Sunscreens are used to provide protection against adverse effects of ultraviolet (UV)B (290-320 nm) and UVA (320-400 nm) radiation. According to the United States Food and Drug Administration, the protection factor against UVA should be at least one-third of the overall sun protection factor. Titanium dioxide (TiO2) and zinc oxide (ZnO) minerals are frequently employed in sunscreens as inorganic physical sun blockers. As TiO2 is more effective in UVB and ZnO in the UVA range, the combination of these particles assures a broad-band UV protection. However, to solve the cosmetic drawback of these opaque sunscreens, microsized TiO2 and ZnO have been increasingly replaced by TiO2 and ZnO nanoparticles (NPs) (<100 nm). This review focuses on significant effects on the UV attenuation of sunscreens when microsized TiO2 and ZnO particles are replaced by NPs and evaluates physicochemical aspects that affect effectiveness and safety of NP sunscreens. With the use of TiO2 and ZnO NPs, the undesired opaqueness disappears but the required balance between UVA and UVB protection can be altered. Utilization of mixtures of micro- and nanosized ZnO dispersions and nanosized TiO2 particles may improve this situation. Skin exposure to NP-containing sunscreens leads to incorporation of TiO2 and ZnO NPs in the stratum corneum, which can alter specific NP attenuation properties due to particle-particle, particle-skin, and skin-particle-light physicochemical interactions. Both sunscreen NPs induce (photo)cyto- and genotoxicity and have been sporadically observed in viable skin layers especially in case of long-term exposures and ZnO. Photocatalytic effects, the highest for anatase TiO2, cannot be completely prevented by coating of the particles, but silica-based coatings are most effective. Caution should still be exercised when new sunscreens are developed and research that includes sunscreen NP stabilization, chronic exposures, and reduction of NPs' free-radical production should receive full attention.

https://www.dovepress.com/getfile.php?fileID=11179

Titanium dioxide and zinc oxide nanoparticles in sunscreens: focus on their safety and effectiveness

Photodynamic therapy for localized infections--state of the art.

Zinc oxide nanoparticles (ZnO NPs) are used in an increasing number of industrial products such as rubber, paint, coating, and cosmetics In the past two decades, ZnO NPs have become one of the most popular metal oxide nanoparticles in biological applications due to their excellent biocompatibility, economic, and low toxicity ZnO NPs have emerged a promising potential in biomedicine, especially in the fields of anticancer and antibacterial fields, which are involved with their potent ability to trigger excess reactive oxygen species (ROS) production, release zinc ions, and induce cell apoptosis In addition, zinc is well known to keep the structural integrity of insulin So, ZnO NPs also have been effectively developed for antidiabetic treatment Moreover, ZnO NPs show excellent luminescent properties and have turned them into one of the main candidates for bioimaging Here, we summarize the synthesis and recent advances of ZnO NPs in the biomedical fields, which will be helpful for facilitating their future research progress and focusing on biomedical fields

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The Advancing of Zinc Oxide Nanoparticles for Biomedical Applications

Metal-based nanoparticles have been extensively investigated for a set of biomedical applications. According to the World Health Organization, in addition to their reduced size and selectivity for bacteria, metal-based nanoparticles have also proved to be effective against pathogens listed as a priority. Metal-based nanoparticles are known to have non-specific bacterial toxicity mechanisms (they do not bind to a specific receptor in the bacterial cell) which not only makes the development of resistance by bacteria difficult, but also broadens the spectrum of antibacterial activity. As a result, a large majority of metal-based nanoparticles efficacy studies performed so far have shown promising results in both Gram-positive and Gram-negative bacteria. The aim of this review has been a comprehensive discussion of the state of the art on the use of the most relevant types of metal nanoparticles employed as antimicrobial agents. A special emphasis to silver nanoparticles is given, while others (e.g., gold, zinc oxide, copper, and copper oxide nanoparticles) commonly used in antibiotherapy are also reviewed. The novelty of this review relies on the comparative discussion of the different types of metal nanoparticles, their production methods, physicochemical characterization, and pharmacokinetics together with the toxicological risk encountered with the use of different types of nanoparticles as antimicrobial agents. Their added-value in the development of alternative, more effective antibiotics against multi-resistant Gram-negative bacteria has been highlighted.

/pdf/metal-based-nanoparticles-as-antimicrobial-agents-an-y9sfybpk7p.pdf

Metal-based nanoparticles as antimicrobial agents: an overview.

