Novel approaches for drug delivery systems in nanomedicine: effects of particle design and shape

Applications of functionalized nanoparticles and research aims in nanomedicine. The surface of nanoparticles can be modified with various molecules such as fluorescence dyes or biological ligands (e.g., antibodies). Furthermore, drug molecules can be encapsulated or adsorbed to nanoparticles. Adding parts or all of these functionalities turns the nanoparticle into a sensor, an imaging aid for diagnosis, or a directed carrier, respectively.

Schematic representation of silica‐lipid hybrid (SLH) microcapsule formation and scanning electron micrograph of the microcapsules. Celecoxib‐containing SLH microcapsules were prepared via a two‐step process including the homogenization and the following spray‐drying of the silica‐stabilized emulsions. (Reprinted with permission from Ref 78. Copyright 2009)

Colored SEM images of alveolar macrophages (brown) interacting with polystyrene (PS) particles (purple). (a) The cell body (brown) can be seen at the end of an elliptical disk and the membrane has progressed down the length of the particle. (b) A cell has attached to the flat side of an elliptical disk and has spread on the particle. (c) A spherical particle has attached to the top of a cell and the membrane has progressed over approximately half the particle. Scale bar: (a) 10 µm, (b) and (c) 5 µm. (Reprinted with permission from Ref 25. Copyright 2007 NCBI)

Illustration of vessel with bifurcation. Certain nonspherical particles are reported to accumulate in close proximity to the walls and therefore can exit main vasculature more easily. This is depicted through the gradual transition of the lightness from the center towards the lateral regions. Lighter regions contain more nonspherical objects. The smaller vessel is supplied from the lateral region of the main vessel and consequently lighter.

Membranes used for the formation of cylindrical and nonspherical particles formed via molds, or template‐assisted techniques. (a) SEM image of a cross section of an alumina membrane (internal diameter = 210 nm) with an extremely high aspect ratio (>1000) of uniform nanopores. (Reprinted with permission from Ref 38. Copyright 2006 ACS Publications) (b) SEM image showing the (top) surface of the alumina membrane with a perfect hexagonal arrangement of the nanopores. (Reprinted with permission from Ref 38. Copyright 2006 ACS Publications) (c) SEM image of a track‐etched polycarbonate membrane (PC) with a pore diameter of 1 µm. (Reprinted with permission from Ref 36. Copyright 1997 RSC Publishing) (d) Fluorescence micrograph of poly(lactic‐co‐glycolic acid) (PLGA) particles created through the hydrogel template approach representing some symbols of a computer keyboard. (Reprinted with permission from Ref 44. Copyright 2010 Springer) (e) SEM images of 3 µm arrow‐shaped poly(ethylene glycol) (PEG) particles fabricated by the particles replication in nonwetting templates (PRINT) technique. (Reprinted with permission from Ref 45. Copyright 2005 ACS Publications) (f) SEM image of a polymeric particle that was made in a microfluidic device polymerized by light. The inset shows the transparency mask feature that was used to make the corresponding particle. (Reprinted with permission from Ref 46. Copyright 2006 Nature Publishing Group) (g) SEM image of artificial red blood cells which were formed using the layer‐by‐layer (LbL) technique. Inset shows close up image. (Reprinted with permission from Ref 33. Copyright 2009 NCBI)

Sketch of the possible approaches to increase the drug loading capacity of nanoparticles which is offered by porous and nonspherical particles in comparison to spherical particles. Different biological responses and subsequent application schemes are the consequence.

Selection of nonspherical particles fabricated using different strategies: SEM images of nonspherical polystyrene (PS) particles created by a stretching technique in the form of (a) elliptical disks and (b) UFOs. (Reprinted with permission from Ref 25. Copyright 2006 NCBI) (c) Fluorescence microscopy shows an isolated filamentous block copolymer associate (filomicelle). (Reprinted with permission from Ref 4. Copyright 2007 Nature Publishing Group) (d) Schematic of the filomicelle structure: yellow/green indicates hydrophobic polymer, orange/blue is hydrophilic. (Reprinted with permission from Ref 4. Copyright 2007 Nature Publishing Group)