Nikiforos Kollias

Nikiforos Kollias
University of British Columbia - Vancouver | UBC · Department of Dermatology and Skin Science

PhD

About

219
Publications
70,548
Reads
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8,936
Citations
Additional affiliations
September 1999 - October 2011
Johnson & Johnson, Consumer Products, Skillman NJ
Position
  • Distinguished Research Fellow
January 1999 - December 2011
Johnson & Johnson
August 1989 - September 1999
Harvard Medical School
Position
  • Professor (Assistant)

Publications

Publications (219)
Article
Full-text available
Excess amounts of skin surface oil can lead to adverse psychological consequences. Grease-spot photometry-based techniques measure sebum production rate. However, besides being tedious, these measurements are influenced by contact area, applied pressure, and time of application. Image analysis of polarized images has the potential to provide object...
Article
Human skin is exposed to visible light (VL; 400‐700 nm) and long wavelength ultraviolet A1 (UVA1) radiation (370‐400 nm) after the application of organic broad‐spectrum sunscreens. The biologic effects of these wavelengths have been demonstrated; however, a dose response has not been investigated. Ten subjects with Fitzpatrick skin phototype IV‐VI...
Article
The pigment responses of human skin to broad band UVA radiation (320‐400nm) occurs in three distinct phases. The first phase includes immediate pigment darkening (IPD), the pigment that appears immediately after irradiation. The second phase involves an intermediate step, termed persistent pigment darkening (PPD), which leads to the third phase of...
Article
Solar radiation is a major contributor to the development of skin cancer. Recent studies have shown that visible light (VL), a major portion of solar spectrum, induces biologic effects on the skin. Ultraviolet filters in currently available broad spectrum sunscreens do not offer protection against VL. This study was designed to identify the spectra...
Article
Background The main chromophores of human skin are melanins and hemoglobins along with carotenoids, bilirubin and other compounds. In an effort to study the spectral signatures of skin melanin we measured absorption spectra in a variety of situations, including a method to show early signs of re‐pigmentation in vitiligo. Methods To measure skin in...
Chapter
Aging, photoaging, dryness, and skin thickness (following a proliferative response) play an important role in changes or loss of skin elasticity. Although the changes in the mechanical properties of the skin have proved to be difficult to document but not impossible. It is very important to mention that the mechanical properties of the skin are not...
Article
Background: There is a rationale for adding systemic photoprotective agents to the current photoprotection regimen. Objective: This study was designed to objectively evaluate the molecular and photobiologic effects of oral administration of Polypodium leucotomos extract (PLE). Methods: In all, 22 subjects with Fitzpatrick skin phototype I to I...
Conference Paper
Fluorescence signals depend on the intensity of the exciting light, the absorption properties of the constituent molecules, and the efficiency with which the absorbed photons are converted to fluorescence emission. The optical features and appearance of vitiligo have been explained primarily on the basis of reduced epidermal pigmentation, which res...
Article
Full-text available
Background/objective: Epidermal structure, function, and composition are different in white infants and adults. We investigated whether ethnicity and location contribute to differences in functional and clinical measurements of skin barrier function during the first years of life and in adults. Methods: Children (n = 397, ages 3-49 mos) and wome...
Article
Endogenous molecules that exhibit fluorescence hold the potential to serve as reporters of tissue structure, activity and physiology. Fluorescence excitation spectroscopy is one means to measure and express tissue innate fluorescence. This review focuses on the application of endogenous fluorescence ultraviolet excitation spectroscopy to dermatolog...
Article
Full-text available
Visible light (400-700 nm) lies outside of the spectral range of what photobiologists define as deleterious radiation and as a result few studies have studied the effects of visible light range of wavelengths on skin. This oversight is important considering that during outdoors activities skin is exposed to the full solar spectrum, including visibl...
Article
Vitiligo is a skin disorder that results from the loss of pigmentation (S8) due to the destruction of melanocytes. It affects 1 to 2% of the world population and affects all skin types (1). It can be a very psychologically distressing disease that can negatively affect the subject's quality of life (2). Unfortunately although there have been many q...
