Think of a neuron as a house with its own generator in the basement. In Alzheimer's, Parkinson's and Huntington's, that generator falters early: oxygen handling goes wrong, worn-out mitochondria stop being cleared, and the cell starts running on an energy deficit long before anyone notices a symptom. The obvious response is to send repairs to the basement. The hard part has never been the idea; it has been the delivery. A drug swallowed in the morning must survive the gut, cross the blood-brain barrier, get inside a neuron, then cross two more membranes to reach the mitochondrion itself. Most of it never arrives.
A review published on 19 August 2026 in Advanced Healthcare Materials, led by Dnyandev G. Gadhave with co-authors including Keshav Raj Paudel of the NICM Health Research Institute at Western Sydney University, sets out to audit the vehicles built for that last leg. It is a synthesis of existing literature rather than a new experiment, and it is open access, so families can read it. Its catalogue is a tour of a small industry: fat-based carriers such as liposomes and solid lipid particles, generally built at 80 to 200 nanometres across; polymeric particles including PLGA, micelles, dendrimers and DQAsomes, spanning roughly 20 to 250 nanometres; and metallic and inorganic particles such as cerium oxide, gold nanoclusters and quantum dots. Many are decorated with triphenylphosphonium, a positively charged chemical tag that is drawn toward the negative interior of a working mitochondrion, which the authors note can push a particle's surface charge to around plus 20 to plus 40 millivolts.
The review's honest centre is in its first pages, where the authors state that no clinically approved mitochondria-targeting treatment exists to date. The animal work is genuinely encouraging and the authors say so: in rodent models of Alzheimer's, Parkinson's and Huntington's, targeted carriers reduced reactive oxygen species, restored mitochondrial membrane potential and improved cognitive and motor performance. That is a sentence about mice and rats, and it should be read as one. What has reached people so far are small molecules that act on mitochondria without any nanoparticle to carry them. The review's own trial table lists Anavex 2-73, a sigma-1 receptor modulator, as having completed Phase 2 and 3 testing with 300 people in Alzheimer's, and flags that it is not a nanoparticle-delivered therapy; it lists EPI-743 (vatiquinone) as a Phase 2 and 3 programme terminated with 68 participants in mitochondrial disease with refractory epilepsy, and notes metformin's weak penetration into the brain.
There is a longer memory here that the field keeps returning to. In 2010, Barry Snow and colleagues published in Movement Disorders a double-blind, placebo-controlled trial of MitoQ, a mitochondria-targeted antioxidant taken by mouth, in 128 people with newly diagnosed, untreated Parkinson's disease, followed for twelve months against two doses and placebo. The result was flat: no difference on any measure of progression, including the Unified Parkinson's Disease Rating Scale. MitoQ used the same triphenylphosphonium trick that the new generation of nanoparticles relies on. The reason the current review spends so much space on biodistribution, immune clearance, manufacturing reproducibility, long-term safety and patient heterogeneity is that a good targeting chemistry is not the same thing as a drug that arrives, in enough quantity, in the right brain, in a person who is seventy-eight and has three other diagnoses.
Aging itself is one of the barriers the authors catalogue, which is the part most relevant to anyone reading this from a kitchen table rather than a lab bench. An older blood-brain barrier is not the barrier these particles were optimised against in young laboratory animals, and an older immune system clears foreign material differently. The review also points to artificial intelligence as a route to designing and screening carriers faster, which is a statement about where the field hopes to go, not about anything available in a clinic. So the practical reading is narrow and worth being plain about: nothing in this paper changes what any person with a diagnosis can be offered today, and no mitochondria-targeted nanoparticle is sitting in a pharmacy waiting for a prescription.
What the review does offer is a map of where the real obstacles sit, which is useful because it tells you what to listen for in the next few years of announcements. A particle that works in a mouse is a chemistry result. A particle that shows, in people, that it reaches the brain in measurable amounts without provoking an immune response is the result that would matter. The review suggests that the field knows the difference. Families should insist on it too.