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

New mRNA jabs could change how vaccines chase viruses.

The apparent benefits of updated COVID-19 vaccines in older adults may be influenced by more than the vaccines themselves, according to a study examining the “healthy vaccinee effect,” a form of bias that can complicate observational research. Published in Nature Communications, the work by Lyth, Spreco, Hinkula and colleagues focuses on how differences between people who receive vaccination and those who do not can alter estimates of vaccine effectiveness, particularly in elderly populations whose health status can change rapidly.

Updated COVID-19 vaccines are designed to improve protection against circulating SARS-CoV-2 variants, especially protection against severe disease, hospitalization and death. Because randomized clinical trials are not usually repeated for every reformulated vaccine and every emerging variant, researchers frequently rely on real-world health data. These studies compare outcomes among vaccinated and unvaccinated people, but the two groups may differ in important ways before vaccination occurs. Such differences can produce an apparent vaccine benefit—or obscure a real one—even when the analysis carefully accounts for age and medical conditions.

The healthy vaccinee effect arises when people who are vaccinated are temporarily healthier, more active or better connected to healthcare services than those who remain unvaccinated. Individuals may postpone vaccination during an acute illness, after hospitalization or when they are approaching the end of life. At the same time, people who attend vaccination appointments may be more likely to receive preventive care, follow medical advice and seek treatment early. These characteristics are not necessarily caused by vaccination, but they can lower the vaccinated group’s risk of death or hospitalization during the period used for analysis.

This issue is particularly important in older populations. Elderly people often have multiple chronic conditions, fluctuating functional status and frequent contact with hospitals or long-term care facilities. A person may be eligible for a vaccine campaign but unable to receive the dose because of an acute health problem. If that person later dies or is hospitalized, conventional analyses may attribute the worse outcome to the absence of vaccination, even though the underlying illness was already present. Conversely, if researchers compare groups immediately after vaccination without accounting for this selection process, the vaccine may appear more protective than it truly is.

The study evaluates how this bias affects assessments of updated COVID-19 vaccines in elderly populations. Its central scientific contribution is to treat vaccination not simply as an exposure, but as an event embedded in a changing health trajectory. The health of older adults is not static: frailty, infection, recent hospitalization and access to care can all influence whether and when vaccination occurs. By examining these time-dependent factors, the researchers draw attention to the difference between a vaccine’s biological effect and the characteristics of the people who are able to receive it at a particular moment.

In epidemiological terms, the healthy vaccinee effect is a form of confounding and selection bias. Confounding occurs when another factor is associated with both vaccination and the outcome being measured. Selection bias occurs when inclusion in the vaccinated or comparison group depends on health-related circumstances. Timing can intensify both problems. If follow-up begins on the day of vaccination for one group but at an arbitrary date for another, the groups may not have equivalent baseline risks. Researchers therefore need to define an appropriate index date, align observation periods and account for recent illness, healthcare use and changes in eligibility.

The challenge is not merely statistical. A vaccine can provide strong protection against severe COVID-19 while producing a smaller or more variable effect against infection, depending on the variant, time since vaccination, prior immunity and the outcome being studied. If an observational analysis reports a lower mortality rate among vaccinated people, that result may reflect a combination of direct vaccine protection and the healthier profile of vaccine recipients. Separating these components requires careful design, including adjustment for measured risk factors and, where possible, comparison strategies that mimic a randomized trial.

The findings have practical implications for interpreting public-health evidence. Estimates of updated vaccine effectiveness should not be read in isolation from the population being studied, the timing of vaccination and the definition of the unvaccinated comparison group. Researchers may need to conduct sensitivity analyses, use negative-control outcomes, examine short intervals after vaccination and account for healthcare-seeking behavior. Analyses that compare people with similar recent health histories, or that use methods designed for time-varying confounding, can help determine whether an observed association is likely to represent a genuine vaccine effect.

The study does not undermine the value of COVID-19 vaccination for older adults; rather, it highlights the methodological care required to measure that value accurately. For clinicians, policymakers and the public, the message is that real-world vaccine evidence is strongest when biological protection is evaluated alongside the circumstances that determine who gets vaccinated and when. As SARS-CoV-2 continues to evolve and vaccine formulations are periodically updated, understanding the healthy vaccinee effect will remain essential for distinguishing the protection delivered by immunization from the protection that appears because healthier people are more likely to receive it.

Subject of Research: Healthy vaccinee effect and the evaluation of updated COVID-19 vaccines in elderly populations.

Article Title: Healthy vaccinee effect in the evaluation of updated COVID-19 vaccines in elderly populations.

Article References:

Lyth, J., Spreco, A., Hinkula, J. et al. Healthy vaccinee effect in the evaluation of updated COVID-19 vaccines in elderly populations. Nat Commun 17, 8014 (2026). https://doi.org/10.1038/s41467-026-76312-x

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41467-026-76312-x

Keywords: COVID-19 vaccines, updated vaccines, SARS-CoV-2, elderly populations, healthy vaccinee effect, vaccine effectiveness, epidemiology, observational studies, confounding, public health.

In a widely expected move, a committee organized by the Food and Drug Administration (FDA) has voted to endorse removing restrictions on the manufacture of peptides for human use. Thursday's panel meeting saw a sharply divided group recommend lifting limits on four peptides; votes on three additional peptides are scheduled for today. The move comes despite a continuing lack of evidence regarding their safety and effectiveness.

The move had been telegraphed months earlier as peptide enthusiast and Health and Human Services Secretary Robert F. Kennedy Jr. took steps to ensure this outcome.

Like proteins, peptides are composed of amino acids that are chemically linked into a chain. Peptides differ merely by length; they're often 10–20 amino acids long, in contrast to proteins, which can be hundreds or thousands. Some of them, such as insulin, are specifically made by targeted processing of a protein into shorter fragments, and the resulting peptide interacts with receptors that have evolved to send signals to cells based on its levels.

Read full article

Comments

© Getty | Michael M. Santiago

COVID mRNA vaccines are harmful bioweapons and part of a depopulation agenda. Studies reveal negative vaccine efficacy after six months and significant spikes in heart-related diseases post-vaccination. The mainstream media is culpable for omitting these findings.