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Background: Site-directed mutagenesis (SDM) is a key method in molecular biology; allowing to modify DNA sequences at single base pair resolution. Although many SDM methods have been developed, methods that increase efficiency and versatility of this process remain highly desired. Method: We present a versatile and simple method to efficiently introduce a variety of mutation schemes using Gibson-assembly but without the need to design uniquely designated Gibson primers. Instead, we explore the re-use of standard SDM primers (completely overlapping in sequence) in combination with regular primers (~ 25 bps long) for amplification of fragments flanking the site of mutagenesis. We further introduce a rapid amplification step of the Gibson-assembled product for analysis and quality control, as well as for ligation, or re-ligation at instances the process fails (avoiding expenditure of added Gibson reaction mixtures). Results: We first demonstrate that standard SDM primers can be used with the Gibson assembly method and, despite the need for extensive digestion of the DNA past the entire primer sequence, the reaction is attainable within as short as 15 min. We also find that the amount of the assembled Gibson product is too low to be visualized on standard agarose gel. Our added amplification step (by use of the same short primers initially employed) remedies this limitation and allows to resolve whether the desired Gibson-assembled product has been obtained on agarose gel or by sequencing of amplicons. It also provides large amounts of amplicons for subsequent ligations, bypassing the need to re-employ Gibson mixtures. Lastly, we find that our method can easily accommodate SDM primers with degenerate sequences. Conclusion: We employ our alternative approach to delete, replace, insert, and degenerate sequences within target DNA sequences, specifically DNA sequences that proved very resistant to mutagenesis by multiple other SDM methods (standard and commercial). Importantly, our approach involves the re-use of SDM primers from our primer-inventory. Our scheme thereby reduces the need (and time and money) to design and order new custom Gibson-primers. Together, we provide a simple and versatile protocol that spans only 4 days (including the added amplification step), requires minimal primer sets and provides very high yields and success rates (> 98%). [ABSTRACT FROM AUTHOR]

The current consensus holds that optically‐cleared specimens are unsuitable for Magnetic Resonance Imaging (MRI); exhibiting absence of contrast. Prior studies combined MRI with tissue‐clearing techniques relying on the latter's ability to eliminate lipids, thereby fostering the assumption that lipids constitute the primary source of ex vivo MRI‐contrast. Nevertheless, these findings contradict an extensive body of literature that underscores the contribution of other features to contrast. Furthermore, it remains unknown whether non‐delipidating clearing methods can produce MRI‐compatible specimens or whether MRI‐contrast can be re‐established. These limitations hinder the development of multimodal MRI‐light‐microscopy (LM) imaging approaches. This study assesses the relation between MRI‐contrast, and delipidation in optically‐cleared whole brains following different tissue‐clearing approaches. It is demonstrated that uDISCO and ECi‐brains are MRI‐compatible upon tissue rehydration, despite both methods' substantial delipidating‐nature. It is also demonstrated that, whereas Scale‐clearing preserves most lipids, Scale‐cleared brain lack MRI‐contrast. Furthermore, MRI‐contrast is restored to lipid‐free CLARITY‐brains without introducing lipids. Our results thereby dissociate between the essentiality of lipids to MRI‐contrast. A tight association is found between tissue expansion, hyperhydration and loss of MRI‐contrast. These findings then enabled us to develop a multimodal MRI‐LM‐imaging approach, opening new avenues to bridge between the micro‐ and mesoscale for biomedical research and clinical applications. [ABSTRACT FROM AUTHOR]

We present a new strategy for the fabrication of magneto-fluorescent nanoparticles designed for bimodal imaging. These hybrid nanostructures comprise an optically active semiconductor nanoparticle quantum dot core with tunable fluorescence, encapsulated within a hollow paramagnetic iron oxide shell that serves as an MRI contrast agent. The yolk-shell morphology enables incorporation of the semiconductor and magnetic domains into a single structure, while avoiding direct contact between them, which typically results in quenching of the desired optical fluorescence. We successfully demonstrate utilization of the ultrasmall (15 nm hydrodynamic size) magneto-fluorescent CdSe@CdS@Hollow-Fe2O3 nanoparticles for multimodal imaging of cells at the intracellular level. [ABSTRACT FROM AUTHOR]