In Vivo Tracking of Fluorinated Polypeptide Gene Carriers by Positron Emission Tomography Imaging

Fluorinated amphiphilic Poly(β-Amino ester) nanoparticle for highly efficient and specific delivery of nucleic acids to the Lung capillary endothelium

Endothelial cell dysfunction occurs in a variety of acute and chronic pulmonary diseases including pulmonary hypertension, viral and bacterial pneumonia, bronchopulmonary dysplasia, and congenital lung diseases such as alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV). To correct endothelial dysfunction, there is a critical need for the development of nanoparticle systems that can deliver drugs and nucleic acids to endothelial cells with high efficiency and precision. While several nanoparticle delivery systems targeting endothelial cells have been recently developed, none of them are specific to lung endothelial cells without targeting other organs in the body. In the present study, we successfully solved this problem by developing non-toxic poly(β-amino) ester (PBAE) nanoparticles with specific structure design and fluorinated modification for high efficiency and specific delivery of nucleic acids to the pulmonary endothelial cells. After intravenous administration, the PBAE nanoparticles were capable of delivering non-integrating DNA plasmids to lung microvascular endothelial cells but not to other lung cell types. IVIS whole body imaging and flow cytometry demonstrated that DNA plasmid were functional in the lung endothelial cells but not in endothelial cells of other organs. Fluorination of PBAE was required for lung endothelial cell-specific targeting. Hematologic analysis and liver and kidney metabolic panels demonstrated the lack of toxicity in experimental mice. Thus, fluorinated PBAE nanoparticles can be an ideal vehicle for gene therapy targeting lung microvascular endothelium in pulmonary vascular disorders.

Synthesis of Short Peptides with Perfluoroalkyl Side Chains and Evaluation of Their Cellular Uptake Efficiency

With an increasing demand for macromolecular biotherapeutics, the issue of their poor cell-penetrating abilities requires viable and relevant solutions. Herein, we report tripeptides bearing an amino acid with a perfluoroalkyl (RF ) group adjacent to the α-carbon. RF -containing tripeptides were synthesized and evaluated for their ability to transport a conjugated hydrophilic dye (Alexa Fluor 647) into the cells. RF -containing tripeptides with the fluorophore showed high cellular uptake efficiency and none of them were cytotoxic. Interestingly, we demonstrated that the absolute configuration of perfluoroalkylated amino acids (RF -AAs) affects not only nanoparticle formation but also the cell permeability of the tripeptides. These novel RF -containing tripeptides are potentially useful as short and noncationic cell-penetrating peptides (CPPs).

Fluorous Tagged Peptides for Intracellular Delivery and Biomedical Imaging

Fluorous tagged peptides have shown promising features for biomedical applications such as drug delivery and multimodal imaging. The bioconjugation of fluoroalkyl ligands onto cargo peptides greatly enhances their proteolytic stability and membrane penetration via a proposed "fluorine effect". The tagged peptides also efficiently deliver other biomolecules such as DNA and siRNA into cells via a co-assembly strategy. The fluoroalkyl chains on peptides with antifouling properties enable efficient gene delivery in the presence of serum proteins. Besides intracellular biomolecule delivery, the amphiphilic peptides can be used to stabilized perfluorocarbon-filled microbubbles for ultrasound imaging. The fluorine nucleus on fluoroalkyls provides intrinsic probes for background-free magnetic resonance imaging. Labeling of fluorous tags with radionuclide 18 F also allows tracing the biodistribution of peptides via positron emission tomography imaging. This mini-review will discuss properties and mechanism of the fluorous tagged peptides in these applications.

