Polylysine-based transfection systems utilizing receptor-mediated delivery

Nanoplatform-Based In Vivo Gene Delivery Systems for Cancer Therapy

Gene therapy uses modern molecular biology methods to repair disease-causing genes. As a burgeoning therapeutic, it has been widely applied for cancer therapy. Since 1989, there have been numerous clinical gene therapy cases worldwide. However, a few are successful. The main challenge of clinical gene therapy is the lack of efficient and safe vectors. Although viral vectors show high transfection efficiency, their application is still limited by immune rejection and packaging capacity. Therefore, the development of non-viral vectors is overwhelming. Nanoplatform-based non-viral vectors become a hotspot in gene therapy. The reasons are mainly as follows. 1) Non-viral vectors can be engineered to be uptaken by specific types of cells or tissues, providing effective targeting capability. 2) Non-viral vectors can protect goods that need to be delivered from degradation. 3) Nanoparticles can transport large-sized cargo such as CRISPR/Cas9 plasmids and nucleoprotein complexes. 4) Nanoparticles are highly biosafe, and they are not mutagenic in themselves compared to viral vectors. 5) Nanoparticles are easy to scale preparation, which is conducive to clinical conversion and application. Here, an overview of the categories of nanoplatform-based non-viral gene vectors, the limitations on their development, and their applications in cancer therapy.

Immunological nanomaterials to combat cancer metastasis

Metastasis causes greater than 90% of cancer-associated deaths, presenting huge challenges for detection and efficient treatment of cancer due to its high heterogeneity and widespread dissemination to various organs. Therefore, it is imperative to combat cancer metastasis, which is the key to achieving complete cancer eradication. Immunotherapy as a systemic approach has shown promising potential to combat metastasis. However, current clinical immunotherapies are not effective for all patients or all types of cancer metastases owing to insufficient immune responses. In recent years, immunological nanomaterials with intrinsic immunogenicity or immunomodulatory agents with efficient loading have been shown to enhance immune responses to eliminate metastasis. In this review, we would like to summarize various types of immunological nanomaterials against metastasis. Moreover, this review will summarize a series of immunological nanomaterial-mediated immunotherapy strategies to combat metastasis, including immunogenic cell death, regulation of chemokines and cytokines, improving the immunosuppressive tumour microenvironment, activation of the STING pathway, enhancing cytotoxic natural killer cell activity, enhancing antigen presentation of dendritic cells, and enhancing chimeric antigen receptor T cell therapy. Furthermore, the synergistic anti-metastasis strategies based on the combinational use of immunotherapy and other therapeutic modalities will also be introduced. In addition, the nanomaterial-mediated imaging techniques (e.g., optical imaging, magnetic resonance imaging, computed tomography, photoacoustic imaging, surface-enhanced Raman scattering, radionuclide imaging, etc.) for detecting metastasis and monitoring anti-metastasis efficacy are also summarized. Finally, the current challenges and future prospects of immunological nanomaterial-based anti-metastasis are also elucidated with the intention to accelerate its clinical translation.

Nucleic acid liquids

The confluence of recent discoveries of the roles of biomolecular liquids in living systems and modern abilities to precisely synthesize and modify nucleic acids (NAs) has led to a surge of interest in liquid phases of NAs. These phases can be formed primarily from NAs, as driven by base-pairing interactions, or from the electrostatic combination (coacervation) of negatively charged NAs and positively charged molecules. Generally, the use of sequence-engineered NAs provides the means to tune microsopic particle properties, and thus imbue specific, customizable behaviors into the resulting liquids. In this way, researchers have used NA liquids to tackle fundamental problems in the physics of finite valence soft materials, and to create liquids with novel structured and/or multi-functional properties. Here, we review this growing field, discussing the theoretical background of NA liquid phase separation, quantitative understanding of liquid material properties, and the broad and growing array of functional demonstrations in these materials. We close with a few comments discussing remaining open questions and challenges in the field.