Chapter
The cascade of events following an injury that significantly alters epidermal structures and leads to epidermal necrosis depends on the type of injury. We have studied epidermal necrosis caused by solar-simulated radiation, laser therapy, and liquid nitrogen (N2) with reflectance laser scanning confocal microscopy in vivo. In the present study we i...
Chapter
In this chapter, we present a methodology of documenting the angular anisotropy of skin elasticity with high sensitivity and dynamic range using the Reviscometer® RVM 600 and its use to document changes in keratinocyte morphology elicited by topical application of a reversible antagonist to keratinocyte nicotinic acetylcholine receptors (nAChRs). T...
Article
Erythema and pigment responses of human skin following an acute exposure to ultraviolet radiation (UVR) are frequently used to determine the photosensitivity of the skin. In this study we investigated the responses of the skin to a micro-scale area of UVR exposure (MiR) and compared the responses to a macro-scale area of exposure (MaR). Ten human v...
Patent
Full-text available
A method for demonstrating pre-emergent pimples is disclosed. The method includes providing a camera having a 25 mm macro lens and a linear polarizing filter including from 10 to 50 narrow band filters in the spectral range of 400-970 nm, and a light source having a linear polarizer oriented vertical to a polarization plane of the camera polarizer;...
Article
In the past 56 years many different in vitro methodologies have been developed and published to assess the SPF of products but there is no method that has 1:1 correlation with in vivo measurements. Spectroscopic techniques have been used to non-invasively assess the UVA protection factor with good correlation to in vivo UVA-PF methodologies. To ass...
Chapter
Full-text available
Acne is a pleomorphic skin disease. The evolution of an acne lesion involves several stages (a) preclinical manifestations (noninflammatory lesions), (b) emergence of inflammatory lesions, (c) clearance, and (d) leftover marks such as post-inflammatory hyperpigmentation (PIH) and scars (affected dermal structures).
Patent
The present invention relates to a method of determining skin health of an area of skin and overall health of an individual by exposing the area of skin to a first exposure radiation to induce the area of skin to emit a first fluorescent emission, measuring the intensity of the first fluorescent emission, exposing the area of skin to a second expos...
Article
The stratum corneum (SC) serves a primary function of skin barrier and understanding the kinetics of SC formation may provide great insight for skin diagnosis and evaluation of therapies. Besides trans-epidermal water loss (TEWL), few methods have been characterized to assess skin barrier non-invasively in vivo, particularly for dynamic measurement...
Article
As people mature, their skin gradually presents lines, wrinkles, and folds that become more pronounced with time. Skin wrinkles are perceived as important cues in communicating information about the age of the person. Nowadays, documenting the facial appearance through imaging is prevalent in skin research, therefore detection and quantitative asse...
Article
Full-text available
Daily skin exposure to solar radiation causes cells to produce reactive oxygen species (ROS), which are a primary factor in skin damage. Although the contribution of the UV component to skin damage has been established, few studies have examined the effects of non-UV solar radiation on skin physiology. Solar radiation comprises <10% of UV, and thus...
Article
Full-text available
Colorimetry has been used as an objective measure of perceived skin color by human eye to document and score physiological responses of the skin from external insults. CIE color space values (L*, a* and b*) are the most commonly used parameters to correlate visually perceived color attributes such as L* for pigment, a* for erythema, and b* for sall...
Chapter
Full-text available
Due to metabolic processes inside the body, most nutrients cannot be detected directly on skin, and only a few might be detected in either their original molecular form or as one of their metabolic products. Based on their Raman spectral fingerprint, lycopene and β-carotene can be detected noninvasively on skin. Their apparent concentration increas...
Article
The objective of this communication is to present the calculated ratio between UVA and UVB irradiance from sunrise to sunset and under a number of weather conditions. UVA plays an important role in the sun spectrum and a lot of attention has been paid lately regarding the protection of people from UVA. Solar spectra were collected in Kuwait City lo...
Article
An ageing study was conducted to capture skin colour parameters in the CIELab system from Caucasians of both genders and all available adult ages. This study produced a linear correlation between L* and age for a Caucasian population between 20 and 59 years of age as follows: (L* value) = −0.13 × (Age in years) + 63.01. Previous studies have addres...
