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Tunable Mechanical Properties of Nanoparticle Monolayer Membranes via Ligand Phase Control and Defect Distribution.

ABSTRACT: In this study, the effects of ligand phase, morphology, and temperature on the elastic modulus of free-standing alkanethiol-capped gold nanoparticle membranes are reported. Langmuir films of 2.5 nm gold nanoparticles capped with tetradecanethiol were prepared at temperatures above and below the phase transition temperature (T _m) of the ligand shell and transferred to holey carbon grids (containing 1.2 ?m holes) to form free-standing membranes. Force-indentation measurements are used to measure the elastic modulus of the membranes using an atomic force microscope in the temperature range 10-40 °C. These films are compared with membranes of dodecanethiol-capped gold nanoparticles, which do not undergo a ligand order-disorder transition in the temperature range investigated. The ligand phase effect is observed in the tetradecanethiol-capped gold nanoparticle films, where an abrupt change in the elastic modulus is seen near T _m. The temperature (relative to T _m) during the fabrication of the films is determined to play an important role in tuning the mechanical strength of these films in this temperature range by both changing the nature of the interparticle interactions and by affecting microscale film morphology.

SUBMITTER: Raveendran A

PROVIDER: S-EPMC6641765 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature

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Tunable Mechanical Properties of Nanoparticle Monolayer Membranes via Ligand Phase Control and Defect Distribution.

Raveendran Abhilash A Meli M-Vicki MV

ACS omega 20170810 8

In this study, the effects of ligand phase, morphology, and temperature on the elastic modulus of free-standing alkanethiol-capped gold nanoparticle membranes are reported. Langmuir films of 2.5 nm gold nanoparticles capped with tetradecanethiol were prepared at temperatures above and below the phase transition temperature (<i>T</i> <sub>m</sub>) of the ligand shell and transferred to holey carbon grids (containing 1.2 μm holes) to form free-standing membranes. Force-indentation measurements are ...[more]

PMID: 31457732

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Project description:The vitreous humor of the eye is a biological hydrogel principally composed of collagen fibers interspersed with hyaluronic acid. Certain pathological conditions necessitate its removal and replacement. Current substitutes, like silicone oils and perfluorocarbons, are not biomimetic and have known complications. In this study, we have developed an in situ forming two-component biomimetic hydrogel with tunable mechanical and osmotic properties. The components are gellan, an analogue of collagen, and poly(methacrylamide-co-methacrylate), an analogue of hyaluronic acid; both endowed with thiol side groups. We used response surface methodology to consider seventeen possible hydrogels to determine how each component affects the optical, mechanical, sol-gel transition temperature and swelling properties. The optical and physical properties of the hydrogels were similar to vitreous. The shear storage moduli ranged from 3 to 358Pa at 1Hz and sol-gel transition temperatures from 35.5 to 43°C. The hydrogel had the ability to remain swollen without degradation for four weeks in vitro. Three hydrogels were tested for biocompatibility on primary porcine retinal pigment epithelial cells, human retinal pigment epithelial cells, and fibroblast (3T3/NIH) cells, by electric cell-substrate impedance sensing system. The two-component hydrogels allowed for the tuning and optimizing of mechanical, swelling, and transition temperature to obtain three biocompatible hydrogels with properties similar to the vitreous. Future studies include testing of the optimized hydrogels in animal models for use as a long-term substitute, whose preliminary results are mentioned.Although hydrogels are researched as long-term vitreous substitute, none have advanced sufficiently to reach clinical application. Our work focuses on the development of a novel two component in situ forming hydrogel that bio-mimic the natural vitreous. Our thiol-containing copolymers can be injected as an aqueous solution into the vitreous cavity wherein, at physiological temperature, the rigid component will instantaneously form a physical gel imbedding the random coil copolymer. Upon subsequent oxidation, the two components will form disulfide cross-links and a stable reversible hydrogel capable of providing osmotic pressure to reattach the retina. It may be left in the eye permanently or easily removed by injection of a simple reducing agent to cleave the disulfide bonds, rather than surgery. This contribution is significant because it is expected to provide patients with a much better quality of life by improving surgical outcomes, creating much less post-operative burden, and reducing the need for secondary surgeries.

Dataset Information

Tunable Mechanical Properties of Nanoparticle Monolayer Membranes via Ligand Phase Control and Defect Distribution.

Publications

Tunable Mechanical Properties of Nanoparticle Monolayer Membranes via Ligand Phase Control and Defect Distribution.

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