The yin of exofacial protein sulfhydryls and the yang of intracellular glutathione in in vitro transfection with SS14 bioreducible lipoplexes

Protein corona investigations of polyplexes with varying hydrophobicity - From method development to in vitro studies

In the field of non-viral drug delivery, polyplexes (PXs) represent an advanced investigated and highly promising tool for the delivery of nucleic acids. Upon encountering physiological fluids, they adsorb biological molecules to form a protein corona (PC), that influence PXs biodistribution, transfection efficiencies and targeting abilities. In an effort to understand protein - PX interactions and the effect of PX material on corona composition, we utilized cationic branched 10 kDa polyethyleneimine (b-PEI) and a hydrophobically modified nylon-3 polymer (NM0.2/CP0.8) within this study to develop appropriate methods for PC investigations. A centrifugation procedure for isolating hard corona - PX complexes (PCPXs) from soft corona proteins after incubating the PXs in fetal bovine serum (FBS) for PC formation was successfully optimized and the identification of proteins by a liquid chromatography-tandem mass spectrometry (LC-MS-MS) method clearly demonstrated that the PC composition is affected by the underlying PXs material. With regard to especially interesting functional proteins, which might be able to induce active targeting effects, several candidates could be detected on b-PEI and NM0.2/CP0.8 PXs. These results are of high interest to better understand how the design of PXs impacts the PC composition and subsequently PCPXs-cell interactions to enable precise adjustment of PXs for targeted drug delivery.

GSH-Activatable Aggregation-Induced Emission Cationic Lipid for Efficient Gene Delivery

The key to gene therapy is the design of biocompatible and efficient delivery systems. In this work, a glutathione (GSH)-activated aggregation-induced-emission (AIE) cationic amphiphilic lipid, termed QM-SS-KK, was prepared for nonviral gene delivery. QM-SS-KK was composed of a hydrophilic biocompatible lysine tripeptide headgroup, a GSH-triggered disulfide linkage, and a hydrophobic AIE fluorophore QM-OH (QM: quinoline-malononitrile) tail. The peptide moiety could not only efficiently compact DNA but also well modulate the dispersion properties of QM-SS-KK, leading to the fluorescence-off state before GSH treatment. The cleavage of disulfide in QM-SS-KK by GSH generated AIE signals in situ with a tracking ability. The liposomes consisted of QM-SS-KK, and 1,2-dioleoylphosphatidylethanolamine (DOPE) (QM-SS-KK/DOPE) delivered plasmid DNAs (pDNAs) into cells with high efficiency. In particular, QM-SS-KK/DOPE had an enhanced transfection efficiency (TE) in the presence of 10% serum, which was two times higher than that of the commercial transfection agent PEI25K. These results highlighted the great potential of peptide and QM-based fluorescence AIE lipids for gene delivery applications.

Reducible amino acid based cationic lipids with a naphthalimide moiety as non-viral gene vehicles

Three basic amino acid–based cationic lipids bearing a fluorescent naphthalimide moiety and a reducible disulfide linkage are synthesized and applied as non-viral gene vehicles. Their DNA interactions are investigated by agarose-gel retardant and ethidium bromide replacement assays. The sizes and zeta potentials of the liposome/DNA complexes are measured by dynamic light scattering. The cytotoxicities of the liposome/DNA complexes are examined using HeLa and 7702 cell lines by MTT assays. The glutathione-responsive DNA release process is studied through time-dependent fluorescence assays. Luciferase gene expression showed the transfection efficiency of the liposome is dramatically increased in the presence of 10% serum. Confocal laser scanning microscopy studies corroborated that the liposome/DNA complexes are successfully uptaken into HeLa cells. These results demonstrate the promising use of amino acids and naphthalimide-containing lipids for safe and efficient gene delivery.

Vibropolyfection: coupling polymer-mediated gene delivery to mechanical stimulation to enhance transfection of adherent cells

Background

With the success of recent non-viral gene delivery-based COVID-19 vaccines, nanovectors have gained some public acceptance and come to the forefront of advanced therapies. Unfortunately, the relatively low ability of the vectors to overcome cellular barriers adversely affects their effectiveness. Scientists have thus been striving to develop ever more effective gene delivery vectors, but the results are still far from satisfactory. Therefore, developing novel strategies is probably the only way forward to bring about genuine change. Herein, we devise a brand-new gene delivery strategy to boost dramatically the transfection efficiency of two gold standard nucleic acid (NA)/polymer nanoparticles (polyplexes) in vitro.

