Micro and nanocarriers Micro and nanoscale technologies Oral drug delivery Tissue models Oral administration is a pillar of the pharmaceutical industry and yet it remains challenging to administer hydrophilic therapeutics by the oral route. Smart and controlled oral drug delivery could bypass the physiological barriers that limit the oral delivery of these therapeutics. Micro-and nanoscale technologies, with an unprecedented ability to create, control, and measure micro-or nanoenvironments, have found tremendous applications in biology and medicine. In particular, significant advances have been made in using these technologies for oral drug delivery. In this review, we briefly describe biological barriers to oral drug delivery and micro and nanoscale fabrication technologies. Micro and nanoscale drug carriers fabricated using these technologies, including bioadhesives, microparticles, micropatches, and nanoparticles, are described. Other applications of micro and nanoscale technologies are discussed, including fabrication of devices and tissue engineering models to precisely control or assess oral drug delivery in vivo and in vitro, respectively. Strategies to advance translation of micro and nanotechnologies into clinical trials for oral drug delivery are mentioned. Finally, challenges and future prospects on further integration of micro and nanoscale technologies with oral drug delivery systems are highlighted.

Droplet-based microfluidic systems have been employed to manipulate discrete fluid volumes with immiscible phases. Creating the fluid droplets at microscale has led to a paradigm shift in mixing, sorting, encapsulation, sensing, and designing high throughput devices for biomedical applications. Droplet microfluidics has opened many opportunities in microparticle synthesis, molecular detection, diagnostics, drug delivery, and cell biology. In the present review, we first introduce standard methods for droplet generation (i.e., passive and active methods) and discuss the latest examples of emulsification and particle synthesis approaches enabled by microfluidic platforms. Then, the applications of droplet-based microfluidics in different biomedical applications are detailed. Finally, a general overview of the latest trends along with the perspectives and future potentials in the field are provided.

The exceptional chemical and physical properties of graphene oxide (GO) make it an attractive nanomaterial for biomedical applications, particularly in drug delivery. In this work we synthesized a novel, GO-based nanocarrier for the delivery of docetaxel (DTX), a potent hydrophobic chemotherapy drug. The GO was functionalized with transferrin (Tf)-poly(allylamine hydrochloride) (PAH), which provided targeted and specific accumulation to extracellular Tf receptors and stabilized GO in physiological solutions. Tf was conjugated to PAH via amide covalent linkages, and Tf-PAH coated the surface of DTX-loaded GO through electrostatic interactions. The morphology and structure of the resulting nanostructure, along with its surface modifications, were verified by use of Fourier transform infrared (FT-IR) and UV-vis spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM). DTX was loaded at a relatively high loading capacity of 37% and released in a pH-dependent and sustained manner under physiological conditions. The targeting efficiency and cytotoxicity of this drug delivery system were evaluated on MCF-7 breast cancer cells. Improved efficacy of targeted DTX-loaded nanocarrier was observed compared to nontargeted carrier and free DTX, especially at high drug concentrations. The Tf-PAH-functionalized GO nanocarrier is a promising candidate for targeted delivery and controlled release of DTX.

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