UV Absorption Properties Research Articles

(+)-Usnic Acid as a Promising Candidate for a Safe and Stable Topical Photoprotective Agent.

The study aimed to examine whether usnic acid—a lichen compound with UV-absorbing properties—can be considered as a prospective photoprotective agent in cosmetic products. Moreover, a comparison of two usnic acid enantiomers was performed to preselect the more effective compound. To meet this aim, an in vitro model was created, comprising the determination of skin-penetrating properties via skin-PAMPA assay, safety assessment to normal human skin cells (keratinocytes, melanocytes, fibroblasts), and examination of photostability and photoprotective properties. Both enantiomers revealed comparable good skin-penetrating properties. Left-handed usnic acid was slightly more toxic to keratinocytes (IC50 80.82 and 40.12 µg/mL, after 48 and 72 h, respectively) than its right-handed counterpart. The latter enantiomer, in a cosmetic formulation, was characterized by good photoprotective properties and photostability, comparable to the UV filter octocrylene. Perhaps most interestingly, (+)-usnic acid combined with octocrylene in one formulation revealed enhanced photoprotection and photostability. Thus, the strategy can be considered for the potential use of (+)-usnic acid as a UV filter in cosmetic products. Moreover, the proposed model may be useful for the evaluation of candidates for UV filters.

Green and Scalable Preparation of Colloidal Suspension of Lignin Nanoparticles and Its Application in Eco-friendly Sunscreen Formulations.

Lignin nanoparticles (LNPs) are applied in several industrial applications. The nanoprecipitation of LNPs is fast and inexpensive but currently still limited to the use of hazardous organic solvents, making it difficult to apply them on a large scale. Here, we report a scalable nanoprecipitation procedure for the preparation of colloidal lignin nanoparticles (cLNPs) by the use of the green solvents dimethylisosorbide and isopropylidene glycerol. Irrespective of the experimental conditions, cLNPs showed higher UV absorbing properties and radical scavenging activity than parent LNPs and raw lignin. cLNPs were successively used in the preparation of eco-friendly sunscreen formulations (SPF 15, 30, and 50+, as evaluated by the COLIPA assay), which showed high UV-shielding activity even in the absence of synthetic boosters (microplastics) and physical filters (TiO2 and ZnO). Biological assays on human HaCaT keratinocytes and human skin equivalents demonstrated the absence of cytotoxicity and genotoxicity, associated with an optimal protection of the skin from UV-A damage.

Transparent and UV-absorbing nanocellulose films prepared by directly dissolving microwave liquefied bamboo in TBAA/DMSO co-solvent system

Bamboo is a potential resource to produce renewable materials with replacement of plastic. In this study, cellulose-rich bamboo fibers and parenchyma with partial lignin (4–10 %) retained were prepared from microwave liquefaction, thereafter nanocellulose with uniform diameter (less than 10 nm) distribution were obtained by directly dissolving the cellulose-rich bamboo cells in TBAA/DMSO system. By solvent-casting, transparent nanocellulose films with efficient UV-absorbing ability especially the excellent UVA (82 %) and UVB (99 %) absorbing performance were fabricated. The films showed homogeneous network structure and had good tensile strength (15−25 MPa). Changes in cellulose crystallinity structure was observed during the film preparation process. Results also showed that the lignin in the cellulose-rich bamboo could distribute uniformly in the nanocellulose films and had effect on the film formation, UV-absorbing ability and physical-mechanical properties. Overall, microwave liquefaction coupling with TBAA/DMSO dissolving system could be selected as a facile and simple method to produce transparent nanocellulose films with UV-absorbing property.