Polymeric Vehicles for Nucleic Acid Delivery: Enhancing the Therapeutic Efficacy and Cellular Uptake

BACKGROUND

Therapeutic gene delivery may be facilitated by the use of polymeric carriers. When combined with nucleic acids to form nanoparticles or polyplexes, a variety of polymers may shield the cargo from in vivo breakdown and clearance while also making it easier for it to enter intracellular compartments.

AIM AND OBJECTIVES

Polymer synthesis design choices result in a wide variety of compounds and vehicle compositions. Depending on the application, these characteristics may be changed to provide enhanced endosomal escape, longer-lasting distribution, or stronger connection with nucleic acid cargo and cells. Here, we outline current methods for delivering genes in preclinical and clinical settings using polymers.

METHODOLOGY

Significant therapeutic outcomes have previously been attained using genetic material- delivering polymer vehicles in both in-vitro and animal models. When combined with nucleic acids to form nanoparticles or polyplexes, a variety of polymers may shield the cargo from in vivo breakdown and clearance while also making it easier for it to enter intracellular compartments. Many innovative diagnoses for nucleic acids have been investigated and put through clinical assessment in the past 20 years.

RESULTS

Polymer-based carriers have additional delivery issues due to their changes in method and place of biological action, as well as variances in biophysical characteristics. We cover recent custom polymeric carrier architectures that were tuned for nucleic acid payloads such genomemodifying nucleic acids, siRNA, microRNA, and plasmid DNA.

CONCLUSION

In conclusion, the development of polymeric carriers for gene delivery holds promise for therapeutic applications. Through careful design and optimization, these carriers can overcome various challenges associated with nucleic acid delivery, offering new avenues for treating a wide range of diseases.

Serum-Resistant Ternary DNA Polyplexes for Suicide Gene Therapy of Uterine Leiomyoma

Uterine leiomyoma (UL) is a prevalent benign tumor in women that frequently gives rise to a multitude of reproductive complications. The use of suicide gene therapy has been proposed as a highly promising method for treating UL. To achieve successful gene therapy, it is essential to develop carriers that can efficiently transport nucleic acids into targeted cells and tissues. The instability of polyplexes in blood and other biological fluids is a crucial factor to consider when using non-viral carriers. In this study, we present serum-resistant and cRGD-modified DNA complexes for targeted delivery genes to UL cells. Ternary polyplexes were formed by incorporating cystine-cross-linked polyglutamic acid modified with histidine residues. We employed two techniques in the production of cross-linked polyanionic coating: matrix polymerization and oxidative polycondensation. In this study, we investigated the physicochemical properties of ternary DNA complexes, including the size and zeta-potential of the nanoparticles. Additionally, we evaluated cellular uptake, toxicity levels, transfection efficiency and specificity in vitro. The study involved introducing the HSV-TK gene into primary UL cells as a form of suicide gene therapy modeling. We have effectively employed ternary peptide-based complexes for gene delivery into the UL organtypic model. By implementing in situ suicide gene therapy, the increase in apoptosis genes expression was detected, providing conclusive evidence of apoptosis occurring in the transfected UL tissues. The results of the study strongly suggest that the developed ternary polyplexes show potential as a valuable tool in the implementation of suicide gene therapy for UL.

Polypeptide-Based Systems: From Synthesis to Application in Drug Delivery

Synthetic polypeptides are biocompatible and biodegradable macromolecules whose composition and architecture can vary over a wide range. Their unique ability to form secondary structures, as well as different pathways of modification and biofunctionalization due to the diversity of amino acids, provide variation in the physicochemical and biological properties of polypeptide-containing materials. In this review article, we summarize the advances in the synthesis of polypeptides and their copolymers and the application of these systems for drug delivery in the form of (nano)particles or hydrogels. The issues, such as the diversity of polypeptide-containing (nano)particle types, the methods for their preparation and drug loading, as well as the influence of physicochemical characteristics on stability, degradability, cellular uptake, cytotoxicity, hemolysis, and immunogenicity of polypeptide-containing nanoparticles and their drug formulations, are comprehensively discussed. Finally, recent advances in the development of certain drug nanoformulations for peptides, proteins, gene delivery, cancer therapy, and antimicrobial and anti-inflammatory systems are summarized.