Results

We conceived a device to generate milli-to-nanoscale vibrational cues as a function of the frequency set, and deliver vertical uniaxial displacements to adherent cells in culture. A short-lived high-frequency vibrational load (t = 5 min, f = 1,000 Hz) caused abrupt and extensive plasmalemma outgrowths but was safe for cells as neither cell proliferation rate nor viability was affected. Cells took about 1 hr to revert to quasi-naïve morphology through plasma membrane remodeling. In turn, this eventually triggered the mechano-activated clathrin-mediated endocytic pathway and made cells more apt to internalize polyplexes, resulting in transfection efficiencies increased from 10-to-100-fold. Noteworthy, these results were obtained transfecting three cell lines and hard-to-transfect primary cells.

Conclusions

In this work, we focus on a new technology to enhance the intracellular delivery of NAs and improve the transfection efficiency of non-viral vectors through priming adherent cells with a short vibrational stimulation. This study paves the way for capitalizing on physical cell stimulation(s) to significantly raise the effectiveness of gene delivery vectors in vitro and ex vivo.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01571-x.

Genetic recombination of poly(l-lysine) functionalized apoferritin nanocages that resemble viral capsid nanometer-sized platforms for gene therapy

Currently, bioengineered apoferritin nanocages with flexible protein shells and functionalized modifications have become an attractive approach for efficient anti-tumor therapy. Here, we modified the N-terminus of H-chain subunits in apoferritin with different amounts of lysine via genetic recombination to obtain a poly(l-lysine) modified H-chain apoferritin (nL-HFn) nanocage for siRNA delivery and gene therapy. To achieve excellent cellular affinity and uptake, the nanocarriers were internalized through transferrin receptor-mediated endocytosis, then escaped from the endosome for cytoplasmic transport. Compared with natural apoferritin, the siRNA-loaded genetic recombination NPs modified with lysine exhibit stronger RNA-interference and antitumor efficiency both in vitro and in 4T1 tumor model mice. Therefore, bioengineered apoferritin nanocages modified with lysine might be a promising platform for nucleic acid drug delivery.

Gradient Redox-Responsive and Two-Stage Rocket-Mimetic Drug Delivery System for Improved Tumor Accumulation and Safe Chemotherapy

Recent drug delivery nanosystems for cancer treatment still suffer from the poor tumor accumulation and low therapeutic efficacy due to the complex in vivo biological barriers. To resolve these problems, in this work, a novel gradient redox-responsive and two-stage rocket-mimetic drug nanocarrier is designed and constructed for improved tumor accumulation and safe chemotherapy. The nanocarrier is constructed on the basis of the disulfide-doped organosilica-micellar hybrid nanoparticles and the following dual-functional modification with disulfide-bonded polyethylene glycol (PEG) and amido-bonded polyethylenimine (PEI). First, prolonged circulation duration in the bloodstream is guaranteed due to the shielding of the outer PEG chains. Once the nanocarrier accumulates at the tumoral extracellular microenvironment with low glutathione (GSH) concentrations, the first-stage redox-responsive behavior with the separation of PEG and the exposure of PEI is triggered, leading to the improved tumor accumulation and cellular internalization. Furthermore, with their endocytosis by tumor cells, a high concentration of GSH induces the second-stage redox-responsiveness with the degradation of silsesquioxane framework and the release of the encapsulated drugs. As a result, the rocket-mimetic drug carrier displays longer circulation duration in the bloodstream, higher tumor accumulation capability, and improved antitumor efficacy (which is 2.5 times higher than that with inseparable PEG). It is envisioned that the rocket-mimetic strategy can provide new solutions for improving tumor accumulation and safety of nanocarriers in further cancer chemotherapy.

