The Contribution of PEG Molecular Weights in PEGylated Emulsions to the Various Phases in the Accelerated Blood Clearance (ABC) Phenomenon in Rats

Development of Lipid Nanoparticle Formulation for the Repeated Administration of mRNA Therapeutics

During the COVID-19 pandemic, mRNA vaccines emerged as a rapid and effective solution for global immunization. The success of COVID-19 mRNA vaccines has increased interest in the use of lipid nanoparticles (LNPs) for the in vivo delivery of mRNA therapeutics. Although mRNA exhibits robust expression profiles, transient protein expression is often observed, raising uncertainty regarding the frequency of its administration. Additionally, various RNA therapeutics may necessitate repeated dosing to achieve optimal therapeutic outcomes. Nevertheless, the impact of repeated administrations of mRNA/LNP on immune responses and protein expression efficacy remains unclear. In this study, we investigated the influence of the formulation parameters, specifically ionizable lipids and polyethylene glycol (PEG) lipids, on the repeat administration of mRNA/LNP. Our findings revealed that ionizable lipids had no discernible impact on the dose-responsive efficacy of repeat administrations, whereas the lipid structure and molar ratio of PEG lipids were primary factors that affected mRNA/LNP performance. The optimization of the LNP formulation with PEG lipid confirmed the sustained dose-responsive efficacy of mRNA after repeated administrations. This study highlights the critical importance of optimizing LNP formulations for mRNA therapeutics requiring repeated administrations.

Striving for Uniformity: A Review on Advances and Challenges To Achieve Uniform Polyethylene Glycol

Poly(ethylene glycol) (PEG) is the polymer of choice in drug delivery systems due to its biocompatibility and hydrophilicity. For over 20 years, this polymer has been widely used in the drug delivery of small drugs, proteins, oligonucleotides, and liposomes, improving the stability and pharmacokinetics of many drugs. However, despite the extensive clinical experience with PEG, concerns have emerged related to its use. These include hypersensitivity, purity, and nonbiodegradability. Moreover, conventional PEG is a mixture of polymers that can complicate drug synthesis and purification leading to unwanted immunogenic reactions. Studies have shown that uniform PEGylated drugs may be more effective than conventional PEGylated drugs as they can overcome issues related to molecular heterogeneity and immunogenicity. This has led to significant research efforts to develop synthetic procedures to produce uniform PEGs (monodisperse PEGs). As a result, iterative step-by-step controlled synthesis methods have been created over time and have shown promising results. Nonetheless, these procedures have presented numerous challenges due to their iterative nature and the requirement for multiple purification steps, resulting in increased costs and time consumption. Despite these challenges, the synthetic procedures went through several improvements. This review summarizes and discusses recent advances in the synthesis of uniform PEGs and its derivatives with a focus on overall yields, scalability, and purity of the polymers. Additionally, the available characterization methods for assessing polymer monodispersity are discussed as well as uniform PEG applications, side effects, and possible alternative polymers that can overcome the drawbacks.

Immunogenicity of lipid nanoparticles and its impact on the efficacy of mRNA vaccines and therapeutics

Several studies have utilized a lipid nanoparticle delivery system to enhance the effectiveness of mRNA therapeutics and vaccines. However, these nanoparticles are recognized as foreign materials by the body and stimulate innate immunity, which in turn impacts adaptive immunity. Therefore, it is crucial to understand the specific type of innate immune response triggered by lipid nanoparticles. This article provides an overview of the immunological response in the body, explores how lipid nanoparticles activate the innate immune system, and examines the adverse effects and immunogenicity-related development pathways associated with these nanoparticles. Finally, we highlight and explore strategies for regulating the immunogenicity of lipid nanoparticles.

