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Nanoparticles Carrying Biological Molecules
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2020
Suryani Saallah, Wuled Lenggoro
Generally, physical conjugation offers a simple and rapid route to bind biomolecule to the NP and requires minimal modification steps (Saallah and Lenggoro, 2018). Thus, the biomolecules’ functionalities can be preserved. Nevertheless, this method suffers from weak binding, random orientation, high likelihood of desorption, and poor reproducibility (Liebana and Drago, 2016). Such drawbacks can be overcome by introducing specific functional groups or targeting ligands to the nanoparticles through affinity interactions. The most well-known example in the last several decades is the avidin–biotin system. Avidin comprises four identical subunits that provide four binding pockets which specifically recognize and bind to biotin, resulting in a strong and stable interaction with a dissociation constant, KD, of the order of 10–15 M. The combination of basic pI and carbohydrate content, however, results in nonspecific binding as observed in several applications (Sapsford et al., 2013). Alternatively, streptavidin, a non-glycosylated homologous tetrameric protein displaying similar affinity to biotin, can be used as avidin analog (Saallah and Lenggoro, 2018). The mechanism of the most widely applied non-covalent interactions is illustrated in Figure 4.7.
Nanobiosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
Biotin-streptavidin interactions are well-studied binding partners, that interact with very high affinity (Figure 9.18). Shu et al. (2007) investigated biotin-streptavidin binding interactions using microcantilever sensors. Three structurally different biotin-modified cantilever surfaces were produced as shown in Figure 9.19. The cantilever response to the binding of SA on these biotin-sensing monolayers was compared. The mechanical response of the cantilever strongly depends upon the nature of the biotin-modified surfaces: (i) biotin/PEG-coated microcantilevers did not bend upon the injection of SA; (ii) biotin-HPDP, (N-(6-(biotinamido)hexyl)-3’-(2’-pyridyldithio)-propionamide (a reversible biotinylation reagent)-coated microcantilevers bent downward; and (iii) biotin-SS-NHS (succinimidyl 2-(biotinamido)-ethyl-1,3′-dithiopropionate)-coated microcantilevers bent upward. Biotin-SS-NHS enables simple and efficient biotinylation of antibodies, proteins, and other primary amine-containing molecules. (a) Structure of streptavidin and (b) biotin molecules represented by spheres, attached to streptavidin.Difference in behavior of microcantilevers with various surface modifications on the upper gold surfaces: (a) biotin-PEG; (b) biotin-HPDP; and (c) biotin-SS-NHS. Lower gold surfaces of all the microcantilevers are coated with PEG, known to hinder nonspecific adsorption of proteins. (Shu, W. et al., Biosens. Bioelectron., 22, 2003, 2007.)
Introduction to Biological Light Microscopy
Published in Jay L. Nadeau, Introduction to Experimental Biophysics, 2017
Jay L. Nadeau, Michael W. Davidson
Quite often in molecular biophysics there is no exact fluorescent conjugate that targets the structure or protein of choice. In this case, you can make your own. All of the common dyes are available as conjugates to avidin or streptavidin (see Chapter 1) or as reactive intermediates that bind to a specific functional group, for example, a thiol, primary amine, carboxylate, or aldehyde. Streptavidin may be conjugated to anything with a biotin, and kits are available to bind biotin to any protein or small molecule with a reactive group. A very useful class of reactive termini are the amine-reactive molecules such as the succidimydyl esters, which react with primary amines to form amide bonds. The most commonly used is sulfo-N-hydroxysulfosuccinimide (sulfo-NHS; Figure 7.30a). Amine-reactive probes will react with any protein, as multiple amino acid residues within all proteins contain these groups. Thiol-reactive probes will react with cysteine residues, either native or engineered as discussed in Chapter 2, as well as other thiols that may be chemically or genetically engineered onto the molecule of interest (Figure 7.30b). Most of these labeling reactions are best done with a purified dye and target molecule in a test tube before applying to cells. However, both streptavidin dyes and thiol-reactive dyes may be used to label proteins that are already expressed in cells, provided that these proteins are either biotinylated or contain an easily accessible cysteine residue. The latter can be tricky, as other native proteins may also possess extracellular cysteines. We will return to this subject in Chapters 11 through 13 when we discuss cell labeling using nanoparticles.
A review on magnetic polymeric nanocomposite materials: Emerging applications in biomedical field
Published in Inorganic and Nano-Metal Chemistry, 2023
Zhou et al.[278] proposed biomimetic magnetic nanoparticles composed of magnetic nanoparticles, graphene nanosheets, leukocytes, and PEG-modified lipid linker. This preparation was simple and facile. Magnetic nanoparticles were integrated with graphene nanosheets by layer-by-layer assembly, and then coated with a layer of leukocyte membranes due to easy extraction of graphene nanosheets. Next, a biotin-labeled PEG-lipid (distearyl phosphatidyl ethanolamine) was inserted into the cell membranes owing to the interaction of lipid in polymer with lipid bilayer in cell membranes. Biotinylated antibodies were conjugated on materials through streptavidin as a bridge specifically interact with biotin. These leukocyte membranes and PEG could greatly reduce nonspecific capture and achieve high-purity CTC isolation. The capture efficiency and purity were > 85% and > 94.4%, respectively, from 1 ml blood with 20–200 CTCs after 2 min incubation; this demonstrated high specificity and good sensitivity.
Peptide-enabled receptor-binding-quantum dots for enhanced detection and migration inhibition of cancer cells
Published in Journal of Biomaterials Science, Polymer Edition, 2020
Ruijuan Zu, Xiaocui Fang, Yuchen Lin, Shilin Xu, Jie Meng, Haiyan Xu, Yanlian Yang, Chen Wang
From the above-observed results, the molar ratio of QDs: E5 of E5@QDs used in this work was 1: 10, in this case, the streptavidin binding sites on the surface of QDs is unsaturated, together with the strong binding interactions between biotin and streptavidin (KD value around 10−16 M), we therefore assumed approximately 100% yield of E5 streptavidin-biotin binding. In addition, we also used the dual-label E5 (biotin-E5-FITC) to validate the binding strength between biotinylated E5 and SA-coated QDs. Briefly, SA-coated QDs (1 μM) were incubated with biotin-E5-FITC (10 μM) at a molar ratio of 1: 10 (QDs: biotin-E5-FITC) for 2 h in the sodium borate buffer (10 mM, pH 8.0) at 25 °C. Then unbound biotin-E5-FITC molecules were separated and its concentration was determined by a FITC-E5 fluorescence quantitative method. The results further confirmed that almost all E5 were successfully bound to the surface of QDs via the strong binding interactions between biotin and streptavidin (data not shown).