Examining the UV-Absorbing Properties of Scaevola taccada (Goodeniaceae) and Its Potential Use as a Sunscreen

The native Hawaiian plant, Scaevola taccada, commonly grows in tropical coastal areas throughout the Pacific and Indian oceans. Oral tradition suggests that the fruit of this species may have been used as a natural sunblock. To examine this, an extract of S. taccada fruit was tested to determine whether it had UV-absorbing properties, and if so, to determine its stability and potential toxicity to coral. Scaevola taccada contained UV-absorbing compound(s) with a sun-protection factor of 20, on average, that absorbed in the UVB and UVA (19.6% and 24.4% absorbance, respectively). The UV stability of the fruit extract over time and to various treatments (fresh, heated, and frozen) did not change (ANOVA, p = .396, F = 1.018). In addition, we examined the toxicity of S. taccada juice by exposing coral fragments of Porites compressa (n = 7) to four treatments (fresh and heated S. taccada extract, cytotoxic Montipora capitata eggs, and filtered seawater control). Changes in color and photosynthetic yield in treated tissue areas were measured after 4 days. Only the concentrated S. taccada fruit extract and M. capitata eggs resulted in significant changes in pigmentation or photosynthetic yield of the coral (p ≤ .0001). Further investigation is needed to isolate and expand tests on the UV-absorbing component(s) to understand this toxicity more clearly.

Booster Effect of a Natural Extract of Polypodium leucotomos (Fernblock®) That Improves the UV Barrier Function and Immune Protection Capability of Sunscreen Formulations.

Background: Novel approaches to photoprotection must go beyond classical MED measurements, as discoveries on the effect of UV radiation on skin paints a more complex and multi-pronged scenario with multitude of skin cell types involved. Of these, photoimmunoprotection emerges as a crucial factor that protects against skin cancer and photoaging. A novel immune parameter is enabled by the precise knowledge of the wavelength and dose of solar radiation that induces photoimmunosupression. Natural substances, that can play different roles in photoprotection as antioxidant, immune regulation, and DNA protection as well as its possible ability as sunscreen are the new goals in cosmetic industry.Objective: To analyze the effect of a specific natural extract from Polypodium leucotomos (PLE, Fernblock®), as part of topical sunscreen formulations to protect from photoimmunosuppression, as well as other deleterious biological effects of UV radiation.Methods: The possible sunscreen effect of PLE was analyzed by including 1% (w/w) PLE in four different galenic formulations containing different combinations of UVB and UVA organic and mineral filters. In vitro sun protection factor (SPF), UVA protection factor (UVA-PF), contact hypersensitivity factor (CHS), and human immunoprotection factor (HIF) were estimated following the same protocol as ISO 24443:2012 for in vitro UVA-PF determination.Results: PLE-containing formulations significantly reduced UV radiation reaching to skin. Combination of UVB and UVA filters with PLE increased SPF and UVAPF significantly. PLE also increased UV immune protection, by elevating the contact hypersensitivity factor and the human immunoprotective factor of the sunscreen formulations.Conclusion: This study confirms the double role of PLE in photoprotection. Together to the biological activity shown in previous works, the UV absorption properties of PLE confers a booster effect when it is supplemented in topical sunscreens increasing the protection not only at level of erythema and permanent pigment darkening but also against two photoimmunoprotection factors.

Phenolic Ester-Decorated Cellulose Nanocrystals as UV-Absorbing Nanoreinforcements in Polyvinyl Alcohol Films

Grafting novel and nature-inspired phenolic esters onto cellulose nanocrystals (CNCs) provides nanofibers with excellent protection against UV radiation when incorporated into a polymer matrix. In this work, CNCs decorated with a novel UV-absorbing phenolic diester (CNC-diethyl ferulate or CNC-DEF) obtained via a click-type copper-catalyzed azide/alkyne cycloaddition reaction were incorporated into a polyvinyl alcohol (PVA) matrix to produce transparent films with excellent photostability and UV-absorbing properties. PVA films filled with 20 wt % CNC-DEF exhibited complete UV protection (0% transmittance) and high transparency in the visible region (70–90% transmittance). In contrast, PVA films loaded with the pristine CNCs do not show any UV-shielding properties. Importantly, the grafting of DEF moieties on CNCs significantly aids the dispersion of the phenolic diester in the aqueous PVA matrix, which was not achieved with DEF blended with PVA. Mechanical tests also show that the addition of 20 wt % CNC-DEF in PVA increases the tensile strength and modulus by 91 and 150%, respectively, relative to neat PVA. The oxygen barrier properties of the composite film also improve with CNC-DEF addition. This study shows the great potential of the phenolic-ester-decorated CNCs as dispersible, multifunctional UV-absorbing nanoreinforcements in PVA films for industrial and packaging applications.

