Fabrication of Microcrystalline cellulose and nano-titanium dioxide composites with broad-spectrum UV protection
Huizhong Yu, Junxian Xie, Lan Yao, Haitao Yang
Abstract
As a popular physical sunscreen, nano-titanium dioxide (nano-TiO 2 ) can provide protection against UV radiation penetration into the skin and to avoid health problems caused by UVB and UVA irradiation. However, it was found that nano-TiO 2 can penetrate the stratum corneum to induce health problems. To address concerns about the safety of nano-TiO 2 , a micro-sized core–shell microcrystalline cellulose (MCC) and nano-TiO 2 composite (MCC@nano-TiO 2 ) was fabricated by low-temperature hydrolysis under strong acidic conditions. The nano-TiO 2 was loaded onto MCC, and obtained excellent UV protection performance with a lower dosage of nano-TiO 2 . First, an MCC suspension with a particle size distribution of 4–20 μm was prepared with good suspension stability by direct acid hydrolysis and ultrasonic-assisted acid hydrolysis, which could be used as an ideal carrier of nano-TiO 2 . Furthermore, MCC@nano-TiO 2 was fabricated via low-temperature hydrolysis at different pH values. The structures and properties of the MCC@nano-TiO 2 were determined. The results showed that nano-TiO 2 and MCC were closely connected through Ti-O-C bonds to form a core–shell structure. MCC@nano-TiO 2 exhibited exceptional UV protection performance. In particular, MCC@nano-TiO 2 with a mixed-crystal phase prepared at pH = 0.4 showed the potential for broad-spectrum UV protection. The relative content of rutile (W R ) was 73.1%, the critical wavelength (λ c ) of the UV absorption of the powder was greater than 370 nm, the in vitro SPF value (SPF in vitro ) of the cream with 5% addition was 7.99, and the ratio of initial UVA protection index to SPF in vitro (UVAPF 0 /SPF in vitro ) was 0.61. The results could bring new insight into UV protection.