Abstract
Nanotechology in Dermatology is an informative account of the current state of how nanotechnology is being applied to advance skin care. The chapters span a diverse set of topics, ranging from the design of high performance hair and nail care consumer products to the development of truly innovative therapeutic approaches that promise to revolutionize treatment of skin disease. Editors Adnan Nasir, Adam Friedman and Steven Wang in this first edition book have recruited a set of esteemed worldwide experts to author short chapters that are easy to read and written at a level that will appeal to and inform a broad readership, including seasoned professionals and curious citizens. Each chapter concludes with an extensive reference list that will serve as a starting point for follow-up scholarly research. This book is the first of its kind and is a must read for professionals and students interested in the field of nanodermatology.
Nanotechology in Dermatology is the first book ever published dealing with the emerging trends in the application of nanotechnology to the scientific study of skin, and the clinical translation of this knowledge to diagnose and treat skin disease. This rapidly advancing nanodermatology field takes advantage of the unique size-dependent optical, mechanical, electrical and physiochemical properties imparted to materials when manipulated on the nanoscale. These properties are also exploited in an expanding array of nanoenabled consumer products, which consequently has raised the potential for unintended nanoparticle skin contact through occupational or environmental exposures. This has spurred a growing negative perception of nanotechnology, a concern for skin nanotoxicity, and the need for informed and improved communication among professionals and the public. The editors of this book have assembled a list of esteemed worldwide (China, England, France, Germany, Portugal and USA) experts from academia, industry and government to contribute their unique perspectives in this remarkably diverse and rapidly advancing field.
The book contains 25 short easy-to-read chapters that are sequentially organized into six general topic areas that consider the impact of nanotechnology on commercial products, skin penetration, cancer and gene therapy, controlling skin immunity for treatment of infectious diseases, toxicology, public communication and regulatory concerns. The book is prefaced with comments from the editors, who suggest that dermatology and the cosmetic industry are at the cutting edge of applying nanotechnology, and that the aim of the book is “to present the multifacets of nanodermatology in a succinct manner to be useful to all stakeholders so that they can be generally informed and enabled to delve deeper into their particular areas of interest.” There are many figures that help convey the concepts discussed, and at the end of each chapter there is an extensive reference list (average of 73 references per chapter) that provides a starting point for follow-up scholarly research. The chapters inform the reader about skin biology and include topics on skin immunity, nails, hair follicles, skin cancer, wound healing, infection and how nanotechnology is used to impact these areas generally, as well as treatment of specific skin diseases such as urticaria, vitiligo and bullous dermatoses. The reader will learn how nanotechnology is used for cutaneous drug, vaccine and gene delivery. Readers new to the field will be astonished to learn how nanotechnology is impacting the design of high performance textiles, and personal hair and skin care products such as shampoos, finger nail coatings and sunscreen formulations. Several chapters are devoted to the topics of nanotoxicity and the challenges faced by stakeholders in choosing the appropriate language with which to communicate about nanotechnology; whether it is with the public, the consumer, the patient or even communication among professionals. Most of the chapters are succinct and written at a level that will educate nonexperts on the current state of knowledge in nanodermatology. However, each topic covered is at the forefront of innovation in the field, and, therefore, the perspectives and challenges presented will be recognized by the experienced professional as exciting new opportunities for advancing the field in future research.
For example, most people who are sensitive to UV radiation (UVR) exposure have at some time topically applied sunscreen and understand the need for its use. However, few consumers or professionals may fully appreciate the complexity of the technology behind formulating UVR protective cosmetics and the numerous considerations that are required to ensure product safety. Authors Chen, Tooley and Wang (Chapter 2) provide an informative discussion on the physiochemical and functional characteristics of nanosized TiO2 and ZnO particles used in UVR protective sunscreens, and they introduce the hotly debated concerns over nanoparticle skin penetration and toxicity. Similarly, human beings become acutely aware from an early age of their hair and the hair of others. We tend to note whether it is long or short, thick or thin, clean or dirty, and light or dark. However, few among us, including clinical dermatologists, may fully appreciate that our hair follicles and their associated structures (e.g., sebaceous glands and bulge stem cell compartments) can be important reservoirs or targets for nanoparticle-based transdermal drug, vaccine and gene delivery. Authors Vogt, Combadiere and coworkers (Chapters 9 and 16) provide fascinating in-depth descriptions of the hair follicle anatomy, life cycle and function, and reveal how nanotechnology is being utilized to treat disease and carry out transcutaneous vaccination through targeting the hair follicle. They note that “depending upon their physiochemical properties nanoparticles penetrate to different depths in the hair follicle canal.” Since hair follicles originate in the dermis, which is vascularized, the follicle has long been considered to provide a shunt to systemic delivery of small molecular weight drugs. Studies have shown that the hair density (follicles per centimeter squared) and follicular diameter vary among body sites. Maibach and coworkers (Chapter 7) point out that “since hair follicles appear to facilitate particle penetration, such regional distributions will also be an important consideration when evaluating risk of nanoparticle exposure.” Such studies have not yet been attempted.
