Conventional Sunscreens Research Articles

HERBAL SUNSCREEN DEVELOPMENT: SPF, ANTIOXIDANTS, COMPARATIVE ANALYSIS

Introduction: The effective sun protection amidst growing concerns about UV radiation’s impact on skin health, the integration of ancient herbal wisdom with modern scientific advancements has gained prominence. This convergence has led to a renewed interest in herbal skincare formulations as lternatives to conventional sunscreens. Rooted in centuries-old medicinal practices, herbal remedies offer a promising avenue for shielding the skin from UV damage while nourishing it with botanical benefits. Objective: This study aims to develop herbal sunscreen creams enriched with polyphenols from Lemon, Tomato, and Aloe vera, evaluate their SPF, assess antioxidant activity, and compare their efficacy with commercial formulations, offering insights into their potential as natural sun protection alternatives. Materials and Methods: The study utilized Lemon (Citrus limon), Tomato (Solanum lycopersicum), and Aloe vera (Aloe barbadensis) extracts as primary ingredients. Extraction methods were employed to obtain bioactive compounds from each plant, followed by phytochemical screening to identify their chemical constituents. The sunscreen formulations were prepared by combining these extracts with excipients such as cetostearyl alcohol, stearic acid, and carbopol. Various physical parameters, SPF values, and antioxidant activity were evaluated to assess the formulations’ efficacy and stability. Results: Extraction yielded 0.98g, 1.85g, and 1.57g of extracts per 100g of raw material for Lemon, Tomato, and Aloe vera, respectively. Phytochemical screening revealed distinct profiles of bioactive compounds in each extract. Formulation development resulted in three sunscreen formulations, each containing different proportions of plant extracts and excipients. SPF determination showed that Formulation 3 exhibited the highest SPF value, indicating superior protection against UV radiation compared to the other formulations. Conclusion: The research demonstrates the potential of herbal sunscreen formulations in providing effective sun protection while harnessing the antioxidant properties of botanical extracts. The formulations exhibited desirable physical characteristics and significant SPF values, highlighting their promise as natural alternatives to conventional sunscreens. Further refinement and optimization could enhance their efficacy and stability, positioning them as compelling options in skincare and sun protection.

The Role of Nanoparticles in Sunscreen: UV Protection and Particle Size

Sunscreen formulas are essential for protecting the skin from damaging UV rays, which reduces the risk of sunburn, skin cancer, and premature aging. However, conventional sunscreens frequently lack further advantages including anti-aging and antioxidant capabilities. Strong polyphenolic component epigallocatechin-3-gallate (EGCG), present in green tea extracts, has anti-inflammatory, antioxidant, and photoprotective properties. Similar to this, poly amino acids and hyaluronic acid (HA) have hydrating, anti-aging, and skin-repairing qualities. In this work, we investigated the co-delivery of EGCG and HA/poly amino acids in sunscreen formulations using nano-carriers, namely transferosomes and polymeric nanoparticles. To increase the effectiveness of these nano-carriers, a number of formulation factors, such as the drug-polymer ratio, surfactant concentration, homogenization speed, and sonication time, were improved. When compared to normal EGCG solutions, the optimized nano-formulations showed superior properties such reduced particle size, higher encapsulation efficiency, and improved skin permeability. Studies on cytotoxicity showed that the nano-formulations were not harmful to skin cells and that they increased cell viability when compared to EGCG in its purest form. Because the nano-formulations contained EGCG and HA/poly amino acids, they offered considerable protection against skin damage caused by UV radiation. The spherical shape of the nano-carriers was shown by transmission electron microscopy, and the lack of interactions between EGCG and excipients was validated by differential scanning calorimetry and Fourier-transform infrared spectroscopy.

Recent Insight into UV-induced Oxidative Stress and Role of Herbal Bioactives in the Management of Skin Aging.

