Self-assembly of gold nanorods coated with phospholipids: a coarse-grained molecular dynamics study

Phase transfer-driven rapid and complete ligand exchange for molecular assembly of phospholipid bilayers on aqueous gold nanocrystals

A phase transfer-mediated ligand exchange method is developed for highly selective and rapid synthesis of colloidal phospholipid bilayer-coated gold nanocrystals. The complete replacement of strongly bound surface ligands such as cetyltrimethylammonium bromide (CTAB) and citrate by phospholipid bilayer can be quickly achieved by water-chloroform phase transfer.

Photoluminescence modulation of silicon nanoparticles via highly ordered arrangement with phospholipid membranes

Highly ordered self-assembly of nanoparticles (NPs) in a large scale promises attractive potential in optical modulation of the NPs for illuminating, imaging and sensing applications. In this work, a type of multi-lamellar nanocomposite membranes composed of phospholipid multilayers and Si NPs sandwiched between each adjacent lipid layers was fabricated via a facile co-assembly method. X-ray reflectivity (XRR), grazing incident X-ray diffraction (GIXRD) and TEM measurements verified the highly ordered arrangement of NPs within the multilayers with a controlled in-plane inter-particle separation from ∼7 nm to ∼14 nm. Due to such an arrangement, the photoluminescence (PL) properties of the Si NPs were effectively modulated. Compared to the NPs in suspension or its pure film, the PL of the NPs in the membranes blue-shifted and remarkably narrowed, with the full-width-at-half-maximum (FWHM) value reduced from >110 nm of the pure Si NP film to below 43 nm. The radiative lifetime of the NPs was also significantly reduced from ∼16.7 ns to ∼3.3 ns depending on the inter-particle distance in the membrane. Meanwhile, the Si NPs within membranes maintained robust photostability under UV irradiation.

The Effect of Photothermal Therapy on Osteosarcoma With Polyacrylic Acid-Coated Gold Nanorods

Background:

Polyacrylic acid (PAA)–coated gold nanorods (GNRs) were prepared in this research, and then the structure, stability, temperature increment efficiency, and biocompatibility of GNRs@PAA were detected.

Methods:

It was demonstrated that GNRs@PAA coupled with an 808 nm laser had superior efficiency of hyperthermia therapy for MG63 human osteosarcoma cell.

Results:

The mechanism of photothermal therapy of GNRs@PAA was explored, and it was proved that damaged cell membrane and DNA integration caused cell apoptosis and death, and the cell apoptosis rate had been obviously promoted by in vitro photothermal therapy which exhibited time–dose dependence.

Conclusion:

The results demonstrated that the GNRs@PAA could be a promising candidate for phototherapeutic applications in human osteosarcoma.

Implicit-solvent dissipative particle dynamics force field based on a four-to-one coarse-grained mapping scheme

A new set of efficient solvent-free dissipative particle dynamics (DPD) force fields was developed for phospholipids and peptides. To enhance transferability, this model maps around four heavy atoms and their connected hydrogen atoms into a coarse-grained elementary bead based on functional group. The effective hybrid potential between any pair of beads is composed of a short-range repulsive soft-core potential that directly adopts the form of an explicit-solvent DPD model and a long-range attractive hydrophobic potential. The parameters of the attractive potentials for lipid molecules were obtained by fitting the explicit-solvent DPD simulation of one bead of any type in a water box, then finely tuning it until the bilayer membrane properties obtained in the explicit-solvent model were matched. These parameters were further extended to amino acids according to bead type. The structural and elastic properties of bilayer membranes, free energy profiles for a lipid flip-flop and amino acid analogues translocating across the membrane, and membrane pore formation induced by antimicrobial peptides obtained from this solvent-free DPD force field considerably agreed with the explicit-solvent DPD results. Importantly, the efficiency of this method is guaranteed to accelerate the assembly of vesicles composed of several thousand lipids by up to 50-fold, rendering the experimental liposome dynamics as well as membrane-peptide interactions feasible at accessible computational expense.

Antibody-Conjugated Silica-Modified Gold Nanorods for the Diagnosis and Photo-Thermal Therapy of Cryptococcus neoformans: an Experiment In Vitro

BACKGROUND

Cryptococcus neoformans is an encapsulated yeast. There is still little quick and effective solution for the diagnosis or treatment of C. neoformans infection at an early stage in clinical. Antibody-conjugated silica-modified gold nanorods (GNR-SiO₂-Ab) can conjugate C. neoformans selectively. It may provide a possibility for treatment of cryptococcosis safely and effectively.

METHODS

Gold nanorods (GNRs) were synthesized according to the seed-mediated template-assisted protocol. Anti-C. neoformans antibody was covalently anchored on the surface of GNRs with silane coupling agent. In vitro computer tomography imaging was performed to explore the diagnostic effect of the GNR-SiO₂-Ab. The viability of cells was evaluated to confirm the photo-thermal therapy effect of GNR-SiO₂-Ab combined with near-infrared (NIR) laser light.

RESULTS

GNR-SiO₂-Ab has a potential application as a positive X-ray/CT imaging contrast agent. An antibody can induce a much greater aggregation of GNRs by binding to the surface of C. neoformans cells resulting in a much higher attenuation values than ever. After irradiation, C. neoformans cells suffered photo-thermal damages and the normal structure of cells were destroyed. The viability of cells reduced significantly compared to the untreated cells.

CONCLUSIONS

Our work confirmed that antibody-conjugated silica-modified gold nanorods could enhance X-ray attenuation of C. neoformans cells in CT images. And immune GNRs, which were mediated by antibodies, could increase the effects of NIR-induced photo-thermal therapy in C. neoformans cells.

Kinetics-Controlled Amphiphile Self-Assembly Processes

Amphiphile self-assembly is an essential bottom-up approach of fabricating advanced functional materials. Self-assembled materials with desired structures are often obtained through thermodynamic control. Here, we demonstrate that the selection of kinetic pathways can lead to drastically different self-assembled structures, underlining the significance of kinetic control in self-assembly. By constructing kinetic network models from large-scale molecular dynamics simulations, we show that two largely similar amphiphiles, 1-[11-oxo-11-(pyren-1-ylmethoxy)-undecyl]pyridinium bromide (PYR) and 1-(11-((5a1,8a-dihydropyren-1-yl)methylamino)-11-oxoundecyl)pyridinium bromide (PYN), prefer distinct kinetic assembly pathways. While PYR prefers an incremental growth mechanism and forms a nanotube, PYN favors a hopping growth pathway leading to a vesicle. Such preference was found to originate from the subtle difference in the distributions of hydrophobic and hydrophilic groups in their chemical structures, which leads to different rates of the adhesion process among the aggregating micelles. Our results are in good agreement with experimental results, and accentuate the role of kinetics in the rational design of amphiphile self-assembly.