A tiny microscope weighing just five grams could give neuroscientists an unprecedented view of how individual brain cells control behavior while animals move naturally. Researchers at the University of Colorado Anschutz Medical Campus and the University of Colorado Boulder have developed a head-mounted device that can both record neural activity and selectively activate individual neurons during movement. The technology could help scientists investigate how brain circuits generate behavior and how those circuits become disrupted in conditions such as Alzheimer’s disease, Parkinson’s disease and epilepsy.

The device, called Opto2P-FCM, combines two powerful techniques that have traditionally been difficult to use together in a freely moving animal. Two-photon microscopy provides detailed images of living brain tissue at cellular resolution, while optogenetics uses light-sensitive proteins to control selected neurons. By integrating both capabilities into a miniature instrument, the researchers can observe specific cells as they become active and then stimulate chosen neurons to test how they influence the surrounding network.

“These miniature microscopes have been increasingly used to study the neural basis of behavior in freely moving animals,” said Emily Gibson, PhD, associate professor of biomedical engineering at CU Anschutz and the study’s senior author. “This new microscope allows deeper penetration and higher resolution images in the brain. Importantly, it can also excite select neurons using optogenetics.”

For decades, conventional two-photon microscopes have been regarded as the gold standard for imaging neurons in living brains. These systems use infrared laser light to produce high-resolution images deep within tissue, allowing researchers to track calcium signals and other indicators of neural activity. However, conventional microscopes are generally large, stationary instruments. Animals must often remain immobilized beneath the objective, making it difficult to study brain activity during walking, exploration, social interaction or other natural behaviors.

Miniature microscopes have helped overcome that limitation by moving the imaging system onto the animal’s head. Yet reducing the size and weight of the equipment has often required compromises. Some compact systems provide lower-resolution images, while others can record neural activity but cannot stimulate precisely selected cells. The Colorado team designed Opto2P-FCM to address both problems through a dual-path optical architecture that separates imaging from stimulation.

In the imaging pathway, infrared light is directed through the brain to generate two-photon signals from fluorescent markers inside neurons. These markers can report changes in calcium concentration, which occur when neurons fire. The resulting signals are collected to create detailed images of neural activity at the level of individual cells. A separate optical pathway delivers patterned light for optogenetic stimulation, allowing researchers to activate specific neurons without disrupting the imaging beam or overwhelming the detectors.

This separation is technically important because imaging and stimulation place different demands on an optical system. High-resolution imaging requires precise focusing, efficient light collection and minimal optical distortion. Optogenetic activation, by contrast, requires intense, accurately positioned light capable of reaching the light-sensitive proteins expressed by selected neurons. Designing both functions into a device small enough to be carried by an animal required careful control of the alignment, geometry and weight of every optical component.

“This microscope is a game changer,” said Juliet Gopinath, PhD, professor of electrical, computer and energy engineering and physics at CU Boulder and a study co-author. “Being able to demonstrate a state-of-the-art instrument for both read-out and photo-stimulation of neurons is amazing.” The research team included engineers, physicists and neuroscientists who worked together to solve problems involving miniature lenses, mechanical tolerances, optical alignment and three-dimensional fabrication.

The device weighs approximately five grams, but its small size made construction unusually demanding. Mo Zohrabi, PhD, a senior research scientist at CU Boulder and co-first author, said the team initially thought such an instrument might be impossible to build because of the tight tolerances required by the optics and available 3D-printing technology. Gregory Futia, PhD, a senior research associate at CU Anschutz and co-first author, said that every component had to be designed and accounted for with extreme precision. Even slight misalignment could reduce image quality or prevent the stimulation beam from reaching the intended cells.

The researchers believe the platform could transform experiments designed to distinguish correlation from causation in the brain. Recording a neuron’s activity can show that it is associated with a behavior, but it does not prove that the cell helps produce that behavior. With optogenetic stimulation, scientists can activate a selected population and observe whether movement, decision-making or other actions change. At the same time, the microscope can record how neighboring neurons respond, providing a view of how local circuits coordinate activity.

The current Opto2P-FCM system is a prototype, and the researchers are working on future versions that could be smaller, lighter and faster. They also hope to expand the field of view so that more neurons can be monitored at once. Such improvements could make it possible to track larger networks over longer periods while animals engage in increasingly complex behaviors. By combining cellular-resolution observation with targeted manipulation in a freely moving subject, the technology may help reveal how healthy neural circuits operate and how neurological disease changes the communication between them.

Subject of Research: Miniature two-photon microscopy, optogenetics, neural circuits and brain activity during natural movement

Article Title: New Miniature Microscope Allows Scientists to Watch and Control Brain Cells During Natural Movement

News Publication Date: Aug. 11, 2026

Web References: University of Colorado Anschutz Medical Campus; University of Colorado Boulder; Optica study

References: Optica, “New Miniature Microscope Allows Scientists to Watch and Control Brain Cells During Natural Movement,” article publication date: Aug. 7, 2026

Keywords

Miniature microscope, two-photon microscopy, optogenetics, neuroscience, brain imaging, neural circuits, freely moving animals, biomedical engineering, applied physics, neurological disease, brain research

Lipid nanoparticles (LNPs) have become one of the most important delivery technologies in modern medicine, helping transport messenger RNA into cells for vaccines, protein replacement therapies and experimental treatments. Yet a formulation that performs well in mice can behave very differently in humans. This species gap makes nonhuman primate studies an important step in drug development, but conventional methods for comparing multiple nanoparticles often require euthanasia and extensive tissue collection. A new study reports a way to measure the functional activity of several LNPs in the same animal using only a small blood sample.