Recent Progress of Rational Modified Nanocarriers for Cytosolic Protein Delivery

Therapeutic proteins garnered significant attention in the field of disease treatment. In comparison to small molecule drugs, protein therapies offer distinct advantages, including high potency, specificity, low toxicity, and reduced carcinogenicity, even at minimal concentrations. However, the full potential of protein therapy is limited by inherent challenges such as large molecular size, delicate tertiary structure, and poor membrane penetration, resulting in inefficient intracellular delivery into target cells. To address these challenges and enhance the clinical applications of protein therapies, various protein-loaded nanocarriers with tailored modifications were developed, including liposomes, exosomes, polymeric nanoparticles, and nanomotors. Despite these advancements, many of these strategies encounter significant issues such as entrapment within endosomes, leading to low therapeutic efficiency. In this review, we extensively discussed diverse strategies for the rational design of nanocarriers, aiming to overcome these limitations. Additionally, we presented a forward-looking viewpoint on the innovative generation of delivery systems specifically tailored for protein-based therapies. Our intention was to offer theoretical and technical support for the development and enhancement of nanocarriers capable of facilitating cytosolic protein delivery.

Fluorinated vectors for gene delivery

INTRODUCTION

Gene delivery vectors are a crucial determinant for gene therapeutic efficacy. Usually, it is necessary to use an excess of cationic vectors to achieve better transfection efficiency. However, it will cause severe cytotoxicity. In addition, cationic vectors are not resistant to serum, suffering from reduced transfection efficiency by forming large aggregates. Therefore, there is an urgent need to develop optimized gene delivery vectors. Recently, fluorination of vectors has been extensively applied to increase the gene delivery performance because of the unique properties of both hydrophobicity and lipophobicity, and chemical and biological inertness.

AREAS COVERED

This review will discuss the fluorophilic effects that impact gene delivery efficiency, and chemical modification approaches for fluorination. Next, recent advances and applications of fluorinated polymeric and lipidic vectors in gene therapy and gene editing are summarized.

EXPERT OPINION

Fluorinated vectors are a promising candidate for gene delivery. However, it still needs further studies to obtain pure and well-defined fluorinated polymers, guarantee the biosafety, and clarify the detailed mechanism. Apart from the improvements in gene delivery, exploiting other versatility of fluorinated vectors, such as oxygen-carrying ability, high affinity with fluorine-containing drugs, and imaging property upon introducing 19^F, will further facilitate their applications in gene therapy.

Cationic Polysaccharide Conjugates as Antibiotic Adjuvants Resensitize Multidrug-Resistant Bacteria and Prevent Resistance

In recent years, traditional antibiotic efficacy has rapidly diminished due to the advent of multidrug-resistant (MDR) bacteria, which poses severe threat to human life and globalized healthcare. Currently, the development cycle of new antibiotics cannot match the ongoing MDR infection crisis. Therefore, novel strategies are required to resensitize MDR bacteria to existing antibiotics. In this study, novel cationic polysaccharide conjugates Dextran-graft-poly(5-(1,2-dithiolan-3-yl)-N-(2-guanidinoethyl)pentanamide) (Dex-g-PSS_n ) is synthesized using disulfide exchange polymerization. Critically, bacterial membranes and efflux pumps are disrupted by a sub-inhibitory concentration of Dex-g-PSS₃₀ , which enhances rifampicin (RIF) accumulation inside bacteria and restores its efficacy. Combined Dex-g-PSS₃₀ and RIF prevents bacterial resistance in bacteria cultured over 30 generations. Furthermore, Dex-g-PSS₃₀ restores RIF effectiveness, reduces inflammatory reactions in a pneumonia-induced mouse model, and exhibits excellent in vivo biological absorption and degradation capabilities. As an antibiotic adjuvant, Dex-g-PSS₃₀ provides a novel resensitizing strategy for RIF against MDR bacteria and bacterial resistance. This Dex-g-PSS₃₀ research provides a solid platform for future MDR applications.

