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

Cancer researchers have reported a new strategy that combines bacterial tumor targeting, nutrient deprivation and immune stimulation in a single therapeutic design. The approach uses an engineered conjugate built from L-asparaginase and flagellin, linked to a system that directs the treatment toward calreticulin-bearing cancer cells. In experiments involving Salmonella-mediated tumor therapy, the conjugate enhanced antitumor activity compared with bacterial treatment alone, according to a study published in Cell Death Discovery.

The work addresses a long-standing challenge in cancer therapy: how to make powerful treatments concentrate inside tumors while limiting damage to healthy tissues. Attenuated strains of Salmonella have attracted interest because they can preferentially accumulate in the abnormal environment of solid tumors. Tumors often contain regions with poor oxygen levels, disorganized blood vessels and local immune suppression, conditions that can support bacterial growth. Once inside these sites, therapeutic Salmonella can act as a biological delivery platform and stimulate immune responses against malignant cells.

The researchers focused on calreticulin, a protein normally found inside the endoplasmic reticulum, where it helps regulate calcium storage and protein folding. Under cellular stress, including stress caused by chemotherapy, radiation or other anticancer treatments, calreticulin can move to the outer surface of a cancer cell. There, it functions as an “eat-me” signal, alerting immune cells that the damaged cell should be engulfed. Because surface-exposed calreticulin is associated with immunogenic forms of cell death, it provides a potential molecular address for directing therapeutic agents toward stressed tumor cells.

The experimental construct combines this targeting concept with L-asparaginase, an enzyme already used in clinical oncology, especially in the treatment of acute lymphoblastic leukemia. L-asparaginase breaks down circulating L-asparagine into aspartic acid and ammonia. Some cancer cells, particularly those with limited capacity to synthesize their own asparagine, depend heavily on the amino acid supplied through the bloodstream. Depleting extracellular asparagine can therefore interrupt protein production, trigger metabolic stress and promote cancer-cell death. The enzyme’s effectiveness, however, can be limited by immune reactions, pharmacological instability and toxicity, making targeted delivery an important goal.

The second component, flagellin, is the structural protein that forms the filament of bacterial flagella. It is also a potent molecular signal for the innate immune system. Immune cells recognize flagellin primarily through Toll-like receptor 5, while intracellular sensing pathways can activate inflammasome components such as NLRC4. These signals can promote the release of inflammatory mediators, stimulate antigen-presenting cells and help convert an immunologically “cold” tumor into one more visible to the immune system. By incorporating flagellin into the therapeutic design, the researchers sought to make the treatment not only directly toxic to tumor cells but also capable of amplifying antitumor immunity.

The study’s central finding was that the calreticulin-targeting L-asparaginase–flagellin conjugate strengthened the antitumor effects of Salmonella-based therapy. Rather than relying on a single mechanism, the treatment brings together several forms of pressure on the tumor. Salmonella can concentrate within the tumor microenvironment, the targeting component can help associate the conjugate with calreticulin-exposing cancer cells, L-asparaginase can deprive vulnerable cells of an essential nutrient, and flagellin can activate immune surveillance. The resulting combination is designed to produce a chain reaction in which metabolic stress and immune stimulation reinforce one another.

This type of combination may be particularly valuable because tumors frequently adapt when exposed to one therapeutic pressure. A cancer cell that survives nutrient deprivation may still be eliminated if immune recognition is intensified. Likewise, an immune response that is too weak to control a tumor may become more effective when bacterial localization and enzyme-mediated damage increase the number of abnormal antigens and danger signals released by dying cells. The researchers’ findings suggest that coordinating these mechanisms can improve the performance of bacteria-assisted cancer treatment in experimental settings.

The approach also reflects a broader shift in cancer research toward programmable biological medicines. Instead of treating bacteria only as infectious threats, scientists are redesigning them as localized delivery vehicles capable of carrying enzymes, immune activators or molecular probes. The advantage is spatial: a therapeutic payload can be produced or concentrated near the tumor rather than distributed uniformly throughout the body. The challenge is equally significant. Any clinical version would need precise control over bacterial attenuation, immune activation, enzyme exposure and potential inflammation, while also demonstrating reliable performance across genetically diverse tumors.

Calreticulin targeting may provide a useful way to address some of that complexity because the protein’s appearance on the cell surface is linked to cellular stress and treatment response. However, the extent and duration of calreticulin exposure can vary between tumor types and individual patients. Future studies will need to determine which cancers are most suitable for this strategy, how calreticulin levels predict treatment response and whether the conjugate can be combined safely with established immunotherapies such as immune-checkpoint inhibitors. Researchers will also need to assess pharmacology, manufacturing consistency and the possibility of immune reactions against the bacterial or enzymatic components.

The findings position the engineered conjugate as a promising experimental platform rather than an immediately available therapy. By merging tumor-homing bacteria with a calreticulin-directed enzyme and an innate immune stimulant, the study illustrates how cancer treatments can be designed to attack malignant cells on multiple biological fronts. If the results are confirmed in further preclinical testing and eventually in carefully controlled clinical trials, this strategy could help turn Salmonella from a passive carrier into an active, multifunctional partner in cancer immunotherapy.

Subject of Research: Calreticulin-targeted L-asparaginase–flagellin conjugate used with Salmonella-mediated cancer therapy.

Article Title: Calreticulin-targeting L-asparaginase-flagellin conjugate enhances Salmonella-mediated antitumor efficacy.

Article References: Nguyen, DH., Afzal, A.R., Nguyen, P.TM. et al. Calreticulin-targeting L-asparaginase-flagellin conjugate enhances Salmonella-mediated antitumor efficacy. Cell Death Discov. (2026). https://doi.org/10.1038/s41420-026-03300-x

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41420-026-03300-x

Keywords: cancer immunotherapy, Salmonella, calreticulin, L-asparaginase, flagellin, tumor targeting, bacterial therapy, antitumor efficacy, immunogenic cell death

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