Study on polyurethane‐acrylate/cerium dioxide modified by 3‐(Methylacryloxyl)propyltrimethoxy silane and its UV absorption property

AbstractFirstly, cerium dioxide(CeO2) was modified by 3‐(Methylacryloxyl)propyltrimethoxy silane (KH‐570), and modified CeO2 (mCeO2) was prepared. Then poly (urethane‐acrylate) was modified by mCeO2, and poly (urethane‐acrylate)/modified CeO2 (PUA/mCeO2) composites with ultraviolet absorption property were prepared. The morphology, thermal hydrophobicity, mechanical properties, optical properties, and UV‐absorption properties of PUA/mCeO2 composites were studied. XRD and SEM analysis showed that the modified CeO2 had better dispersion in the matrix than that of pure CeO2. Ultraviolet–visible spectrum and thermogravimetric analysis were used to characterize the optical properties and thermal stability of PUA/mCeO2 composites. The results showed that with the increasing of the mCeO2 content, the UV‐absorption property of PUA/mCeO2 composites was improved gradually. When the content of mCeO2 is 3%, the absorption of ultraviolet of PUA/mCeO2 composites is about 5 times of pure PUA film, and the absorption band is mainly in the UVA section. The thermal stability of PUA/mCeO2 composites was improved with the adding of mCeO2. With the increasing of mCeO2 content, the contact angle of PUA/mCeO2 composites increased significantly. And the UV‐absorption mechanism of PUA/mCeO2 Composites was studied. UV‐curable PUA/mCeO2 composites have good UV absorption property and water resistance. They will be used in the sun screen and protect people's skin.

Fabrication and characterization of alginate-based films functionalized with nanostructured lipid carriers

This study focuses on the fabrication and characterization of alginate-based films functionalized by incorporating nanostructured lipid carriers (NLCs). The effect of different NLC/alginate mass ratios (R = 0.05, 0.1, 0.2, and 0.35) on the physical, morphological, mechanical, and barrier properties of the calcium-alginate films was evaluated. The addition of the NLCs significantly improved the UV-absorbing properties, without greatly altering their transparent appearance. As the NLC concentration increased, the tensile strength, elastic modulus, and swelling ratio of the films decreased, while their thermal stability, water vapor permeability, and contact angle increased. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images of the films revealed that NLC incorporation led to a more porous internal structure and a rougher surface. Fourier Transform Infrared (FTIR) analysis indicated that there were no new interactions between the calcium-alginate and NLC constituents within the films. Overall, this study shows that NLCs can be successfully incorporated into calcium-alginate films and used to modulate their physicochemical properties. In future, it will be useful to examine the potential of these films to incorporate hydrophobic bioactives such as drugs, nutraceuticals, antimicrobials, antioxidants, and pigments for specific pharmaceutical or food applications.

Preparation of ammonium polyphosphate and dye co-intercalated LDH/polypropylene composites with enhanced flame retardant and UV resistance properties

In this paper, ammonium polyphosphate (APP) with flame retardant performance and acid red 88 (AR88) with UV absorption property were intercalated into layered double hydroxide (LDH) interlayers together, aiming to improve the flame retardancy and UV resistance properties of polypropylene (PP) simultaneous in one system. The synthesized LDHs and PP/LDH composites were characterized systematically and the results showed that AR88 and APP were intercalated into LDH interlayers successfully, and the content of APP and AR88 in LDH interlayers can be controlled through the synthesis process. Both APP-LDHs and AR88/APP-LDHs can greatly improve the flame retardancy performance of PP, with 25 wt% LDH addition, the peak heat release rate (PHRR) decreased by 42–63%, respectively. Temperature at 50% mass loss (T50) of PP also increased to some extent. In addition, the intercalation of AR88 in LDH also possessed good UV adsorption which can delay the ageing of PP during their use. Thus, a new approach to improve both flame retardant and UV resistance properties for polymers at the same time is achieved.

