Polysarcosine-Coated liposomes attenuating immune response induction and prolonging blood circulation

Investigating the stability of RNA-lipid nanoparticles in biological fluids: Unveiling its crucial role for understanding LNP performance

Lipid nanoparticles (LNPs) are the most established and clinically advanced platform for RNA delivery. While significant efforts have been made to improve RNA delivery efficiency for improved protein production, the interplay between physiological stability, target specificity, and therapeutic efficacy of RNA-LNPs remains largely unexplored. This review highlights the crucial, yet often overlooked, impact of in vivo stability or instability of RNA-LNPs in contact with biological fluids on delivery performance. We discuss the various factors, including lipid composition, particle surface properties and interactions with proteins in physiological conditions, and provide an overview of the current methods for assessing RNA-LNP stability in biological fluids, such as dynamic laser light scattering, liquid chromatography, and fluorescent and radiolabeled techniques. In the final part, we propose strategies for enhancing stability, with a focus on shielding lipids. Therefore, this work highlights the importance of investigating and understanding the balance between stability and instability of LNPs in the biological context to achieve a more meaningful correlation between formulation properties and in vivo performance.

Emerging strategies against accelerated blood clearance phenomenon of nanocarrier drug delivery systems

Nanocarrier drug delivery systems (NDDS) have gained momentum in the field of anticancer or nucleic acid drug delivery due to their capacity to aggrandize the targeting efficacy and therapeutic outcomes of encapsulated drugs. A disadvantage of NDDS is that repeated administrations often encounter an obstacle known as the "accelerated blood clearance (ABC) phenomenon". This phenomenon results in the rapid clearance of the secondary dose from the bloodstream and markedly augmented liver accumulation, which substantially undermines the accurate delivery of drugs and the therapeutic effect of NDDS. Nevertheless, the underlying mechanism of this phenomenon has not been elucidated and there is currently no effective method for its eradication. In light of the above, the aim of this review is to provide a comprehensive summary of the underlying mechanism and potential countermeasures of the ABC phenomenon, with a view to rejuvenating both the slow-release property and expectation of NDDS in the clinic. In this paper, we innovatively introduce the pharmacokinetic mechanism of ABC phenomenon to further elucidate its occurrence mechanism after discussing its immunological mechanism, which provides a new direction for expanding the mechanistic study of ABC phenomenon. Whereafter, we conducted a critical conclusion of potential strategies for the suppression or prevention of the ABC phenomenon in terms of the physical and structural properties, PEG-lipid derivatives, dosage regimen and encapsulated substances of nanoformulations, particularly covering some novel high-performance nanomaterials and mixed modification methods. Alternatively, we innovatively propose a promising strategy of applying the characteristics of ABC phenomenon, as the significantly elevated hepatic accumulation and activated CYP3A1 profile associated with the ABC phenomenon are proved to be conducive to enhancing the efficacy of NDDS in the treatment of hepatocellular carcinoma. Collectively, this review is instructive for surmounting or wielding the ABC phenomenon and advancing the clinical applications and translations of NDDS.

Regulating Immune Responses Induced by PEGylated Messenger RNA-Lipid Nanoparticle Vaccine

Messenger RNA (mRNA)-based therapeutics have shown remarkable progress in the treatment and prevention of diseases. Lipid nanoparticles (LNPs) have shown great successes in delivering mRNAs. After an mRNA-LNP vaccine enters a cell via an endosome, mRNA is translated into an antigen, which can activate adaptive immunity. mRNAs can bind to various pattern recognition receptors (PRRs), including toll-like receptors (TLRs), and increase the production of inflammatory cytokines. This review summarizes mechanisms of innate immunity induced by mRNAs. Polyethylene glycol (PEG) has been employed as a component of the mRNA-LNP vaccine. PEGylated nanoparticles display enhanced stability by preventing aggregation of particles. However, PEGylation can cause adverse reactions, including blood clearance (ABC) of nanoparticles via complement activation and anaphylaxis. Mechanisms of PEG-induced ABC phenomenon and anaphylaxis are presented and discussed. There have been studies aimed at reducing immune responses associated with PEG to make safe and effective vaccines. Effects of modifying or replacing PEG in reducing immune responses associated with PEGylated nanoparticles are also discussed. Modifying mRNA can induce immune tolerance, which can prevent hypersensitivity reactions induced by PEGylated mRNA-LNP vaccines. Current progress of immune tolerance induction in association with mRNA-LNP is also summarized. This review might be helpful for developing safe and effective PEGylated mRNA-LNP vaccines.

Recent progress on polySarcosine as an alternative to PEGylation: Synthesis and biomedical applications

Biotherapeutic PEGylation to prolong action of medications has gained popularity over the last decades. Various hydrophilic natural polymers have been developed to tackle the drawbacks of PEGylation, such as its accelerated blood clearance and non-biodegradability. Polypeptoides, such as polysarcosine (pSar), have been explored as hydrophilic substitutes for PEG. pSar has PEG-like physicochemical characteristics such as water solubility and no reported cytotoxicity and immunogenicity. This review discusses pSar derivatives, synthesis, characterization approaches, biomedical applications, in addition to the challenges and future perspectives of pSar based biomaterials as an alternative to PEG.