Designing Synthetic Polymers for Nucleic Acid Complexation and Delivery: From Polyplexes to Micelleplexes to Triggered Degradation

Gene delivery as a therapeutic tool continues to advance toward impacting human health, with several gene therapy products receiving FDA approval over the past 5 years. Despite this important progress, the safety and efficacy of gene therapy methodology requires further improvement to ensure that nucleic acid therapeutics reach the desired targets while minimizing adverse effects. Synthetic polymers offer several enticing features as nucleic acid delivery vectors due to their versatile functionalities and architectures and the ability of synthetic chemists to rapidly build large libraries of polymeric candidates equipped for DNA/RNA complexation and transport. Current synthetic designs are pursuing challenging objectives that seek to improve transfection efficiency and, at the same time, mitigate cytotoxicity. This Perspective will describe recent work in polymer-based gene complexation and delivery vectors in which cationic polyelectrolytes are modified synthetically by introduction of additional components─including hydrophobic, hydrophilic, and fluorinated units─as well as embedding of degradable linkages within the macromolecular structure. As will be seen, recent advances employing these emerging design strategies are promising with respect to their excellent biocompatibility and transfection capability, suggesting continued promise of synthetic polymer gene delivery vectors going forward.

Controllable Disulfide Exchange Polymerization of Polyguanidine for Effective Biomedical Applications by Thiol-Mediated Uptake

New preparation methods of vectors are the key to developing the next generation of biomacromolecule delivery systems. In this study, a controllable disulfide exchange polymerization was established to obtain low-toxicity and efficient bioreducible polyguanidines (mPEG₂₂₅ -b-PSS_n , n=13, 26, 39, 75, 105) by regulating the concentration of activated nucleophiles and reaction time under mild reaction conditions. The relationship between the degrees of polymerization and biocompatibility was studied to identify the optimal polyguanidine mPEG₂₂₅ -b-PSS₂₆ . Such polyguanidine exhibited good in vitro performance in delivering different functional nucleic acids. The impressive therapeutic effects of mPEG₂₂₅ -b-PSS₂₆ were further verified in the 4T1 tumor-bearing mice as well as the mice with full-thickness skin defects. Controllable disulfide exchange polymerization provides an attractive strategy for the construction of new biomacromolecule delivery systems.

Fluorination and Betaine Modification Augment the Blood-Brain Barrier-Crossing Ability of Cylindrical Polymer Brushes

Blood-brain barrier (BBB)-crossing ability of drugs is of paramount importance for the treatments of central nervous system diseases. However, the known methods for drug transport across the BBB are generally complicated and inefficient, and exhibit serious side effects in some cases. Herein, we report an exciting finding that fluorination and betaine modification can significantly augment the BBB-crossing ability of cylindrical polymer brushes (CPBs), which was demonstrated by the comparison with the CPBs modified with alkyl and poly(ethylene glycol) chains, respectively. We surmise that fluorination enhances the BBB penetration of the CPBs by increasing the hydrophobicity and reducing the surface energy, and betaine medication achieves this function via a betaine transporter BGT1 expressed on brain capillaries. By means of an in vitro BBB model, we demonstrated that the CPBs penetrated the BBB through transendothelial transport. This work provides a novel strategy for enhancing the BBB-crossing ability of nanomaterials.