Diluted Aqueous Dispersed Systems of 4-Aminopyridine: The Relationship of Self-Organization, Physicochemical Properties, and Influence on the Electrical Characteristics of Neurons.

A variety of physicochemical methods were used to examine the self-organization, physicochemical, UV absorption, and fluorescent properties of diluted aqueous solutions (calculated concentrations from 1·10−20 to 1·10−2 M) of the membrane voltage-dependent potassium channels blocker 4-aminopyridine (4-AP). Using the dynamic light scattering method, it was shown that 4-AP solutions at concentrations in the range of 1·10−20–1·10−6 M are dispersed systems in which domains and nanoassociates of hundreds of nm in size are formed upon dilution. An interrelation between the non-monotonic concentration dependencies of the size of the dispersed phase, the fluorescence intensity (λ ex 225 nm, λ em 340 nm), specific electrical conductivity, and pH has been established. This allows us to predict the bioeffects of the 4-AP systems at low concentrations. The impact of these diluted aqueous systems on the electrical characteristics of identified neurons of Helix lucorum snails was studied. Incubation of neurons in the 4-AP systems for which the formation of domains and nanoassociates had been established lead to a nonmonotonic decrease of the resting potential by 7–13%. An analysis of the obtained results and published data allows for a conclusion that a consistent change in the nature and parameters of the dispersed phase, as well as the pH of the medium, apparently determines the nonmonotonic nature of the effect of the 4-AP systems in a 1·10−20–1·10−6 M concentration range on the resting membrane potential of neurons. It was found that the pre-incubation of neurons in the 4-AP system with a concentration of 1·10−12 M led to a 17.0% synergistic decrease in the membrane potential after a subsequent treatment with 1·10−2 M 4-AP solution. This finding demonstrates a significant modifying effect of self-organized dispersed systems of 4-AP in low concentrations on the neurons’ sensitivity to 4-AP.

Ultraviolet blocking and antioxidant polyvinyl alcohol films incorporated with baicalin extraction from Scutellaria baicalensis Georgi

Abstract Baicalin, an active flavonoid ingredient of Scutellaria baicalensis Georgi, was extracted by heat reflux extraction and showed the same significance UV absorption property with standard baicalin. Active films were prepared from polyvinyl alcohol (PVA) containing baicalin extract by casting method. The effect of baicalin extracts on the UV-blocking, optical, antioxidant property, water vapor permeability, swelling and mechanical properties of the films were studied. UV–vis transmittance spectra showed that PVA films incorporated with baicalin extract blocked ultraviolet light range from 280–400 nm even with low concentration of baicalin (0.5 wt%) and maintain the high transparency in visible spectrum. The outstanding UV-blocking properties of PVA films incorporated with baicalin extract were also confirmed by Rhodamine B degradation. Baicalin conferred antioxidant properties to PVA films as determined by DPPH radical scavenging activity. Due to the interaction between hydroxy groups of baicalin and PVA molecule, water vapor permeability, swelling and elongation at break of the films were decreased accompanied with the increasing in tensile strength and Young’s modulus. FTIR reveal that the interaction between PVA molecules was significant changed by the introduction of baicalin. These results suggest that PVA film incorporated with baicalin extract can be used for the development of functional protective film.