Preparation and stability of pegylated poly(S-alkyl-L-homocysteine) coacervate core micelles in aqueous media

We report development and preparation of synthetic polypeptide based, coacervate core polyelectrolyte complex micelles, PCMs, in aqueous media, which were characterized and evaluated for the encapsulation and in vitro release of a model single-stranded RNA, polyadenylic acid, poly(A). Cationic, α-helical polypeptides pegylated at their N-termini, PEG113-b-5bn and PEG113-b-5cn, were designed to form coacervate core PCMs upon mixing with multivalent anions in aqueous media. Sodium tripolyphosphate (TPP) and poly(A) were used as model multivalent anions that allowed optimization of polypeptide composition and chain length for formation of stable, nanoscale PCMs. PEG113-b-5c27 was selected for preparation of PCMs that were characterized under different environmental conditions using dynamic light scattering, atomic force microscopy and cryoelectron microscopy. The PCMs were found to efficiently encapsulate poly(A), were stable at physiologically relevant pH and solution ionic strength, and were able to release poly(A) in the presence of excess polyvalent anions. These PCMs were found to be a promising model system for further development of polypeptide based therapeutic delivery vehicles.

Therapeutic Oligonucleotides: An Outlook on Chemical Strategies to Improve Endosomal Trafficking

The potential of oligonucleotide therapeutics is undeniable as more than 15 drugs have been approved to treat various diseases in the liver, central nervous system (CNS), and muscles. However, achieving effective delivery of oligonucleotide therapeutics to specific tissues still remains a major challenge, limiting their widespread use. Chemical modifications play a crucial role to overcome biological barriers to enable efficient oligonucleotide delivery to the tissues/cells of interest. They provide oligonucleotide metabolic stability and confer favourable pharmacokinetic/pharmacodynamic properties. This review focuses on the various chemical approaches implicated in mitigating the delivery problem of oligonucleotides and their limitations. It highlights the importance of linkers in designing oligonucleotide conjugates and discusses their potential role in escaping the endosomal barrier, a bottleneck in the development of oligonucleotide therapeutics.

Polyethylenimine-Conjugated Hydroxyethyl Cellulose for Doxorubicin/Bcl-2 siRNA Co-Delivery Systems

Hydroxyethyl cellulose (HEC), widely known for its biocompatibility and water solubility, is a polysaccharide with potential for pharmaceutical applications. Here, we synthesized polyethylenimine2k (PEI2k)-conjugated hydroxyethyl cellulose (HECP2k) for doxorubicin/Bcl-2 siRNA co-delivery systems. HECP2ks were synthesized by reductive amination of PEI2k with periodate-oxidized HEC. The synthesis of the polymers was characterized using ¹H NMR, ¹³C NMR, primary amine quantification, FT-IR, and GPC. Via agarose gel electrophoresis and Zeta-sizer measurement, it was found that HECP2ks condensed pDNA to positively charged and nano-sized complexes (100-300 nm, ~30 mV). The cytotoxicity of HECP2ks was low and HECP2k 10X exhibited higher transfection efficiency than PEI25k even in serum condition, showing its high serum stability from ethylene oxide side chains. Flow cytometry analysis and confocal laser microscopy observation verified the superior cellular uptake and efficient endosome escape of HECP2k 10X. HECP2k 10X also could load Dox and Bcl-2 siRNA, forming nano-particles (HECP2k 10X@Dox/siRNA). By median effect analysis and annexin V staining analysis, it was found that HECP2k 10X@Dox/siRNA complexes could cause synergistically enhanced anti-cancer effects to cancer cells via induction of apoptosis. Consequently, it was concluded that HECP2k possesses great potential as a promising Dox/Bcl-2 siRNA co-delivery carrier.