Nanomaterials have emerged as an amazing class of materials that consists of a broad spectrum of examples with at least one dimension in the range of 1 to 100 nm. Exceptionally high surface areas can be achieved through the rational design of nanomaterials. Nanomaterials can be produced with outstanding magnetic, electrical, optical, mechanical, and catalytic properties that are substantially different from their bulk counterparts. The nanomaterial properties can be tuned as desired via precisely controlling the size, shape, synthesis conditions, and appropriate functionalization. This review discusses a brief history of nanomaterials and their use throughout history to trigger advances in nanotechnology development. In particular, we describe and define various terms relating to nanomaterials. Various nanomaterial synthesis methods, including top-down and bottom-up approaches, are discussed. The unique features of nanomaterials are highlighted throughout the review. This review describes advances in nanomaterials, specifically fullerenes, carbon nanotubes, graphene, carbon quantum dots, nanodiamonds, carbon nanohorns, nanoporous materials, core–shell nanoparticles, silicene, antimonene, MXenes, 2D MOF nanosheets, boron nitride nanosheets, layered double hydroxides, and metal-based nanomaterials. Finally, we conclude by discussing challenges and future perspectives relating to nanomaterials.

/pdf/nanomaterials-a-review-of-synthesis-methods-properties-5ebdqaoboz.pdf

Nanomaterials: a review of synthesis methods, properties, recent progress, and challenges

Dermatophytes are fungi that can cause infections (known as tinea) of the skin, hair and nails because of their ability to use keratin. Superficial mycoses are probably the most prevalent of infectious diseases worldwide. One of the most distinct limitations of the current therapeutic options is the recurrence of the infection and duration of treatment. The present study shows that Trichophyton rubrum in suspension culture is susceptible to photodynamic treatment (PDT), a completely new application in this area. T. rubrum could be effectively killed with the use of the light-activated porphyrins deuteroporphyrin monomethylester (DP mme) and 5,10,15-tris(4-methylpyridinium)-20-phenyl-[21H,23H]-porphine trichloride (Sylsens B). The photodynamic efficacy was compared with that of some other photosensitizers that are well known in the field of PDT: the porphyrins deuteroporphyrin and hematoporphyrin, the drug Photofrin and several phthalocyanines. It was demonstrated that with the use of broadband white light, the phthalocyanines and Photofrin displayed a fungistatic effect for about 1 week, whereas all the porphyrins caused photodynamic killing of the dermatophyte. Sylsens B was the most effective sensitizer and showed no dark toxicity; therefore, in an appropriate formulation, it could be a promising candidate for the treatment of various forms of tinea. For Sylsens B and DP mme, which displayed the best results, a concentration-dependent uptake by T. rubrum was established.

Photodynamic Inactivation of the Dermatophyte Trichophyton rubrum

The application of photosensitizers for the treatment of fungal infections is a new and promising development within the field of photodynamic treatment (PDT). Dermatophytes, fungi that can cause infections of the skin, hair and nails, are able to feed on keratin. Superficial mycoses are probably the most prevalent of infectious diseases in all parts of the world. One of the most important restrictions of the current therapeutic options is the return of the infection and the duration of the treatment. This is especially true in the case of infections of the nail (tinea unguium) caused by Trichophyton rubrum, an anthropophilic dermatophyte with a worldwide distribution. Recently, we demonstrated that 5,10,15-tris(4-methylpyridinium)-20-phenyl-[21H,23H]-porphine trichloride (Sylsens B) and deuteroporphyrin monomethylester were excellent photosensitizers toward T. rubrum when using broadband white light. This study demonstrates the photodynamic activity of these photosensitizers with red light toward both a suspension culture of T. rubrum and its isolated microconidia. The higher penetration depth of red light is important for the PDT of nail infections. In addition, we tested the photodynamic activity of a newly synthesized porphyrin, quinolino-[4,5,6,7-efg]-7-demethyl-8-deethylmesoporphyrin dimethylester, displaying a distinct peak in the red part of the spectrum. However, its photodynamic activity with red light toward a suspension culture of T. rubrum appeared to be only fungistatic. Sylsens B was the best photosensitizer toward both T. rubrum and its microconidia. A complete inactivation of the fungal spores and destruction of the fungal hyphae was found. In studies into the photostability, Sylsens B appeared to be photostable under the conditions used for fungal PDT. A promising result of this study is the demonstration of the complete degradation of the fungal hyphae in the time after the PDT and the inactivation of fungal spores, both with red light. These results offer the ingredients for a future treatment of fungal infections, including those of the nail.