Durable functionalization of polyethylene terephthalate fabrics using metal oxides nanoparticles

The share of polyester (polyethylene terephthalate, PET) in textiles has been continuously increasing over the last several years due to its high mechanical durability and low cost and has reached 80%. However, polyester suffers from many problems and most of them arise from its poor hydrophilicity and inability to get functionalized as it lacks sufficient functional groups on its surface. In this study, a facile method is reported to impart durable functionalization of PET substrate, wherein different metal oxide NPs were mixed with a nonreactive hydrophilic resin and applied on the fabric using a simple pad-dry-cure method. The treated PET fabrics were characterized for changes in the surface morphology and chemical composition both in as-applied state and after several cycles of laundry washes. The treatment effectively and durably enhanced the hydroxyl group concentration on the surface of PET fabric even with the application at a very low concentration of ∼ 1 wt%, which is very critical for its industrial viability. This finishing methodology opens up the possibility of imparting durable functionalities such as photocatalytic, UV absorption, antistatic, and/or moisture management properties to otherwise inert hydrophobic PET fabric.

Surface Properties of 1DTiO2 Microrods Modified with Copper (Cu) and Nanocavities.

This work deals with Cu-modified 1DTiO2 microrods (MRs) and their surface properties. The pristine lyophilized precursor Cu_1DTiO2, prepared by an environmentally friendly cryo-lyophilization method, was further annealed in the temperature interval from 500 to 950 °C. The microstructure of all samples was characterized by electron microscopy (SEM/EDS and HRTEM/SAED), X-ray powder diffraction (XRD), infrared spectroscopy, simultaneous DTA/TGA thermoanalytical measurement, and mass spectroscopy (MS). Special attention was paid to the surface structure and porosity. The 1D morphology of all annealed samples was preserved, but their surface roughness varied due to anatase-rutile phase transformation and the change of the nanocrystals habits due to nanocavities formation after releasing of confined ice-water. The introduction of 2 wt.% Cu as electronically active second species significantly reduced the direct bandgap of 1DTiO2 in comparison with undoped TiO2 and the standard Degussa TiO2_P25. All samples were tested for their UV absorption properties and H2 generation by PEC water splitting. We presented a detailed study on the surface characteristics of Cu doped 1DTiO2 MRs due to gain a better idea of their photocatalytic activity.

Biobased “rigid-to-stretchable” conversion for strong and tough poly(lactic acid) with UV-protective property

• Hetero-profiled morphology of lignin-based complex for “rigid-to-stretchable” conversion for the first time. • Specialized assembly of particles for the recalcitrant issues of interfacial compatibility and filler dispersion. • Rigidity-sourced complex as toughening plasticizer and interfacial modifier for improved toughness, stiffness, strength and excellent anti-ultraviolet properties. The major obstacles to expand the applications of biodegradable poly(lactic acid) (PLA) are the poor toughness and the lack of UV protection in many fields, such as food and goods packaging. In this work, a bio-based “rigid-to-stretchable” conversion approach was presented for the first time to construct the plasticized lignin-based complex through mechanochemistry for the simultaneous improvement of toughness and strength on PLA matrix. With the aid of polymer-based surfactants as an interfacial modifier, the rigid lignin particles were significantly softened through a facile and green ball-milling process to form the plasticized complex with hetero-profiles. Apart from the conventional approach to the rubber-like toughener, the morphology-structured lignin-based complex was controllably regulated as the rigidity-sourced plasticizer to address the recalcitrant issues of interfacial compatibility and dispersion. With the strong and tough PLA-based composite films (PLA/Lg@TWN) successfully prepared, the tensile strength and the ultimate elongation simultaneously increases to 58.2 MPa and 32.5 % compared to those of the neat PLA of 15.8 MPa and 15.7 % respectively. The toughness was also enhanced from 7.21 MJ/m 3 for pure PLA to 15.57 MJ/m 3 for PLA/Lg@TWN. The specialized assembly of bio-derived aromatic structures was conducive to exploring ultraviolet resistance, exhibiting superb UV absorption property in UV A (100 %) and UV B (99.5 %) range compared to low UV absorption of UV A (57 %) and UV B (75 %) for neat PLA. Therefore, the developed multifunctional PLA films would present the promising potential for applications in the fields of packaging and agricultural materials with favorable mechanical properties and UV protection performance.