Skin is a defensive barrier that protects the body against sun rays and other harmful environmental elements. Sun rays contain ultraviolet rays, UVA (320-400 nm) and UVB (280-320 nm), which are highly harmful to the skin, leading to photoaging. Nowadays, sunscreen products are being utilized to protect the skin against photodamage. Conventional sunscreens are useful but cannot provide skin protection against UV rays for a longer period of time. Therefore, they need to be applied frequently. Aromatic compounds (ACs)-based sunscreens may filter out the UV rays but give rise to several side effects, like premature aging, stress, atopic dermatitis, keratinocytes (KCs) damage, genetic interruption, and malignant melanoma due to deposition of their toxic metabolites on the skin. The concept of natural medicines has become popular worldwide because of their safety and efficacy. Natural medicines have been proven to possess a wide array of biological properties, including antioxidant, antityrosinase, antielastase, antiwrinkle, antiaging, anti-inflammatory, anticancer, etc., against sun rays-mediated skin damage. The present review article is focused on UV-induced oxidative stress, and pathological and molecular targets with updates on herbal bioactives for the management of skin aging.

Formulation, Characterization and In Vitro Evaluation of ProShine MBTMGMIHS Herbal Sunscreen cream containing Flower Extract

The primary goal of this research was to develop and test a herbal sunscreen cream containing Hibiscus (Hibiscus rosasinensis) and Rose flower extracts (Rosaceae). Hibiscus and Rose extractswere used in the formulation of oil in water (O/W) emulsion-based cream. Flower extracts were preparedusing the Soxhlet apparatus. The physicochemical parameters of the formulated herbal sunscreen creams were tested, including colour, odour, spreadability, pH, and viscosity.The centrifugation process was used to conduct the stability and sensitivity tests. A UV Spectrophotometric method of Mansur et al. was used to calculate the in-vitro SPF of the formulations. The flower extract-based sunscreen cream provided high absorbance in the 290-320nm wavelength range, with an SPF of 38.12-42.24. The ProShine MBTMGMIHS herbal formulation was found to be stable, spreadable, homogeneous, non-greasy, and displayed no signs of phase separation. The pH of the cream was found to between 5.5-6 which is nearer to the skin's pH.Also, after the microbial evaluation of ProShine MBTMGMIHS herbal sunscreen, no bacterial or fungal contamination was observed after incubation for a long period.We may assume from the study's findings that the formulated sunscreen can greatly improve and add to the UV absorption properties of conventional sunscreen formulations. It would also aid in the broadening of the sunscreen's UV defence performance, with the added benefit of preventing the negative and undesirable effects of synthetic sunscreen compounds.

Microalgae Photo-Protectants and Related Bio-Carriers Loaded with Bioactive Entities for Skin Applications-An Insight of Microalgae Biotechnology.

Microalgae are photosynthetic organisms known for producing valuable metabolites under different conditions such as extreme temperatures, high salinity, osmotic pressure, and ultraviolet radiation. In recent years, these metabolites have become a trend due to their versatility in applications such as pharmaceuticals, cosmetics, and others. They have even been proposed as an alternative source of bioactive metabolites to avoid the harmful effects on the environment produced by active compounds such as oxybenzone in commercials sunscreens. One of the most studied applications is the use of microalgae for skin care and topical use as cosmeceuticals. With the increasing demand for more environmentally friendly products in cosmetics, microalgae have been further explored in relation to this application. It has been shown that some microalgae are resistant to UV rays due to certain compounds such as mycosporine-like amino acids, sporopollenin, scytonemin, and others. These compounds have different mechanisms of action to mitigate UV damage induced. Still, they all have been proven to confer UV tolerance to microalgae with an absorbance spectrum like the one in conventional sunscreens. This review focuses on the use of these microalgae compounds obtained by UV stimulation and takes advantage of their natural UV-resistant characteristics to potentially apply them as an alternative for UV protection products.

