Dihydroxyacetone: A User Guide for a Challenging Bio-Based Synthon

1,3-dihydroxyacetone (DHA) is an underrated bio-based synthon, with a broad range of reactivities. It is produced for the revalorization of glycerol, a major side-product of the growing biodiesel industry. The overwhelming majority of DHA produced worldwide is intended for application as a self-tanning agent in cosmetic formulations. This review provides an overview of the discovery, physical and chemical properties of DHA, and of its industrial production routes from glycerol. Microbial fermentation is the only industrial-scaled route but advances in electrooxidation and aerobic oxidation are also reported. This review focuses on the plurality of reactivities of DHA to help chemists interested in bio-based building blocks see the potential of DHA for this application. The handling of DHA is delicate as it can undergo dimerization as well as isomerization reactions in aqueous solutions at room temperature. DHA can also be involved in further side-reactions, yielding original side-products, as well as compounds of interest. If this peculiar reactivity was harnessed, DHA could help address current sustainability challenges encountered in the synthesis of speciality polymers, ranging from biocompatible polymers to innovative polymers with cutting-edge properties and improved biodegradability.

Vitiligo Treatments: Review of Current Therapeutic Modalities and JAK Inhibitors

Vitiligo is a chronic autoimmune disease characterized by loss of pigment of the skin, affecting 0.5-2% of the population worldwide. It can have a significant impact on patients' quality of life. In recent years, there has been significant progress in our understanding of the pathogenesis of vitiligo. It is believed that vitiligo develops due to a complex combination of genetics, oxidative stress, inflammation, and environmental triggers. Conventional treatments include camouflage, topical corticosteroids, topical calcineurin inhibitors, oral corticosteroids, phototherapy, and surgical procedures, with the treatment regimen dependent on the patient's preferences and characteristics. With increased understanding of the importance of the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway in the pathogenesis of vitiligo, treatment has expanded to include the first US FDA-approved cream to repigment patients with vitiligo. This review summarizes our understanding of the major mechanisms involved in the pathogenesis of vitiligo and its most common available treatments.

In search of the perfect tan: Chemical activity, biological effects, business considerations, and consumer implications of dihydroxyacetone sunless tanning products

As the desire and popularity of a tanned appearance continues, the social effects of UV-free tanning are becoming more important. Dihydroxyacetone (DHA) has seen extensive use as the main tanning agent in sunless tanners. The DHA-induced tan is a result of brown melanoidins formed by a non-enzymatic Maillard reaction between DHA and amino acid species found in the stratum corneum. DHA, thereby, provides a safer route to a tanned appearance compared with exposure to ultraviolet radiation. However, DHA is a highly reactive molecule, posing a multitude of challenges for potential product formulations. With their increased use, the safety considerations of topically applied DHA tanners have been investigated. Many different vehicles have been used for topical delivery of DHA, and they are becoming increasingly multifunctional. This review provides a holistic overview of dihydroxyacetone sunless tanning products.

Comparison of Color Development Kinetics of Tanning Reactions of Dihydroxyacetone with Free and Protected Basic Amino Acids

Sunless tanning has become incredibly prevalent due to the increasing fashionable demand and the awareness of photodamage risks. The brown pigments are induced by dihydroxyacetone (DHA) and amino groups in the stratum corneum (SC) of skin via the Maillard reaction. While most studies concerning sunless tanning reactions have focused on free amino acids (AAs), little information is available on the impact of the side chain of AAs or proteins on this important reaction in cosmetic chemistry. To explore the reactivity and color development kinetics of different types of amino groups, three basic free AAs (Arg, His, and Lys) and three Nα-protected AAs (Boc-Arg-OH, Boc-His-OH, and Boc-Lys-OH) were used to react with DHA using a simplified model system at different reaction times, pH, and temperatures. Full factorial experiments were employed to design and analyze the effects of these three factors. The browning intensity and color characteristics were quantitatively evaluated. The factorial experiments showed that temperature had the most significant influence on the browning intensity and played a dominant role in the interactions with the reaction time and pH. It was found, for the first time, that Arg and His reacted with DHA more rapidly than Boc-Arg-OH and Boc-His-OH, while Boc-Lys-OH developed a stronger color than Lys under the same conditions, suggesting that ε-NH₂ of a lysine residue in peptides or proteins of SC may play a crucial role in the color development of DHA tanning. This study not only clearly illustrates the capability of the side chain of AAs to produce colored compounds but also provides a deeper understanding of DHA tanning.