Polymer- and lipid-based gene delivery technology for CAR T cell therapy

Chimeric antigen receptor T cell (CAR T cell) therapy is a revolutionary approach approved by the FDA and EMA to treat B cell malignancies and multiple myeloma. The production of these T cells has been done through viral vectors, which come with safety concerns, high cost and production challenges, and more recently also through electroporation, which can be extremely cytotoxic. In this context, nanosystems can constitute an alternative to overcome the challenges associated with current methods, resulting in a safe and cost-effective platform. However, the barriers associated with T cells transfection show that the design and engineering of novel approaches in this field are highly imperative. Here, we present an overview from CAR constitution to transfection technologies used in T cells, highlighting the lipid- and polymer-based nanoparticles as a potential delivery platform. Specifically, we provide examples, strengths and weaknesses of nanosystem formulations, and advances in nanoparticle design to improve transfection of T cells. This review will guide the researchers in the design and development of novel nanosystems for next-generation CAR T therapeutics.

A Novel Piggyback Strategy for mRNA Delivery Exploiting Adenovirus Entry Biology

Molecular therapies exploiting mRNA vectors embody enormous potential, as evidenced by the utility of this technology for the context of the COVID-19 pandemic. Nonetheless, broad implementation of these promising strategies has been restricted by the limited repertoires of delivery vehicles capable of mRNA transport. On this basis, we explored a strategy based on exploiting the well characterized entry biology of adenovirus. To this end, we studied an adenovirus-polylysine (AdpL) that embodied "piggyback" transport of the mRNA on the capsid exterior of adenovirus. We hypothesized that the efficient steps of Ad binding, receptor-mediated entry, and capsid-mediated endosome escape could provide an effective pathway for transport of mRNA to the cellular cytosol for transgene expression. Our studies confirmed that AdpL could mediate effective gene transfer of mRNA vectors in vitro and in vivo. Facets of this method may offer key utilities to actualize the promise of mRNA-based therapeutics.

Electrically Switchable Polymer Brushes for Protein Capture and Release in Biological Environments

Interfaces functionalized with polymers are known for providing excellent resistance towards biomolecular adsorption and for their ability to bind high amounts of protein while preserving their structure. However, making an interface that switches between these two states has proven challenging and concepts to date rely on changes in the physiochemical environment, which is static in biological systems. Here we present the first interface that can be electrically switched between a high‐capacity (>1 μg cm⁻²) multilayer protein binding state and a completely non‐fouling state (no detectable adsorption). Switching is possible over multiple cycles without any regeneration. Importantly, switching works even when the interface is in direct contact with biological fluids and a buffered environment. The technology offers many applications such as zero fouling on demand, patterning or separation of proteins as well as controlled release of biologics in a physiological environment, showing high potential for future drug delivery in vivo.

Targeting nucleic acid-based therapeutics to tumors: Challenges and strategies for polyplexes

The current medical reality of cancer gene therapy is reflected by more than ten approved products on the global market, including oncolytic and other viral vectors and CAR T-cells as ex vivo gene-modified cell therapeutics. The development of synthetic antitumoral nucleic acid therapeutics has been proceeding at a lower but steady pace, fueled by a plethora of alternative nucleic acid platforms (from various antisense oligonucleotides, siRNA, microRNA, lncRNA, sgRNA, to larger mRNA and DNA) and several classes of physical and chemical delivery technologies. This review summarizes the challenges and strategies for tumor-targeted nucleic acid delivery. Focusing primarily on polyplexes (polycation complexes) as nanocarriers, delivery options across multiple barriers into tumor cells are illustrated.

Poly-L-Lysine/Hyaluronan Nanocarriers As a Novel Nanosystem for Gene Delivery

The present research comes up with a novel DNA-loaded poly-l-lysine (PLL) / hyaluronan (HA) nanocarrier (DNA-loaded PLL/HA NCs) for gene delivery applications, as a promising candidate for gene delivery into diverse cells. A straightforward approach was employed to prepare such a nanosystem through masking DNA-loaded PLL molecules by HA. Fourier-transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), field emission-scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) were used to analyze the interaction of the molecules as well as the physicochemical properties of the NCs. The NCs showed a negative charge of -24 ± 3 mV, with an average size of 138 ± 6 nm, in a ellipsoid-shape with smooth surfaces. The DNA loading efficiency (LE) measured by DNA absorbance was around 95 %. The MTT assay showed that the developed NCs are non-toxic to the cells. Furthermore,the uptake of the DNA-loaded PLL/HA NCs by the human embryonic kidney (HEK)-293T cells was evaluated by a flow cytometry method, and demonstrated high potential cellular uptake over 90% for transferring the gene to HEK-293T cells at the optimized conditions. Therefore, the DNA-loaded PLL/HA NCs are the potent strategy for developing nanosystems for gene delivery applications. This article is protected by copyright. All rights reserved.