Article
In vivo confocal scanning laser microscopy (CSLM) is a recently developed non-invasive technique for visualizing microscopic structures with the skin. CSLM has been used to characterize proliferative and inflammatory skin diseases, neoplastic skin lesions and pigmented lesions. Here, we assessed the ability of CSLM to evaluate the formation of neog...
Patent
Instruments and methods are described for performing non-invasive measurements of analyte levels and for monitoring, analyzing and regulating tissue status, such as tissue glucose levels.
Article
The stratum corneum (SC) serves a primary function of skin barrier and its maintenance is vital for the existence of terrestrial life. Few studies have been performed for evaluation of human SC repair in vivo, non-invasively. In the present study tape stripping was performed on the arms and legs of seven volunteers until all the SC was removed. The...
Article
Full-text available
The minimal erythema dose induced by solar-simulated radiation is a useful measure of UV sensitivity of skin. Most skin phototests have been conducted by projecting a flat field of UV radiation onto the skin in an area greater than 15 cm × 15 cm with an increment of radiation doses. In this study, we investigated the responses of human skin to sola...
Conference Paper
Full-text available
The minimal erythema dose induced by solar-simulated radiation is a useful measure of UV sensitivity of skin. Most skin phototests have been conducted by projecting a flat field of UV radiation onto the skin in an area greater than 15 cm × 15 cm with an increment of radiation doses. In this study, we investigated the responses of human skin to sola...
Article
Infant skin is often presented as the cosmetic ideal for adults. However, compared to adult skin it seems to be more prone to develop certain pathological conditions, such as atopic dermatitis and irritant contact dermatitis. Therefore, understanding the physiology of healthy infant skin as a point of reference is of interest both from the cosmetic...
Article
We present a variety of methods based on optical spectroscopy for assessing human skin health status.
Article
Scaling skin involves an imbalance between cell proliferation and desquamation, resulting in partially detached corneocytes at the stratum corneum (SC) surface that become visible as they scatter light. The purpose of this study was to document scaling skin with no associated pathology, to estimate the range of normal corneocyte detachment in the a...
Article
Full-text available
We present a simple and cost-effective optical technique for the simultaneous assessment of pulsating and total blood noninvasively in an inflammatory skin lesion. Acquisitions of diffuse reflectance spectra in the visible range at 6 Hz are used to trace the oscillating components of reflectance. Measurements on erythematous lesions from a UV insul...
Article
Full-text available
The purpose of this study was to determine the effect of visible light on the immediate pigmentation and delayed tanning of melanocompetent skin; the results were compared with those induced by long-wavelength UVA (UVA1). Two electromagnetic radiation sources were used to irradiate the lower back of 20 volunteers with skin types IV-VI: UVA1 (340-40...
Article
Determination of skin surface texture is of particular importance in the field of dermatology as such measurements can be used for skin diagnostics and evaluation of therapeutic or cosmetic treatments. Profilometry of skin replicas, three-dimensional imaging and computer vision have been successfully used to measure and document skin texture. Never...
Article
Full-text available
It is known that effectiveness of acne treatment increases when the lesions are detected earlier, before they could progress into mature wound-like lesions, which lead to scarring and discoloration. However, little is known about the evolution of acne from early signs until after the lesion heals. In this work we computationally characterize the ev...
Article
Full-text available
Measurement of cutaneous microcirculation is of great importance for clinical evaluations as many biological processes (i.e. inflammation) activate superficial vessels. Diffuse Reflectance Spectroscopy (DRS) is a widely used method to assess cutaneous microcirculation since it is based on the spectral characteristics of skin chromophores, particula...
Article
Full-text available
In rhytidectomy the postoperative edema (swelling) and ecchymosis (bruising) can influence the cosmetic results. Evaluation of edema has typically been performed by visual inspection by a trained physician using a fourlevel or, more commonly, a two-level grading(1). Few instruments exist capable of quantitatively assessing edema and ecchymosis in s...
Article
Full-text available
The stratum corneum provides a vital physical barrier that protects against external insults and excessive internal water loss. Water activity is thought as a key factor to maintain proper skin barrier integrity via regulating enzyme activities and lipid phase behavior. Consequently, maintenance of an optimal hydration level in SC becomes an import...