NOVEL COSMECEUTICAL FORMULATIONS: A BETTER APPROACH TO PHOTOPROTECTION

Using photoprotection, it is possible to prevent UV-induced skin damage and skin cancers. Radiation that falls between visible light and X-rays is defined as ultraviolet. By biological consequences, UVR is classified into five types, UVA, UVB, UVC, Far UV, and Vacuum UV. However, sunscreen functions as an essential device in our accessories of photo protective action, whose goal is to protect us from sunburn and from the harmful effects of ultraviolet radiation. Sunscreens are categorized as systemic and topical, depending on how they are administered. Again, topical sunscreen divides into organic and inorganic sunscreen. Despite the main objective of sunscreen is to be secure, chemically inert, non-toxic and protected against wide-ranging radiation so as to combat photo aging and photocarcinogenesis. But chemical and synthetic sunscreen causes several undesirable effects, which is a matter of concern. Therefore, a better and safer photoprotective agent is needed in sunscreen. In this regard, nanoparticles, or nanoparticulate systems, are becoming increasingly popular as a form of sunscreen for many different reasons, such as boosting SPF and stability, customizing the release profile, and minimizing adverse effects. In this review, the nanoformulation approach of sunscreen has been described, which has more demand than conventional sunscreen, including liposomes, ethosomes, microemulsions, nano-emulgel, solid-lipid nanoparticles, nano-transferosomes, and niosomes which received a lot of attention worldwide. In short, this review provides an outline of novel advent to sunscreen formulations.

Mycosporine-like amino acids: Algal metabolites shaping the safety and sustainability profiles of commercial sunscreens

The dramatically changing climatic conditions globally have equipped the Earth's early inhabitants with some evolutionary advancement. With the increasing influx of harmful solar radiation into the atmosphere, photo-protective mechanisms have become necessary. Microalgae and macroalgae are such groups of organisms housing various photo-protective compounds, individually and in symbiotic associations. A notable example of an algal-secondary metabolite involved in photoprotection is the mycosporine-like amino acids (MAAs). After the concerns regarding harmful implications of conventional sunscreen filters made consumers more aware, econometrics of commercial sunscreens present a shift from accustomed synthetic molecules. However, the need for a practical yet harmless sunscreen is indispensable. Being ecologically and dermatologically safer, MAAs make algae a promising source of natural sunscreens. With the discovery of more unknown compounds, the field of MAAs is continuously expanding. Their anti-oxidative, anti-inflammatory, and anti-aging properties are strengthening their cosmetic acceptability as sunscreen filters. This review analyse the data related to MAAs from research, ecological and commercial perspectives. It aims to provide a holistic understanding of the relevant findings achieved so far and the future potential.

DNA Repair Enzymes as Therapeutic Agents: a Review

DNA damage is long recognized factor for development and progression of cancer in humans. Genome instability is the leading factor behind development of cancer. There are some DNA repair pathways and DNA damage checkpoints present in all creatures, without them the functional stability gets compromised. Impaired DNA repair results in genomic instability leading to development of cancer, limited lifespan, early ageing. UV rays and Ionizing radiations are the major exogenous forces responsible for DNA damage, causing lesions in DNA. These lesions are cause of photoageing. Protection administered by conventional sunscreen is merely prophylactic if lesions have already occurred. There is an increasing demand for such product which can reverse or delay the effects of photoageing thus the protection offered by conventional sunscreen can be improved. This review focuses on recent developments on involvement of various DNA repair enzymes in treatment of cancer as well as in skincare products such as sunscreen.

3,4-dimethoxychalcone novel ultraviolet-A-protection factor in conventional sunscreen cream.

