No skin off your back: the sampling and extraction of sebum for metabolomics

Abstract

Introduction Sebum-based metabolomics (a subset of “sebomics”) is a developing field that involves the sampling, identification, and quantification of metabolites found in human sebum. Sebum is a lipid-rich oily substance secreted by the sebaceous glands onto the skin surface for skin homeostasis, lubrication, thermoregulation, and environmental protection. Interest in sebomics has grown over the last decade due to its potential for rapid analysis following non-invasive sampling for a range of clinical and environmental applications. Objectives To provide an overview of various sebum sampling techniques with their associated challenges. To evaluate applications of sebum for clinical research, drug monitoring, and human biomonitoring. To provide a commentary of the opportunities of using sebum as a diagnostic biofluid in the future. Methods Bibliometric analyses of selected keywords regarding skin surface analysis using the Scopus search engine from 1960 to 2022 was performed on 12th January 2023. The published literature was compartmentalised based on what the work contributed to in the following areas: the understanding about sebum, its composition, the analytical technologies used, or the purpose of use of sebum. The findings were summarised in this review. Results Historically, about 15 methods of sampling have been used for sebum collection. The sample preparation approaches vary depending on the analytes of interest and are summarised. The use of sebum is not limited to just skin diseases or drug monitoring but also demonstrated for other systemic disease. Most of the work carried out for untargeted analysis of metabolites associated with sebum has been in the recent two decades. Conclusion Sebum has a huge potential beyond skin research and understanding how one’s physiological state affects or reflects on the skin metabolome via the sebaceous glands itself or by interactions with sebaceous secretion, will open doors for simpler biomonitoring. Sebum acts as a sink to environmental metabolites and has applications awaiting to be explored, such as biosecurity, cross-border migration, localised exposure to harmful substances, and high-throughput population screening. These applications will be possible with rapid advances in volatile headspace and lipidomics method development as well as the ability of the metabolomics community to annotate unknown species better. A key issue with skin surface analysis that remains unsolved is attributing the source of the metabolites found on the skin surface before meaningful biological interpretation.

Assessment of Human Exposure to Traditional and Novel Organophosphate Esters via Multiple Personal Matrices

“…For example, males have more electronic products in dormitories and lower frequency of skin and clothing cleaning than females (Table S1), leading to more pollutants being accumulated on males’ skin. Additionally, men usually have a higher sebum secretion rate than women of the same age, , further attracting more pollutants on the skin.…”

Transforming Parkinson's Care in Africa (TraPCAf): protocol for a multimethodology National Institute for Health and Care Research Global Health Research Group project

“…We are collaborating with the team leading this work to investigate whether metabolites can be used to diagnose PD [ 22 , 58 ] (covered by patent rights US20230077659A1 and US20230080918A1). The team have developed a diagnostic platform, using mass spectrometry, that can classify PD from sebum samples with up to 78–88% accuracy (for detailed methodology see [ 22 , 59 ]). Briefly, sebum samples will be taken by a research nurse with a cotton bud rubbed on the upper back (a sebum-rich area of the body) for metabolite analysis.…”

Critical Factors in Sample Collection and Preparation for Clinical Metabolomics of Underexplored Biological Specimens

“…The epidermis lipid surface in humans is uniquely composed of squalene and wax esters, not found anywhere else in the body. The metabolic pathways regulating its composition and secretion rate are still not understood; however, changes in sebum secretion rates have already been associated with some pathophysiologies such as acne and Parkinson’s disease [ 57 , 59 , 60 ]. Due to the interface between sebum and blood circulation, this specimen has potential for biomarker discovery.…”

“…Developing sebum-based metabolomics (“sebomics”) involves the sampling, identification, and quantification of metabolites found in human sebum [ 59 , 63 ]. Multiple non-invasive sampling techniques have been developed, but no standardized approach exists.…”

“…Multiple non-invasive sampling techniques have been developed, but no standardized approach exists. The intervariability of the skin surface and the sebum production rates of each individual presents a considerable challenge for sample collection, as this results in an uncontrollable measurement of the sample volume [ 59 ]. The most popular sampling technique is the application of adhesives, such as Sebutape ® (CuDerm Corp., Dallas, TX, USA) [ 64 ] or gauze [ 65 ], on the back or forehead.…”