https://bioone.org/journals/photochemistry-and-photobiology/volume-80/issue-2/2004-04-22-RA-146.1/Photodynamic-Treatment-of-the-Dermatophyte-Trichophyton-rubrum-and-its-Microconidia/10.1562/2004-04-22-RA-146.1.pdf

Photodynamic Treatment of the Dermatophyte Trichophyton rubrum and its Microconidia with Porphyrin Photosensitizers

Today, various anthropogenic sources account for an increasing atmospheric nanoparticle (NP) concentration and thus increase of human exposure to NPs. The situation may become problematic since commercial applications of nanotechnology expand more rapidly than the scientific knowledge on NP exposure. This review focuses on skin as a route of exposure for NPs and the toxicological impact in skin with special attention to physicochemical properties of NPs and skin. We will review data published on NP skin penetration, toxicological issues and on physicochemical NP characterisation. NPs are reported to be localised mainly in hair follicle openings and on the stratum corneum surface. Some studies report the localisation of NPs in the deeper layers of the stratum corneum, the viable epidermis and deeper hair follicle parts. Sporadically, penetration into the dermis is reported for 4 to 5 nm sized quantum dots. NP interactions with epidermal and dermal cells may cause cytotoxicity and undesired immune responses, especially in damaged skin. NP characteristics promoting skin penetration are still unclear. For sunscreen NP substances there are indications for cytotoxicity (TiO2) and genotoxicity (ZnO). Significant data gaps comprise skin penetration and toxicological areas of (metal) particles smaller than 10 nm. The importance of skin barrier function in NP exposure is underlined by NP's skin cell damaging potential. Although NP skin studies display, increasingly, a multidisciplinary character (penetration, toxicity studies) the results are often contradicting. Standardisation of available test systems for NPs and focusing on the correlating physicochemical NP properties to penetration potential is recommended.

Focus on skin as a possible port of entry for solid nanoparticles and the toxicological impact.

Background Dermatophytes are fungi that can cause infections of skin, hair and nails because of their ability to feed on keratin. Superficial mycoses are among the most prevalent infectious diseases worldwide. Two important restrictions of current therapeutic options are the recurrence of the infection and prolonged treatment. This is especially true for infections caused by Trichophyton rubrum, a widely distributed dermatophyte. The application of photosensitizers for treatment of fungal infections is, within the field of photodynamic treatment (PDT), relatively new. Recently, we demonstrated that the porphyrins 5,10,15-tris(4-methylpyridinium)-20-phenyl-[21H,23H]-porphine trichloride (Sylsens B) and deuteroporphyrin monomethylester (DP mme) were excellent photosensitizers towards T. rubrum when using red light. Objectives and methods To evaluate the photodynamic effectiveness of the porphyrins in a situation that mimics the clinical situation, we developed an ex vivo model using human stratum corneum. This model offers the possibility of applying PDT at different time points during the germination and subsequent development of T. rubrum microconidia. The model was used for two different incubation media, Dulbecco's modified Eagle medium (DMEM) and distilled water. Results and conclusions We demonstrated that the PDT susceptibility of T. rubrum depended on the time of PDT application after spore inoculation. A decrease in susceptibility was observed with increasing time of PDT application for both photosensitizers in DMEM. Changing the incubation medium to distilled water resulted in an increased fungicidal effect for Sylsens B and in a decreased effect for DP mme. We conclude that T. rubrum is susceptible to PDT in a situation that mimics the clinical situation. The fungicidal effect of PDT on fungal spores is of particular importance.

Threes G. M. Smijs

Papers

Titanium dioxide and zinc oxide nanoparticles in sunscreens: focus on their safety and effectiveness

Photodynamic Inactivation of the Dermatophyte Trichophyton rubrum

Photodynamic Treatment of the Dermatophyte Trichophyton rubrum and its Microconidia with Porphyrin Photosensitizers

Focus on skin as a possible port of entry for solid nanoparticles and the toxicological impact.

A novel ex vivo skin model to study the susceptibility of the dermatophyte Trichophyton rubrum to photodynamic treatment in different growth phases