Over the past 10 years the development of nanomaterials for use on skin has greatly expanded. As introduced by authors Draelos (Chapter 8), and Paller and coworkers (Chapter 10), the cosmetic and pharmaceutical industries have marketed products containing soft nanoparticles comprised of liposomes, emulsions or other lipid-based nanocarriers for a long time. In very recent years, however, a much more diverse set of hard-nanoscale materials are being engineered for diagnosing and treating skin cancer and other skin diseases. These materials include, for example, fluorescent semiconductor quantum dots, carbon nanotubes, superparamagnetic iron oxide nanoparticles, and gold and silver metal nanoparticles. The inorganic nature of these materials and the huge diversity in particle size, shape and surface coatings applied to these materials has created a daunting challenge as stated by author Monteiro-Riviere (Chapter 6), “before many of these nanomaterials can be used in biological systems, their toxicology must first be evaluated under realistic environment, occupation, and medicinal exposure conditions.” This eloquently written chapter presents a review of the current state of understanding regarding skin penetration of TiO2, ZnO, gold, silver and quantum dot nanoparticles through both barrier intact and damaged skin as well as the effects of vehicle composition and mechanical action on nanoparticle skin penetration. The effect of UVR damage on penetration is also considered. The chapter concludes pointing out the need to conduct relevant experiments, noting that at this time, “studies of chronic exposure and evaluation for toxicity are lacking making definitive statements of safety impossible to make.” The enormity of the task to investigate and quantify nanoparticle skin penetration is captured by Maibach and coworkers (Chapter 7), who discuss 15 perspectives on the dynamics of percutaneous absorption, mainly from the skin perspective, and by Wilkerson and coworkers (Chapter 22), who focus more on nanoparticle properties. The toxicogenomic evaluation approach presented by Moos and coworkers (Chapter 23) advocates the use of high-throughput gene array screening as a means to assess skin toxicity on the ever expanding list of engineered nanomaterials used in consumer products and research. This contribution is the only chapter in the book with a focused discussion on methodology; touching on the advantages and limitations of an analytic approach.
Qualitative and quantitative evaluations of nanomaterial–skin penetration and systemic translocation are key metrics required for assessing not only toxicity but also the efficiency of targeted therapeutics. However, analytical results are limited by instrument detection sensitivity. The very nature of nanomaterial size, and an inherent difficulty to distinguish them above tissue background, are key factors limiting quantification, which is a subject area not directly addressed in this book and is unheeded to a large extent by the scientific community. In point of fact, in discussing studies performed investigating the penetration of TiO2 nanoparticles through normal and UVR-damaged skin, Monteiro-Riviere (Chapter 6) states that “only by using more sophisticated techniques like TOF secondary ion mass spectrometry could Ti be seen within the epidermis and superficial dermis.” The conclusion made by authors Lowe, Hunter-Ellul and Wilkerson (Chapter 22) that “the current data regarding the toxicology of nanoparticles is incomplete and, at times, conflicting”, illustrates the challenge faced by governmental groups who rely on scientific data to assess risk, set policy and communicate to the public.
