G-quadruplex DNAzymes are short DNA aptamers with repeating G4 quartets bound in a non-covalent complex with hemin. These G4/Hemin structures exhibit versatile peroxidase-like catalytic activity with a wide range of potential applications in biosensing and biotechnology. Current efforts are aimed at gaining a better understanding of the molecular mechanism of DNAzyme catalysis as well as devising strategies for improving their catalytic efficiency. Multimerisation of discrete units of G-quadruplexes to form multivalent DNAzyes is an emerging design strategy aimed at enhancing the peroxidase activities of DNAzymes. While this approach holds promise of generating more active multivalent G-quadruplex DNAzymes, few examples have been studied and it is not clear what factors determine the enhancement of catalytic activities of multimeric DNAzymes. In this study, we report the design and characterisation of multimers of five G-quadruplex sequences (AS1411, Bcl-2, c-MYC, PS5.M and PS2.M). Our results show that multimerisation of G-quadruplexes that form parallel structure (AS1411, Bcl-2, c-MYC) leads to significant rate enhancements characteristic of cooperative and/or synergistic interactions between the monomeric units. In contrast, multimerisation of DNA sequences that form non-parallel structures (PS5.M and PS2.M) did not exhibit similar levels of synergistic increase in activities. These results show that design of multivalent G4/Hemin structures could lead to a new set of versatile and efficient DNAzymes with enhanced capacity to catalyse peroxidase-mimic reactions.

The health benefits and nutritional value of pawpaw or papaya (Carica papaya Linn.) are well established. The entire papaya plant—including the leaves, fruit, bark, root, juice, seeds and latex - is used for dietary, medicinal and other purposes. However, papaya seeds are the under-exploited part since they are typically seen as waste after the edible fruits have been processed and consumed. Hence, the aim of this review is to document the nutraceutical and therapeutic potential of Carica papaya seeds with a view of enhancing its prospect in drug development. The following title search criteria were used “Carica papaya” OR “Papaya” OR “Pawpaw OR C. papaya” AND “seed” OR “seed oil”; while “fruits OR leaves OR stem OR root OR juice OR latex” were excluded. The articles used for this research were limited to the original research articles and those written in English Language only. The seeds which are often seen as waste products offer countless possibilities for developing new nutritional supplements and medicines due to the huge vital micronutrients and a variety of secondary metabolites that have been reported to be embedded in them. Papaya seeds contain beneficial phytochemicals such as carotenoids, flavonoids, alkaloids, phytosterols and tocopherols. These substances, have intriguing nutraceutical qualities and are important in the treatment and amelioration of several medical disorders. Benzyl glucosinolates, caricin, fatty acids, crude fibre, carpaine, glucotropaeolin, benzyl isothiocyanate, crude protein, benzyl thiourea, hentriacontane, ß-sitostrol and enzymes (myrosinase and papain) were discovered as nutritional components in papaya seeds. Papaya seeds may be used medicinally as antioxidant, antidiabetic, antiulcerogenic, liver cirrhosis treatment and menstrual cycle modulation.

G-quadruplex (G4) DNAzymes with peroxidase activities hold potential for applications in biosensing. While these nanozymes are easy to assemble, they are not as efficient as natural peroxidase enzymes. Several approaches are being used to better understand the structural basis of their reaction mechanisms, with a view to designing constructs with improved catalytic activities. Spermine alters the structures and enhances the activities of some G4 DNAzymes. The reported effect of spermine in shifting the conformation of some G4 DNAzymes from antiparallel to parallel has not been tested on multimeric G4 DNAzymes. In this study, we examined the effects of spermine on the catalytic activities of multivalent constructs of Bcl2, c-MYC, PS2.M, and PS5.M. Our findings show that spermine significantly improved the peroxidase activity of PS2.M, an antiparallel G4 DNAzyme, while there was no significant effect on c-MYC, which already exists in a parallel conformation. The addition of spermine led to a substantial increase in the initial velocity of PS2.M and its multimeric form, enhancing it by approximately twofold. Therefore, spermine enhancement offers promise in expanding the range of DNAzymes available for use as biosensing tools.

Discharge of untreated industrial effluents has been associated with soil contamination. Biochemical alterations in Lumbricus terrestris and remediation capacity of Azadirachta indica tree from industrial effluent discharge locations in Challawa (A and B) and Kura village (control location C) were assessed. Levels of nitrate, phosphate, iron, chloride, and hardness at locations A and B were significantly (p < 0.05) higher than those at location C, but their sulfate concentrations were significantly (p < 0.05) weaker. pH and magnesium concentration at location A were significantly higher than those at locations B and C. Levels of Fe, Cu, Zn, Pb and Mn in soils at the discharge locations were significantly (p < 0.05) higher than those of C. Azadirachta indica tree (AIT) had a translocation factor (TF) > 1 for Pb and Zn, while its biological concentration factor (BCF) was > 1 for Fe. Values of biological accumulation coefficient (BAC) for AIT and soil contamination factor (CF) were < 1 for the metals. Bioindicators of oxidative stress (MDA, GST, CAT and SOD) in earthworm supernatants from the discharge locations were significantly higher (p < 0.05) compared to that at location C, while their GSH levels were significantly (p < 0.05) lower. Acetylcholinesterase (AChE) activity in earthworm supernatants from discharge locations was significantly lower (p < 0.05) in comparison with the control. Trends in results revealed that AIT may be useful for extraction and stabilization of heavy metals in polluted soils. Also, the biochemical alterations in L. terrestris may serve as sensitive bioindicators of soil contamination.

Split G-quadruplex DNAzymes offer unique opportunities for building gated biosensors with a wide range of applications. Splitting G4 DNAzymes involves separating guanine tracts in the G-quadruplex DNA sequence into two non-functional sequences that reconstitute into a functional G-quadruplex with peroxidase activity upon hybridisation of the aptamer probe region within the split system with the target molecule. Several studies have demonstrated the reassembly of split G4 DNAzymes and their applications in the detection of various analytes. This approach offers unique opportunities for modular biosensor construction, target-dependent activation, lack of requirement for labelling, amplification-free high sensitivity, and specificity over traditional G4 sensing. In this review, we explore the strategies of splitting G-quadruplex and their applications in biomedical diagnosis, environmental sensing, food safety monitoring, cell detection, and the integration of the technology with nanomaterials for enhanced stability and sensitivity. We considered the classical intermolecular split strategies that utilise binary probes and intramolecular split systems, which integrate the spacer DNA that allow for single probes as the model G4 sequence. Finally, we explore the current challenges required to develop split G-quadruplex DNAzymes into tools for routine practical applications.