The interplay between PEGylated nanoparticles and blood immune system

During the last two decades, an increasing number of reports have pointed out that the immunogenicity of polyethylene glycol (PEG) may trigger accelerated blood clearance (ABC) and hypersensitivity reaction (HSR) to PEGylated nanoparticles, which could make PEG modification counterproductive. These phenomena would be detrimental to the efficacy of the load and even life-threatening to patients. Consequently, further elucidation of the interplay between PEGylated nanoparticles and the blood immune system will be beneficial to developing and applying related formulations. Many groups have worked to unveil the relevance of structural factors, dosing schedule, and other factors to the ABC phenomenon and hypersensitivity reaction. Interestingly, the results of some reports seem to be difficult to interpret or contradict with other reports. In this review, we summarize the physiological mechanisms of PEG-specific immune response. Moreover, we speculate on the potential relationship between the induction phase and the effectuation phase to explain the divergent results in published reports. In addition, the role of nanoparticle-associated factors is discussed based on the classification of the action phase. This review may help researchers to develop PEGylated nanoparticles to avoid unfavorable immune responses based on the underlying mechanism.

Progress in research and development of temozolomide brain-targeted preparations: a review

Gliomas are a heterogeneous group of brain tumours with high malignancy, for which surgical resection remains the mainstay of treatment at present. However, the overall prognosis of gliomas remains poor because of their aggressiveness and high recurrence. Temozolomide (TMZ) has anti-proliferative and cytotoxic effects and is indicated for glioblastoma multiforme and recurrent mesenchymal astrocytoma. However, TMZ is disadvantaged by low efficacy and drug resistance, and therefore it is necessary to enhance the brain drug concentration of TMZ to improve its effectiveness and reduce the toxic and adverse effects from systemic administration. There have been many nano-formulations developed for the delivery of TMZ to gliomas that overcome the limitations of TMZ penetration to tumours and increase brain targeting. In this paper, we review the research progress of TMZ nano-formulations, and also discuss challenges and opportunities in the research and development of drug delivery systems, hoping that the data and information summarised herein could provide assistance for the clinical treatment of gliomas.

Branched PEG-modification: A new strategy for nanocarriers to evade of the accelerated blood clearance phenomenon and enhance anti-tumor efficacy

PEGylation is one of the most successful technologies for reducing immunogenicity, improving the stability and circulation time of nanocarriers, and has been applied in the clinic for over three decades. However, linear PEG-modified nanocarriers have been found to induce anti-PEG IgM at the first injection, which triggers the accelerated blood clearance (ABC) phenomenon upon repeated injections. Furthermore, clinical and research evidence has revealed that anti-PEG antibodies also cause serious complement activation-related pseudoallergies (CARPA), which greatly reduce the safety of linear PEGylated nanocarriers. In this study, as an alternative to linear PEG, branched PEG was selected owing to its low antigenicity. We pioneer the use of branched PEG lipid derivatives [DSPE-mPEG_2,n (n = 2, 10, and 20 kDa)] to modify nanoemulsions (PE_2,n) and liposomes (PL_2,n). Upon characterization, PE_2,n and PL_2,n showed similar physicochemical properties to linear DSPE-mPEG₂₀₀₀-modified nanocarriers in terms of size, polydispersity index (PDI), and zeta potential. However, our pharmacokinetics study surprisingly indicated that PE_2,n and PL_2,n did not induce the ABC phenomenon after repeated injection. This may be attributed to the fact that PE_2,n and PL_2,n induced noticeably lower levels of anti-PEG IgM than linear PEG-modified nanocarriers and did not activate the complement system. Furthermore, we are the first to investigate the anti-tumor efficacy of DSPE-mPEG_2,n-modified liposomal doxorubicin (DOX). The pharmacodynamic experiments showed that DSPE-mPEG_2,n-m-modified liposomal DOX had better in vivo anti-tumor effects than linear DSPE-mPEG₂₀₀₀-modified liposomes. Therefore, we speculate that DSPE-mPEG_2,n-modified nanocarriers possess promising prospects in avoiding the ABC phenomenon, reducing CARPA, and improving the anti-tumor efficacy of encapsulated drugs.