Fluorination Promotes the Cytosolic Delivery of Genes, Proteins, and Peptides

The cytosolic delivery of biomolecules such as genes, proteins, and peptides is of great importance for biotherapy but usually limited by multiple barriers during the process. Cell membrane with high hydrophobic character is one of the representative biological barriers for cytosolic delivery. The introduction of hydrophobic ligands such as aliphatic lipids onto materials or biomolecules could improve their membrane permeability. However, these ligands are lipophilic and tend to interact with the phospholipids in the membrane as well as serum proteins, which may hinder efficient intracellular delivery. To solve this issue, our research group proposed the use of fluorous ligands with both hydrophobicity and lipophobicity as ideal alternatives to aliphatic lipids to promote cytosolic delivery.In our first attempt, fluorous ligands were conjugated onto cationic polymers to increase their gene delivery efficacy. The fluorination dramatically increased the gene delivery performance at low polymer doses. In addition, the strategy greatly improved the serum tolerance of cationic polymers, which is critical for efficient gene delivery in vivo. Besides serum tolerance, mechanism studies revealed that fluorination increases multiple steps such as cellular uptake and endosomal escape. Fluorination also allowed the assembly of low-molecular-weight polymers and achieved highly efficient gene delivery with minimal material toxicity. The method showed robust efficiency for polymers, including linear polymers, branched polymers, dendrimers, bola amphiphilies, and dendronized polymers.Besides gene delivery, fluorinated polymers were also used for intracellular protein delivery via a coassembly strategy. For this purpose, two lead fluoropolymers were screened from a library of amphiphilic materials. The fluoropolymers are greatly superior to their nonfluorinated analogues conjugated with aliphatic lipids. The fluorous lipids are beneficial for polymer assembly and protein encapsulation, reduced protein denaturation, facilitated endocytosis, and decreased polymer toxicity compared to nonfluorinated lipids. The materials exhibited potent efficacy in therapeutic protein and peptide delivery to achieve cancer therapy and were able to fabricate a personalized nanovaccine for cancer immunotherapy. Finally, the fluorous lipids were directly conjugated to peptides via a disulfide bond for cytosolic peptide delivery. Fluorous lipids drive the assembly of cargo peptides into uniform nanoparticles with much improved proteolytic stability and promote their delivery into various types of cells. The delivery efficacy of this strategy is greatly superior to traditional techniques such as cell-penetrating peptides both in vitro and in vivo. Overall, the fluorination techniques provide efficient and promising strategies for the cytosolic delivery of biomolecules.

Fluorinated paclitaxel prodrugs for potentiated stability and chemotherapy

Robust colloidal stability is an essential prerequisite for effective drug delivery. Herein, a series of fluorinated paclitaxel prodrugs bridged with redox-responsive linkages were synthesized, and the effect of fluorination on the assembly behavior and physiological stability was investigated. The 17-fluorinated ethanol-modified paclitaxel prodrug could self-assemble into stable nanoparticles without the addition of any surfactants. Fluorinated paclitaxel prodrug nanoparticles possessed potent cytotoxicity toward cancer cells and superior antitumor activity. This study offers a universal fluorination approach to improve drug delivery efficacy by enhancing the self-assembly capability and improving the colloidal stability of prodrugs for potentiating chemotherapy.

Methyl to trifluoromethyl substitution as a strategy to increase the membrane permeability of short peptides

Here, we investigated the effect of CH3 to CF3 substitution on the membrane permeability of peptides. We synthesized a series of peptides with CF3 groups and corresponding nonfluorinated peptides and measured the membrane permeability of the peptides. As a result, we demonstrated that CH3 to CF3 substitution is useful for increasing the membrane permeability of di-/tri-peptides.

Recent Progress and Perspectives on Cell Surface Modification

The cell membrane is a biological interface consisting of phospholipid bilayer, saccharides and proteins that maintains a stable metabolic intracellular environment as well as regulating and controlling the exchange of substances inside and outside the cell. Cell membranes provide a highly complex biological surface carrying a variety of essential surfaces ligands and receptors for cells to receive various stimuli of external signals, thereby inducing corresponding cell responses regulating the life activities of the cell. These surface receptors can be manipulated via cell surface modification to regulate cellular functions and behaviors Thus, cell surface modification has attracted considerable attention due to its significance in cell fate control, cell engineering and cell therapy. In this minireview, we describe the recent developments and advances of cell surface modification, and summarize the main modification methods with corresponding functions and applications. Finally, the prospect for the future development of the modification of the living cell membrane is discussed.

Fluoropolymers in biomedical applications: state-of-the-art and future perspectives

Biomedical applications of fluoropolymers in gene delivery, protein delivery, drug delivery, ¹⁹F MRI, PDT, anti-fouling, anti-bacterial, cell culture, and tissue engineering.