UltravioletA (UVA) rays with an intensity of 95% can induce skin cancer due to the activation of reactive oxygen species (ROS). The 3,4-dimethoxychalcone (3,4-DMC) chalcone derivative has a wide wavelength, antioxidant activity, presumed has activity as sunscreen (UVA rays). Topical delivery of water-insoluble 3,4-DMC with log P 3.84 required capable, cream formulation was chosen because it was suitable for application this chemical sunscreen. This study aims to obtain the optimal formulation of 3,4-DMC in a sunscreen cream dosage form as a UVA-protection factor (UVA-PF). This study involves experimental design. The cream 3,4-DMC was evaluated physically for 4 weeks by measuring pH, viscosity, spreadability, adhesion, centrifugation, freeze–thaw, photostability, UVA-PF used TranporeTM tape, and skin irritation test on animals. The result obtained was evaluated statistically using ANOVA (SPSS version 24). The ratio UVA/UVB value of 3,4 DMC sunscreen cream having 5 stars (*****) for all concentrations, shows the product in this study can be used as an anti-UVA agent in sunscreen cream cosmetic products. The stability of the cream has pH 4.0–4.2; spreadability 5–6 cm; viscosity 4.470–5.763; and adhesion <1 s. Freeze-thaw and centrifugation were known did not affect the stability due to the absence of separation. There was no wavelength shift in the photostability test and no skin irritation due to in vivo examination using New Zealand rabbits. The 3,4-DMC as a new agent in conventional sunscreen cream dosage form has good properties as a protection against UVA rays.

DNA repair enzymes in sunscreens and their impact on photoageing-A systematic review.

BackgroundDNA damage is one of the main factors responsible for photoageing and is predominantly attributed to ultraviolet irradiation (UV‐R). Photoprotection by conventional sunscreens is exclusively prophylactic, and of no value, once DNA damage has occurred. As a result, the demand for DNA repair mechanisms inhibiting, reversing or delaying the pathologic events in UV‐exposed skin has sparked research on anti‐photoageing and strategies to improve the effect of conventional sunscreens. This review provides an overview of recent developments in DNA repair enzymes used in sunscreens and their impact on photoageing.MethodsA systematic review of the literature, up to March 2019, was conducted using the electronic databases, PubMed and Web of Science. Quality assessment was carried out using the Newcastle‐Ottawa scale (NOS) to ensure inclusion of adequate quality studies only (NOS > 5).ResultsOut of the 352 publications, 52 were considered relevant to the key question and included in the present review. Two major enzymes were found to play a major role in DNA damage repair in sunscreens: photolyase and T4 endonuclease V. These enzymes are capable of identifying and removing UV‐R‐induced dimeric photoproducts. Clinical studies revealed that sunscreens with liposome‐encapsulated types of photolyase and/or T4 endonuclease V can enhance these repair mechanisms.ConclusionThere is a lack of randomized controlled trials demonstrating the efficacy of DNA repair enzymes on photoageing, or a superiority of sunscreens with DNA repair enzymes compared to conventional sunscreens. Further studies are mandatory to further reveal pathogenic factors of photoageing and possible therapeutic strategies against it.

Bioinspired Lignin-Polydopamine Nanocapsules with Strong Bioadhesion for Long-Acting and High-Performance Natural Sunscreens

UV filters that contain one or two aromatic rings in conventional sunscreens generally have a poor photo- and thermal stability and can easily penetrate through stratum corneum and dermis into the blood vessel, thus causing potential health-threatening issues. Herein, a series of bioinspired photostable and biocompatible polydopamine-grafted lignin (AL-PDA) with strong bioadhesion have been synthesized through free radical addition of dopamine (DA) and alkali lignin (AL). AL-PDA was used to emulsify organic UV filters and further cross-linked to form nanocapsules through ultrasonic cavitation. The retention rate of optimal AL-PDA nanocapsules on the skin surface reached 87% after a thorough rinse with water and negligible penetration was observed, which demonstrates their excellent bioadhesion property. Force measurements using atomic force microscopy (AFM) quantitatively revealed the adhesion between the nanocapsules and skin. An average DA grafting number of 4 would be required to endow the AL-PDA nanocapsules with suitable water-penetration resistance. The nanocapsules were used as the sole active ingredient for formulating sunscreen, whose sun protection factor (SPF) value could reach 195.33 with a dosage ∼10 wt % lasting for over 8 h under UV radiation. The as-prepared nanocapsules possess excellent antioxidant capacity and biocompatibility, ensuring their superior performance and safe use in the sunscreen. This work provides new insights into the development of biomass lignin for advanced function materials and high-end products.

