Antibody-Functionalized Halloysite Nanotubes for Targeting Bacterial Cells

Abstract

Halloysite nanotubes (HNTs) are naturally occurring tubular clay particles which have emerged in recent years as a promising nanomaterial for numerous applications. Specifically, HNTs’ large pore volume and high specific surface area in combination with their biocompatibility make them ideal nanocarriers for bioactive compounds. This research aims to design and synthesize functionalized HNTs, which could selectively bind to target bacterial cells in suspension. Such a system can allow us to treat target cells within a challenging heterogeneous population, such as contaminated ecosystems or gut flora. HNTs functionalization is achieved by immobilizing specific antibodies onto the nanotube surface. The synthetic route is realized by the following subsequent steps: acidic etching of the HNTs, silanization of reactive surface hydroxyls, conjugation of protein A, and oriented immobilization of the antibody. HNT functionalization is studied by a set of analytical techniques including attenuated total reflectance Fourier-transform infrared spectroscopy, zeta potential measurements, thermal gravimetric analysis, scanning and transmission electron microscopy, as well as fluorescence microscopy. The selective binding of the functionalized HNTs to their target bacteria is observed upon incubation with live homogenous and heterogeneous cultures using fluorescence microscopy and high-throughput flow cytometry. Plate count and live/dead staining experiments demonstrate the biocompatibility of the antibody-HNT hybrid with its target bacteria. The suggested HNT-based smart carrier constitutes a generic platform for targeted delivery that could be selectively tailored against any microorganism by facile antibody adjustment.

Gold Nanorod-Incorporated Halloysite Nanotubes Functionalized with Antibody for Superior Antibacterial Photothermal Treatment

“…HNTs modification consists of two main steps: (1) the surface immobilization of anti- E. coli antibody onto a PA-decorated HNTs surface via carbodiimide chemistry [ 45 ], and (2) the incorporation of gold nanorods onto HNTs via the freezing-induced loading technique, as schematically illustrated in Scheme 1 .…”

“…The immobilization of anti- E. coli antibody onto the HNTs surface was investigated using FTIR-ATR and immunogenic labeling, as depicted in Figure 1 a,b, respectively. The FTIR-ATR spectrum of HNTs depicts two characteristic peaks at 3698 and 3618 cm −1 ascribed to the Al-OH groups of the alumina portion of HNTs [ 45 , 48 ]. These diminish upon the acidic etching of HNTs, indicating a high degree of alumina removal [ 29 , 48 ].…”

“…Anti- E. coli were immobilized onto HNTs, as was previously reported by our group [ 45 ]. Briefly, HNTs were first etched under acidic conditions in a solution of sulfuric acid (17 vol.%) at 110 °C for 16 h. After washing with water and drying, the etched HNTs were aminosilanized in an APTES solution in toluene (7 vol.%) at 120 °C for 16 h under reflux.…”

“…In this work, we combine for the first time the advantages of AuNR immobilization onto HNTs and the modification of HNTs with antibodies against Escherichia coli ( E. coli , as a model microorganism) for targeted APTT. Anti- E. coli antibodies were immobilized onto HNTs at their proper orientation using surface-conjugated protein A, as we recently reported [ 45 ]. Then, AuNRs were incorporated onto the Ab-functionalized HNTs (Ab-HNTs) using the freezing-induced loading technique, by which the directional growth of ice crystals presses the AuNRs onto the HNTs surface to generate intermolecular adsorptive interactions [ 43 , 46 ].…”

Sustainable and safer nanoclay composites for multifaceted applications

“…, kaolinite-serpentine (kaolinite, halloysite), smectite (montmorillonites, saponites), micas (illite), and chlorite groups based on variations in their layered structures, chemical compositions, and particle morphology. 116–118 Each member is composed of silicate sheets (Si 2 O 5 ) bonded to aluminum oxide/hydroxide layers (Al 2 (OH) 4 ). The kaolinite/halloysite group constitutes kaolinite, where silicate sheets (Si 2 O 5 ) are linked to aluminum oxide/hydroxide layers (Al 2 (OH) 4 ).…”