The World Health Organization (WHO) model “List of Essential Medicines” includes among indispensable medicines antibacterials and pain and migraine relievers. Monitoring their concentration in the environment, while challenging, is important in the context of antibiotic resistance as well as their production of highly toxic compounds via hydrolysis. Traditional detection methods such as high-performance liquid chromatography (HPLC) or LC combined with tandem mass spectrometry or UV–vis spectroscopy are time-consuming, have a high cost, require skilled operators and are difficult to adapt for field operations. In contrast, (electrochemical) sensors have elicited interest because of their rapid response, high selectivity, and sensitivity as well as potential for on-site detection. Previously, we reported a novel sensor system based on a type II photosensitizer, which combines the advantages of enzymatic sensors (high sensitivity) and photoelectrochemical sensors (easy baseline subtraction). Under red-light illumination, the photosensitizer produces singlet oxygen which oxidizes phenolic compounds present in the sample. The subsequent reduction of the oxidized phenolic compounds at the electrode surface gives rise to a quantifiable photocurrent and leads to the generation of a redox cycle. Herein we report the optimization in terms of pH and applied potential of the photoelectrochemical detection of the hydrolysis product of paracetamol, i.e., 4-aminophenol (4-AP), and two antibacterials, namely, cefadroxil (CFD, β-lactam antibiotic) and doxycycline (DXC, tetracycline antibiotic). The optimized conditions resulted in a detection limit of 0.2 μmol L–1 for DXC, but in a 10 times higher sensitivity, 20 nmol L–1, for CFD. An even higher sensitivity, 7 nmol L–1, was noted for 4-AP.

The design of self oxidation-resistant catalytic materials based on organic molecules, although advantageous due to the ability to control their structures, is limited by the presence of labile C–H bonds. This mini review summarizes recent work aimed at first-row transition metal complexes of a new class of coordinating ligands, fluoroalkyl-substituted fluorophthalocyanines, R[Formula: see text]Pcs, ligands in which all, or the majority of their C–H bonds are replaced by a combination of fluoro- and perfluoroalkyl groups yielding porphyrin-bioinspired catalyst models. In the case of homogeneous systems, cobalt(II) complexes catalyze the aerobic oxidation of thiols to disulfides, a reaction of both biological significance and industrial importance. Zinc(II) complexes photo-generate excited state singlet oxygen, [Formula: see text]O[Formula: see text], resulting in both the incorporation of O[Formula: see text] in C–H bonds or, depending on the reaction parameters, oxidation of dyes, model pollutants. Catalyst heterogenization using oxidic and other supports yields stable, active hybrid materials. Functionalized R[Formula: see text]Pcs with acidic (–COOH) or basic (–NH[Formula: see text]R[Formula: see text], [Formula: see text] 2) groups exhibit scaffolds that afford both conjugation with biological vectors for theranostic applications as well as solid-supported materials with superior stability. Electrodes modified with hybrid R[Formula: see text]Pc-containing supports have also been used in photo-oxidations, replacing enzymes and H[Formula: see text]O[Formula: see text] associated reagents with a combination of light and air. An analytical device employed for the nano-level detection of environmentally deleterious antibiotics has been constructed.

Detection of antigenic biomarkers present in trace amounts is of crucial importance for medical diagnosis. A parasitic disease, human toxocariasis, lacks an adequate diagnostic method despite its worldwide occurrence. The currently used serology tests may stay positive even years after a possibly unnoticed infection, whereas the direct detection of a re-infection or a still active infection remains a diagnostic challenge due to the low concentration of circulating parasitic antigens. We report a time-efficient sandwich immunosensor using small recombinant single-domain antibodies (nanobodies) derived from camelid heavy-chain antibodies specific to Toxocara canis antigens. An enhanced sensitivity to pg/mL levels is achieved by using a redox cycle consisting of a photocatalytic oxidation and electrochemical reduction steps. The photocatalytic oxidation is achieved by a photosensitizer generating singlet oxygen ( 1 O 2 ) that, in turn, readily reacts with p-nitrophenol enzymatically produced under alkaline conditions. The photooxidation produces benzoquinone that is electrochemically reduced to hydroquinone, generating an amperometric response. The light-driven process could be easily separated from the background, thus making amperometric detection more reliable. The proposed method for detection of the toxocariasis antigen marker shows superior performances compared to other detection schemes with the same nanobodies and outperforms by at least two orders of magnitude the assays based on regular antibodies, thus suggesting new opportunities for electrochemical immunoassays of challenging low levels of antigens.

The functionalized, asymmetric fluoro-fluoroalkyl scaffold FHCOOHPcZn (3) was used to prepare FHCOOPcZn-6-amino-hexanoate-CTVALPGGYVRVC (5), a Pep42 peptide bioconjugate envisioned for photodynamic therapy, which can specifically target the GRP78 chaperone protein overexpressed and exclusively localized on some cancer cell surfaces. The analogous FHCOOHPcCu (4) has also been prepared, and its single-crystal X-ray structure was elucidated. Despite reduced steric hindrance relative to the nonfunctionalized, single-site complexes of the FPc scaffold, no aggregation was detected in solution via UV-vis spectroscopy, for either 3, 4, or 5, consistent with the lack of π stacking observed for the crystalline 4. The 6-aminohexanoic acid-Pep42 moiety diminishes the fluorescence efficiency of 5, relative to 3, but for singlet oxygen (O) generation, photochemical hydroperoxidation of β-(-)-citronellol using 5 and 3 occurs with comparable substrate turnover efficiency, albeit at a slower initial triplet oxygen uptake for 5. The bioconjugate 5 is durable; it does not decompose under O photoreaction conditions. These results suggest a synthetic coupling pathway for obtaining diverse biotargeting polypeptide-fluorinated phthalocyanine bioconjugates of potential utility as both fluorescence reporters and photocatalysts and highlight the importance of fluorinated scaffolds for generating chemically resilient, catalytic, theranostic materials.

We report the synthesis, redox and photo-physical properties, as well as singlet oxygen reactivity of the first representatives of Group III perfluoroalkyl perfluoro metal phthalocyanines, gallium and indium complexes. Microwave-assisted synthesis was used to produce F[Formula: see text]PcM, M [Formula: see text] Ga, In in reasonable yields. Both Ga and In complexes exhibit high thermal and chemical stability properties, attributed to the perfluoroalkyl perfluoro phthalocyanine ligand. Electrochemical and spectroelectrochemical measurements show reversible redox processes for both compounds, including spontaneous re-oxidations following electrochemical or photochemical reductions. No electrochemical or chemical oxidations of the neutral complexes are observed. Photo-hydroperoxidation of ([Formula: see text]-(-)-citronellol occurs with rates of 13.5 and 1.7 [Formula: see text]mol O2 min[Formula: see text] mol[Formula: see text] Pc and substrate turnovers of 225 and 28.2 mmol ([Formula: see text]-Cit s[Formula: see text] mol[Formula: see text] Pc for the In and Ga complexes, respectively. The solid state materials are stable and can be sublimed at temperatures higher than 380°C. Related complexes are candidates for similar chemistry and photophysics based on the observation that the fluorinated ligand determines most of the favorable properties.