Overcoming the blood–brain barrier (BBB) remains a significant hurdle in effective drug delivery to the brain. While the BBB serves as a crucial protective barrier, it poses challenges in delivering therapeutic agents to their intended targets within the brain parenchyma. To enhance drug delivery for the treatment of neurological diseases, several delivery technologies to circumvent the BBB have been developed in the last few years. Among them, nanoparticles (NPs) are one of the most versatile and promising tools. Here, we summarize the characteristics of NPs that facilitate BBB penetration, including their size, shape, chemical composition, surface charge, and importantly, their conjugation with various biological or synthetic molecules such as glucose, transferrin, insulin, polyethylene glycol, peptides, and aptamers. Additionally, we discuss the coating of NPs with surfactants. A comprehensive overview of the common in vitro and in vivo models of the BBB for NP penetration studies is also provided. The discussion extends to discussing BBB impairment under pathological conditions and leveraging BBB alterations under pathological conditions to enhance drug delivery. Emphasizing the need for future studies to uncover the inherent therapeutic properties of NPs, the review advocates for their role beyond delivery systems and calls for efforts translating NPs to the clinic as therapeutics. Overall, NPs stand out as a highly promising therapeutic strategy for precise BBB targeting and drug delivery in neurological disorders.

A novel microfluidic device for high-throughput particle separation using a viscoelastic fluid, which enables the rapid detection of extremely rare malaria parasites by using PCR analysis, is proposed. Our device consists of two segments: the 1st stage for sheathless pre-alignment and the 2nd stage for separation based on size-dependent viscoelasticity-induced lateral migration. The use of a high-aspect ratio channel and a viscoelastic polymer solution with low viscosity enables high-throughput processing. The device performance was first optimized using synthetic particles. A mixture of 2 and 10 μm particles was focused at the center plane in the 1st stage. The smaller particles, serving as surrogates for malaria parasites, were subsequently separated in the 2nd stage with a recovery rate of ∼96% at 400 μl min⁻¹. Finally, separation of the malaria parasites from the white blood cells was performed. At 400 μl min⁻¹, almost all white blood cells were removed and the malaria parasites were separated with a ∼94% recovery rate and ∼99% purity. Although the initial concentration of the malaria parasites was too low to be detected by PCR analysis, WBC depletion and buffer removal increased the parasite concentration sufficiently such that PCR detection was possible.

A novel microfluidic device which consists of two stages for particle focusing and separation using a viscoelastic fluid has been developed. A circular capillary tube was used for three-dimensional particle pre-alignment before the separation process, which was inserted in a polydimethylsiloxane microchannel. Particles with diameters of 5 and 10 μm were focused at the centerline in the capillary tube, and the location of particles was initialized at the first bifurcation. Then, 5 and 10 μm particles were successfully separated in the expansion region based on size-dependent lateral migration, with ∼99% separation efficiency. The proposed device was further applied to separation of MCF-7 cells from leukocytes. Based on the cell size distribution, an approximate size cutoff for separation was determined to be 16 μm. At 200 μl/min, 94% of MCF-7 cells were separated with the purity of ∼97%. According to the trypan blue exclusion assay, high viability (∼90%) could be achieved for the separated MCF-7 cells. The use of a commercially available capillary tube enables the device to be highly versatile in dealing with particles in a wide size range by using capillary tubes with different inner diameters.

Carbon quantum dots (CQDs) are a class of nanomaterials known for their remarkable photostability, chemical inertness and biocompatibility. Changing their size, structure, and surface chemistry enable the tuning of their luminescence property, which gives them tremendous potential for various applications. CQDs synthesis typically involves long tedious processes, requiring multiple steps and harsh reaction conditions. Here, a new reliable, economical, and ultra‐rapid one‐step fabrication method is introduced to obtain CQDs with well‐defined and reproducible photoluminescence properties via a simple heat treatment. These solid‐state CQDs are homogenous in size and are ready to use without the need for further purification. The size of the fabricated CQDs and their corresponding peak fluorescence intensity are confirmed to be tunable by simple adjustment of the heat treatment conditions. Coupled with their selective fluorescence quenching by metal ions, the clinical potential of CQDs is demonstrated for biosensing applications by designing a new nano‐biosensor to assess the quality of stored blood units through hemolysis quantification without disrupting storage conditions. This may pave the way for a new standard in blood bank inventory management.

A low-cost portable device was developed with a coin vibration motor for quantification of red blood cell aggregation.

White blood cells (WBCs) are the only cellular constituent containing genetic materials, and, hence, are candidate biomarkers for a host of diseases. However, conventional methods for WBC separation tend to have low sample purity and separation efficiency, which will have adverse implications on downstream polymerase chain reaction (PCR) analyses. In this study, we introduce a two-stage microfluidic device which harnesses the elastic property of a non-Newtonian fluid for size-based separation of WBCs from whole blood. The device displayed high resolution and efficiency in separating polystyrene particles and blood cells of different sizes up to a flow rate of 150 μL/min in polyvinylpyrrolidone solutions. We performed a separate parametric study to evaluate the effects of the fluid elasticity and flow rate on the separation performance. The hematocrit of the blood sample was varied from 0.01% to 20% to investigate the effect of increased intercellular interactions on the separation efficiency. An optimized set of parameters was selected to demonstrate the applicability of the device to the separation of WBCs from diluted whole blood, with excellent efficiency and purity (>90%). This microfluidic device will be especially useful for blood fractionation applications requiring high sample purity and speedy processing. Additionally, the apparent flow-rate insensitivity of the separation allows for its potential use in point-of-care applications.