Synthesis and Characterization of Nanostructured Lipid Nanocarriers for Enhanced Sun Protection Factor of Octyl p-methoxycinnamate.

Sunlight is important to health, but higher exposure to radiation causes early aging of the skin and skin damage that can lead to skin cancers. This study aimed at producing a stable octyl p-methoxycinnamate (OMC)-loaded nanostructured lipid carrier (NLC) sunscreen, which can help in the photoprotective effect. NLC was produced by emulsification-sonication method and these systems were composed of myristyl myristate (MM), caprylic capric triglyceride (CCT), Tween® 80 (TW), and soybean phosphatidylcholine (SP) and characterized by dynamic light scattering (DLS), zeta potential (ZP) measurement, atomic force microscopy (AFM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and in vitro release studies. Pre-formulation studies were performed changing TW concentrations and no differences were found at concentrations of 1.0 and 2.0%. Two selected formulations were designed and showed an average size of 91.5-131.7, polydispersity index > 0.2, and a negative value of ZP. AFM presented a sphere-like morphology and SEM showed ability to form a thin film. DSC exhibited that the incorporation of OMC promoted reduction of enthalpy due to formation of a more amorphous structure. Drug release shows up to 55.74% and 30.57%, and this difference could be related to the presence of SP in this formulation that promoted a more amorphous structure; the release mechanism study indicated Fickian diffusion and relaxation. Sun protection factor (SPF) evaluation was performed using NLC and presented values around 40, considerably higher than those observed in the literature. The developed formulations provide a beneficial alternative to conventional sunscreen formulations.

Skin protection efficacy from UV irradiation and skin penetration property of polysaccharide-benzophenone conjugates as a sunscreen agent

Sunscreen materials have been developed to protect skin from UV radiation. However, many organic sunscreen materials are small molecules and absorbed into human skin after topical application and lead to systemic side effects. To improve the adverse effects of conventional sunscreen materials, we designed a sunscreen agent using an organic sunscreen material and a polymer. Dioxybenzone, an organic sunscreen compound is selected and polymerized with natural polymer pullulan. Polymerization not only provides a long polymer backbone to dioxybenzone, but also keeps the distance between benzene rings of the dioxybenzone and prevents reduction of photoabsorption intensity. UV/vis spectrophotometry confirmed that dioxybenzone-pullulan polymer (DOB-PUL) and dioxybenzone (DOB) demonstrated similar UV absorption. To measure the accumulation of sunscreen materials on skin, Franz diffusion cell was used to confirm the accumulation of DOB and lack of penetration of DOB-PUL. Most importantly, DOB showed higher plasma concentration after multiple applications compared to that of DOB-PUL.

Role of solid lipid nanoparticles as photoprotective agents in cosmetics.

Novel drug delivery systems have gained popularity since last two decades because of its advantages over conventional dosage forms. Effect of UV radiation on skin can cause either acute or chronic damage to our skin. Solid lipid nanoparticles (SLNs) were developed as novel carrier over the conventional carrier systems like liposomes and emulsions. The SLNs were selected as a carrier for the formulation because of its ability to protect the labile drug particles, the ability to make the drug release in a controlled manner, and occlusive property of the SLNs. The current review is an attempt to focus on the characteristics of solid lipid nanoparticles, methods for the preparations, and their cosmetic applications along with some future perspectives of the nanodrug delivery systems. A review of the current literature of solid lipid nanoparticles (SLNs) as novel carrier showed better photoprotection in sunscreens. The disadvantages of conventional sunscreens can be overcome by incorporation of solid lipid nanoparticles. On comparing the lipid nanobased systems with traditional cosmetic products, the occlusion can be achieved without the use of paraffin and other greasy oils. The film formed by lipid nanoparticles will be smooth as compared to the inflexible films formed by the paraffin. Newer approaches may lead to even better results. They also possess excellent UV-blocking activity and showed better photoprotection.