Advanced Delivery Systems Based on Lysine or Lysine Polymers

Polylysine and materials that integrate lysine form promising drug delivery platforms. As a cationic macromolecule, a polylysine polymer electrostatically interacts with cells and is efficiently internalized, thereby enabling intracellular delivery. Although polylysine is intrinsically pH-responsive, the conjugation with different functional groups imparts smart, stimuli-responsive traits by adding pH-, temperature-, hypoxia-, redox-, and enzyme-responsive features for enhanced delivery of therapeutic agents. Because of such characteristics, polylysine has been used to deliver various cargos such as small-molecule drugs, genes, proteins, and imaging agents. Furthermore, modifying contrast agents with polylysine has been shown to improve performance, including increasing cellular uptake and stability. In this review, the use of lysine residues, peptides, and polymers in various drug delivery systems has been discussed comprehensively to provide insight into the design and robust manufacturing of lysine-based delivery platforms.

Increased Toxicity of Doxorubicin Encapsulated into pH-Responsive Poly(β-Amino Ester)-Functionalized MCM-41 Silica Nanoparticles

BACKGROUND

The encapsulation of anti-cancer drugs in stimulus-sensitive release systems may provide advantages such as enhanced drug toxicity in tumour tissue cells due to increased intracellular drug release. Encapsulation may also improve release in targeted tissue due to the response to a stimulus such as pH, which is lower in the tumour tissue microenvironment. Here, we evaluated the in vitro toxicity of the Drug Doxorubicin (DOX) loaded into a release system based on poly(β-amino ester)- modified MCM-41 silica nanoparticles.

METHODS

The MCM-41-DOX-PbAE release system was obtained by loading DOX into MCM-41 nanoparticles amino-functionalized with 3-aminopropyltriethoxysilane (APTES) and then coated with a pH-responsive poly(β-amino ester) (PbAE). The physicochemical characteristics of the release system were evaluated through TEM, FTIR and TGA. Cytotoxicity assays were performed on the MCM-41- DOX-PbAE system to determine their effects on the inhibition of human MCF-7 breast cancer cell proliferation after 48 h of exposure through crystal violet assay; the investigated systems included MCF-7 cells with MCM-41, PbAE, and MCM-41-PbAE alone. Additionally, the release of DOX and the change in pH in vitro were determined.

RESULTS

The physicochemical characteristics of the synthesized MCM-41-PbAE system were confirmed, including the nanoparticle size, spherical morphology, mesoporous ordered structure, and presence of PbAE on the surface of the MCM-41 nanoparticles. Likewise, we demonstrated that the release of DOX from the MCM-41-DOX-PbAE system promoted an important reduction in MCF-7 cell viability (~ 70%) compared to the values obtained with MCM-41, PbAE, and MCM-41-PbAE, as well as a reduction in the viability under treatment with just DOX (~ 50%).

CONCLUSION

The results suggest that all the components of the release system are biocompatible and that the encapsulation of DOX in MCM-41-PbAE could allow better intracellular release, which would probably increase the availability and toxic effect of DOX.

Design Principles of Lipid-like Ionic Liquids for Gene Delivery

We developed lipid-like ionic liquids, containing 2-mercaptoimidazolium and 2-mercaptothiazolinium headgroups tethered to two long saturated alkyl chains, as carriers for in vitro delivery of plasmid HEK DNA into 293T cells. We employed a combination of modular design, synthesis, X-ray analysis, and computational modeling to rationalize the self-assembly and desired physicochemical and biological properties. The results suggest that thioamide-derived ionic liquids may serve as a modular platform for lipid-mediated gene delivery. This work represents a step toward understanding the structure-function relationships of these amphiphiles with long-range ordering and offering insight into design principles for synthetic vectors based on self-assembly behavior.

