On the injectability of free-standing magnetic nanofilms

Abstract

Free-standing films with sub-micrometric thickness, composed of soft polymers and functional nanostructures are promising candidates for many potential applications in the biomedical field, such as reduced port abdominal surgery. In this work, freely suspended poly(L-lactic acid) nanofilms with controlled morphology embedding superparamagnetic iron oxide nanoparticles were fabricated by spin-coating deposition. The mechanical properties of magnetic nanofilms were investigated by Strain-Induced Elastic Buckling Instability for Mechanical Measurements (SIEBIMM) test. Our results show that these freely suspended nanocomposite nanofilms are highly flexible and deformable, with Young's moduli of few GPa. Since they can be handled in liquid with syringes, a quantitative description of the nanofilms behavior during the manipulation with clinically applicable needles has been also provided. These magnetic nanofilms, remotely controllable by external electromagnetic fields, have potential applications in minimally invasive surgery as injectable nanopatches on inner organs wall. Graphical abstract ᅟ.

Free‐Standing 2D Nanoassemblies

“…Sandwiching nanoparticles between polymer layers through either a directly spin-coating deposition or layer-by-layer self-assembly could also be used to construct free-standing 2D nanoassemblies. [47,50,[136][137][138][139][140] The obtained free-standing films typically consisted of long and entangled polymer chains, with random packed nanoparticles in a low volume fraction. This approach in general does not subject to the limitation on the type of building blocks.…”

“…Gold nanospheres and nanorods, silver nanorods, iron oxide nanoparticles, and quantum dots have been successfully embedded into free-standing polymer matrixes. [50,83,136,[141][142][143] The resulting nanoassemblies may be chosen to be responsive to external stimuli. [143][144] In one demonstration, a free-standing and flexible magnetic nanofilm with superparamagnetic iron oxide nanoparticles embedded in poly (L-latic acid) was "injectable" with syringes and were able to be remotely manipulated by electromagnetic fields.…”

“…[143][144] In one demonstration, a free-standing and flexible magnetic nanofilm with superparamagnetic iron oxide nanoparticles embedded in poly (L-latic acid) was "injectable" with syringes and were able to be remotely manipulated by electromagnetic fields. [50] Figure 8a illustrates a classical layer-by-layer self-assembled multilayered nanocomposite membrane by sandwiching a central layer of gold nanoparticles with multiple polymer bilayers on both sides. The membrance contains oppositely charged poly(allylamine hydrochloride) (PAH) and (polystyrene sulfonate) (PSS), with a general formula of (PAH/PSS) n PAH/nanoparticle/(PAH/PSS) n /PA, [48,66,136,[141][142]145] in which n represents the number of polymer bilayers with each bilayer having a thickness of ~2.7 nm.…”

“…Ultrathin polymer films will form regular buckling patterns under mechanical stress due to "strain-induced" micromechanical instabilities. [50,142] Such elastic buckling instability is meaningful for measuring their mechanical properties, and have been extended to test the compressive or stress-strain elastic modulus of different free-standing nanoparticle assemblies. [119,[139][140]151] In general, the buckling instability test was achieved by applying compression or stress over the particle films which were deposited on a soft, elastic substrate such as PDMS elastomers.…”

“…Young's modulus of free-standing membranes from 1-2 GPa to 4 GPa with increasing concentration of the particles (Figure 9a). [50] Note that the concentration of the particles in the free-standing membranes has an optimum value, over which the film becomes brittle. [139] An optimum concentration was found to be 0.2 % in free-standing membrane embedded with silica polyhedral oligomeric silsesquioxane, below which the mechanical strength was proportional to the particle concentration.…”