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Summary Background Laser scanning confocal microscopy (LSCM) is a nondestructive method for observing the samples in three dimensions as well in their natural environment. Therefore, it is well suited for studying human hair. This investigation is focused on evaluating the comparative penetration ability of vegetable vs mineral oils and their formulations with excipient, in human hair. Aims Laser scanning confocal microscopy was employed to assess thin cross sections of human hair, treated with oils and their formulations, to comprehend their penetration capability and pattern. Methods Hair incubated with individual oils or their formulations were labeled with the fluorescent dye was cross‐sectioned into thin fragments and visualized under the LSCM. Results The mineral oil demonstrated better penetration through the hair than the vegetable oils. Combination of these oils with excipient, in an appropriate ratio, had a substantial influence on oil penetration in terms of the depth of penetration. Conclusions Our investigation proved the suitability of fluorescent‐based imaging for studying the penetration of oils across human hair. This method can be employed as a potential analytical tool to study the penetration of various hair‐care formulations and/or their additives, to estimate their effects on human hair.

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.

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