Conventional sunscreen application does not lead to sufficient body coverage.

This study aimed to assess sunscreen application habits and relative body coverage after single whole body application. Fifty-two healthy volunteers were asked to use the test product once, following their usual sunscreen application routine. Standardized UV photographs, which were evaluated by Image Analysis, were conducted before and immediately after product application to evaluate relative body coverage. In addition to these procedures, the volunteers completed an online self-assessment questionnaire to assess sunscreen usage habits. After product application, the front side showed significantly less non-covered skin (4.35%) than the backside (17.27%) (P=0.0000). Females showed overall significantly less non-covered skin (8.98%) than males (13.16%) (P=0.0381). On the backside, females showed significantly less non-covered skin (13.57%) (P=0.0045) than males (21.94%), while on the front side, this difference between females (4.14%) and males (4.53%) was not significant. In most cases, the usual sunscreen application routine does not provide complete body coverage even though an extra light sunscreen with good absorption properties was used. On average, 11% of the body surface was not covered by sunscreen at all. Therefore, appropriate consumer education is required to improve sunscreen application and to warrant effective sun protection.

In vitro photoprotection and antioxidant capacity of Sphagnum meridense extracts, a novel source of natural sunscreen from the mountains of Colombia

Abstract Excessive ultraviolet radiation can cause skin cancer and related health problems in humans. Traditionally, organic and inorganic sunscreens have been used to minimize these effects. Besides, some phenolic compounds present in plants play an important role as photoprotectors. Sphagnum meridense (L), found in Colombia, is continuously exposed to sunlight on high mountain ecosystems. In this work, we evaluated the potential of S. meridense extracts to be applied as UVA-UVB filter in cosmetic formulations and its antioxidant capacity. The mixture acetone-37% hydrochloric acid (1%, v/v) showed the best polyphenol content and UVA-UVB absorption coefficient. These extracts also exhibited promissory UVAPF values, UVA/UVB ratio, critical wavelength (λc) and antioxidant capacity in vitro, comparable to that of conventional sunscreens.

Formulation, characterization and in vitro evaluation of herbal sunscreen lotion

Natural substances extracted from plants have recently been considered as potential sunscreen resources owing to high ultraviolet ray absorption and antioxidant activity. The decrease in the intensity of UV radiation reaching the skin through sunscreens may reduce the risk of sun-induced skin cancer. The present study attempts to develop sunscreen lotions, possessing broad spectrum of anti-UV radiation effectiveness with reduced concentration of chemical UV filters, from the extracts of bioactive products such as Curcuma longa L. (Zingiberaceae), Aloe vera (Liliaceae) and Alpinia galanga Willd. The effectiveness of the product was evaluated using Sun Protection Factor (SPF). Curcumin was selected as potential bioactive agents due to their phytochemical compositions possessing considerable content of polyphenolic compounds and Alpinia galanga is used as key ingredient in various commercial sunscreen lotions as it has skin protectant action against UV rays and boosts the activity of conventional sunscreens. The sunscreen lotions were prepared using three different compositions F1, F2 and F3 and evaluated for their stability, safety and SPF. Results showed that the sunscreen lotions were non-mutagenic, non-irritant, stable and possess SPF for normal skin. The efficacy when tested with a standard was observed to be same as that of a marketed sunscreen with SPF 55 and SPF 20. From the present study, formulation F2 having curcumin extract was proved to be stable and effective with high SPF compared to F1 and F3.

