What Are Lipid Nanoparticles for Drug Delivery? 

LNPs are spherical lipid-based carriers, typically formulated with ionizable lipids, that enable the encapsulation and delivery of a range of therapeutic payloads. They are widely used for in vivo applications requiring the intracellular delivery of a therapeutic payload —small molecular drugs, proteins, and nucleic acids, such as mRNA, siRNA, oligonucleotides— after systemic administration.

The ‘core-shell’ structure of LNPs (typical diameter, 50–150 nm) is central to their ability to protect and transport various payloads¹. The ‘core’ is formed through electrostatic and hydrophobic interactions between the chosen payload and specially selected ionizable cationic lipids (ICLs)¹. The ‘shell’ is comprised of ‘helper’ lipids, cholesterol, and PEGylated lipids, and it encapsulates the core and imparts biocompatibility¹. Once administered, LNPs circulate through the bloodstream, with the PEG- and phospholipids reducing clearance by the immune system, until they encounter target cells. Following cell binding and endocytosis of the LNPs, the cell forms endosomes around the internalized LNPs. In the acidic environment of these endosomes, ICLs become protonated, and this destabilizes the negatively-charged endosomal membrane¹. A minor fraction of the LNPs subsequently escapes the endosome and releases their payload into the cytoplasm. By adjusting the lipid composition of the core and shell layers of LNPs it is possible to optimize their pharmacokinetics, uptake by cells, and overall therapeutic efficacy¹. However, the efficiencies of payload encapsulation, endosomal escape, and transfection—the functional outcome of nucleic acid payload delivery—largely depend on the choice of ICLs².

Why LNPs Are Used — and Where They Break Down 

The many applications of LNPs are made possible through their advantageous characteristics, which include:

• a high encapsulation efficiency,
• high stability,
• low toxicity,
• enhanced efficacy of on-target therapeutic action.

Importantly, LNPs also offer significant protection for labile payloads such as mRNA³. Additionally, the clinical safety features of LNPs have been thoroughly investigated⁴. As of 2024, three nucleic acid-based medicines that use LNPs for delivery have been approved by the FDA¹. In one especially successful application, the BNT162b2 mRNA vaccine ‘Comirnaty’ against COVID-19 saw widespread adoption⁵.

These important advantages notwithstanding, LNPs may be unsuitable for some next-generation biopharma programs. To date, most therapeutic applications involving LNPs have relied on their passive biodistribution. In many cases, payload delivery is dependent on ApoE (a naturally occurring protein found in blood serum that plays a key role in lipid transport and metabolism) adsorption to the LNP shell and subsequent hepatic uptake via ApoE binding to low-density lipoprotein receptors on liver cells. Typically, systemically administered LNPs have limited access to other tissues, and exhibit poor cell-type specificity. Hence, a key challenge is to facilitate delivery to tissues beyond the liver. This progression is essential to improve therapeutic effects at extrahepatic targets, reduce potential side-effects, and to expand the range of diseases that can be targeted using this delivery platform.

The Real Delivery Problem: Targeting, Internalization, Biodistribution

The often-asked questions around the limitations of LNP delivery platforms that still need answering include:

• How do we improve delivery to tissues beyond the liver?
• How do we achieve cell-type specificity, not just tissue exposure?
• How do we improve receptor-mediated internalization, and minimize nonspecific uptake?
• How do we tune circulation time without compromising delivery efficiency?
• How do we address manufacturing and scalability concerns?

Notably, the outstanding problems to be addressed are predominantly targeting problems that cannot be solved through lipid chemistry alone. Hence, the focus of current research is on the development of functionalized LNP systems that facilitate payload delivery to specific cells, tissues, and organs following intravenous administration or direct injection^1,6.

One promising approach for the targeted delivery of therapeutic LNPs involves the incorporation of specific molecules (e.g., antibodies, antibody fragments, peptides, or small molecules) that bind cell-specific receptors on target cells¹. To accomplish this, functionalized auxiliary components can be incorporated into the shell of LNPs to reduce liver accumulation, enable cell-type specificity, and improve the efficiency of cellular uptake^1,7.

Figure 1 – Schematic showing surface ligand attachment.