Published in Nature Biotechnology, the work introduces a non-invasive nanoparticle barcoding platform called snapCodes. The method is designed to determine which LNP formulation successfully delivers its mRNA cargo and prompts cells to produce the encoded protein. Rather than relying on tissue harvesting, the researchers identify delivery events through DNA barcodes that can be recovered from serum and analyzed by sequencing. The approach could allow scientists to compare many candidate nanoparticles in a single nonhuman primate while reducing both animal use and the logistical burden of downstream analysis.

The central challenge addressed by the study is that nanoparticle delivery is not adequately described by measuring where an LNP travels. An LNP may reach an organ or circulate in the bloodstream without releasing its mRNA in a form that cells can translate. The new system instead records functional mRNA delivery. Each nanoparticle is associated with a distinctive DNA sequence, and the mRNA cargo is engineered to encode a fusion protein containing nanoluciferase and a SNAP-tag. Nanoluciferase is a compact enzyme that produces light in the presence of its substrate, while the SNAP-tag is a protein module capable of forming a covalent bond with specific chemical groups.

For the barcode to become a permanent molecular record of delivery, the researchers modified the DNA tags with benzylguanine. When a cell receives an mRNA molecule encoding the nanoluciferase–SNAP-tag fusion, the resulting protein can react with a benzylguanine-bearing snapCode. This creates a stable DNA–protein complex. The complexes are then exported from cells into the circulation, where they can be isolated from a small serum sample. Sequencing the recovered DNA reveals which barcoded LNPs produced the fusion protein and therefore achieved functional mRNA delivery.

The design turns transient protein expression into a measurable signal that can be collected without sacrificing the animal. This is particularly valuable in studies involving nonhuman primates, where tissue-based nanoparticle profiling can require euthanasia and can limit the number of formulations tested in each subject. A blood-based assay also makes it possible to monitor delivery over time, potentially showing how the activity of a formulation changes after dosing. The study used just 30 microliters of serum, a volume small enough to support repeated sampling and longitudinal measurements.

Before comparing nanoparticle performance, the researchers validated the molecular components of the system, including the activity of the snapCode chemistry and the ability of the fusion protein to participate in the intended covalent reaction. These steps were necessary to establish that the barcode signal reflected genuine expression of the delivered mRNA rather than nonspecific interactions. Once the platform had been characterized, the team used it to evaluate multiple chemically distinct LNPs in living animals.

The investigators intravenously administered six snapCoded LNP formulations to mice and nonhuman primates. Each formulation carried its own molecular identity, allowing all six candidates to be assessed in parallel. Serum collected after administration was analyzed for the DNA–fusion protein complexes, and sequencing was used to quantify the relative delivery activity associated with each barcode. By testing the same barcoded set across species, the researchers could directly examine whether patterns observed in mice were reproduced in nonhuman primates.

Such cross-species comparisons are crucial because LNP composition strongly influences biological behavior. Changes in ionizable lipids, helper lipids, cholesterol, polyethylene glycol-lipid components or particle structure can affect stability, organ distribution, cellular uptake and endosomal escape. These properties may differ substantially between rodents and primates because of differences in blood proteins, immune responses, tissue physiology and cellular trafficking. A method that measures expression from several formulations in the same animal may therefore reveal species-specific delivery patterns more efficiently than traditional one-formulation-per-animal experiments.

The snapCode strategy does not replace every form of nanoparticle analysis. It reports successful expression of a particular engineered mRNA and depends on the recovery and sequencing of the associated molecular complexes. It does not, by itself, provide a complete map of tissue distribution, long-term safety or therapeutic efficacy. Nevertheless, it adds a functional layer to LNP evaluation: scientists can ask not only where particles go, but which particles actually release mRNA that cells translate. In early development, that distinction can help prioritize candidates before more resource-intensive studies begin.

By combining multiplexed dosing with low-volume serum sampling, the researchers aim to make nonhuman primate testing more informative while using fewer animals. The platform could be adapted for screening delivery systems designed for different organs or therapeutic proteins, provided that the encoded reporter and barcode chemistry remain compatible with the intended experiment. As mRNA medicines expand beyond vaccines into gene editing, immunotherapy and protein replacement, tools that connect nanoparticle chemistry to real biological output may become increasingly important. Non-invasive barcoding offers a way to track those differences in living subjects and could help narrow the path from promising LNP design to clinically relevant drug candidate.

Subject of Research: A non-invasive method for comparing functional mRNA delivery by multiple lipid nanoparticles in mice and nonhuman primates using serum-based DNA barcodes.

Article Title: Non-invasive nanoparticle barcoding in nonhuman primates

Article References: Jang, B., Zenhausern, R., Lian, L. et al. Non-invasive nanoparticle barcoding in nonhuman primates. Nat Biotechnol (2026). https://doi.org/10.1038/s41587-026-03262-6

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41587-026-03262-6

Keywords: lipid nanoparticles, mRNA delivery, nanoparticle barcoding, snapCodes, SNAP-tag, nanoluciferase, nonhuman primates, serum sequencing, drug delivery, RNA therapeutics