The Efficacy and Psychoneuroimmunology Mechanism of Camouflage Combined With Psychotherapy in Vitiligo Treatment

Background and Objectives

The efficacy of camouflage combined with psychotherapy and the underlying mechanisms are poorly understood in vitiligo management. This study aimed to investigate the joint efficacy and further explore psycho-neuro-endocrine-immune-skin interactions.

Patients and Methods

In a prospective, non-randomized and concurrent controlled trial, patients were divided into two groups. Quality of life (QOL) was evaluated using the Chinese version of the Vitiligo Life Quality Index (VLQI-C). Serum levels of neuropeptides and cytokines were detected by enzyme-linked immunosorbent assay.

Results

A total of 149 patients were included for final evaluation. After treatment for 4 weeks, total and subcategory quality of life scores in the intervention group were much lower than in the control group. Serum levels of neuropeptide-Y (NPY) and melanin-concentrating hormone (MCH) significantly decreased, and serum level of adrenocorticotropic hormone (ACTH) increased in both active and stable patients of the intervention group, but not in the control group. In addition, the serum levels of interferon-γ (IFN-γ), CXC chemokine ligand 10 (CXCL10), and interleukin-1β (IL-1β) decreased in both the active and stable patients of the intervention group and only in the active patients of the control group.

Conclusions

The combination of camouflage and psychotherapy provided a clinically meaningful improvement in quality of life and ameliorated the outcome by likely modulating the psycho-neuro-endocrine-immuno-skin system during vitiligo management.

Clinical Trial Registration

www.clinicaltrials.gov/ct2/show/NCT03540966, identifier: NCT03540966.

The industrial versatility of Gluconobacter oxydans: current applications and future perspectives

Gluconobacter oxydans is a well-known acetic acid bacterium that has long been applied in the biotechnological industry. Its extraordinary capacity to oxidize a variety of sugars, polyols, and alcohols into acids, aldehydes, and ketones is advantageous for the production of valuable compounds. Relevant G. oxydans industrial applications are in the manufacture of L-ascorbic acid (vitamin C), miglitol, gluconic acid and its derivatives, and dihydroxyacetone. Increasing efforts on improving these processes have been made in the last few years, especially by applying metabolic engineering. Thereby, a series of genes have been targeted to construct powerful recombinant strains to be used in optimized fermentation. Furthermore, low-cost feedstocks, mostly agro-industrial wastes or byproducts, have been investigated, to reduce processing costs and improve the sustainability of G. oxydans bioprocess. Nonetheless, further research is required mainly to make these raw materials feasible at the industrial scale. The current shortage of suitable genetic tools for metabolic engineering modifications in G. oxydans is another challenge to be overcome. This paper aims to give an overview of the most relevant industrial G. oxydans processes and the current strategies developed for their improvement.

Dermocosmetic applications of microalgal pigments

Among photosynthetic microorganisms, Cyanobacteria and Microalgae species have been highly studied thank to their high value-added compounds for several industrial applications. Thus, their production is increasing in the last decade to produce raw material for cosmetics. In fact, the daily routine includes the use of cosmetics and sunscreens to protect against the environmental changes, mainly the increment of ultraviolet (UV) radiation rate with a consequent skin damage and premature aging due to this overexposure. As it is well discussed, chemical UV filters are extensively incorporated into sunscreens formulas; however, they can induce allergenic reactions as well. For these reasons, some pigments derived from microalgae, such as astaxanthin, lutein, β-carotene as well as other biocompounds are now well described in the literature as well as biotechnologically manufactured as natural ingredients to be incorporated into skin care products with multifunctional benefits even for sunscreen purposes. Hence, this investigation summarizes the recent studies about the main pigments from photosynthetic microorganisms' biomasses as well as their uses in dermocosmetics with novel attributes, such as anti-aging agents, makeups, skin lightening and whitening, among others.

