Sulfur quantum dots as sustainable materials for biomedical applications: Current trends and future perspectives

Discovered over a decade ago, sulfur quantum dots (SQDs) have rapidly emerged as a sustainable, safe, and inexpensive quantum material. Sustainably synthesizing SQDs using sublimed sulfur powders, typically produced as waste in industrial petrochemical refining processes, has attracted researchers to use these functional quantum materials in various research fields. SQDs quickly found applications in various research fields, such as electronics, environmental sensing, food packaging, and biomedical engineering. Although low production yields, time-consuming and energy-intensive synthetic methods, and low photoluminescence quantum yield (PLQY) have been some problems, researchers have found ways to improve synthetic methods, develop passivating agents, and systematically modify reaction schemes and energy sources to achieve large-scale synthesis of stable SQDs with high PLQY. Nonetheless, SQDs have succeeded tremendously in biomedical and related applications due to their low toxicity, antibacterial and antioxidant properties, biocompatibility, appropriate cellular uptake, and photoluminescent properties. Although the bioimaging applications of SQDs have been extensively studied, their other reported properties indicate their suitability for use as antimicrobial agents, free radical scavengers, and drug carriers in other biomedical applications, such as tissue regeneration, wound healing, and targeted drug delivery.

Antibacterial and Anti-Glucosyltransferase Activity of Verbascum speciosum Against Cariogenic Streptococci

Objectives

Dental caries is a prevalent chronic human infection worldwide and several plants have shown anticariogenic properties through antibacterial activity against oral pathogens. The present study aimed to assess anticariogenic activity of Verbascum speciosum, in search of novel agents for the prevention and treatment of dental caries.

Methods

Hydro-alcoholic extracts from flowers and total aerial parts of the plant were prepared by maceration. Antibacterial activity of the extracts against Streptococcus mutans (ATCC 35668) and Streptococcus sobrinus (ATCC 27607) was investigated by agar diffusion and microdilution techniques. Inhibitory concentration-fifty values of the flowers' extract against Streptococcus mutans glucosyltransferase enzymes were determined. The total flavonoid content of the extracts was determined using an aluminum chloride reaction.

Results

Verbascum speciosum flowers' extract showed significantly higher flavonoid content and antibacterial activity; with minimum inhibitory concentrations of 100 and 200 µg/mL for Streptococcus mutans and Streptococcus sobrinus, respectively. The extract inhibited the synthesis of glucan by cell-associated and extracellular glucosyltransferase enzymes in a dose-dependent manner with higher activity against the extracellular enzyme.

Conclusion

This study indicated effective anticariogenic activity of Verbascum speciosum flowers extract. This extract can be considered as an alternative to current anticaries therapies or an additive to dental care products.

In vitro Antibacterial Activity and Wound Healing Effects of Achillea millefolium Essential Oil in Rat

Objectives

In this study we aimed to evaluate the in vitro antibacterial activity and wound healing properties of Achillea millefolium essential oil (AMEO) in full-thickness wound model in rat. The antibacterial activity of AMEO was evaluated against Staphylococcus aureus and Pseudomonas aeruginosa using the broth dilution method.

Methods

The 2 cm × 2 cm full-thickness excisional wounds were created on the back of animals. Topical therapy was applied twice a day using 1%, 2%, and 3% w/w AMEO ointments, and the measurement of the wounds area was carried out every 3 days, after that the wound closure percentage was calculated in these days. Hydroxyproline content and histopathological evaluation of wound tissue samples were carried out on day 7 and 14 post wounding. Eucerin was used for the treatment of vehicle control group and negative control group received no treatment.

Results

Our results revealed the bacteriostatic activity of AMEO against S. aureus and P. aeruginosa. Wound healing activity evaluation of AMEO showed the significant increase (p < 0.05) in the wound closure percentages in rats treated with AMEO 1% and 2% comparing to those of non-treatment group. In addition, hydroxyproline contents of tissue significantly (p < 0.01) increased in AMEO 1% and 2% comparing to non-treatment group. Histopathological evaluations of wound tissue samples on day 7 and 14 demonstrated higher accumulation of collagen fibers, reduction of edema and inflammation and also formation of tissue appendages in 1% and 2% AMEO treated groups in comparison with non-treatment group.

