Single-Step Injection of Gold Nanoparticles through Phospholipid Membranes

Abstract

We propose and demonstrate a new method of an all-optical, contactless, one-step injection of single gold nanoparticles through phospholipid membranes. The method is based on the combination of strong optical forces acting on and simultaneous optical heating of a gold nanoparticle exposed to laser light tuned to the plasmon resonance of the nanoparticle. A focused laser beam captures single nanoparticles from the colloidal suspension, guides them towards a phospholipid vesicle and propels them through the gel-phase membrane, resulting in the nanoparticle internalization into the vesicle. Efficient resonant optical heating of the gold nanoparticle causes a pore to form in the gel-phase membrane, a few-hundred nanometers in size, which remains open for several minutes. Keywordsgold; nanoparticle; phospholipid; membrane; vesicle; injection; drug-delivery The delivery of hydrophilic biological molecules, such as proteins, DNA and RNA, to the interior of living cells is of extreme importance for biocellular research, gene therapy and drug development. 1 The cellular membrane, which is impermeable to most hydrophilic substances, is a barrier shielding the interior of a cell from its surrounding. To pass through this barrier a number of advanced biological, chemical and physical methodologies have been developed in the last three decades, including lipoplex 2 and polyplex 3 injection, a "gene gun", 4 electroporation, 5 photoporation 6 and liposomal release. 7,8,9,10 Each of these methods has its advantages and disadvantages, which must be considered carefully taking into account the delivery purpose and the cell type. 11 Among others the photoporation or optical injection has increasingly attracted attention as it is a contactless, all-optical and therefore aseptic technique. It relies on the transient increase of a phospholipid membrane permeability induced by a laser beam, allowing hydrophilic substances to diffuse across the membrane. Although the effect of photoporation has been extensively studied and employed for DNA and RNA delivery, the mechanism of the membrane permeability increase upon illumination by light has still not been completely understood. Often the photoporation mechanism is discussed as a combination of several processes, depending on the laser source used: heating, thermoelastic stress, multi-photon absorption and generation of a free electron plasma. 12 Occurrence of these processes requires extremely high peak laser powers 13 and therefore poses a danger of inducing photochemical damage to cell regions illuminated by out-of-focus light. 14,15 In this regard, * Corresponding author: andrey.lutich@physik.lmu.de. Europe PMC Funders GroupAuthor Manuscript ACS Nano. Author manuscript; available in PMC 2013 November 25. Europe PMC Funders Author ManuscriptsEurope PMC Funders Author Manuscripts novel, less harmful approaches to the optical poration of phospholipid membranes and injection of hydrophilic substances through membranes are in strong demand.Here we introduce a novel strategy for ac...

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