A colorimetric comparison of sunless with natural skin tan

The main ingredient of sunless tanning products is dihydroxyacetone (DHA). DHA reacts with the protein and amino acid composition in the surface layers of the skin, producing melanoidins, which changes the skin colour, imitating natural skin tan caused by melanin. The purpose of this study was to characterise DHA-induced skin colour changes and to test whether we can predict the outcome of DHA application on skin tone changes. To assess the DHA-induced skin colour shift quantitatively, colorimetric and spectral measurements of the inner forearm were obtained before, four hours and 24 hours after application of a 7.5% concentration DHA gel in the experimental group (n = 100). In a control group (n = 60), the same measurements were obtained on both the inner forearm (infrequently sun-exposed) and the outer forearm (frequently sun-exposed); the difference between these two areas was defined as the naturally occurring tan. Skin colour shifts caused by DHA tanning and by natural tanning were compared in terms of lightness (L*), redness (a*) and yellowness (b*) in the standard CIELAB colour space. Naturalness of the DHA-induced skin tan was evaluated by comparing the trajectory of the chromaticity distribution in (L*, b*) space with that of naturally occurring tan. Twenty-four hours after DHA application, approximately 20% of the skin colour samples became excessively yellow, with chromaticities outside the natural range in (L*, b*) space. A principal component analysis was used to characterise the tanning pathway. Skin colour shifts induced by DHA were predicted by a multiple regression on the chromaticities and the skin properties. The model explained up to 49% of variance in colorimetric components with a median error of less than 2 ΔE. We conclude that the control of both the magnitude and the direction of the colour shift is a critical factor to achieve a natural appearance.

Evaluation of the potential interference of camouflage on the treatment of vitiligo: An observer-blinded self-controlled study

Camouflage improves the quality of life in vitiligo patients. However, whether the use of camouflage interferes the efficacy of the treatment of vitiligo remains controversial. To evaluate the impact and safety of dihydroxyacetone (DHA)-containing camouflage on the treatment of vitiligo. Thirty patients were enrolled. Comparable vitiliginous patches in each patient were randomly divided into camouflage group or blank group. The therapeutic modalities including topical corticosteroids with or without NB-UVB phototherapy were applied to both groups of lesions. The outcomes were assessed at baseline and then every 4 weeks for up to 12 weeks, including types of repigmentation patterns, percentage of repigmentation, trans epidermal water loss (TEWL), and adverse events. Twenty-eight patients completed the study. There were no differences in repigmentation types and percentage of repigmentation at the endpoint of study between two groups. No difference in TEWL was found at the end of the study between the two groups. Temporary skin irritation (itching and tingling) occurred in one patient in camouflage group after phototherapy between 8 and 12 weeks' treatment. DHA-containing camouflage is a safe make-up for vitiligo. It has little impact on the efficacy of the treatment of vitiligo or on the function of skin barrier.

Micropigmentation for vitiligo on light to moderately colored skin: Updated evidence from a clinical and animal study

Micropigmentation, also termed medical tattooing, can be a useful alternative treatment for patients with vitiligo who are resistant to conventional treatments. To assess the benefits and risks of micropigmentation in the treatment of refractory vitiligo, 25 lesions of 14 patients with vitiligo (Fitzpatrick skin types III and IV) were subjected to micropigmentation using an electric tattooing machine between December 2018 and March 2019. The procedure was repeated until satisfactory results were obtained. Treatment response was assessed by color matching of the treated lesion and surrounding skin using a 4-point scale (poor, fair, good and excellent). Excellent color matching was achieved in 80% (20/25) of cases after a median of three (range, 1-5) treatment sessions. Procedure-associated pain was considerable, but no anesthetic injection was needed. Immediate erythema and swelling were noticed after each procedure, but resolved within a few days. Overall, the treatment was tolerable. This study was limited by a small sample, no control group and a short follow-up period. This study revealed that micropigmentation was beneficial for patients with refractory vitiligo who had light to moderately colored skin. Pigment selection, implantation depth and selection of body parts amenable to treatment were critical.

Innovations in skin camouflaging techniques: Where are we scientifically?

