In vitro - in vivo correlation in dermal delivery: the role of excipients

The composition of topical and transdermal formulations is known to determine the rate and the extent of drug delivery to and through the skin. However, to date, the role of excipients in these formulations on skin delivery of actives has received little attention from scientists in the field. Monitoring skin absorption of both drug and vehicle may provide insights into the mechanism by which excipients promote permeation and may facilitate the design of effective and safer products. Previously, we have investigated the use of quantitative Confocal Raman Spectroscopy (CRS) to investigate the delivery of an active to the skin, and we also reported the first fully quantitative study that compared this method with the well-established in vitro permeation test (IVPT) model. To further explore the potential of quantitative CRS in assessing topical delivery, the present work investigated the effects of commonly used excipients on the percutaneous absorption of a model drug, ibuprofen (IBU). Permeation of IBU and selected solvents following finite dose applications to human skin was determined in vitro and in vivo by Franz diffusion studies and quantitative CRS, respectively. The solvents used were propylene glycol (PG), dipropylene glycol (DPG), tripropylene glycol (TPG), and polyethylene glycol 300 (PEG 300). Overall, the cumulative amounts of IBU that permeated at 24 h in vitro were similar for PG, DPG, and TPG (p > 0.05). These three vehicles outperformed PEG 300 (p TPG, while PEG 300 did not permeate the skin. A linear relationship between maximum vehicle and IBU flux in vitro was found, with a correlation coefficient (R2) of 0.95. When comparing in vitro with in vivo data, a positive in vitro–in vivo (IVIV) correlation between the cumulative permeation of IBU in vitro and the total amount of IBU that penetrated the stratum corneum (SC) in vivo was observed, with a Pearson correlation coefficient (R2) of 0.90. A strong IVIV correlation, R2 = 0.82, was found following the linear regression of the cumulative number of solvents permeated in vitro and the corresponding skin uptake in vivo measured with CRS. This is the first study to correlate in vivo permeation of solvents measured by CRS with data obtained by in vitro diffusion studies. The IVIV correlations suggest that CRS is a powerful tool for profiling drug and vehicle delivery from dermal formulations. Future studies will examine additional excipients with varying physicochemical properties. Ultimately, these findings are expected to lead to new approaches for the design, evaluation, and optimization of formulations that target actives to and through the skin

A high‐throughput Raman notch filter set

A chevron‐type Raman notch filter (RNF) set is described. lt combines a high signal throughput (up to 90% around 1600 cm−1 and ≳80% between and 700 and 2700 cm−1) with a laser line suppression of 108–109. The filter set can be used to replace the first two dispersion stages in triple‐stage Raman monochromators commonly employed in multichannel detection systems. This yields a gain in intensity of the detected Raman signal of a factor of 4. It is shown that in Raman spectrometers with a backscatter geometry, the filter set can also be used to optically couple the microscope and the spectrometer. This leads to a further increase in signal intensity of a factor of 3–4 as compared to the situation where a beam splitter is used. Additional advantages of the RNF set are the fact that signal throughput is almost polarization independent over a large spectral interval and that it offers the possibility to simultaneously record Stokes and anti‐Stokes spectra

The use of Raman spectroscopy in the epidemiology of methicillin-resistant Staphylococcus aureus of human- and animal-related clonal lineages

AbstractIn order to perform a cost-effective search and destroy policy for methicillin-resistant Staphylococcus aureus (MRSA), a quick and reliable typing method is essential. In an area with a high level of animal-related MRSA ST398, pulsed field gel electrophoresis (PFGE) typing and spa-typing are not sufficient to discriminate between co-incidental findings and true transmission of MRSA. This study is the first to retrospectively show the performance of Raman spectroscopy in 16 well-documented outbreaks. We analysed 525 isolates, 286 MRSA ST398 and 239 from other PFGE clusters with Raman spectroscopy. When epidemiologically linked isolates from the outbreaks were analysed with PFGE as the reference standard, Raman spectroscopy correctly identified 97% of cases that were indistinguishable from the index case. With Raman cluster analysis, the most dominant distinction was between MRSA ST398 and other MRSA of human clonal lineages. Within MRSA ST398, 22 different Raman clusters were identified. Raman typing correctly identified an ST398 (spa type t567) outbreak in a hospital setting. No direct correlation was observed between Raman clusters and spa types. We conclude that Raman spectroscopy is a quick and reliable method of MRSA typing, which can be used in outbreak settings and it is comparable to PFGE, with the added advantage that PFGE non-typeable isolates can also be readily typed using the same sample preparation protocol