Evasion of the accelerated blood clearance phenomenon by branched PEG lipid derivative coating of nanoemulsions

PEGylation increases the circulation time of the nanocarrier, but also triggers accelerated blood clearance (ABC) phenomenon. It is well-known that the ABC phenomenon results in shortened blood circulation and aberrant increase in liver and spleen accumulation, which greatly limits the application of PEGylated nano-preparations. For many years, researchers have been working hard to find ways to reduce or eliminate the ABC phenomenon. Previous studies have focused on PEG molecular weight and PEG alternative materials, but there has never been any research on the effect of different PEG chain types on the ABC phenomenon. Therefore, 40 kDa molecular weight of linear PEG lipid derivatives (DSPE-mPEG_40k) and branched PEG lipid derivatives (DSPE-mPEG_2,40k) were selected to modify nanoemulsions to explore the influence of distinct PEG chain types on avoiding the ABC phenomenon for the first time. We pioneer the use of linear and branched PEG lipid derivatives (DSPE-mPEG_40k and DSPE-mPEG_2,40k) to modify nanoemulsions (PE_40k and PE_2,40k). Upon characterization, PE_40k and PE_2,40k showed good physicochemical properties in the aspect of size, polydispersity index (PDI value), and zeta potential. Surprisingly, the pharmacokinetics study indicated that repeated injection of PE_40k and PE_2,40k did not trigger the ABC phenomenon. More importantly, PE_2,40k possessed a long circulation time and did not cause ABC phenomenon after repeated injection. This may be attributed to the fact that PE_2,40k induced noticeably lower anti-PEG IgM levels compared to linear PEG-modified nanocarriers and did not activate the complement system. Therefore, we speculate that DSPE-mPEG_2,40k-modified nanocarriers possess promising prospects in avoiding the ABC phenomenon, which may improve the possibility of wide application of nanoformulations.

A Critical Review of the Use of Surfactant-Coated Nanoparticles in Nanomedicine and Food Nanotechnology

Surfactants, whose existence has been recognized as early as 2800 BC, have had a long history with the development of human civilization. With the rapid development of nanotechnology in the latter half of the 20th century, breakthroughs in nanomedicine and food nanotechnology using nanoparticles have been remarkable, and new applications have been developed. The technology of surfactant-coated nanoparticles, which provides new functions to nanoparticles for use in the fields of nanomedicine and food nanotechnology, is attracting a lot of attention in the fields of basic research and industry. This review systematically describes these "surfactant-coated nanoparticles" through various sections in order: 1) surfactants, 2) surfactant-coated nanoparticles, application of surfactant-coated nanoparticles to 3) nanomedicine, and 4) food nanotechnology. Furthermore, current progress and problems of the technology using surfactant-coated nanoparticles through recent research reports have been discussed.

Chemical and physical Chitosan modification for designing enzymatic industrial biocatalysts: How to choose the best strategy?

Chitosan is one of the most abundant natural polymer worldwide, and due to its inherent characteristics, its use in industrial processes has been extensively explored. Because it is biodegradable, biocompatible, non-toxic, hydrophilic, cheap, and has good physical-chemical stability, it is seen as an excellent alternative for the replacement of synthetic materials in the search for more sustainable production methodologies. Thus being, a possible biotechnological application of Chitosan is as a direct support for enzyme immobilization. However, its applicability is quite specific, and to overcome this issue, alternative pretreatments are required, such as chemical and physical modifications to its structure, enabling its use in a wider array of applications. This review aims to present the topic in detail, by exploring and discussing methods of employment of Chitosan in enzymatic immobilization processes with various enzymes, presenting its advantages and disadvantages, as well as listing possible chemical modifications and combinations with other compounds for formulating an ideal support for this purpose. First, we will present Chitosan emphasizing its characteristics that allow its use as enzyme support. Furthermore, we will discuss possible physicochemical modifications that can be made to Chitosan, mentioning the improvements obtained in each process. These discussions will enable a comprehensive comparison between, and an informed choice of, the best technologies concerning enzyme immobilization and the application conditions of the biocatalyst.