Characterisation and cytotoxicity assessment of UV absorbers-intercalated zinc/aluminium-layered double hydroxides on dermal fibroblast cells

Zn/Al-layered double hydroxide (LDH) was used as a host to intercalate various organic ultraviolet (UV) radiation absorbers. The intercalation compounds were prepared via the co-precipitation method. Powder X-ray diffraction (PXRD) confirmed the successful intercalation of anions into the interlayer regions of the LDH nanocomposites. As a result of intercalation, the resulting nanocomposites loaded with UV-ray absorbers, cinnamic acid (CA), benzophenone 4 (B4) and Eusolex®232 (EUS)—exhibited basal spacings of 17.9 Å, 21.3 Å and 21.0 Å, respectively. Photochemical analysis revealed an increase in the UV-ray absorption capability of UV absorber/LDH nanocomposites compared to pure UV-ray absorbers. The retention ability of the organic moieties in the LDH host was tested in a skin pH simulation and was found to demonstrate low release over an extended period of time. Cytotoxicity findings indicated that none of the nanocomposites exhibit significant cytotoxicity towards human dermal fibroblast (HDF) cells up to the test concentration of 25 μg/mL

Synthesis of (cinnamate-zinc layered hydroxide) intercalation compound for sunscreen application

Background: Zinc layered hydroxide (ZLH) intercalated with cinnamate, an anionic form of cinnamic acid (CA), an efficient UVA and UVB absorber, have been synthesized by direct method using zinc oxide (ZnO) and cinnamic acid as the precursor. Results: The resulting obtained intercalation compound, ZCA, showed a basal spacing of 23.9 Å as a result of cinnamate intercalated in a bilayer arrangement between the interlayer spaces of ZLH with estimated percentage loading of cinnamate of about 40.4 % w/w. The UV–vis absorption spectrum of the intercalation compound showed excellent UVA and UVB absorption ability. Retention of cinnamate in ZLH interlayers was tested against media usually came across with sunscreen usage to show low release over an extended period of time. MTT assay of the intercalation compound on human dermal fibroblast (HDF) cells showed cytotoxicity of ZCA to be concentration dependent and is overall less toxic than its precursor, ZnO. Conclusions: (Cinnamate-zinc layered hydroxide) intercalation compound is suitable to be used as a safe and effective sunscreen with long UV protection effect

Synthesis of zinc-layered hydroxide and zinc-aluminium-layered double hydroxide as host of ultraviolet ray absorbing molecules for sunscreen application

