Computed temperature dependence of membrane/water partition coefficients log K lip/wat [mol mol −1 ] (panel A) and permeability coefficients log P erm [cm s −1 ] (panel B) for a series of five fluorescent dyes on the DPPPC : DPPG : Chol mixed membrane.
Liposomal formulations can be advantageous in a number of scenarios such as targeted delivery to reduce the systemic toxicity of highly potent Active Pharmaceutical Ingredients (APIs), to increase drug bioavailability by prolonging systemic circulation, to protect labile APIs from degradation in the gastrointestinal tract, or to improve skin permea...
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... COSMO-based partitioning and permeability calculations for fluorescent dyes. The values of temperaturedependent partition coefficients log K lip/wat obtained from the COSMOmic calculations compared in Fig. 2A showed no significant changes with increasing temperature for the given fluorescent compounds. The compounds' lipophilic character increased in the order of Cal < 6-CF < 5-CF < F < FITC but the drug partitioning between water and the lipidic membrane was not found to be much sensitive to temperature changes while all the compounds ...
... changes while all the compounds became only slightly more hydrophobic at elevated temperatures. 46 In contrast, the permeability coefficients log P erm obtained from COSMOperm calculations have shown a significant increase with the temperature of about two orders of magnitude within 40 K difference and varied widely between the compounds (Fig. 2B). Therefore, we have analysed each dye's performance in both partitioning and permeability at the lowest (293 K) and the highest (333 K) temperature in more ...
... effect of high membrane partitioning coefficient was even more pronounced in the case of FITC (log K lip/wat 293K = 2.94). Although FITC was visibly encapsulated into liposomes (Fig. 4C), no release upon heating was detected (Table 2). Despite high permeability prediction for FITC, on par with fluorescein as shown in Fig. 2B. Only when a more invasive method of membrane disruption with TRITON® was used, a significant release of FITC was observed (0.6 ± 0.2 μg dye mg lipid −1 , being 18% of the theoretical capacity suitable for thermally controlled release from liposomes. This does not necessarily make lipophilic molecules unsuitable for liposomal ...
Encapsulation into liposomes is a formulation strategy that can improve efficacy and reduce side effects of active pharmaceutical ingredients (APIs) that exhibit poor biodistribution or pharmacokinetics when administered alone. However, many APIs are unsuitable for liposomal formulations intended for parenteral administration due to their inherent physicochemical properties─lipid bilayer permeability and water-lipid equilibrium partitioning coefficient. Too high permeability results in premature leakage from liposomes, while too low permeability means the API is not able to pass across biological barriers. There are several options for solving this issue: (i) change of the lipid bilayer composition, (ii) addition of a permeability enhancer, or (iii) modification of the chemical structure of the API to design a prodrug. The latter approach was taken in the present work, and the effect of small changes in the molecular structure of the API on its permeation rate across a lipidic bilayer was systematically explored utilizing computer simulations. An in silico methodology for prodrug design based on the COSMOperm approach has been proposed and applied to four APIs (abiraterone, cytarabine, 5-fluorouracil, and paliperidone). It is shown that the addition of aliphatic hydrocarbon chains via ester or amide bonds can render the molecule more lipophilic and increase its permeability by approximately 1 order of magnitude for each 2 carbon atoms added, while the formation of fructose adducts can provide a more hydrophilic character to the molecule and reduce its lipid partitioning. While partitioning was found to depend only on the size and type of the added group, permeability was found to depend also on the added group location. Overall, it has been shown that both permeability and lipid partitioning coefficient can be systematically shifted into the desired liposome formulability window by appropriate group contributions to the parental drug. This can significantly increase the portfolio of APIs for which liposome or lipid nanoparticle formulations become feasible.
Three-dimensional cell culture systems are increasingly used for biological and anticancer drug screening as they mimic the structure and microenvironment of tumors more closely than conventional two-dimensional cell models. In this study, the growth kinetics of colon adenocarcinoma-derived spheroids (HT-29 cell line) cultivated in liquid marble micro-bioreactors and nonadherent PDMS-coated well plates was investigated in detail and enabled precise control of the spheroid size by the seed cell density and cultivation time. The therapeutic effect of 5-fluorouracil and irinotecan hydrochloride in 2D monolayer cell culture and 3D tumor spheroids revealed an unexpected twist in their efficacy due to different ability to penetrate through 3D microtissue. For 5-fluorouracil, the inhibitory concentration IC50 after 48 h exposure increased from 11.3 µM for a 2D cell culture to 707.7 µM for a 3D spheroid. In the case of irinotecan, IC50 increased from 24.9 µM to 77.8 µM. Despite its higher molar weight, irinotecan appeared to penetrate the 3D spheroid structure more efficiently than 5-fluorouracil. While 5-fluorouracil mainly caused a suppression of spheroid growth from the outside, irinotecan affected the entire spheroid and caused its originally compact structure to disintegrate. The acquired results highlight the need to screen cancer chemotherapeutics on 3D tumor models, as contrasting results can be obtained compared to standard 2D cell cultures.
Pharmaceutical nanocrystals represent a promising new formulation that combines the benefits of bulk crystalline materials and colloidal nanoparticles. To be applied in vivo, nanocrystals must meet several criteria, namely colloidal stability in physiological media, non-toxicity to healthy cells, avoidance of macrophage clearance, and bioactivity in the target tissue. In the present work curcumin, a naturally occurring poorly water-soluble molecule with a broad spectrum of bioactivity has been considered as a candidate substance for preparing pharmaceutical nanocrystals. Curcumin nanocrystals in the size range of 40-90 nm were prepared by wet milling using the following combination of steric and ionic stabilizers: Tween 80, sodium dodecyl sulfate, Poloxamer 188, hydroxypropyl methylcellulose, phospholipids (with and without polyethylene glycol), and their combination. Nanocrystals stabilized by a combination of phospholipids enriched with polyethylene glycol proved to be the most successful in all evaluated criteria; they were colloidally stable in all media, exhibited low macrophage clearance, and proved non-toxic to healthy cells. This curcumin nanoformulation also exhibited outstanding anticancer potential comparable to commercially used cytostatics (IC50=73 µM; 24 h, HT-29 colorectal carcinoma cell line) which represents an improvement of several orders of magnitude when compared to previously studied curcumin formulations. This work shows that the preparation of phospholipid-stabilized nanocrystals allows for the conversion of poorly soluble compounds into a highly effective “solution-like” drug delivery system at pharmaceutically relevant drug concentrations.
Fully acetylated deoxyfluorinated hexosamine analogues and non-fluorinated 3,4,6-tri-O-acylated N-acetyl-hexosamine hemiacetals have previously been shown to display moderate anti-proliferative activity. We prepared a set of deoxyfluorinated GlcNAc and GalNAc hemiacetals that comprised both features: O-acylation at the non-anomeric positions with an acetyl, propionyl and butanoyl group, and deoxyfluorination at selected positions. Determination of the in vitro cytotoxicity towards the MDA-MB-231 breast cancer and HEK-293 cell lines showed that deoxyfluorination enhanced cytotoxicity in most analogues. Increasing the ester alkyl chain length had a variable effect on the cytotoxicity of fluoro analogues, which contrasted with non-fluorinated hemiacetals where butanoyl derivatives had always higher cytotoxicity than acetates. Reaction with 2-phenylethanethiol indicated that the recently described S-glyco-modification is an unlikely cause of cytotoxicity.