Representative surface modification strategies for LNP targeting have already been summarized elsewhere^1,7. For example, antibodies against tumor cell antigens have been coupled to LNPs to effectively target tumor cells in vivo, thereby improving the efficacy of tumor treatments^1,8. In other research, for treatment of fibrosis, a CD5-conjugated LNP containing modified mRNA has been demonstrated to bind CD5 receptors expressed on mouse T-cells, mediating the subsequent endocytosis of mRNA-LNPs and generation of transient chimeric antigen receptor (CAR) T-cells^1,9. Similarly, an anti-CD4 antibody has been developed to target CD4+ helper T-cells¹⁰. For the targeting of lung tissues, an anti-PECAM-1 antibody can be coupled to the LNP shell¹¹. Analogously, an anti-VCAM-1 antibody can be coupled to the LNP shell to target brain (or spleen) tissues¹¹. A modular platform —the Anchored Secondary scFv Enabling Targeting (ASSET) system— has also been developed to facilitate the addition of specific targeting antibodies to LNPs¹².

Why VHHs Are a Better Targeting Ligand for LNP Systems

Isolated variable antigen binding domains derived from the heavy-chain-only antibodies of camelids are known as VHH¹³. The small size, stability, and binding precision of these single-domain antibodies make them well suited for challenging applications (where conventional antibodies may fail). As shown in the table below, VHH offer several structural and functional advantages compared with other commonly used targeting ligands.

Main advantages of VHHs over other targeting ligands

Figure 2 – Schematic showing ligand attachment to LNPs.

Critically, VHHs enable receptor-mediated internalization without destabilizing particle size, disrupting formulation, or impacting manufacturability. As mentioned above, manufacturing and scalability are key constraints during the development of new delivery platforms. Hence, VHHs can help facilitate the development of scalable LNP platforms.

A schematic showing extrahepatic compared to cell-type specific delivery of VHH-targeted LNPs is presented in figure 3.

Figure 3 – Non-targeted LNP vs. VHH-targeted LNP.

Practical Use Cases Driving Next-Generation LNP Design

Oncology

To develop LNPs that bind prostate-specific membrane antigen (PSMA) for the targeted delivery of an RNA-based therapeutic into prostate cancer tumors, an anti-PSMA VHH was coupled to LNPs¹⁴. After systemic administration into a mouse model, LNP accumulation in prostate cancer tumors was reportedly increased.

Immune cell targeting

To facilitate selective uptake by endogenous T-cells, LNPs encapsulating minicircle DNA (mcDNA) encoding a CAR construct (and mRNA for a transposase) were modified with a VHH antibody against CD7, a targeting ligand predominantly expressed on T cells¹⁵. While the anti-CD7-LNP conjugate was able to transfect preactivated T-cells, an LNP system targeting CD3 and CD7 delivered its cargo to T-cells in vitro and in vivo without additional stimulation. A single intravenous dose generated stable CAR-T cells exhibiting antigen-specific cytotoxicity and cytokine release.

CNS-adjacent delivery

To target intracranial tumors in a mouse glioma model, LNPs loaded with a hydrophobically modified cisplatin (a cytotoxic chemotherapy agent used to treat several types of cancer) prodrug were conjugated with a VHH against fibrinogen¹⁶. After their intravenous injection, the modified LNPs were observed to bind fibrinogen protein within the bloodstream. The resulting ‘protein corona’ (a layer of proteins, in this case fibrinogen, that form on the surface of nanoparticles) was demonstrated to specifically interact with LRP-1, a receptor expressed on the blood brain barrier (BBB). This interaction facilitated efficient trans-BBB transport and promoted effective brain targeting.

Platform scalability

Interchangeable VHH targeting of LNPs may be achieved through post-insertion of VHH clicked to a PEG-lipid¹⁴. First, azide residues must be added to the C-terminus of a VHH via Sortase A-mediated conjugation: an LPXTG sequence in the VHH is necessary for recognition by Sortase A. VHH-azide is obtained through replacement of the terminal Glycine residue with Gly3-azide, added to the reaction. The Gly3-azide is then reacted with DBCO-conjugated-PEG-lipids via click chemistry. These DSPE-PEG-VHHs can then be inserted onto the surface of LNPs.

Isogenica’s role:

We can help your biotech team design, screen, and optimize candidate VHH antibodies for use in LNP targeting. Our synthetic, humanized VHH antibodies offer a flexible solution to a range of therapeutic applications. Isogenica’s VHHs can be used to target a range of payloads to their biological target. Moreover, our VHH antibody design process is backed by modular technologies and a peer-level partnership model.