Investigation of the Antioxidant and UV Absorption Properties of 2-(2’-hydroxy-5’-methylphenyl)-benzotriazole and Its Ortho-Substituted Derivatives via DFT/TD-DFT

The demand and pursuit of chemical entities with UV filtration and antioxidant properties for enhanced photoprotection have been driven in recent times by acute exposure of humans to solar ultraviolet radiations. The structural, electronic, antioxidant and UV absorption properties of drometrizole (PBT) and designed ortho-substituted derivatives are reported via DFT and TD-DFT in the gas and aqueous phases. DFT and TD-DFT computations were performed at the M062x-D3Zero/6-311++G(d,p)//B97-3c and PBE0-D3(BJ)/def2-TZVP levels of theory respectively. Reaction enthalpies related to hydrogen atom transfer (HAT), single-electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) mechanisms were computed and compared with those of phenol. Results show that the presence of -NH2 substituent reduces the O-H bond dissociation enthalpy and ionization potential, while that of -CN increases the proton affinity. The HAT and SPLET mechanisms are the most plausible in the gas and aqueous phases respectively. The molecule with the -NH2 substituent (PBT1) was identified to be the compound with the highest antioxidant activity. The UV spectra of the studied compounds are characterized by two bands in the 280 - 400 nm regions. Results from this study provide a better comprehension antioxidant mechanism of drometrizole and present a new perspective for the design of electron-donor antioxidant molecules with enhanced antioxidant-photoprotective efficiencies for applications in commercial sunscreens.

Residual lignin in cellulose nanofibrils enhances the interfacial stabilization of Pickering emulsions

Lignocellulose nanofibrils (LCNF) were used to prepare oil-in-water Pickering emulsions and to assess the role residual lignin in interfacial stabilization. Two LCNF fractions of similar morphology (length ∼700 nm and width ∼8 nm) and structure (polymorphism and crystallinity) were obtained by microfluidization of fibers obtained by hydrothermal treatment of wood with a recyclable organic acid. The LCNF with higher residual lignin was less hydrophilic and, correspondingly, performed better as Pickering stabilizer, producing emulsions of smaller droplet size and higher resistance to creaming. Long-term emulsion stabilization (over 40 days) was achieved with LCNF at concentrations as low as 0.24 (w/v)% based on emulsion volume. We conclude that LCNF-stabilized Pickering emulsions can be finely tuned by varying the residual lignin content, providing a rationale for LCNF selection according to lignin type and concentration as variables affecting stabilization. Complementary considerations include the possible benefits of the residual lignin in LCNF, including antioxidant and UV absorption properties.

Photopolymerization-Based Synthesis of Uniform Magnetic Hydrogels and Colorimetric Glucose Detection.

Magnetic hydrogels have been commonly used in biomedical applications. As magnetite nanoparticles (MNPs) exhibit peroxidase enzyme-like activity, magnetic hydrogels have been actively used as signal transducers for biomedical assays. Droplet microfluidics, which uses photoinitiated polymerization, is a preferred method for the synthesis of magnetic hydrogels. However, light absorption by MNPs makes it difficult to obtain fully polymerized and homogeneous magnetic hydrogels through photoinitiated polymerization. Several methods have been reported to address this issue, but few studies have focused on investigating the light absorption properties of photoinitiators. In this study, we developed a simple method for the synthesis of poly(ethylene glycol) (PEG)-based uniform magnetic hydrogels that exploits the high ultraviolet absorption of a photoinitiator. Additionally, we investigated this effect on shape deformation and structural uniformity of the synthesized magnetic hydrogels. Two different photoinitiators, Darocur 1173 and lithium phenyl (2,4,6–trimethylbenzoyl) phosphinate (LAP), with significantly different UV absorption properties were evaluated based on the synthesis of magnetic hydrogels. The magnetic characteristics of the PEG-stabilized MNPs in hydrogels were investigated with a vibrating sample magnetometer. Finally, the colorimetric detection of hydrogen peroxide and glucose was conducted based on the enzyme-like property of MNPs and repeated several times to observe the catalytic activity of the magnetic hydrogels.