One-Step All-Aqueous Interfacial Assembly of Robust Membranes for Long-Term Encapsulation and Culture of Adherent Stem/Stromal Cells

The therapeutic effectiveness and biological relevance of technologies based on adherent cells depend on platforms that enable long-term culture in controlled environments. Liquid-core capsules have been suggested as semipermeable moieties with spatial homogeneity due to the high mobility of all components in their core. The lack of cell-adhesive sites in liquid-core structures often hampers their use as platforms for stem cell-based technologies for long-term survival and cell-directed self-organization. Here, the one-step fast formation of robust polymeric capsules formed by interfacial complexation of oppositely charged polyelectrolytes in an all-aqueous environment, compatible with the simultaneous encapsulation of mesenchymal stem/stromal cells (MSCs) and microcarriers, is described. The adhesion of umbilical cord MSCs to polymeric microcarriers enables their aggregation and culture for more than 21 days in capsules prepared either manually by dropwise addition, or by scalable electrohydrodynamic atomization, generating robust and stable capsules. Cell aggregation and secretion overtime can be tailored by providing cells with static or dynamic (bioreactor) environments.

In Vivo T Cell-Targeting Nanoparticle Drug Delivery Systems: Considerations for Rational Design

T cells play an important role in immunity and repair and are implicated in diseases, including blood cancers, viral infections, and inflammation, making them attractive targets for the treatment and prevention of diseases. Over recent years, the advent of nanomedicine has shown an increase in studies that use nanoparticles as carriers to deliver therapeutic cargo to T cells for ex vivo and in vivo applications. Nanoparticle-based delivery has several advantages, including the ability to load and protect a variety of drugs, control drug release, improve drug pharmacokinetics and biodistribution, and site- or cell-specific targeting. However, the delivery of nanoparticles to T cells remains a major technological challenge, which is primarily due to the nonphagocytic nature of T cells. In this review, we discuss the physiological barriers to effective T cell targeting and describe the different approaches used to deliver cargo-loaded nanoparticles to T cells for the treatment of disease such as T cell lymphoma and human immunodeficiency virus (HIV). In particular, engineering strategies that aim to improve nanoparticle internalization by T cells, including ligand-based targeting, will be highlighted. These nanoparticle engineering approaches are expected to inspire the development of effective nanomaterials that can target or manipulate the function of T cells for the treatment of T cell-related diseases.

Biopolymeric Materials Used as Nonviral Vectors: A Review

Bacterial transformation and gene transfection can be understood as being the results of introducing specific genetic material into cells, resulting in gene expression, and adding a new genetic trait to the host cell. Many studies have been carried out to investigate different types of lipids and cationic polymers as promising nonviral vectors for DNA transfer. The present study aimed to carry out a systematic review on the use of biopolymeric materials as nonviral vectors. The methodology was carried out based on searches of scientific articles and applications for patents published or deposited from 2006 to 2020 in different databases for patents (EPO, USPTO, and INPI) and articles (Scopus, Web of Science, and Scielo). The results showed that there are some deposits of patents regarding the use of chitosan as a gene carrier. The 16 analyzed articles allowed us to infer that the use of biopolymers as nonviral vectors is limited due to the low diversity of biopolymers used for these purposes. It was also observed that the use of different materials as nonviral vectors is based on chemical structure modifications of the material, mainly by the addition of cationic groups. Thus, the use of biopolymers as nonviral vectors is still limited to only a few polysaccharide types, emphasizing the need for further studies involving the use of different biopolymers in processes of gene transfer.

Highly Osmotic Oxidized Sucrose-Crosslinked Polyethylenimine for Gene Delivery Systems