OBJECTIVE

Cutaneous disorders can impact on the psycho-social well-being of children and adults alike, which has been reviewed elsewhere (Body Image 27, 2018 and 98). The present review sets out to evaluate progressions in skin masking and camouflaging techniques together with evaluating the efficacy of these. There does not appear to have been any recent reviews about innovations in skin camouflaging techniques.

METHODS

Using the National Centre for Biotechnology Information PubMed database, a search was made for all studies published between 2000 and 2019 that met defined inclusion criteria. A total of seven relevant publications were identified.

RESULTS

Of the seven studies identified, skin camouflaging improved quality of life in three studies and reduced anxiety, depression and social isolation in others. Of the camouflaging methods used, liquidized simulated second skin technology (Microskin™) appears to look particularly promising. This method of colour matching and a spray/stippling application uses a technology that binds to the epidermis of the skin helping to overcome previous concerns about the colour, coverage and application of camouflage and masking bases. Two studies showed that this innovative mode of camouflaging raised confidence, feelings of happiness and social experiences in children and adolescents with burn scarring. Very few studies reported drawbacks of camouflaging techniques, with limited colour matches and 'itching' appearing to be the main shortcomings. New technologies now appear to be addressing these.

CONCLUSION

Results show that there is wide variation in the quality and modes of skin camouflaging. Of the methods used, simulated second skin technology appears to be an important and effective therapy for individuals with cutaneous skin disorders. Training schemes along with increased awareness of this technique must now be communicated to medical professionals who come into contact with children and adults who could benefit physically, psychologically and socially from this therapy.

Dihydroxyacetone production from glycerol using Gluconobacter oxydans: Study of medium composition and operational conditions in shaken flasks

The production of dihydroxyacetone from glycerol employing aerobic cultures of Gluconobacter oxydans is studied. Dihydroxyacetone is one of the most important value-added products obtained from glycerol, a by-product of biodiesel production. The effect of organic nitrogen source and initial substrate concentrations has been studied together with the possibility of product inhibition. Afterward, the influence of the main operating conditions (temperature, shaking speed, and initial biomass concentration) on in vivo glycerol dehydrogenase activity has also been considered. The results show no evidence of glycerol inhibition, but an important product inhibition was detected, which has been taken into account in a kinetic model for enzymatic activity description. In terms of operating conditions, pH was found to exert a great impact on glycerol conversion, being necessary to keep it above 4 to ensure complete glycerol conversion. The minimum temperature that maximized enzymatic activity was found to be 30°C. In addition, a surprising decoupling between biomass concentration and dihydroxyacetone production rate was observed when adding increasing nitrogen source concentrations at a fixed shaking speed. Glycerol dehydrogenase activity remains constant despite the increase in biomass concentration, contrary to what would be expected. This fact revealed the existence of a rate limiting factor, identified subsequently as oxygen transfer rate depending on the biomass concentration.

Therapeutic interventions to lessen the psychosocial effect of vitiligo in children: A review

Vitiligo commonly affects children, with half of affected individuals experiencing disease onset before the age of 20. Because childhood is a time of advancement in social and psychological development, understanding the extent of the effect of the disease and means of alleviation is crucial. Vitiligo has been shown to decrease children's quality of life, with greater distress in children with highly visible lesions and darker skin tones. This article reviews the literature regarding interventions that have been analyzed in children. Studies evaluating the effect of camouflage, cognitive behavioral therapy, psychological self-help tools, and support groups on the psychosocial aspects of vitiligo were included. The review highlights the ongoing need for studies to better understand the modalities described in this article, as well as others, such as skin dyes, bleaching creams, medical tattooing; week-long camps that cater to children with chronic skin disease; and biofeedback, that might have a role in preventing the psychosocial sequelae of childhood vitiligo.

Dihydroxyacetone: An Updated Insight into an Important Bioproduct

Currently obtained from glycerol through microbial fermentation, the demand of 1,3-dihydroxyacetone (DHA) has significantly grown during the course of the last decade, driven by the consumer passion for a tan and increasing awareness of UV photodamage to the skin caused by prolonged exposure to the sun. We provide an updated bioeconomy perspective into a valued bioproduct (DHA), whose supply and production from glycerol, we argue in this study, will rapidly expand and diversify, with important global health benefits.

