Highly monodisperse rattle-structured nanomaterials with gold nanorod core–mesoporous silica shell as drug delivery vehicles and nanoreactors

ACS Appl. Mater. Interfaces

Sun

et al. 2015

ABSTRACT:The Raman enhancing ability of noble metal nanoparticles (NPs) is an important factor for surface enhanced Raman scattering (SERS) substrate screening, which is generally evaluated by simply mixing as-prepared NPs with Raman reporters for Raman signal measurements. This method usually leads to incredible results because of the NP surface coverage nonuniformity and reporter-induced NP aggregation. Moreover, it cannot realize in situ, continuous SERS characterization. Herein, we proposed a dynamic SERS monitoring strategy for NPs with precisely tuned structures based on a simplified spatially confined NP growth method. Gold nanorod (AuNR) seed NPs were coated with a mesoporous silica (mSiO 2 ) shell. The permeability of mSiO 2 for both reactive species and Raman reporters rendered the silver overcoating reaction and SERS indication of NP growth. Additionally, the mSiO 2 coating ensured monodisperse NP growth in a Raman reporter-rich reaction system. Moreover, "elastic" features of mSiO 2 were observed for the first time, which is crucial for holding the growing NP without breakage. This feature makes the mSiO 2 coating adhere to metal NPs throughout the growing process, providing a stable Raman reporter distribution microenvironment near the NPs and ensuring that the substrate's SERS ability comparison is accurate. Three types of NPs, i.e., core−shell Au@AgNR@mSiO 2 , Au@AuNR@mSiO 2 , and yolk−shell Au@void@AuNR@mSiO 2 NPs, were synthesized via core−shell overgrowth and galvanic replacement methods, showing the versatility of the approach. The living cell SERS labeling ability of Au@AgNR@mSiO 2 -based tags was also demonstrated. This strategy addresses the problems of multiple batch NP preparation, aggregation, and surface adsorption differentiation, which is a breakthrough for the dynamic comparison of SERS ability of metal NPs with precisely tuned structures and optical properties.

Section: ■ Results and Discussionmentioning

confidence: 83%

Section: ■ Introductionmentioning

confidence: 99%

“Elastic” Property of Mesoporous Silica Shell: For Dynamic Surface Enhanced Raman Scattering Ability Monitoring of Growing Noble Metal Nanostructures via a Simplified Spatially Confined Growth Method

Lin

ACS Appl. Mater. Interfaces

Sun

et al. 2015

“…32 Various simple and robust methods have been reported for the synthesis of multifunctional mesoporous silica-encapsulated AuNPs (core-shell Au@mSiO 2 NPs) for use as cancer theranostics. 33,34 Previously, we successfully designed and synthesized Janus Au@mSiO 2 NPs, which might not only efficiently deliver imaging agents or drugs into cancer cells but also exhibit good photothermal properties, thus representing a promising theranostic candidate for use in combined photothermo-/chemo-cancer therapy. 30 Given …”

Section: Discussionmentioning

confidence: 99%

Cytotoxicity of various types of gold-mesoporous silica nanoparticles in human breast cancer cells

Liu

et al. 2015

IJN

Recently, gold nanoparticles (AuNPs) have shown promising biological applications due to their unique electronic and optical properties. However, the potential toxicity of AuNPs remains a major hurdle that impedes their use in clinical settings. Mesoporous silica is very suitable for the use as a coating material for AuNPs and might not only reduce the cytotoxicity of cetyltrimethylammonium bromide-coated AuNPs but might also facilitate the loading and delivery of drugs. Herein, three types of rod-like gold-mesoporous silica nanoparticles (termed bare AuNPs, core–shell Au@mSiO 2 NPs, and Janus Au@mSiO 2 NPs) were specially designed, and the effects of these AuNPs on cellular uptake, toxic behavior, and mechanism were then systematically studied. Our results indicate that bare AuNPs exerted higher toxicity than the Au@mSiO 2 NPs and that Janus Au@mSiO 2 NPs exhibited the lowest toxicity in human breast cancer MCF-7 cells, consistent with the endocytosis capacity of the nanoparticles, which followed the order, bare AuNPs > core–shell Au@mSiO 2 NPs > Janus Au@mSiO 2 NPs. More importantly, the AuNPs-induced apoptosis of MCF-7 cells exhibited features that were characteristic of intracellular reactive oxygen species (ROS) generation, activation of c-Jun-N-terminal kinase (JNK) phosphorylation, an enhanced Bax-to-Bcl-2 ratio, and loss of the mitochondrial membrane potential. Simultaneously, cytochrome c was released from mitochondria, and the caspase-3/9 cascade was activated. Moreover, both ROS scavenger ( N -acetylcysteine) and JNK inhibitor (SP600125) partly blocked the induction of apoptosis in all AuNPs-treated cells. Taken together, these findings suggest that all AuNPs induce apoptosis through the ROS-/JNK-mediated mitochondrial pathway. Thus, Janus Au@mSiO 2 NPs exhibit the potential for applications in biomedicine, thus aiding the clinical translation of AuNPs.

“…Gold nanorod (GNR) exhibits unique optical properties that make it attractive for photothermal therapy [1,2], biosensing [3,4], molecular imaging [5] and controlled drug delivery [6,7]. These applications require the GNRs to be functionalized with different biochemical groups.…”

Section: Introductionmentioning

confidence: 99%

Gold nanorod biochip functionalization by antibody thiolation

Mei

et al. 2015

Talanta

Conjugation of biomolecules on gold nanorod (GNR) surfaces is the basis for successful applications in biosensing, imaging, and drug delivery. Current functionalization methods are often problematic, involving multi-step nanoparticle modification to replace surfactant bilayer, delicate nanoparticle protection during surfactant exchange, and material loss due to inevitable aggregation. Instead of intensive surface modification of GNRs, we describe herein a facile method to functionalize gold nanorod surfaces via covalent Au–S bonds by thiolating receptors. The resulting GNR-bioconjugates showed superior dispersion and stability in buffer for months without morphology change and aggregation. ELISA tests confirmed the high biofunctionality of the thiolated anti-IgG moieties immobilized on the GNR surfaces. Furthermore, this simple method facilitated a straightforward functionalization of GNR assembly on glass substrate to construct a specific biochip, which can detect human IgG targets in a label-free fashion with high sensitivity and specificity. Compared to electropolymeric coating to functionalize the GNR, our method exhibited a five-fold enhancement in the spectral sensitivity to refractive index change caused by the target binding. This universal GNR bioconjugation method can be extended to bind different proteins and antibodies for development of biosensors or drug delivery.