methods to determine the loading of rhodamine 6G (R6G) surrogate cargo mimicking hydrophilic small molecule drugs across four common API loading methods: sonication, electroporation, freeze-thaw cycling and passive incubation. Loading efficiencies and alterations in the physical properties of EVs were assessed, as well as co-localization with common EV-associated tetraspanins (i.e., CD63, CD81 and CD9) for insight into EV subpopulations. Sonication had the highest loading efficiency, yet significantly decreased particle yield, while electroporation led to the greatest number of loaded API particles, albeit at a lower efficiency. Moreover, results were often inconsistent between repeated runs within a given method, demonstrating the difficulty in developing a rigorous loading method that consistently loaded EVs across their heterogeneous subpopulations. This work highlights the significance of how chosen quantification metrics can impact apparent conclusions and the importance of single-particle characterization of EV loading

A spectroscopic study of interaction of cationic dyes with heparin

<div align="justify">The interaction of two cationic dyes namely, acridine orange and pinacyanol chloride with an anionic polyelectrolyte, heparin, has been investigated by spectrophotometric method.The polymer induced metachromasy in the dyes resulting in the shift of the absorption maxima of the dyes towards shorter wavelengths. The stability of the complexes formed between acridine orange and heparin was found to be lesser than that formed between pinacyanol chloride and heparin. This fact was further confirmed by reversal studies using alcohols, urea and surfactants. The interaction of acridine orange with heparin has also been investigated fluorimetrically.The interaction parameters revealed that binding between acridine orange and heparin arises due to electrostatic interaction while that between pinacyanol chloride and heparin is found to involve both electrostatic and hydrophobic forces. The effect of the structure of the dye in inducing metachromasy has also been discussed.</div

Spectophotometric Study of Interaction between Sodium Carrageenate and Cationic Dyes

The interaction of two cationic dyes, namely, methylene (MB) and acridine orange (AO) with an anionic polyelectrolyte, namely, sodium carrageenate (NaCar) has been investigated by spectrophotometric method and spectrofluorimetric method. The polymer induced metachromasy in the dyes resulting in the shift of the absorption maxima of the dyes towards shorter wavelengths.The stability of the complexes formed between acridine orange and sodium carrageenate was found to be lesser than that formed between methylene blue and sodium carrageenate. This fact was further confirmed by reversal studies using alcohols, urea, surfactants and electrolytes. The interaction parameters revealed that binding between acridine orange and sodium carrageenate was mainly due to electrostatic interaction while that between methylene blue and carrageenate is found to involve both electrostatic and hydrophobic forces. The effect of the structure of the dye and its relation to metachromasy has been discussed

A Study of Interaction of Methyl Orange with Some Polycations

The interaction between an anionic dye methyl orange and three poly cations namely, poly (N-methy-4-vinylpyridinium iodide) (PM4VPI), poly (vinylbenzyltriphenyl phosphonium chloride) (PVBTPPC) and poly (N-methy-4-vinylpyridinium iodide) (PM2VPI) has been investigated by spectrophotometric method. The polymers were observed to induce metachromasy in the dye as evidenced from the considerable blue shift in the absorption maxima of the dye. The interaction constant and thermodynamic parameters of interaction have been determined by absorbance measurements at the metachromatic band. The effect of additives such as ionic salts, alcohols, urea and polyelectrolytes on the reversal of metachromasy has been studied and used to determine the stability of the metachromatic complex and to understand the nature of binding

Case Report - Aleukemic leukemia cutis

Aleukemic leukemia cutis has always been a dermatological curiosity. It is a rare condition characterized by the infiltration of skin by leukemic cells before their appearance in the peripheral blood or bone marrow. A 20 year old man had presented with nodular swelling on the scalp of 6 months duration along with cervical lymphadenopathy. Biopsy and immunohistochemistry revealed myeloid sarcoma. The initial presentation was aleukemic and repeated peripheral blood counts and marrow examinations were normal. However, the outcome was fatal within 3 months of diagnosis of cutaneous lesions

Navier Slip and Heat Transfer in a Nanofluid Due to a Stretching/Shrinking Sheet: An Analytical Study

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