If you are interested in exploring ways to facilitate tissue-specific and/or cell-specific targeting of loaded LNPs for therapeutic applications, we encourage you to book a discovery call with our team. We can discuss how our VHH platform can expand the range of therapeutic applications for LNPs and increase their on-target efficacy.

References

1. Liu Y, Huang Y, He G, et al. (2024). Development of mRNA Lipid Nanoparticles: Targeting and Therapeutic Aspects. International Journal of Molecular Sciences, 25(18):10166. https://doi.org/10.3390/ijms251810166.
2. Xu S, Hu Z, Song, F et al. (2025). Lipid nanoparticles: Composition, formulation, and application. Molecular Therapy Methods & Clinical Development, 33(2): 101463. https://doi.org/10.1016/j.omtm.2025.101463.
3. Swetha K, Kotla NG, Tunki L, et al. (2023). Recent Advances in the Lipid Nanoparticle-Mediated Delivery of mRNA Vaccines. Vaccines, 11(3): 658. https://doi.org/10.3390/vaccines11030658.
4. Wang J, Ding Y, Chong K, et al. (2024). Recent Advances in Lipid Nanoparticles and Their Safety Concerns for mRNA Delivery. Vaccines, 12(10): 1148. https://doi.org/10.3390/vaccines12101148.
5. Polack FP, Thomas SJ, Kitchin N, et al. (2020). Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine. The New England Journal of Medicine, 383 (27): 2603-2615. https://doi.org/10.1056/NEJMoa2034577.
6. Cullis PR, Felgner PL (2024). The 60-year evolution of lipid nanoparticles for nucleic acid delivery. Nature Reviews Drug Discovery, 23: 709–722. https://doi.org/10.1038/s41573-024-00977-6.
7. Moulahoum H, Ghorbanizamani F, Zihnioglu F, Timur S (2021). Surface Biomodification of Liposomes and Polymersomes for Efficient Targeted Drug Delivery. Bioconjugate Chemistry, 32(8): 1491-1502. https://doi.org/10.1021/acs.bioconjchem.1c00285.
8. Nabih NW, Hassan HAFM, Preis E, et al (2025). Antibody-functionalized lipid nanocarriers for RNA-based cancer gene therapy: advances and challenges in targeted delivery. Nanoscale Advances, 7(19): 5905-5931. https://doi.org/10.1039/d5na00323g.
9. Rurik JG, Tombácz I, Yadegari A, et al. (2022). CAR T cells produced in vivo to treat cardiac injury. Science, 375(6576): 91-96. https://doi.org/10.1126/science.abm0594.
10. Tombácz I, Laczkó D, Shahnawaz H, et al. (2021). Highly efficient CD4+ T cell targeting and genetic recombination using engineered CD4+ cell-homing mRNA-LNPs. Molecular Therapy, 29(11): 3293-3304. https://doi.org/10.1016/j.ymthe.2021.06.004.
11. Marzolini N, Brysgel TV, Rahman RJ, et al. (2026). Targeting DNA-LNPs to Endothelial Cells Improves Expression Magnitude, Duration, and Specificity. Advanced Science: e15480. https://doi.org/10.1002/advs.202515480
12. Veiga N, Goldsmith M, Granot Y, et al. (2018). Cell specific delivery of modified mRNA expressing therapeutic proteins to leukocytes. Nature Communications, 9: 4493. https://doi.org/10.1038/s41467-018-06936-1.
13. Jovčevska I, Muyldermans S. (2020). The Therapeutic Potential of Nanobodies. BioDrugs, 34(1): 11-26. https://doi.org/10.1007/s40259-019-00392-z.
14. Martinez de Castilla PE, Verdi V, de Voogt W, et al. (2025). Nanobody-Decorated Lipid Nanoparticles for Enhanced mRNA Delivery to Tumors In Vivo. Advanced Healthcare Materials, 14(24): e2500605. https://doi.org/10.1002/adhm.202500605.
15. Bimbo JF, van Diest E, Murphy DE, et al. (2025). T cell-specific non-viral DNA delivery and in vivo CAR-T generation using targeted lipid nanoparticles. Journal for ImmunoTherapy of Cancer, 13(7): e011759. https://doi.org/10.1136/jitc-2025-011759.
16. Zhang Y, Qin S, Song T, et al (2025). A novel dual-targeting strategy of nanobody-driven protein corona modulation for glioma therapy. Acta Pharmaceutica Sinica B, 15(9): 4917-4931. https://doi.org/10.1016/j.apsb.2025.07.014.