Polyethylene glycol (PEG) is one of the widely used functional polymer materials in modern biomedicine. From PEGylation modification of proteins and peptide drugs to antibody–drug conjugates (ADCs), nucleic acid delivery, and nanomedicine design, PEG has become an important material tool in drug development due to its excellent hydrophilicity, biocompatibility, and well-established chemical modification chemistry. PEGylation can improve the water solubility and stability of drug molecules, extend their circulation time in vivo, and regulate interactions between drugs and biological environments. However, as drug development has gradually entered an era of molecular-level design, a long-standing question has attracted increasing attention: Can the molecular structure of PEG really be described by only one average molecular weight? From “Average Molecular Weight” to “Defined Structure”: PEG Is Undergoing a Transformation Traditional PEG is typically prepared through polymerization processes. Therefore, the final product is not composed of a single molecular structure, but rather a mixture of PEG molecules with different chain lengths. For example, a product labeled as PEG 5000 does not mean that every PEG molecule has a molecular weight of 5000 Da. Instead, it represents the average molecular weight of the entire sample, which actually contains PEG molecules within a certain molecular weight distribution range. This polydispersity does not limit PEG’s large-scale applications. In many traditional applications, PEG is mainly required to provide functions such as hydrophilic protection and improved stability, and polydisperse PEG systems are sufficient to meet these needs. However, when PEG becomes involved in more complex drug design, the situation begins to change. In drug conjugation systems, PEG chain length can influence linker structures and spatial conformations. In nanodelivery systems, PEG chain length affects surface properties of materials. In functional material development, differences among PEG components may also influence the final performance of the materials. At this stage, researchers are no longer concerned only with: “Is PEG present?” Instead, they are asking: What exactly is the structure of PEG? Does every PEG molecule possess a consistent composition? Monodisperse PEG has emerged in response to these demands. Unlike traditional polydisperse PEG, monodisperse PEG possesses defined chain length, molecular weight, and terminal functional groups, transforming PEG from a material defined by average properties into a molecular module that can be designed and assembled. Monodisperse PEG: Why Is It Called a “Molecular Standard Part”? In industrial manufacturing, the value of standard parts lies in their well-defined specifications, which make the relationship between structure and performance easier to investigate and enable modular assembly. Monodisperse PEG shares similar characteristics. Traditional PEG is mainly regarded as a func...

J Nanobiotechnology. 2024 Nov 16;22(1):716. doi: 10.1186/s12951-024-02993-5. IL-7 promotes mRNA vaccine-induced long-term immunity Abstract Messenger RNA (mRNA) vaccines are a key technology in combating existing and emerging infectious diseases. However, improving the immunogenicity and durability of mRNA vaccines remains a challenge. To elicit optimal immune responses, integrating antigen-encoded mRNA and immunostimulatory adjuvants into a single formulation is a promising approach to enhancing the efficacy of mRNA vaccines. Here, we report an adjuvant strategy to enhance the efficacy of mRNA vaccines by co-loading mRNA encoding the antigen (rabies virus glycoprotein, RABV-G) and mRNA encoding IL-7 into lipid nanoparticles, achieving co-delivery to the same antigen-presenting cells. A single immunization with G&IL-7 mRNA vaccine elicited robust humoral immune responses in mice and conferred complete protection against RABV challenge. Notably, the high levels of neutralizing antibody induced by the G&IL-7 mRNA vaccine were maintained for at least 6 months, providing mice with long-term significant and complete protection against RABV. Additionally, IL-7 also enhanced antibody responses against the SARS-CoV-2. These data demonstrate that IL-7 is a potent mRNA vaccine adjuvant that can provide the required immune stimulation in various mRNA vaccine formulations. Keywords: Adjuvant; IL-7; Lipid nanoparticles; Long-term protection; mRNA vaccine. Ionizable cationic lipid (SM102) (Cat. No. 06040008800), PEG-lipid (Cat. No. 06020112402), cholesterol (Cat. No. 06040010300), and phosphatidylcholine (DSPC) (Cat. No. 06030001100) were purchased from SINOPEG Biotechnology Co., Ltd.  (Xiamen, China).

