Omnidispersible Hedgehog Particles with Multilayer Coatings for Multiplexed Biosensing

Abstract

Hedgehog particles (HPs) replicating the spiky geometry of pollen grains revealed surprisingly high dispersion stability regardless of whether their hydrophobicity/hydrophilicity matches that of the media or not. This property designated as omnidispersibility is attributed to the drastic reduction of van der Waals interactions between particles coated with stiff nanoscale spikes as compared to particles of the same dimensions with smooth surfaces. One may hypothesize but it remains unknown, however, whether HPs modified with polymers or nanoparticles (NPs) would retain this property. Surface modifications of the spikes will expand the functionalities of HPs, making possible their utilization as omnidispersible carriers. Here, we show that HPs carrying dense conformal coatings made by layer-by-layer (LBL/LbL) assembly maintain dispersion stability in environments of extreme polarity and ionic strength. HPs, surface-modified by multilayers of polymers and gold NPs, are capable of surface-enhanced Raman scattering (SERS) and overcome the limited colloidal stability of other SERS probes. The agglomeration resilience of HPs leads to a greater than one order of magnitude increase of SERS intensity as compared to colloids with smooth surfaces and enables simultaneous detection of several targets in complex media with high ionic strength. Omnidispersible optically active colloids open the door for rapid multiplexed SERS analysis in biological fluids and other applications.

Recent advances in applications of nanoparticles in SERS in vivo imaging

“…The modification of biocompatible polymers such as polyethylene glycols (PEG; Jimenez de Aberasturi et al, 2016; Shkilnyy et al, 2009), high molecular weight proteins such as bovine serum albumin (BSA; Yuan et al, 2013; Zheng et al, 2014), and the deposition of a silica shell (C. Wang, Chen, Wang, Ma, & Su, 2008) are typical surface coating methods to improve the signal biostability of SERS nanoparticles. Furthermore, the layer‐by‐layer coating can stably encapsulate a variety of Raman report molecules into SERS nanotags, thus realize the multiplexed SERS detection in complex biological media (Montjoy, Bahng, Eskafi, Hou, & Kotov, 2018). It is worth noting that rational surface coating can bring the SERS nanoparticles with additional functions, including targeting, imaging, drug delivery, and therapy.…”

Omnidispersible Microscale Colloids with Nanoscale Polymeric Spikes

“…To demonstrate the conceptual possibility of loading of cargo in TPs, we first loaded Au NPs using LBL deposition [3] including them in LBL sequence PSS/PDDA/AuNP (AuTP) and PSS/PDDA (0.5 M NaCl)/AuNP (AuSTP).…”

“…58 PAA/FITC-PAH films were deposited on HPs using LBL assembly as described previously. 3 experimental construct. The length and thickness were measured using electron microscopy of a HP (minimum of 50 images), which was used for elaboration of TP model geometry.…”

“…Particles with spikes that were conformably coated with organic layer-by-layer assembled (LBL) films [5][6][7][8][9][10] maintained dispersion stability verifying the role of particle geometry in the reduction of van der Waals forces. 3 There are multiple other examples of spiky and flower-like particles made from different inorganic materials, [11][12][13][14] which were not tested for dispersibility in 'difficult' solvents, but are expected to display similar colloidal properties. Special functionalities were also found for particles with interfaces decorated by pillars at molecular scale 15 substantiating the utility of the topographically engineered colloids.…”

“…Besides omnidispersibility, rigid inorganic spikes impart hedgehog particles (HPs) with other unique properties, such as a broad band extinction band in the near IR part of the spectrum, 2,3,16,17 which is attributed to strong light scattering of the radial spikes. 2,17 Realization of HPs with fully polymeric yet sufficiently rigid spikes would engender these particles with additional functions, exemplified by: (a) tunable extinction bands in the visible spectrum; (b) nanoscale cargo compartments in the spikes; and (c) stimuli-responsive behavior.…”