Reducible Branched Ester-Amine Quadpolymers (rBEAQs) Codelivering Plasmid DNA and RNA Oligonucleotides Enable CRISPR/Cas9 Genome Editing

Functional codelivery of plasmid DNA and RNA oligonucleotides in the same nanoparticle system is challenging due to differences in their physical properties as well as their intracellular locations of function. In this study, we synthesized a series of reducible branched ester-amine quadpolymers (rBEAQs) and investigated their ability to coencapsulate and deliver DNA plasmids and RNA oligos. The rBEAQs are designed to leverage polymer branching, reducibility, and hydrophobicity to successfully cocomplex DNA and RNA in nanoparticles at low polymer to nucleic acid w/w ratios and enable high delivery efficiency. We validate the synthesis of this new class of biodegradable polymers, characterize the self-assembled nanoparticles that these polymers form with diverse nucleic acids, and demonstrate that the nanoparticles enable safe, effective, and efficient DNA-siRNA codelivery as well as nonviral CRISPR-mediated gene editing utilizing Cas9 DNA and sgRNA codelivery.

Bioreducible Hydrophobin-Stabilized Supraparticles for Selective Intracellular Release

One of the main hurdles in nanomedicine is the low stability of drug-nanocarrier complexes as well as the drug delivery efficiency in the region-of-interest. Here, we describe the use of the film-forming protein hydrophobin HFBII to organize dodecanethiol-protected gold nanoparticles (NPs) into well-defined supraparticles (SPs). The obtained SPs are exceptionally stable in vivo and efficiently encapsulate hydrophobic drug molecules. The HFBII film prevents massive release of the encapsulated drug, which, instead, is activated by selective SP disassembly triggered intracellularly by glutathione reduction of the protein film. As a consequence, the therapeutic efficiency of an encapsulated anticancer drug is highly enhanced (2 orders of magnitude decrease in IC₅₀). Biodistribution and pharmacokinetics studies demonstrate the high stability of the loaded SPs in the bloodstream and the selective release of the payloads once taken up in the tissues. Overall, our results provide a rationale for the development of bioreducible and multifunctional nanomedicines.

N-Hydroxyphthalimide catalysts as bioactive pro-oxidants

N-Hydroxyphthalimide organocatalysts bearing lipophilic moieties exhibit a cytotoxic action by promoting oxidative stress in cells.

Characterization and Investigation of Redox-Sensitive Liposomes for Gene Delivery

A number of smart nonviral gene delivery vectors relying on bioresponsiveness have been introduced in the past few years to overcome the limits of the first generation of gene carriers. Among them, redox-sensitive lipidic and polymeric vectors exploit the presence of disulfide bonds in their structure to take advantage of the highly reductive intracellular milieu and to promote complex unpacking and nucleic acids release after cellular uptake (disulfide linker strategy). Glutathione (GSH) has been often identified as the leading actor in the intracellular reduction of bioreducible vectors but their actual mechanisms of action have been rarely investigated in depth and doubts about the real effectiveness of the disulfide linker strategy have been raised. Herein, we outline a simple protocol for the preparation and investigation of nano-sized reducible cationic liposomes, focusing on their thorough characterization and optimization as gene delivery vectors. In addition, we carefully describe the techniques and procedures necessary for the assessment of the bioreducibility of the vectors and to demonstrate that the GSH-mediated intracellular cleavage of disulfide bonds is a pivotal step in their transfection process. Liposomes composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1,2-dioleoyl-sn-glycero-3-phosphatidylethanolamine (DOPE), and of the reducible cationic lipid SS14 are reported as a practical example but the proposed protocol can be easily shifted to other formulations of reducible lipids/liposomes and to reducible polymers.

Nanomedicine delivery: does protein corona route to the target or off road?

Nanomedicine aims to find novel solutions for urgent biomedical needs. Despite this, one of the most challenging hurdles that nanomedicine faces is to successfully target therapeutic nanoparticles to cells of interest in vivo. As for any biomaterials, once in vivo, nanoparticles can interact with plasma biomolecules, forming new entities for which the name protein coronas (PCs) have been coined. The PC can influence the in vivo biological fate of a nanoparticle. Thus for guaranteeing the desired function of an engineered nanomaterial in vivo, it is crucial to dissect its PC in terms of formation and evolution within the body. In this contribution we will review the 'good' and 'bad' sides of the PC, starting from the scientific aspects to the technological applications.