Measuring sunscreen protection against solar-simulated radiation-induced structural radical damage to skin using ESR/spin trapping: Development of an ex vivo test method

The in vitro star system used for sunscreen UVA-testing is not an absolute measure of skin protection being a ratio of the total integrated UVA/UVB absorption. The in vivo persistent-pigment-darkening method requires human volunteers. We investigated the use of the ESR-detectable DMPO protein radical-adduct in solar-simulator-irradiated skin substitutes for sunscreen testing. Sunscreens SPF rated 20+ with UVA protection, reduced this adduct by 40–65% when applied at 2 mg/cm2.SPF 15 Organic UVA-UVB (BMDBM-OMC) and TiO2-UVB filters and a novel UVA-TiO2 filter reduced it by 21, 31 and 70% respectively. Conventional broad-spectrum sunscreens do not fully protect against protein radical-damage in skin due to possible visible-light contributions to damage or UVA-filter degradation. Anisotropic spectra of DMPO-trapped oxygen-centred radicals, proposed intermediates of lipid-oxidation, were detected in irradiated sunscreen and DMPO. Sunscreen protection might be improved by the consideration of visible-light protection and the design of filters to minimise radical leakage and lipid-oxidation.

THE ENERGY EFFICIENCY OF NATURAL SHADING WITH CLIMBING PLANTS

The work presents the results in investigating the thermal behaviour of passive solar elements, for expanding the existing analysis and prediction methodologies. The interest focuses on solar control through natural shading with deciduous plants. This provides a natural path for incorporating all advantages the passive behaviour, available throughout the year. The simulation of the dynamic energy performance of building elements is developed, starting with a physical modelling of the various energy conversion and transport mechanisms (e.g., solar radiation, heat gains, convection and conduction), and followed by a numerical modelling of the considered physical effects. An experimental investigation of using plants as a passive solar system for solar control of building elements by natural shading is carried out. Along these lines, an experimental model is designed consisting of a test cell having its southern fa ade partially shaded by plants, and a set of instruments - placed at the shaded and at the sunlit wall area - is used, which is supported by a data-acquisition system. Several physical parameters for a hot summer period are measured, allowing both the experimental validation of the developed simulation programme and the comparison of the results on heat transmission obtained through theoretical predictions and through measurements. Profiles of the daily measured solar radiation components and of the temperatures on the wall surfaces taken on days with high sky clearness showed a very good agreement with the predicted values. Comparisons of the temperatures on the shaded and on the sunlit wall surface showed that plants constitute an excellent passive system for solar control in buildings, offering significant advantages over conventional artificial sunscreens.

No. 4 Vol. 42, No. 2, pp. 102–109, 2008 A novel water‐based sunscreen gel using a polymer – zinc oxide composite

Conventional sunscreen products generally must strike a compromise between efficacy and product feel; the hydrophobic ingredients that provide the sun protection generally impart an unpleasant, greasy feel and the greater the SPF rating, the worse the greasy feel. We tested an idea that a water‐based sunscreen gel formulation containing inorganic UV absorbers would provide an effective way to address these problems. Our goal was to find a way to disperse inorganic sunscreen materials in water and to incorporate them into a water‐based gel which would provide a more pleasant product feel. After extensive research we discovered a polymer‐zinc oxide composite (P‐ZnO) with high UV protective effect and high dispersibility in water. In dried powdered form, P‐ZnO can be easily dispersed in water. P‐ZnO makes it possible to formulate a gel‐type sunscreen, which is not possible using commercially available inorganic powders. The composite size of P‐ZnO is about 500 nm and its structure consists of a dense aggregate of nano‐ZnO having a size distribution in the 5–10 nm range and amorphous layers of poly acrylic acid coating zinc oxide to control the particle growth, block surface activity and prevent aggregation. The water‐based P‐ZnO sunscreen gel offers UV protection comparable to conventional products in a delivery vehicle that is much more pleasant to use.