Base-Mediated Denitrogenative Sulfonylation/Benzannulation of Conjugated N-Sulfonylhydrazones with 3-Formylchromones for the Construction of Polyfunctionalized Biaryl Sulfones.

Base-promoted benzannulation of conjugated N-sulfonylhydrazones and 3-formylchromones for the synthesis of diverse biaryl sulfones is described. The approach facilitates new C-C and C-S bond formation via the cascade diazo formation/Michael addition/ring opening/denitrogenative sulfonylation/intramolecular cycloaddition/dehydration and introduces diverse functional groups onto biaryl sulfones. The synthesized compounds are converted to aryl sulfones bearing bioactive benzisoxazole and benzofuran frameworks. Moreover, the synthesized biaryl sulfones possess potent turn-on fluorescence sensing and UV absorbance properties.

Reducing cytotoxicity of poly (lactic acid)-based/zinc oxide nanocomposites while boosting their antibacterial activities by thymol for biomedical applications

In the present study, ternary blends based on poly (lactic acid)/poly (ε-caprolactone)/thermoplastic starch were prepared at different concentrations of synthesized zinc oxide nanoparticles (ZnO-NPs) and thymol. The sizes of ZnO-NPs with an average diameter of about 30–50 nm were detected by FE-SEM analysis. Moreover, the effect of ZnO-NPs and thymol on morphological, FT-IR spectrum, UV absorption, thermal stability, cytotoxicity, and antibacterial properties of neat blend was investigated. TGA analysis showed that the addition of ZnO-NPs and/or thymol diminished thermal stability of the system. Incorporating ZnO-NPs improved antibacterial activities of the neat blend, but MTT-assay and AO fluorescent staining test results depicted a decrease in cell viability to less than 20% by the addition of 5 wt% ZnO-NPs. In such a condition, the addition of thymol to the nanocomposites exhibited a dose-dependent increase in cell survival mostly due to thymol antioxidant properties. Interestingly, the antibacterial performance of compounds was also improved by the presence of thymol. Therefore, the obtained nanocomposites have potential to extend applications of innovative biomedical devices for future research in which both high cell viability and superior antibacterial properties are needed such as an antibacterial wound healing film.

Combination of atom transfer radical polymerization and click chemistry toward cellulose-rosin derived UV-absorbent copolymers

UV absorption coating is an important function material, which can protect the substrates from photoaging. In this work, a class of sustainable UV-absorbent copolymers derived from ethyl cellulose (EC), fatty acid and rosin were prepared by a combination of atom transfer radical polymerization (ATRP) and click chemistry. To fulfill this strategy, the pendant azides were first attached onto the backbone of EC. Then, ATRP was applied to fabricate well-defined poly(lauryl methacrylate) (PLMA) bearing terminal alkynes. Finally, click chemistry between the pendant azides in EC and the alkynes in PLMA as well as in rosin esters (DAPE), was performed to achieve the cellulose-rosin graft copolymers (EC-(g-DAPE)-g-PLMA) with UV absorption property. The chemical structure of cellulose-rosin graft copolymers was confirmed by FTIR, 1H NMR and GPC. Thermodynamic performance analysis indicated that these EC-rosin graft copolymers showed better thermal stability than EC. Due to the synergistic hydrophobic interaction of rosin and the hydrophobic lauryl groups in PLMA, these graft copolymers showed excellent hydrophobic property, and the static contact angles were all above 90°. In addition, all the EC-rosin graft copolymers showed outstanding and stable UV absorption capability, and maintained excellent UV absorption capability after continuous UV-irradiation for 1 h or being heated to 100 °C for 0.5 h, which had potential application in UV absorption materials.