Doxorubicin (DOX) is widely used in chemotherapy as an anti-tumor drug. However, DOX is highly cardio-, neuro- and cytotoxic. For this reason, the continuous monitoring of DOX concentrations in biofluids and tissues is important. Most methods for the determination of DOX concentrations are complex and costly, and are designed to determine pure DOX. The purpose of this work is to demonstrate the capabilities of analytical nanosensors based on the quenching of the fluorescence of alloyed CdZnSeS/ZnS quantum dots (QDs) for operative DOX detection. To maximize the nanosensor quenching efficiency, the spectral features of QDs and DOX were carefully studied, and the complex nature of QD fluorescence quenching in the presence of DOX was shown. Using optimized conditions, turn-off fluorescence nanosensors for direct DOX determination in undiluted human plasma were developed. A DOX concentration of 0.5 µM in plasma was reflected in a decrease in the fluorescence intensity of QDs, stabilized with thioglycolic and 3-mercaptopropionic acids, for 5.8 and 4.4 %, respectively. The calculated Limit of Detection values were 0.08 and 0.03 μg/mL using QDs, stabilized with thioglycolic and 3-mercaptopropionic acids, respectively.

The manuscript describes an optical sensing microplate for the high-throughput screening of imidazolinone herbicides in soil extracts. As far as we know, imprinted proteins (IPs) specific to imidazolinone herbicides have not been synthesized and used as a recognition element for their solid-phase extraction before. Imprinted bovine serum albumin (BSA) and glucose oxidase (GOx) were synthesized in the presence of imazamox as a template and then these IPs were immobilized at the bottom of microplate wells. The sorption capacity (Q) of aminated silica nanoparticles modified by IPs (IP–BIS) was 6.38 mg g⁻¹ while the imprinting factor ($IF$) equaled 2.6. The concentration of imazamox was determined by a “turn-off” solid-phase assay using alloyed CdZnSeS/ZnS quantum dots (QDs) as a component of fluorescent substrate. Alloyed CdZnSeS/ZnS QDs were stabilized in an aqueous phase by positively charged cysteamine that, as far we know, had not been used as this type of ligand before. Our method allows for determining the concentration of imazamox in the range of 0.5–9.2 μg mL⁻¹, with a limit of quantification limit of quantitation (LOQ) equal to 0.45 μg mL⁻¹ The sensing microplate enables parallel detection of up to 96 samples containing herbicides using standard fluorescence microplate readers or smartphones. The paper describes how such sensing microplates can be used for the analysis of artificially contaminated soil samples. The proposed approach combines pre-concentration of analyte at the IPs with its subsequent determination on a single analytical platform, thus allowing for both highly sensitive determination in laboratory conditions and mass screening in the field.

A procedure for determining doxorubicin in the presence of bortezomib in model aqueous solutions and blood plasma is developed based on the fluorescence quenching of CdZnSeS/ZnS and AgInS/ZnS quantum dots. Since doxorubicin is often used in combination chemotherapy with bortezomib, monitoring its plasma concentration is important for increasing the effectiveness of chemotherapy and reducing the risk of side effects. The sensitivity of doxorubicin determination in the presence of bortezomib (0.3 μM) is compared using quantum dots with different surface ligands. A trend toward decreased fluorescence quenching efficiency of quantum dots by doxorubicin in the presence of bortezomib is demonstrated. The use of alloyed CdZnSeS/ZnS quantum dots stabilized with 3-mercaptropropionic acid for the determination of doxorubicin in the presence of bortezomib in plasma is demonstrated, with a detection limit of 0.08 μM and a quantification limit of 0.24 μM.

Quantum dots (QDs) are modern nanoparticles with a wide potential for use in medicine, bioanalysis, as well as in optics and energetics. Different types of QDs can be produced depending on their synthesis method. QDs formed by semiconductor components able to mutual solid-solution formation named alloyed. This type of QDs has a high quantum yield and narrow emission peak but less chemical stability relative to core-shell type QDs. Better core-shell QDs stability explains by the additional surface shell covering. This approach can be applied to the alloyed QDs also. One-step hightemperature organometallic procedure is excellent in this regard due to its simplicity and consistency in the synthesis. However, QDs which obtained in this way are hydrophobic and do not dissolve in polar solutions such as water. Hydrophilization is used to convert QDs from a hydrophobic to a hydrophilic state. It was found that when hydrophilizing with β-mercaptoethanol, the quantum yield (QY) significantly increases, although when hydrophilizing with other ligands, it is just a decrease in the quantum yield that appears. This article investigates the process of hydrophilization of core-shell alloyed QDs in which an increase in QY is observed. For this, the effect on the optical properties of the amount of the hydrophilizing agent, long-term storage at room and low temperatures, and the effect of pH on hydrophilized QDs are considered.

Photoluminescent alloyed quantum dots are a promising material for biosensor development due to the high sensitivity of their optical properties to media conditions. Described sensing approaches based on quantum dots photoluminescence quenching. Discussed advantages and perspectives of alloyed quantum dots application.