J. Lademann’s research while affiliated with Charité Universitätsmedizin Berlin and other places

Using the density functional theory (DFT), we calculated the structures and Raman spectra of trans-isomers of α-carotene, β-carotene, γ-carotene and lycopene as well as trans-isomers of modified β-carotene and lycopene molecules with substituted end or/and side groups. The DFT calculations showed that the position of the C=C stretching band depends mainly on the number of conjugated C=C bonds and decreases with an increase in the conjugation length. The weak dependence of the position of the C=C stretching band on the structure of the carotenoid side and end groups suggests that this band can be used to evaluate the conjugation length for trans-isomers of various molecules containing polyene chains. The C-C stretching band shifts towards lower wavenumbers with growth of the conjugation length or masses of the end groups and to higher wavenumbers in the presence of the side CH3 groups. The intensities of the C-C and C=C stretching bands are enhanced with growth of the conjugation length or masses of the end groups. The presence of the side CH3 groups results in bending of the carotenoid backbone, splitting and dumping of intensities of the C-C and C=C stretching bands.

The dependence of Raman spectra of the molecules containing polyene chains on the conjugation length, structure of side and end groups, and isomer type is analyzed theoretically.

The absorption of topically applied substances is challenging due to the effective skin barrier. Encapsulation of substances into nanoparticles was expected to be promising to increase the bioavailability of topically applied products. Since nanoparticles cannot traverse the intact skin barrier, but penetrate into the hair follicles, they could be used to deliver substances via hair follicles, where the active is released and can translocate independently transfollicularly into the viable epidermis. In the present in vivo study, this effect was investigated for caffeine. Caffeine nanocrystals of two sizes, 206 nm and 694 nm, with equal amounts of caffeine were used to study caffeine serum concentration kinetics after topical application on 5 human volunteers. The study demonstrated that at early time points, the smaller nanocrystals were more effective in increasing the bioavailability of caffeine, whereas after 20 min, the serum concentration of caffeine was higher when caffeine was applied by larger nanocrystals. Caffeine was still detectable after 5 days. The area under the curve could be increased by 82% when the 694 nm nanocrystals were applied. Especially larger sized nanocrystals seem to be a promising type of nanoparticulate preparation to increase the bioavailability of topically applied drugs via the transfollicular penetration pathway.

Determination of the molecular composition of the skin is crucial for numerous tasks in medicine, pharmacology, dermatology and cosmetology. Confocal Raman microspectroscopy is a sensitive method for the evaluation of molecular depth profiles in the skin in vivo. Since the Raman spectra of most of the skin constituents significantly superimpose, a spectral decomposition by a set of predefined library components is usually performed to disentangle their contributions. However, the incorrect choice of the number and type of components or differences between the spectra of the basic components measured in vitro and in vivo can lead to incorrect results of the decomposition procedure. Here, we investigate an alternative data-driven approach based on a non-negative matrix factorization (NNMF) algorithm of depth-resolved Raman spectra of skin that does not require a priori information of spectral data for the analysis. Using the model and experimentally measured depth-resolved Raman spectra of the upper epidermis in vivo, we show that NNMF provides depth profiles of endogenous molecular components and exogenous agents penetrating through the upper epidermis for the spectra and concentration. Moreover, we demonstrate that this approach is capable of providing new information on the molecular profiles of the skin.

We carried out calculations of non-resonance Raman spectra of ß-carotene and polyenes CH2=(CH-CH=)n-2CH=CH2 using the density functional theory (DFT). We revealed that the peak positions and intensities of the C-C and C=C stretching bands depend on length of the polyene chain and type of the isomer. Our experimental non-resonance Raman spectra of ß-carotene powder match well the DFT-simulated Raman spectrum of ß-carotene in the all-trans form. The peak positions and relative intensities of the C-C and C=C stretching bands of ß-carotene turned out to be similar in the resonance and non-resonance Raman spectra. An increase in the number of conjugated double bonds (n = 3–30) in a polyene structure results in a monotonous shift of the positions of the most intense C-C and C=C bands towards lower wavenumbers with an increase in the band intensities. An increase in the isomer number results in the monotonous decrease of the C=C stretching band intensity for polyenes with 9, 10, 11, 15 and 24 double bonds. An increase in the isomer number inhomogeneously influences the form, position and intensity of the C-C stretching band.

The topical photodynamic therapy (PDT) is mainly used in the treatment of dermato-oncological diseases. The distribution and functionality of the photosensitizer Tetrahydroporphyrin-Tetratosylat (THPTS) was investigated using microscopic and spectroscopic methods after topical application to excised porcine skin followed by irradiation. The distribution of THPTS was determined by two-photon tomography combined with fluorescence lifetime imaging (TPT/FLIM) and confocal Raman microspectroscopy (CRM). The radicals were quantified and characterized by electron paramagnetic resonance (EPR) spectroscopy. Results show a penetration depth of THPTS into the skin down to around 12 ± 5 µm. A penetration of THPTS through the stratum corneum was not clearly observable after 1 h penetration time, but cannot be excluded. The irradiation within the phototherapeutic window (spectral range of visible and near infrared light in the range ≈ 650–850 nm) is needed to activate THPTS. An incubation time of 10 min showed the highest radical production. A longer incubation time affected the functionality of THPTS, whereby significant less radicals were detectable. During PDT mainly reactive oxygen species (ROS) and lipid oxygen species (LOS) are produced. Overall, the irradiation dose per se influences the radical types formed in skin. While ROS are always prominent at low doses, LOS increase at high doses, independent of previous skin treatment and the irradiation wavelength used.