ACS Appl Mater Interfaces. 2025 Jan 29;17(4):6095-6102. doi: 10.1021/acsami.4c20214. Epub 2025 Jan 14. Hydrogen Bonding-Driven Adaptive Coacervates as Protocells Abstract Coacervation based on liquid-liquid phase separation (LLPS) has been widely used for the preparation of artificial protocells and to mimic the dynamic organization of membrane-free organelles. Most complex synthetic coacervates are formed through electrostatic interactions but cannot withstand high ionic strength conditions (>0.1 M). Alternative components and driving forces are highly desired for the formation of natural organelles to overcome the drawbacks of traditional coacervates. Herein, hydrogen bonding-driven adaptive coacervates are reported via the complexation of poly(ethylene glycol) (PEG) and tannic acid (TA). The LLPS behavior of these adaptive coacervates is dependent on the concentration and mass ratio of PEG and TA, which can be used to tune the size of coacervates ranging from 70 nm to 10 μm as well as the morphology of isotropic particles and hollow capsules. Coacervates are stable at high ionic concentrations up to 1 M and can serve as protocells to mimic cellular behaviors including metabolism (e.g., nutrient uptake), phagocytosis, and membrane fusion. The reported approach provides a platform for the rational design of hydrogen bonding-driven coacervates with controllable size and morphology, offering potential applications in protocell construction and therapeutic delivery. Keywords: coacervates; hydrogen bonding; poly(ethylene glycol); polyphenol; protocells. Product: 8-arm PEG-OH

Nat Biomed Eng. 2025 Aug;9(8):1320-1334. doi: 10.1038/s41551-025-01373-0. Epub 2025 Mar 28. Generation of tolerogenic antigen-presenting cells in vivo via the delivery of mRNA encoding PDL1 within lipid nanoparticles Abstract Tolerogenic antigen-presenting cells (APCs) are promising as therapeutics for suppressing T cell activation in autoimmune diseases. However, the isolation and ex vivo manipulation of autologous APCs is costly, and the process is customized for each patient. Here we show that tolerogenic APCs can be generated in vivo by delivering, via lipid nanoparticles, messenger RNA coding for the inhibitory protein programmed death ligand 1. We optimized a lipid-nanoparticle formulation to minimize its immunogenicity by reducing the molar ratio of nitrogen atoms on the ionizable lipid and the phosphate groups on the encapsulated mRNA. In mouse models of rheumatoid arthritis and ulcerative colitis, subcutaneous delivery of nanoparticles encapsulating mRNA encoding programmed death ligand 1 reduced the fraction of activated T cells, promoted the induction of regulatory T cells and effectively prevented disease progression. The method may allow for the engineering of APCs that target specific autoantigens or that integrate additional inhibitory molecules. Product: SM-102

Nat Commun. 2025 May 20;16(1):4700. doi: 10.1038/s41467-025-60040-9. Freezing induced incorporation of betaine in lipid nanoparticles enhances mRNA delivery Abstract Lipid nanoparticles (LNPs) are key non-viral carriers for mRNA vaccines and therapeutics, but the inherent instability of mRNA necessitates sub-zero storage with cryoprotectants (CPAs) to prevent freeze-induced LNP aggregation and compromised mRNA delivery. Here we show that ice formation during freezing concentrates CPAs with LNPs in the remaining liquid-a phenomenon known as freeze concentration. This creates a steep concentration gradient of CPAs across the lipid membrane that drives passive CPAs diffusion into LNPs. By leveraging this process, we developed betaine-based CPAs that both preserve the stability of LNP and enter LNP during freeze-thaw. The incorporated betaine enhances endosomal escape and boosts mRNA delivery of LNP. In female mice, betaine-loaded LNPs elicit stronger humoral and cellular immune responses, providing dose-sparing advantages. These findings highlight freeze concentration as a promising LNP formulation strategy and underscore the role of CPA as active modulators of LNP structure and function. Product: lipids for LNP

