Enhanced Phototherapy Activity by Employing a Nanosilica-Coumarin–Acifluorfen Conjugate as the Supplementary Light Source Generator

Abstract

Photosensitizers need to be activated by external light to achieve phototherapy. However, unsatisfactory tissue penetration of light and uncontrollable light intensity limit their application. To overcome the limitations, a novel fluorescent conjugate was developed by conjugating coumarin-functionalized nanosilica with acifluorfen to emit fluorescence as the supplementary light to activate protoporphyrin IX (PpIX, a photosensitizer in plant cell that can be induced by acifluorfen) for enhancing phototherapy activity. The results showed that the obtained conjugate could obviously increase the singlet oxygen yield of PpIX and exhibited remarkable photodynamic herbicidal activity against Amaranthus retroflexus. Under low light intensity, its photodynamic herbicidal activity was five to six times higher than that of acifluorfen sodium salt. The conjugate could move upward and downward freely in vascular system of Brassica juncea seedlings and significantly reduced the cytotoxicity of acifluorfen. Moreover, the conjugate was proved to be safe to soybean at concentrations of 200–800 mg/L of acifluorfen. This study gives a novel drug delivery system with the potential of reducing light-dependent drug dosage and harm to nontarget organisms and offers a way to use fluorescent emission as the supplementary light to enhance the phototherapy activity of photosensitizers.

Stable Fluorescent Nanoparticles Based on Co-assembly of Acifluorfen and Poly(salicylic acid) for Enhancing Herbicidal Activity and Reducing Environmental Risks

“…The characteristic absorption peaks of AP NPs contained the features of both ACI and PSA, which demonstrated that AP NPs consisted of ACI and PSA. The results were similar to previous works reported in literature studies. , …”

“…The results were similar to previous works reported in literature studies. 29,31 Thermal Stability. By analyzing the thermogravimetric curves, it is possible to know some information about thermal stability, the composition of the sample, thermal decomposition, and the products generated in relation to the mass.…”

“…Acifluorfen (ACI), a selective post-emergence diphenyl ether herbicide, has been widely used for broadleaf weed control in soybean and peanut fields. Its mechanism of action is inhibition of protoporphyrin oxidase and induction of the accumulation of the photosensitizer protoporphyrin IX (PpIX) in plant cells. − Under the irradiation of light, PpIX is stimulated to generate numerous ROS, which can degrade the cell membrane, proteins, and nucleic acids of weed cells and ultimately kill weeds. , As a result, the herbicidal activity of ACI is closely related to light intensity, and low light can hardly kill weeds. Studies have shown that the wavelengths of light required for the weed control of ACI are between 415 and 615 nm, and the effect of light less than 410 nm on the herbicidal activity of ACI is weak. , ACI has strong leachability (leaching potential index = 3.15) because the water solubilities of ACI acid and sodium salt are 120 and 250,000 mg/L, respectively. , Furthermore, this herbicide is relatively stable in water and not easy to be degraded, which increases the risk of water contamination. − Therefore, it is necessary to construct a novel formulation for ACI to enhance the utilization efficiency of sunlight and reduce the negative impact on the ecological environment.…”

Supramolecular Self-Assembly of Herbicides with Reduced Risks to the Environment

“…The genotoxicities of 2,4-D, B-PEI 10k, and 2,4-D/B-PEI 10k NPs were evaluated by investigating their effects on the root tip cells of V. faba . As an efficient test method, the V. faba bioassay is widely applied to assess the genotoxicity caused by chemicals and nanoparticles. , First, V. faba seeds (Fengdou 6) soaked for 24 h were wrapped in a wet towel at room temperature until their roots grew up to more than 2 cm in length. Then, the root tips of V. faba were subjected to aqueous solutions of the testing samples with various concentrations for periods of 24 h. Afterward, these V. faba seeds were transferred into fresh water and cultivated for recovery for another 24 h. Subsequently, the roots of V. faba were collected and weighed to record the mass.…”

Preparation of Acifluorfen-Based Ionic Liquids with Fluorescent Properties for Enhancing Biological Activities and Reducing the Risk to the Aquatic Environment

“…As a diphenyl ether herbicide, acifluorfen (ACI) (5-[2-chloro-4-(trifluoromethyl)-phenoxy]-2-nitrobenzoic acid) has been used extensively in postemergence for selectively controlling broadleaf weeds in soybeans and peanuts. , It inhibits protoporphyrinogen oxidase (PPO) and consequently induces the accumulation of protoporphyrin and other tetrapyrrole derivatives in weed cells in the presence of light. − Photoexcitation of these porphyrin derivatives in the presence of oxygen produces reactive oxygen, lipid peroxides, and hydrogen peroxide in plant tissues, all of which are very harmful for cell membranes. , Therefore, the activity of ACI was highly affected by sunlight, and irradiating by weak light will lead to poor activity. However, the wavelengths of light required for ACI toxicity to weeds are between 410 and 615 nm, which means that ultraviolet radiation in sunlight has no impact on its herbicidal activity. − ACI is a weak acid (p K a = 3.50) and usually marketed in the form of sodium salt. , It has strong leachability (leaching potential index = 3.15) because the water solubilities of ACI acid and sodium salt are 120 mg L –1 and 250,000 mg L –1 , respectively. , This herbicide is also stable to hydrolysis and difficultly photodegraded and thus increases the possibility of ground and surface water contamination . In addition, ACI exhibits a certain extent of toxicity to aquatic organisms with LC 50 values from 17 mg L –1 to 61 mg L –1 .…”