In vivo biomolecular imaging of zebrafish embryos using confocal Raman spectroscopy

Zebrafish embryos provide a unique opportunity to visualize complex biological processes, yet conventional imaging modalities are unable to access intricate biomolecular information without compromising the integrity of the embryos. Here, we report the use of confocal Raman spectroscopic imaging for the visualization and multivariate analysis of biomolecular information extracted from unlabeled zebrafish embryos. We outline broad applications of this method in: (i) visualizing the biomolecular distribution of whole embryos in three dimensions, (ii) resolving anatomical features at subcellular spatial resolution, (iii) biomolecular profiling and discrimination of wild type and ΔRD1 mutant Mycobacterium marinum strains in a zebrafish embryo model of tuberculosis and (iv) in vivo temporal monitoring of the wound response in living zebrafish embryos. Overall, this study demonstrates the application of confocal Raman spectroscopic imaging for the comparative bimolecular analysis of fully intact and living zebrafish embryos

Applications of raman spectroscopy in dentistry part II: Soft tissue analysis

Raman spectroscopy is rapidly moving from an experimental technique for the analysis of biological molecules to a tool for the real-time clinical diagnosis and in situ evaluation of the oral tissue in medical and dental research. The purpose of this study is to identify various applications of Raman spectroscopy, to evaluate the contemporary status and to explore future directions in the field of dentistry. Several in-depth applications are presented to illustrate Raman spectroscopy in early diagnosis of soft tissue abnormalities. Raman spectroscopy allows to analyze histological and biochemical composition of biological tissues. The technique not only demonstrates its role in the disclosure of dysplasia and malignancy but also in performing guided biopsies, diagnosing sialoliths, and assessment of surgical margins. Raman spectroscopy is used to identify the molecular structures and its components to give substantial information about the chemical structure properties of these molecules. In this paper, we acquaint the utilization of Raman spectroscopy in analyzing the soft tissues in relation to dentistry

Elastic and inelastic light scattering from single bacterial spores in an optical trap allows the monitoring of spore germination dynamics

Raman scattering spectroscopy and elastic light scattering intensity (ESLI) were used to simultaneously measure levels of Ca-dipicolinic acid (CaDPA) and changes in spore morphology and refractive index during germination of individual B. subtilis spores with and without the two redundant enzymes (CLEs), CwlJ and SleB, that degrade sporesâ peptidoglycan cortex. Conclusions from these measurements include: 1) CaDPA release from individual wild-type germinating spores was biphasic; in a first heterogeneous slow phase, Tlag, CaDPA levels decreased â ¼15% and in the second phase ending at Trelease, remaining CaDPA was released rapidly; 2) in L-alanine germination of wild-type spores and spores lacking SleB: a) the ESLI rose â ¼2-fold shortly before Tlag at T1; b) following Tlag, the ESLI again rose â ¼2-fold at T2 when CaDPA levels had decreased â ¼50%; and c) the ESLI reached its maximum value at â ¼Trelease and then decreased; 3) in CaDPA germination of wild-type spores: a) Tlag increased and the first increase in ESLI occurred well before Tlag, consistent with different pathways for CaDPA and L-alanine germination; b) at Trelease the ESLI again reached its maximum value; 4) in L-alanine germination of spores lacking both CLEs and unable to degrade their cortex, the time Î Trelease (Treleaseâ Tlag) for excretion of â ¥75% of CaDPA was â ¼15-fold higher than that for wild-type or sleB spores; and 5) spores lacking only CwlJ exhibited a similar, but not identical ESLI pattern during L-alanine germination to that seen with cwlJ sleB spores, and the high value for Î Trelease. Originally published Analytical Chemistry, Vol. 81, No. 10, May 200