Studies reveal how language and word choice used in communication can greatly impact the perception and understanding of technology. Mills (Chapter 24) examines how the choice of words used to discuss nanotechnology can cause problems that may impact consumer perception, influence intellectual property and regulatory decisions, and even hinder communication among professionals. For example, authors Schoon (Chapter 3) and Draelos (Chapter 8) marvel at the diversity of quantum dot nanoparticles; indicating factually “that some are able to be magnetized and others can emit visible light.” However, a stereotype has emerged in the biological community and across commercial industries that quantum dots are nanoscale light-emitting semiconductors and magnetic nanoparticles are comprised of iron oxide. Mills argues that “it is the very multidisciplinary nature of nanotechnology that leads to the use of a diversity of terminology that is creating unique communication challenges, professionally and publically.” In fact, the methodology used to quantify public opinion also suffers from limitations. Binder (Chapter 25) discusses the difficulties in measuring public opinion on nanotechnology using results from a recent nationwide survey to illustrate key points. He provides a framework for understanding the dynamics of public and consumer opinion, which he advocates is a critical step in the product development process, “consumers want to know when and to what they will be exposed to so they can manage their real or imagined risk.” To paraphrase Wilkerson and coauthors (Chapter 22), the current state of the nanodermatology field is best summarized “as with most medical interventions and many consumer products, the benefits of nanoparticles are not without risks, and the decision regarding nanoparticle use will be made possible when the acute and chronic toxic effects are more fully elucidated.”
Sample excerpts
“Among the largest patent holders of nanotechnology are pharmaceutical companies and cosmetic companies.” Preface.
“The skin care formulator must address a number of challenges in order to create a stable, effective and appealing product. Some nanotechnologies can help to address these issues, improving emulsion stabilisation, rheological properties or delivery of active ingredients.” Chapter 1.
“Despite the tremendous growth of nanotechnology in medicine, training among dermatologists in nanoscience is fundamentally lacking.” Preface.
“The traditional means of diagnosis of inflammatory skin diseases include physical examination, diagnostic tests such as skin biopsy for histology and immunofluorescence and a variety of special serologic assays.” Chapter 14.
“Using nanomethodologies, tissue assessment can be noninvasive or minimally invasive, and has the potential to offer rapid and reliable results.” Chapter 14.
“Investigators studying gene therapy of dermatologic disorders have begun to take advantage of the unique properties of nanoscale therapeutics to overcome traditional barriers to the use of gene therapy, including the inefficient delivery of genetic material across the skin barrier and the instability of oligonucleotides in biological systems.” Chapter 10.
Reading impressions
A clear plus of this book is the shear diversity of topics covered that will appeal to and inform all stakeholders, including academic scientists and students, industrial research and development personnel, clinicians, regulatory agents and, most of all, the public. The book is a must read for those working in the field of nanomaterial–skin interactions and for clinicians interested in understanding how nanotechnology is impacting the field of dermatology. While individuals trained or pursuing careers in biomedical science will benefit the most, the basic concepts of skin biology and nanotechnology that are presented throughout the book will certainly enlighten the curious nonscientist. With a few modifications this book could potentially serve as a text in a special topics course. Although a third of the book has been coauthored by editor Nasir, including chapters that discuss skin cancer, diagnosing, augmenting and suppressing the skin immune system, the text is useful and the basic biological concepts highlighted will inform a broad readership. There is some repetitiveness among chapters in reviewing published literature; however, the positive aspect of this is that it steers the scholarly researcher quickly toward identifying seminal work in the field. A standout feature is the extensive index provided at the back of the book that includes the contributing authors, which will facilitate users to locate information quickly.
On the downside, the authors of some early chapters assume the readers to have a basic understanding of skin biology, including keratinocyte differentiation, epidermal structure and stratum corneum barrier formation. It is not until Chapter 11 that authors Lee, Nasir and Wong introduce skin biology basics and present an overview of transdermal drug delivery, albeit in the context of cancer. An opening tutorial chapter introducing skin biology and nanotechnology is lacking, and would better equip nonscientists and students to gain a wider appreciation of the content in subsequent chapters. Some chapters lack a focused discussion of the analytic instrumentation used to detect nanomaterials in tissues, and the issues of instrument detection sensitivity limits are principally ignored. While author Elston (Chapter 19) provides considerable detail on the use of in situ hybridization, PCR and direct fluorescent antibody assays for use in diagnosing infection from a histologic perspective, some may consider these techniques as successful applications of advances made in molecular biology rather than nanotechnology.
Conclusion
In conclusion, this book is distinguished by the diversity of topics covered on the application of nanotechnology to skin care; ranging from the development of consumer products and novel therapeutics to policy regulation, intellectual property protection and public communication. It clearly informs the reader on how the application of nanotechnology to skin care will impact patient and consumer health and well-being, both now and in the future. Since skin is the largest organ of the body and it is relatable to all human beings through a social perception of health and beauty, this book will surely appeal to a very diverse audience.
Financial & competing interests disclosure
The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.
No writing assistance was utilized in the production of this manuscript.