Conclusion

The results of this study indicated that AMEO has the potential to be used as a safe and effective wound healing agent.

Combined Antimicrobial Activity of Extracts from Quercus infectoria Galls and Scrophularia striata Aerial Parts for an Anticariogenic Herbal Mouthwash

Objectives

Dental caries is one of the most prevalent human diseases worldwide. The disease initiates with bacterial adherence to the tooth surface followed by the formation of dental plaques. Mutans streptococci and Candida albicans are principal oral microorganisms involved in the initiation and development of dental caries. Phytochemicals have been shown to possess promising antimicrobial properties against a wide range of microorganisms and can be used for the prevention and treatment of dental caries. Herein, we reviewed literature on plants that are traditionally used for their antimicrobial properties or possess promising anticariogenic activity. We selected aerial parts of Scrophularia striata (S. striata) and galls of Quercus infectoria (Q. infectoria) and investigated their antimicrobial activity against cariogenic microorganisms.

Methods

Water soluble fractions were obtained from hydroalcoholic extracts of S. striata and Q. infectoria and their antimicrobial activity against Streptococcus mutans (S. mutans), Streptococcus sobrinus (S. sobrinus), and Candida albicans (C. albicans) was evaluated separately and in combination. The extracts were then used for preparing an herbal mouthwash whose stability and tannic acid content were evaluated over 60 days.

Results

Q. infectoria gall extract possesses efficient antimicrobial activity that was synergistically enhanced in the presence of S. striata extract. Mouthwash prepared using these extracts showed desirable organoleptic characteristics, antimicrobial activity, and stability.

Conclusion

Extracts of S. striata and Q. infectoria galls can be used together for preparing dental products with effective anticariogenic properties. Our study highlights the importance of extensive pharmacological investigations when using herbal products alone or in combination with other chemical substances.

Preparation of polyvinyl alcohol hydrogel containing chlorogenic acid microspheres and its evaluation for use in skin wound healing

Chlorogenic acid (CGA) is a phenolic compound widely found in plants. Several studies have shown that CGA possesses antioxidant, antibacterial, anti-inflammatory and wound healing properties. Because of their three-dimensional structure, good permeability, excellent biocompatibility and moisturizing properties, hydrogels are ideal candidates for wound dressing. The aim of the present study was to preparation and characterization of Polyvinyl alcohol (PVA) hydrogel containing CGA microspheres and evaluation its wound healing activity. The double-emulsion solvent evaporation technique was applied for preparing the CGA containing microspheres. The microspheres were characterized using scanning electron microscopy (SEM) and Fourier transformation infrared spectroscopy (FTIR) and subsequently incorporated in the structure of a PVA hydrogel. The effects of prepared hydrogel on NIH3T3 cell line viability were evaluated using MTT method and wound healing activity was investigated in full thickness wound model in rabbit. SEM images showed formation of homogenous CGA microspheres with diameters in the range of 1-2 μm, embedded in the porous structure of the hydrogel. Infra-red results indicated successful incorporation of CGA microspheres into PVA hydrogel. The NIH3T3 cell viability percentage in CGA 2.5% hydrogel treated group significantly (p < .05) increased after 24 h and 48 h comparing to control group. In vivo studies showed that CGA hydrogel significantly (p < .001) stimulated the rate of wounds closures. Histological studies revealed that administration of CGA hydrogel significantly increased epithelialization and production of collagen fibers compared to the control group. It can be concluded that the CGA microsphere loaded PVA hydrogel has the potential for wound healing.

