BSA Adsorption on Titanium Dioxide Nanoparticle Surfaces for Controlling Their Cellular Uptake in Skin Cells

Nanoparticles (NPs) are continuously being developed for many applications including imaging, biomedicine, and everyday products. It is difficult to avoid contact with NPs such as titanium dioxide (TiO2) NPs, which are widely used in sunscreens. However, the safety of TiO2 NPs for skin contact and inhalation remains controversial. If NPs cannot penetrate the skin, they will be unable to circulate in the bloodstream, accumulate in the body, or cause side effects, ensuring their safety. Therefore, this study aimed to modify TiO2 NP surfaces to inhibit their uptake in skin cells. Inspired by protein corona studies, bovine serum albumin (BSA) was chosen to functionalize TiO2 NP surfaces via physical adsorption. The maximum BSA adsorption occurred at pH 5.0. The physicochemical properties (size, ζ-potential, morphology, ultraviolet (UV) absorption efficiency, and sun protection factor (SPF)) of TiO2-BSA NPs were comparable to those of TiO2 NPs, indicating that these properties did not affect cellular uptake. In the safety evaluation, TiO2 NPs and TiO2-BSA NPs exhibited high biocompatibility with skin cells and no phototoxicity after UVA and UVB irradiation. In the efficacy evaluation, both NPs possessed the same photoprotection abilities, reducing membrane damage and DNA breakage after UVA irradiation. Compared with TiO2 NPs, TiO2-BSA NPs showed substantially reduced skin penetration in Franz diffusion cells (91%) and human immortalized keratinocyte (HaCaT) cells (89%). A qualitative cellular uptake study using transmission electron microscopy and confocal laser scanning microscopy confirmed that TiO2 NPs were more abundant than TiO2-BSA NPs inside the HaCaT cells. These findings indicate that TiO2 surface functionalization with BSA inhibits cellular uptake in skin cells while maintaining safety and UV protection efficacy, which might be extended to other NP-based sunscreens.

Multifunctional Cellulosic Natural Rubber and Silver Nanoparticle Films with Superior Chemical Resistance and Antibacterial Properties

Composite films of natural rubber/cellulose fiber/silver nanoparticle were synthesized in a green route via the latex solution process. Hybrid cellulose filler containing carboxymethyl cellulose and cellulose microfibers was used to facilitate facile and fast preparation and to improve mechanical strength to the composites, respectively. All the composites possessed a high tensile strength of ~120 MPa, a high heat resistance of nearly 300 °C, and more than 20% biodegradability in soil in two weeks. Chemical resistance and antibacterial activity of the composite was enhanced depending on sizes and concentrations of silver nanoparticles (AgNPs). The composites containing 0.033-0.1% w/w AgNPs retarded toluene uptake to less than 12% throughout 8 h, whereas the composite containing 0.067-0.1% w/w AgNPs exhibited excellent antibacterial activities against Escherichia coli and Staphylococcus aureus. In comparison, 50 nm-AgNPs presented higher antibacterial activities than 100 nm-AgNPs. In vitro cytotoxicity test assessed after incubation for 24 h and 48 h revealed that almost all AgNPs-composite films exhibited non/weak and moderate cytotoxicity, respectively, to HaCaT keratinocyte cells.

Smaller Is Not Always Better: Large-Size Hollow Polydopamine Particles Act as an Efficient Sun Protection Factor Booster for Sunscreens

Ultraviolet (UV) radiation from the sun is the most harmful factor for human skin, causing sunburn, melasma, freckles, blemishes, and skin cancer. Sunscreens play a key role in blocking UV absorption on the skin. This study focused on the synthesis of hollow polydopamine (h-PDA), whose structure mimics the naturally occurring melanin in humans, for use as an active ingredient in sunscreens by means of a hard-template-based method. The reactions involve a spontaneous polymerization of a dopamine monomer in the presence of tris(hydroxymethyl)aminomethane (Tris) as a catalyst onto a polystyrene (PS) core template. Different sizes of the PS core (about 280 and 450 nm) and weight ratios of PS/DA were applied to elucidate the effect of the hollow diameter and thickness of the shell on the morphology and absorbance of the synthesized h-PDA. From UV absorption results, it was observed that the synthesized h-PDA particles with a larger core diameter (about 450 nm) and a thin shell thickness (about 57 nm) presented high UV absorption. We found that the structure of the synthesized h-PDA is mainly composed of a mixture of 5,6-dihydroxyindole and indole-5,6-quinone precursors covalently linked together. After blending the h-PDA particles with the base cream, the formulation containing h-PDA with a large void diameter of about 450 nm showed the highest sun protection factor (SPF) of up to 7.43, which is related to % booster of 234.7%. In addition, the h-PDA particles exhibited biocompatibility and cellular uptake in keratinocyte HaCaT cells after 24 h of incubation, indicating the potential to mimic natural melanin in preventing UV-induced DNA damage, which could be safely used as an alternative sunscreen.

Alginate as Dispersing Agent for Compounding Natural Rubber with High Loading Microfibrillated Cellulose

Natural rubber (NR) reinforced with high loading of microfibrillated cellulose (MFC) was fabricated in the presence of sodium alginate as a thickening and dispersing agent in NR latex. The tensile strength and Young’s moduli of the 50% wt. MFC loading-NR composites were 13.6 and 1085.7 MPa, which were about 11.3- and 329-times enhanced compared with those of the neat NR film. The maximum elongation at 313.3% was obtained from 30% MFC loading, which was a 3.3-fold increase of that of the NR film. The thermal stability of MFC–NR films was slightly reduced, while the glass transition temperature remained unchanged at −64 °C. The MFC–NR films exhibited high water adsorption ability, toluene resistance, and biodegradability.