Mol Ther Nucleic Acids. 2025 Feb 12;36(2):102485. doi: 10.1016/j.omtn.2025.102485. eCollection 2025 Jun 10. Enhancing mRNA translation efficiency by introducing sequence optimized AU-rich elements in 3' UTR via HuR anchorage Abstract mRNA technology holds immense promise as an innovative therapeutic approach with applications spanning infectious disease vaccines, cancer immunotherapy, protein replacement, and gene editing. However, practical use of mRNA has been hindered by challenges such as low cellular stability and transient protein expression. For addressing these, we propose a novel strategy to optimize mRNA sequences, particularly in the untranslated region, by inserting adenylate/uridylate-rich elements (AU-rich elements) to enhance stability and protein expression. Our investigation revealed that integrating AU-rich elements between the open reading frame (ORF) and the 3' untranslated region (3' UTR) significantly enhances RNA stability compared with other insertion sites. We identified cytoplasmic Human antigen R (HuR) as an essential RNA-binding protein responsible for promoting mRNA stability and translation, confirmed through HuR knockdown experiments and pull-down assays between AU-rich elements and HuR. Through rational design, we optimized the sequence of natural AU-rich elements and identified the essential "AUUUA" element, which, with certain repeats, can increase protein expression up to 5-fold. To demonstrate the universality of AU-rich element sequences in enhancing mRNA translation, we switched the coding proteins from luciferase to EGFP, mCherry, and ovalbumin (OVA), finding that both natural and engineered AU-rich element sequences amplify the expression of these proteins. In conclusion, leveraging the functionalities of RNA-binding proteins and the natural regulation of RNA stability in the untranslated region represents a novel strategy to enhance mRNA pharmacokinetics in the cytoplasm, expanding the potential applications of mRNA in therapeutic drugs. Keywords: 3′ UTR rational design; AU-rich elements; HuR; MT: Oligonucleotides: Therapies and Applications; RNA stability; RNA-binding proteins; mRNA vaccines; sequence optimization. Product: lipids for LNP

ACS Nano. 2025 Dec 16;19(49):41803-41815. doi: 10.1021/acsnano.5c15619. Epub 2025 Dec 4. Engineering of Metal-Organic Networks as Band-Aid for the Repair of Osteoporotic Bone Fractures Abstract The treatment of osteoporotic bone fractures remains a critical challenge due to the dysregulated bone remodeling microenvironment characterized by excessive osteoclastic resorption, impaired osteogenic differentiation, angiogenic dysfunction, and chronic inflammation. In this work, we engineered a metal-organic network as a bone repair "band-aid" by integrating poly(ethylene glycol)-alendronate (PEG-ALN) conjugates with bioactive epigallocatechin gallate (EGCG), zinc, and calcium ions into a multifunctional scaffold. This design leverages the synergistic effects of anti-inflammatory and antioxidant properties of EGCG with the balancing osteogenic and osteoclastic functions of ALN, zinc, and calcium ions. In vitro studies demonstrated that the band-aid significantly enhanced the proliferation and differentiation of osteoblasts while promoting endothelial cell migration and tubule formation, indicating the robust osteogenic and angiogenic potential. In vivo evaluations in an osteoporotic bone fracture model revealed accelerated bone regeneration and improved microvascularization while maintaining a balanced immune response to prevent chronic inflammation. Mechanistically, the band-aid modulated macrophage polarization toward a pro-regenerative M2 phenotype and suppressed excessive osteoclast activity, thereby restoring the osteogenic-osteoclastic equilibrium. This study not only provides a therapeutic implant for osteoporotic bone repair but also proposes a strategy for designing immunomodulatory scaffolds that target the pathological bone microenvironment. Keywords: bone repair; metal−organic networks; osteoporosis; polyphenols; tissue engineering. Product: 8-arm-PEG-NHS

J Phys Chem Lett. 2025 Apr 17;16(15):3874-3878. doi: 10.1021/acs.jpclett.5c00825. Epub 2025 Apr 10. Double-Helix Duality: Rods Bow, Toroids Wow in the Nuclease Arena Abstract Utilizing polyion complexation, the formation of rod-like DNA condensates is driven by the intrinsic rigidity of supramolecular plasmid DNA. Upon interaction with polycationic block copolymers of poly(ethylene glycol)-polylysine (PEG-PLys), these macromolecules undergo a regular self-folding process, during which double-stranded DNA (dsDNA) transitions into single-stranded DNA (ssDNA) at the kinked junctions. Our investigations, employing transmission electron microscopy (TEM), unprecedentedly reveal the absence of a PEG coating at these critical junctions, rendering them susceptible to nuclease degradation. This finding underscores the critical necessity for comprehensive PEG encapsulation in the engineering of robust gene delivery constructs. In stark contrast to the anisotropic rod-like condensates, our novel isotropic toroidal DNA condensates, characterized by comprehensive PEG shielding and a self-spooling mechanism that preserves dsDNA integrity, exhibit a marked enhancement in enzymatic stability (nearly 30-fold greater). Their favorable condensation process also confers superior transcriptional potential, positioning these toroidal condensates as promising platforms for the next generation of gene delivery systems. Product: mPEG-NH2