A holistic review on the autoimmune disease vitiligo with emphasis on the causal factors

Vitiligo is an idiopathic systemic autoimmune disease affecting skin, hair and oral mucosa. This genetic yet acquired disease characterized by melanin loss is a cause of morbidity across all races. Though thyroid disturbance has been recognized as a key trigger of this pathology, an array of other factors plays critical role in its manifestation. Multiple hormones (corticotropin-releasing hormone, adrenocorticotropic hormone, α-melanocyte-stimulating hormone, melatonin, calcitriol, testosterone, estrogen), genes (Human leukocyte antigen (HLA), Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), Forkhead box D3 (FOXD3), Cluster of differentiation 117 (CD117), Estrogen receptor (ESR) 1, Cyclooxygenase-2 (COX2), Vitiligo-associated protein 1 (VIT1)), and lifestyle choices (stress, diet, cosmetic products, and medications) have been suspected as drivers of this disorder. The pathological mechanisms have been understood in recent times, with the aid of genomic studies; however a universally-effective therapy is yet to be achieved. This review discusses these under-investigated facets of vitiligo onset and progression; hence, it is expected to enrich vitiligo research.

Synthetic Biomaterials from Metabolically Derived Synthons

The utility of metabolic synthons as the building blocks for new biomaterials is based on the early application and success of hydroxy acid based polyesters as degradable sutures and controlled drug delivery matrices. The sheer number of potential monomers derived from the metabolome (e.g., lactic acid, dihydroxyacetone, glycerol, fumarate) gives rise to almost limitless biomaterial structural possibilities, functionality, and performance characteristics, as well as opportunities for the synthesis of new polymers. This review describes recent advances in new chemistries, as well as the inventive use of traditional chemistries, toward the design and synthesis of new polymers. Specific polymeric biomaterials can be prepared for use in varied medical applications (e.g., drug delivery, tissue engineering, wound repair, etc.) through judicious selection of the monomer and backbone linkage.

Vitiligo: a comprehensive overview Part II: treatment options and approach to treatment

Vitiligo is a common skin disorder that results in depigmentation. With the appropriate management, many patients can minimize disease progression, attain repigmentation, and achieve cosmetically pleasing results. There are numerous medical and surgical treatments aimed at repigmentation; therapies for depigmentation are available for patients with recalcitrant or advanced disease. The use of cosmetics at all stages of treatment may be vital to the patient's quality of life. Understanding all the available options helps choose the appropriate treatment plan and tailor it to your patient. Part II of this two-part series on vitiligo discusses the indications for, evidence behind, and adverse effects associated with many of the therapies used for vitiligo. Both conventional medical and surgical options are discussed in addition to several alternative and promising new therapies.

Cosmetic camouflage in vitiligo

Vitiligo is not a life–threatening nor a contagious disease. But the disfigurement of vitiligo can be devastating to its sufferers, especially dark-skinned individuals. Available treatment options are disappointing and sufferers often use various forms of camouflage. Remedial cosmetic cover creams help conceal the blemish of vitiligo at least temporarily. A high concentration of pigment is incorporated into water–free or anhydrous foundations to give a color that matches the patient’s skin, thereby concealing vitiligo patches. The article highlights the content and technique of application of these creams.

Update on childhood vitiligo

PURPOSE OF REVIEW

This review addresses recent changes in the understanding and the treatment of vitiligo vulgaris.

RECENT FINDINGS

Two target genes for vitiligo have been identified, NACHT-leucine-rich-repeat protein-1 (NALP1), part of the inflammasome cascade, and tyrosinase, the enzyme that produces melanin. Identification of reactive oxidation species has furthered the understanding of melanocyte destruction. Comorbid autoimmune disease, including thyroid autoimmunity seen in 25%, is genetically linked to generalized vitiligo and is noted in both childhood vitiligo patients and their families. Screening for vitamin deficiencies and concurrent autoimmunity can be beneficial to the overall health of the child with vitiligo. About half of all vitiligo vulgaris patients have onset of their illness during childhood, causing increased psychological stress during the formative years. Fortunately, therapy has improved as well, with the development of newer topical agents for vitiligo, including topical calcineurin inhibitors; new topical combinations such as topical corticosteroids and calcipotriene; and new technological advances including narrowband ultraviolet B and excimer laser.