Rapid determination of metanil yellow in turmeric using a molecularly imprinted polymer dispersive solid-phase extraction and visible light spectrophotometry

The present study aimed to develop a sensitive and available method for determining metanil yellow (MY) as an adulterating agent in food samples. Solid-phase extraction was chosen for pre-concentrating metanil yellow prior to its determination using a validated UV-spectrophotometric method. The precipitation polymerization method was applied to synthesize a range of molecularly imprinted polymers (MIPs) for selective extraction of MY. Polymers were characterized by SEM and FTIR and investigated for MY extraction through batch rebinding experiments. The extraction process was optimized in the term of pH, time, capacity, and the desorbing solvent. Results of this study showed the critical role of template/functional monomer ratio in the preparation of the MIPs. The developed MIP solid-phase extraction/UV-spectrophotometric method was employed for determining MY in spiked samples and showed 88.10-92.76% recovery for turmeric samples containing 0.1-10 mg/kg MY. The developed method was shown selective for MY in the presence of another azo dye.

Enhanced photocatalytic degradation of doxycycline using a magnetic polymer-ZnO composite

A novel magnetic polymer-ZnO composite was prepared by incorporating Fe₃O₄ and ZnO nano-particles in the structure of an adsorbent polymer. Precipitation polymerization was used for synthesizing the adsorbent polymer and its efficiency for extracting doxycycline from aqueous solution was optimized according to several parameters including time, pH and amount of polymer. Results showed the highest extraction efficiency at neutral pH of the doxycycline solution in 20 min, and the capacity of the polymer was about 20 mg/g. The magnetic property of a material is important for fast and facile separation of composite particles after each use. Magnetic polymer-ZnO composite was synthesized by adding Fe₃O₄ and ZnO nano-particles to the polymerization mixture in order to take advantage of both sorption and photocatalytic degradation mechanisms. The obtained composite was characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy equipped with wavelength dispersive X-ray spectroscopy and used for enhanced photocatalytic degradation of doxycycline in aqueous solution. Results showed 76.5% degradation of doxycycline in 6 hours which was significantly higher than the degradation observed by an equivalent amount of ZnO nano-particles. Photocatalytic degradation of doxycycline fitted the pseudo first order kinetic model with a rate constant of 4 × 10^-3 μg mL^-1 min^-1.

Photocatalytic removal of doxycycline from aqueous solution using ZnO nano-particles: a comparison between UV-C and visible light

Zinc oxide nano-particles were synthesized, characterized and used for photocatalytic degradation of doxycycline using UV-C and visible light. Effects of several operational factors including initial pH of antibiotic solution, initial antibiotic concentration and ZnO nano-particles loading amount were investigated. Comparing photocatalytic degradation and mineralization of doxycycline under UV-C and visible light showed successful application of the method under both light sources. However, reaction rate was higher under UV-C irradiation, which degraded doxycycline almost completely in 5 hours, and 68% mineralization was achieved. Synthesized ZnO nano-particles were successfully applied for photocatalytic degradation of doxycycline in a pharmaceutical wastewater sample. The process was fitted to the pseudo first order kinetic model with rate constants in the range of 6-22(×10^-3) mg L^-1 min^-1 with respect to initial concentration of doxycycline under UV-C irradiation. The Langmuir-Hinshelwood model was also employed for describing the photocatalytic reaction with surface reaction kinetic constant k_c and equilibrium adsorption constant K_LH values calculated as 0.12 mg L^-1 min^-1 and 2.2 L mg^-1, respectively. Degradation of doxycycline was followed by UV-visible spectroscopy and a validated stability indicating high-performance liquid chromatography method that was developed using stressed samples of doxycycline and could selectively determine doxycycline in the presence of its degradation products. Mass spectrometry was used for determining final degradation products.

Cytotoxicity of Vinca minor

Vinca minor L. (Apocynaceae) is a medicinal plant that has long been used to treat cerebral and memory disorders in European folk medicine. Furthermore, it contains more than 50 alkaloids, some of them having bisindole structure such as the antineoplastic alkaloids present in Catharanthus roseus (L.) G. Don (Apocynaceae). In this study, the plant's alkaloid extract was divided into three fractions and the cytotoxic effects on cell proliferation of HT-29, Caco-2, T47D, and NIH/3T3 cell lines were examined. All alkaloid fractions showed a dose-dependent cytotoxic effect on the cell lines. IC(50) values confirmed that the growth and proliferation of NIH/3T3 cells were less affected in comparison to other cell lines.