Selective redox-responsive drug release in tumor cells mediated by chitosan based glycolipid-like nanocarrier

The redox responsive nanocarriers have made a considerable progress in achieving triggered drug release by responding to the endogenous occurring difference between the extra- and intra- cellular redox environments. Despite the promises, this redox difference exists both in normal and tumor tissue. So a non-selective redox responsive drug delivery system may result in an undesired drug release in normal cells and relevant side-effects. To overcome these limitations, we have developed a chitosan based glycolipid-like nanocarrier (CSO-ss-SA) which selectively responded to the reducing environment in tumor cells. The CSO-ss-SA showed an improved reduction-sensitivity which only fast degraded and released drug in 10mM levels of glutathione (GSH). The CSO-ss-SA could transport the drug fast into the human ovarian cancer SKOV-3 cells and human normal liver L-02 cells by internalization, but only fast release drug in SKOV-3 cells. By regulating the intracellular GSH concentration in SKOV-3 cells, it indicated that the cellular inhibition of the PTX-loaded CSO-ss-SA showed a positive correlation with the GSH concentration. The CSO-ss-SA was mainly located in the liver, spleen and tumor in vivo, which evidenced the passive tumor targeting ability. Despite the high uptake of liver and spleen, drug release was mainly occurred in tumor. PTX-loaded CSO-ss-SA achieved a remarkable tumor growth inhibition effect with rather low dose of PTX. This study demonstrates that a smartly designed glycolipid-like nanocarrier with selective redox sensitivity could serve as an excellent platform to achieve minimal toxicity and rapid intracellular drug release in tumor cells.

The study of polyplex formation and stability by time-resolved fluorescence spectroscopy of SYBR Green I-stained DNA

Polyplexes are nanoparticles formed by the self-assembly of DNA/RNA and cationic polymers specifically designed to deliver exogenous genetic material to cells by a process called transfection. There is a general consensus that a subtle balance between sufficient extracellular protection and intracellular release of nucleic acids is a key factor for successful gene delivery. Therefore, there is a strong need to develop suitable tools and techniques for enabling the monitoring of the stability of polyplexes in the biological environment they face during transfection. In this work we propose time-resolved fluorescence spectroscopy in combination with SYBR Green I-DNA dye as a reliable tool for the in-depth characterization of the DNA/vector complexation state. As a proof of concept, we provide essential information on the assembly and disassembly of complexes formed between DNA and each of three cationic polymers, namely a novel promising chitosan-graft-branched polyethylenimine copolymer (Chi-g-bPEI), one of its building block 2 kDa bPEI and the gold standard transfectant 25 kDa bPEI. Our results highlight the higher information content provided by the time-resolved studies of SYBR Green I/DNA, as compared to conventional steady state measurements of ethidium bromide/DNA that enabled us to draw relationships among fluorescence lifetime, polyplex structural changes and transfection efficiency.

Synergistic combination therapy using a lipid shell-droplet core nanosphere with tunable thickness

A newly-designed drug carrier composed of an internal droplet core and a thickness-controllable shell was successfully developed. By co-delivering paclitaxel, doxorubicin and quantum dots simultaneously, this combinational drug delivery system could achieve in vitro fluorescence imaging, chemotherapeutic and oxidation therapy.

Linking an α-tocopherol derivative to cobalt(0) nanomagnets: magnetically responsive antioxidants with superior radical trapping activity and reduced cytotoxicity

Covalent attachment of a phenolic antioxidant analogue of α-tocopherol to graphite-coated magnetic cobalt nanoparticles (CoNPs) provided a novel magnetically responsive antioxidant capable of preventing the autoxidation of organic materials and showing a reduced toxicity toward human cells.

Opposing influence of intracellular and membrane thiols on the toxicity of reducible polycations

Toxicity of polycations has been recognized since their first use in gene delivery. Bioreducible polycations attract attention because of their improved safety due to selective intracellular degradation by glutathione (GSH). Here we present a systematic study of the toxicity of bioreducible poly(amido amine)s (PAA). PAA with increasing content of disulfide bonds were synthesized by Michael addition. Toxicity of PAA was evaluated in two cell lines with different innate levels of intracellular GSH. Increasing the content of disulfide bonds decreased the toxicity of PAA, with more significant decrease observed in cells with high GSH. Depleting intracellular GSH by diethyl maleate resulted in increased toxicity of bioreducible PAA. In contrast, increasing the GSH concentrations by growing cells in hypoxic conditions resulted in further decreased toxicity compared with cells grown in normoxic conditions. The presence of exofacial plasma membrane thiols selectively increased toxicity of bioreducible PAA while having no effect on non-degradable controls. These results improve our understanding of the cellular mechanisms of polycation toxicity. They also shed light on the opposing effects of different cellular thiol pools on the toxicity of bioreducible polycations.