SUMMARY

A cyclic approach to therapy should be used wherein topical agents are altered every 6-8 months and technology is used as an alternative after achievement of maximal topical response. With cyclic therapy and early disease intervention, good cosmetic outcomes may be achievable, particularly in localized cases.

Interventions for vitiligo

BACKGROUND

Around one per cent of the world's population has vitiligo, a disease which causes white patches on the skin. There are a variety of treatments available, most of which are unsatisfactory.

OBJECTIVES

To assess all interventions used to manage vitiligo.

SEARCH STRATEGY

In November 2009 we updated searches of the Cochrane Skin Group Specialised Register, the Cochrane Central Register of Controlled Trials in The Cochrane Library (Issue 4, 2009), MEDLINE, EMBASE, AMED, PsycINFO, LILACS and ongoing trials databases.

SELECTION CRITERIA

Randomised controlled trials (RCTs).

DATA COLLECTION AND ANALYSIS

At least 2 review authors independently assessed study eligibility and methodological quality, and carried out data extraction. Two of the 57 included studies could be combined for meta-analysis.

MAIN RESULTS

In this update, 57 trials, including 19 from the original review, were assessed with 3139 participants. Most of the RCTs, which covered a wide range of interventions, had fewer than 50 participants. All of the studies assessed repigmentation, 6 measured cessation of spread, and 5 investigated the effect of treatment on quality of life.Most of the studies assessed combination therapies which generally reported better results. New interventions include monochromatic excimer light (MEL), Polypodium leucotomos, melanocyte transplantation, oral antioxidants, Chinese zengse pill, and pimecrolimus. We analysed the data from 28 studies that met our outcome criteria of improvement in quality of life and greater than 75% repigmentation.Fifteen analyses from studies comparing various interventions showed a statistically significant difference between the proportions of participants achieving more than 75% repigmentation. The majority of analyses showing statistically significant differences were from studies that assessed combination interventions which generally included some form of light treatment.Topical preparations, in particular corticosteroids, reported most adverse effects. However, in the combination studies it was difficult to ascertain which treatment caused these effects. None of the studies was able to demonstrate long-term benefits. Very few studies were conducted on children or included segmental vitiligo. We found one study of psychological interventions and none evaluating micropigmentation, depigmentation, or cosmetic camouflage.

AUTHORS' CONCLUSIONS

This review has found some evidence from individual studies to support existing therapies for vitiligo, but the usefulness of the findings is limited by the different designs and outcome measurements and lack of quality of life measures. There is a need for follow-up studies to assess permanence of repigmentation as well as high quality randomised trials using standardised measures and which also address quality of life.

Foundations and self-tanning products: Do they provide any protection from the sun?

As soon as the weather turns sunny, everyone wants a tan. People with skin phototypes III and IV, called melanocompetent, have no problem meeting this fashion requirement. But things are quite different for people with phototypes I and II and so these individuals look for alternative solutions. In essence, light skin burns easily when exposed to the sun. Therefore, light-skinned people are offered a cosmetic solution through self-tanning products or foundations. It seemed interesting to us to evaluate the sun protection power of this type of product. To do this, we used an in vitro method to determine the typical indicators related to sunscreen products, such as sun protection factor (SPF), ultraviolet (UV)-A protection factor (PF-UVA), UV-B/UV-A ratio as well as the critical wavelength because these artificial tanning products could be considered sunscreen products by users. It is important to know whether a self-tanning product and/or a foundation provide sun protection and whether they meet the standards set for other sunscreen products. Protection which is imbalanced for either UV-B or UV-A radiation is potentially harmful for users believing themselves adequately protected. To do this, we assembled the requisite conditions for forming melanoidins in the cosmetic itself. We tested seven amino acids found in the corneal cells of the epidermis. Regardless of the amino acid used, the corresponding SPF was essentially zero (approximately SPF 2). Foundations, on the other hand, proved to be much more interesting because they possess a non-negligible SPF as well as good photostability making these products safe in terms of their mode of application (applied once daily).