New sunscreen formulation was formulated with the intercalation of organic ultraviolet (UV)-ray absorbing molecules into two layered materials; namely zinc layered hydroxide (ZLH) and Zn/Al layered double hydroxide (LDH). Intercalation in inorganic matrix was attempted with the intention of maintaining UV absorption properties of the otherwise photodegradable organic molecules. Furthermore, ZLH and LDH as host carriers provide a barrier between skin and chemical compounds and consequently prevent the phototoxic and photoallergic reactions. ZLH intercalated with cinnamate (CA) was successfully synthesized using direct reaction of zinc oxide (ZnO) and cinnamic acid. The intercalated compound, ZCA, has a basal spacing of 23.9 Å, with the estimated percentage loading of CA around 40.4 w/w %. The intercalation of benzophenone 9 (B9) into Zn/Al LDH was carried out by two different routes; co-precipitation and ion exchange method. Powder x-ray diffraction (PXRD) patterns of the co-precipitated product (ZB9C) and ion exchanged product (ZB9I) showed basal spacing of 15.9 Å and 16.6 Å, respectively. The percentage loading of B9 anions is 46.6 w/w % for ZB9C and 43.9 w/w % for ZB9I. The intercalation of CA, benzophenone 4 (B4) and eusolex® 232 (EUS) into Zn/Al LDH was also successfully performed via co-precipitation method with the expansion of basal spacing from 8.8 Å in Zn/Al LDH to 17.9 Å, 21.3 Å and 21.0 Å, respectively. Percentages loading of CA, B4 and EUS anions in Zn/Al LDH host are 35.8 w/w %, 41.9 w/w % and 41.7 w/w %, respectively. Co-precipitation of equimolar concentration of B4 and EUS with Zn/Al LDH host showed an intercalation selectivity that is preferential to EUS. It was also shown that the selectivity ratio of intercalated anions was altered by varying molar ratio of guests during the synthesis. Dual-guest nanocomposite synthesized with B4:EUS molar ratio 3:1 (ZEB (3:1)) showed an intercalation percentage of 20.5 w/w % for B4 and 17.9 w/w % for EUS. The selectivity ratio of B4:EUS could be rephrased as 53:47. ZEB (3:1) nanocomposite was monitored using PXRD and showed a basal spacing of 21.8 Å, which is slightly larger than single intercalation product of B4 and EUS in Zn/Al LDH. The solid-state absorbance spectra of UV absorbent-intercalated compounds showed broadened UV absorptivity range compared to pure UV absorbent due to the spatial confinement and host-guest interactions. Retention study of sunscreen molecules in ZLH and LDH was conducted with various release media; namely deionized water, pH 5.5 phosphate buffer (skin pH simulation) and 0.5 mol/L NaCl solution (artificial sea water), to observe nanocomposites performance in close to actual application. Anion release patterns in release media showed a slowed and restricted deintercalation from inorganic host. The cytotoxicity study of intercalation compounds on human dermal fibroblast (HDF) cells was investigated using Methylthiazol Tetrazolium (MTT) assay. In general, 24 h exposure with nanocomposites did not produce any significant cytotoxicity up to maximum concentration of 25 μg/mL. In brief, the UV absorbent/layered material system show great promise as a safe and efficient sunscreen formulation with prolonged UV protection effect

Enhanced anti-inflammatory potential of cinnamate-zinc layered hydroxide in lipopolysaccharide-stimulated RAW 264.7 macrophages

Background: Cinnamic acid (CA) is a phytochemical originally derived from Cinnamomum cassia, a plant with numerous pharmacological properties. The intercalation of CA with a nanocarrier, zinc layered hydroxide, produces cinnamate-zinc layered hydroxide (ZCA), which has been previously characterized. Intercalation is expected to improve the solubility and cell specificity of CA. The nanocarrier will also protect CA from degradation and sustain its release. The aim of this study was to assess the effect of intercalation on the anti-inflammatory capacity of CA. Methods: In this study, the anti-inflammatory activity of ZCA was investigated and compared with that of nonintercalated CA. Evaluations were based on the capacity of ZCA and CA to modulate the release of nitric oxide, prostaglandin E2, interleukin (IL)-6, tumor necrosis factor alpha (TNF-α), IL-1β, and IL-10 in lipopolysaccharide-induced RAW 264.7 cells. Additionally, the expression of proinflammatory enzymes, ie, cyclooxygenase-2, inducible nitric oxide synthase, and nuclear factor kappa B (NF-κB), were examined. Results: Although both ZCA and CA downregulated nitric oxide, prostaglandin E2, tumor necrosis factor alpha, IL-1β, and IL-6, ZCA clearly displayed better activity. Similarly, expression of cyclooxygenase-2 and inducible nitric oxide synthase were inhibited in samples treated with ZCA and CA. The two compounds effectively inactivated the transcription factor NF-κB, but the anti-inflammatory cytokine, IL-10, was significantly upregulated by ZCA only. Conclusion: The present findings suggest that ZCA possesses better anti-inflammatory potential than CA, while zinc layered hydroxide had little or no effect, and these results were comparable with the positive control

An intercalated UV absorbing product and a production method thereof

The present invention relates to ultraviolet (UV) absorbers-intercalated layered double hydroxide (LDH) product. The present invention also provides a simple and energy efficient co-precipitation method for simultaneous intercalation of two UV absorbers into layered double hydroxide (LDH)