Article
Assessing the ultraviolet (UVA) protection factor of sunscreen formulations has been discussed for the past 20 years. The purpose of this study is to correlate the measurements of the UVA protection factor value (PFA value) via in vivo diffuse reflectance spectroscopy (DRS) and to compare this method with the in vitro method of measuring the PFA va...
Article
The measurement and quantification of skin reactions to insults involves certain assumptions about the relation between intensity of color appearance of the skin and the concentration of endogenous chromophores. The underlying assumption is that the Beer-Lambert law is obeyed, i.e., that a linear relation exists between the absorbance and the conce...
Article
The ability to optically section live biological tissue in vivo with laser light is made possible by confocal laser scanning microscopy (CLSM). In this work, the effects of changing the wavelength of incident light used for CLSM imaging of human skin are reported and analyzed. Optical phantoms and the skin of eight human volunteers were imaged usin...
Conference Paper
Purpose: Seasonal variations in skin color due to sun exposure and the associated cumulative photoaging are well known in adults; however, the extent to which these changes occur in infants and the adaptive capacity of infant skin to respond to these changes is not well understood. Methods: To study the seasonal pigmentary changes of infant skin...
Article
Full-text available
Functional differences between infant and adult skin may be attributed to putative differences in skin microstructure. The purpose of this study was to examine infant skin microstructure in vivo and to compare it with that of adult skin. The lower thigh area of 20 healthy mothers (ages 25-43) and their biological children (ages 3-24 months) was exa...
Article
Full-text available
Absorption and reduced scattering coefficients of in-vivo human skin provide critical information on non-invasive skin diagnoses for aesthetic and clinical purposes. To date, very few in-vivo skin optical properties have been reported. Previously, we reported absorption and scattering properties of in-vivo skin in the wavelength range from 650 to 1...
Article
Full-text available
When the skin is exposed to solar irradiation, UVA photons interact with skin tissues and induce excessive reactive oxygen species, resulting in oxidative stress. We have shown in a previous study that in vivo chemiluminescence's measurement can be used to evaluate the overall level of UVA-induced oxidative stress in human skin. However, the origin...
Article
Full-text available
The activity of certain bacteria in skin is known to correlate to the presence of porphyrins. In particular the presence of coproporphyrin produced by P.acnes inside plugged pores has been correlated to acne vulgaris. Another porphyrin encountered in skin is protoporphyrin IX, which is produced by the body in the pathway for production of heme. In...
Article
Full-text available
Currently, most investigations of wound healing rely on invasive biopsy followed by histology and immunohistochemistry staining. There is a great need to develop non-invasive techniques for in vivo diagnostic, clinical and scientific evaluation. Here, we performed a comprehensive investigation on the dynamic wound healing process as a response to l...
Article
Full-text available
Skin water barrier development begins in utero and is believed to be complete by week 34 of gestational age. The goal of this investigation was to assess the dynamic transport and distribution of water of the stratum corneum of infants and compare it to those of adults. The interaction of water with the stratum corneum was assessed by measuring cap...
Article
Various physical, chemical and biological insults, including exposure to ultraviolet (UV) radiation, cause erythema and change in pigmentation in human skin. These reactions provide an important measure of the cutaneous response to the insult. To present a new implementation of a method for objective in vivo measurement of erythema and pigmentation...
Article
Limited depth of penetration significantly limits photodynamic therapy of nodular basal cell carcinoma (BCC) using topical δ(5)-aminolevulinic acid (ALA). To demonstrate safety and efficacy of orally administered ALA in inducing endogenous protoporphyrin IX (PpIX) production in BCC, 13 patients with BCC ingested ALA in a dose-escalation protocol. A...
Conference Paper
Full-text available
Blue-excited fluorescence imaging is used to study solar elastosis. We find that blue fluorescence increases with age. This trend correlates well with the accumulation of elastotic material in skin due to natural aging and photoaging.
Article
Full-text available
Typical manifestations of cutaneous inflammation include erythema and edema. While erythema is the result of capillary dilation and local increase of oxygenated hemoglobin concentration, edema is characterized by an increase in extracellular fluid in the dermis, leading to local tissue swelling. Both of these inflammatory reactions are typically gr...