Haemodialysis is life sustaining but expensive, provides limited removal of uraemic solutes, is associated with poor patient quality of life and has a large carbon footprint. Innovative dialysis technologies such as portable, wearable and implantable artificial kidney systems are being developed with the aim of addressing these issues and improving patient care. An important challenge for these technologies is the need for continuous regeneration of a small volume of dialysate. Dialysate recycling systems based on sorbents have great potential for such regeneration. Novel dialysis membranes composed of polymeric or inorganic materials are being developed to improve the removal of a broad range of uraemic toxins, with low levels of membrane fouling compared with currently available synthetic membranes. To achieve more complete therapy and provide important biological functions, these novel membranes could be combined with bioartificial kidneys, which consist of artificial membranes combined with kidney cells. Implementation of these systems will require robust cell sourcing; cell culture facilities annexed to dialysis centres; large-scale, low-cost production; and quality control measures. These challenges are not trivial, and global initiatives involving all relevant stakeholders, including academics, industrialists, medical professionals and patients with kidney disease, are required to achieve important technological breakthroughs.

The particles of heterogeneous catalysts differ greatly in size, morphology, and most importantly, in activity. Studying these catalyst particles in batch typically results in ensemble averages, without any information at the level of individual catalyst particles. To date, the study of individual catalyst particles has been rewarding but is still rather slow and often cumbersome¹. Furthermore, these valuable in-depth studies at the single particle level lack statistical relevance. Here, we report the development of a droplet microreactor for high-throughput fluorescence-based measurements of the acidities of individual particles in fluid catalytic cracking (FCC) equilibrium catalysts (ECAT). This method combines systematic screening of single catalyst particles with statistical relevance. An oligomerization reaction of 4-methoxystyrene, catalyzed by the Brønsted acid sites inside the zeolite domains of the ECAT particles, was performed on-chip at 95 °C. The fluorescence signal generated by the reaction products inside the ECAT particles was detected near the outlet of the microreactor. The high-throughput acidity screening platform was capable of detecting ~1000 catalyst particles at a rate of 1 catalyst particle every 2.4 s. The number of detected catalyst particles was representative of the overall catalyst particle population with a confidence level of 95%. The measured fluorescence intensities showed a clear acidity distribution among the catalyst particles, with the majority (96.1%) showing acidity levels belonging to old, deactivated catalyst particles and a minority (3.9%) exhibiting high acidity levels. The latter are potentially of high interest, as they reveal interesting new physicochemical properties indicating why the particles were still highly acidic and reactive.

The single particle hydrogenation of methylene blue over a Pd/SiO ₂ catalyst was monitored in a droplet-microreactor, using red/green/blue optical microscopy.

The removal of protein-bound uremic toxins (PBUTs) from the blood of kidney failure patients with conventional dialysis is limited. However, as their harmful effects and association with morbidity and mortality in dialysis patients are increasingly recognized, PBUTs have become important therapeutic targets. In this review, PBUT removal with current state-of-the-art dialysis technologies and future perspectives are discussed. Strategies to enhance PBUT clearance include methods that interfere with PBUT–albumin binding, such as chemical displacers, high ionic strength, pH changes, or electromagnetic fields, thereby increasing the free fraction available for dialysis. While these methods have shown promise in vitro, and some also in vivo, long-term safety data are lacking. PBUT removal can also be increased by adsorption, either directly via hemoperfusion, or indirectly, e.g., via sorbents incorporated in a mixed-matrix membrane or dissolved in the dialysate. In the kidney, PBUTs are secreted in the proximal tubules; hence, a cell-based bioartificial kidney (BAK) that secretes PBUTs is proposed as an add-on to current dialysis. Yet both PBUT adsorption strategies and, in particular, BAKs face considerable challenges in upscaling and mass production at acceptable costs. In conclusion, many novel technologies are under development, all requiring further (pre)clinical testing and upscaling before these strategies can be applied in the clinic.