Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND), is a progressive neurodegenerative disease that affects both upper and lower motor neurons, which results in loss of muscle control and eventual paralysis [1]. Currently, there are as yet unresolved challenges regarding efficient drug delivery into the central nervous system (CNS). These challenges can be attributed to multiple factors including the presence of the blood-brain barrier (BBB), blood-spinal cord barrier (BSCB), as well as the inherent characteristics of the drugs themselves (e.g. low solubility, insufficient bioavailability/bio-stability, 'off-target' effects) etc. As a result, conventional drug delivery systems may not facilitate adequate dosage of the required drugs for functional recovery in ALS patients. Nanotechnology-based strategies, however, employ engineered nanostructures that show great potential in delivering single or combined therapeutic agents to overcome the biological barriers, enhance interaction with targeted sites, improve drug bioavailability/bio-stability and achieve real-time tracking while minimizing the systemic side-effects. This review provides a concise discussion of recent advances in nanotechnology-based strategies in relation to combating specific pathophysiology relevant to ALS disease progression and investigates the future scope of using nanotechnology to develop innovative treatments for ALS patients.

There is considerable interest in developing diagnostic nanotools for early detection and delivery of various therapeutic agents for treatment of neurodegenerative diseases. However, a key challenge remains in the selection of suitable surfaces to overcome the nano–bio interface issue, namely that many nanoparticle surfaces demonstrate instability when administered into biological environments and show substantial cytotoxicity to the central nervous system. In this study, we fabricated an evaluation platform for bio–nano surface selection based on the combination of upconversion nanoparticles (UCNPs), cultured neural cells and zebra fish, and systemically demonstrated how it can evaluate the suitability of nanoparticle surfaces for applications in the central nervous system. Firstly, we fabricated highly lanthanide-doped UCNPs, which generate the strongest tissue penetrable emission at 800 nm. We then functionalized these UCNPs with four popular surfaces for evaluation. Next, we systematically evaluated the spectral emission properties, biophysical stability, cytotoxicity and cell uptake capability of these surface-functionalized UCNPs in biological solutions or with cultured NSC-34 cells. Through these studies, PEG-COOH proved to be the superior surface modification. Accordingly, we further confirmed the bioavailability of unmodified and surface modified UCNPs in the spinal cord of living zebrafish. As predicted, PEG-UCNPs displayed excellent dispersal and uptake into spinal motor neurons in living zebrafish. Collectively, this study developed a versatile upconversion platform for systematic evaluation of nanoparticle surfaces, which can provide valuable information via systemic surface evaluation in vitro and in vivo for future construction of multifunctional nanosystems for theranostic applications in neurodegenerative diseases.

Microfluidic gradient platforms, especially flow‐based types, have emerged as promising tools in 3D tumor spheroid research, as they enable precise control of concentration gradients with rapid establishment and sustained long‐term stability. However, current flow‐based gradient chips are often constrained by limited spheroid culture capacity, restricting their utility for large‐scale drug evaluation. Here, we developed a microfluidic gradient platform embedded with high‐density microwell arrays (MEG platform), which enables high‐throughput and physiologically relevant spheroid culture across multiple chambers on a single chip. The total number of spheroids is flexibly tuned by adjusting the microwell array sheet size, and both monoculture and co‐culture spheroids maintain continuous and stable growth with well‐defined morphology. The platform demonstrates stable gradient delivery under dynamic perfusion. It is further applied to assess drug responses in monoculture and co‐culture spheroids, with co‐cultures exhibiting enhanced resistance compared with monocultures. The high‐throughput MEG platform should facilitate the use of tumor spheroid models in large‐scale drug testing and tumor‐stromal interaction studies.

Tumor spheroids, the most widely used model of 3D cell culture, have emerged as a viable platform for assessing drug responses. However, high‐throughput validation of novel drugs using tumor spheroids remains hindered by the challenges in generating large‐scale, homogeneous, and functionally relevant spheroids. Here, a flow‐focusing droplet microfluidic platform is developed for high‐throughput generation of uniform tumor spheroids, producing over 50 000 droplets within 5 min, with each microdroplet serving as an individual bioreactor for spheroid formation. The initial size of the tumor spheroids is tuned based on cell concentration and water‐to‐oil flow rate ratio during microdroplet generation. After being released from the microdroplets, the 3D tumor spheroids continue growing, reaching diameters exceeding 300 µm. The growth and functional characteristics of the spheroids are examined both in a liquid environment and in a 3D collagen matrix. Moreover, these tumor spheroids enable assessment of the therapeutic efficacy of siRNA‐based nanomedicine that demonstrates enhanced performance compared to free siRNA treatments. This platform offers a robust and scalable approach for evaluating novel nanomedicines, providing valuable insights into their therapeutic potential and underlying mechanisms of action.

The central nervous system (CNS) is protected by the blood-brain barrier (BBB), which acts as a physical barrier to regulate and/or prevent the uptake of endogenous metabolites and xenobiotics. However, the BBB also prevents most non-lipophilic drugs from reaching the CNS following systematic administration. Therefore, there is considerable interest in identifying drug carriers that can maintain the biostability of therapeutic molecules and target their transport across the BBB. In this regard, upconversion nanoparticles (UCNPs) have become popular as a nanoparticle-based solution to this problem, with the additional benefit that they display excellent properties for in vivo visualization. The majority of studies to date have explored basic spherical UCNPs for drug delivery applications. However, the biophysical properties of UCNPs, their cell uptake and BBB transport have not been fully explored. In this study, we described a one-pot seed-mediated approach to precisely control longitudinal growth to produce bright UCNPs with various aspect ratios. We have systematically evaluated the effects of the physical aspect ratios and PEGylation of UCNPs on cellular uptake in different cell lines and an in vivo zebrafish model. We found that PEGylated the original UCNPs can enhance their biostability and cell uptake capacity. We identify an optimal aspect ratio for UCNP uptake into several different types of cultured cells, finding that this is generally in the ratio of 2 (length/width). This data provides a crucial clue for further optimization of UCNPs as a drug carrier to deliver therapeutic agents into the CNS.