In this work, highly osmotic oxidized sucrose-crosslinked polyethylenimine (SP2K) polymers were developed for gene delivery systems, and the transfection mechanism is examined. First, periodate-oxidized sucrose and polyethylenimine 2K (PEI2K) were crosslinked with various feed ratios via reductive amination. The synthesis was confirmed by ¹H NMR and FTIR. The synthesized SP2K polymers could form positively charged (~40 mV zeta-potential) and nano-sized (150–200 nm) spherical polyplexes with plasmid DNA (pDNA). They showed lower cytotoxicity than PEI25K but concentration-dependent cytotoxicity. Among them, SP2K7 and SP2K10 showed higher transfection efficiency than PEI25K in both serum and serum-free conditions, revealing the good serum stability. It was found that SP2K polymers possessed high osmolality and endosome buffering capacity. The transfection experiments with cellular uptake inhibitors suggest that the transfection of SP2K polymers would progress by multiple pathways, including caveolae-mediated endocytosis. It was also thought that caveolae-mediated endocytosis of SP2K polyplexes would be facilitated through cyclooxygenase-2 (COX-2) expression induced by high osmotic pressure of SP2K polymers. Confocal microscopy results also supported that SP2K polyplexes would be internalized into cells via multiple pathways and escape endosomes efficiently via high osmolality and endosome buffering capacity. These results demonstrate the potential of SP2K polymers for gene delivery systems.

Optimizing synthetic nucleic acid and protein nanocarriers: The chemical evolution approach

Optimizing synthetic nanocarriers is like searching for a needle in a haystack. How to find the most suitable carrier for intracellular delivery of a specified macromolecular nanoagent for a given disease target location? Here, we review different synthetic 'chemical evolution' strategies that have been pursued. Libraries of nanocarriers have been generated either by unbiased combinatorial chemistry or by variation and novel combination of known functional delivery elements. As in natural evolution, definition of nanocarriers as sequences, as barcode or design principle, may fuel chemical evolution. Screening in appropriate test system may not only provide delivery candidates, but also a refined understanding of cellular delivery including novel, unpredictable mechanisms. Combined with rational design and computational algorithms, candidates can be further optimized in subsequent evolution cycles into nanocarriers with improved safety and efficacy. Optimization of nanocarriers differs for various cargos, as illustrated for plasmid DNA, siRNA, mRNA, proteins, or genome-editing nucleases.

Photo-induced specific intracellular release EGFR inhibitor from enzyme/ROS-dual sensitive nano-platforms for molecular targeted-photodynamic combinational therapy of non-small cell lung cancer

Molecular targeted-photodynamic combinational therapy is a promising strategy to enhance antitumor effects; meanwhile, current nanocarriers face challenges of limited selective delivery and release of therapeutic agents to specific tumor sites, which significantly compromises their therapeutic efficacy. Herein, we report active-targeting, enzyme- and ROS-dual responsive nanoparticles (HPGBCA) consisting of CD₄₄-targeting hyaluronic acid (HA) shells and afatinib (AFT)-loaded, ROS-sensitive poly(l-lysine)-conjugated chlorin e6 (Ce6) derivative nanoparticle cores (PGBCA). HPGBCA can actively carry AFT and Ce6 specifically to tumor cells due to the negatively charged HA and CD₄₄-mediated active targeting. Subsequently, hyaluronidase in the endosome will further spur the degradation of the HA shell to prompt exposure of the positively charged PGBCA core for rapid endosomal escape and intracellular delivery of AFT and Ce6. Furthermore, the generation of ROS produced by Ce6 under NIR irradiation can trigger the rapid oxidation of the thioether linker to facilitate the release of AFT into the cytoplasm. In vitro and in vivo studies demonstrated that the released AFT and excessive ROS at the local site can synergistically induce cell apoptosis to enhance the therapeutic efficacy without side effects. Our developed intelligent nanoparticle provides new avenues to achieve on-demand, specific intracellular drug release for improved molecular targeted-photodynamic combination therapeutic efficacy.

Poly(l-glutamic acid)-Based Zwitterionic Polymer in a Charge Conversional Shielding System for Gene Therapy of Malignant Tumors

Recently, pH-sensitive polymers have received extensive attention in tumor therapy. However, the rapid response to pH changes is the key to achieving efficient treatment. Here, a novel shielding system with a rapidly pH-responsive polymer (PAMT) is synthesized by click reaction between poly(γ-allyl-l-glutamate) and thioglycolic acid or 2-(Boc-amino)ethanethiol. The zwitterionic biodegradable polymer PAMT, which is negatively charged at physiological pH, can be used to shield positively charged nanoparticles. PAMT is electrostatically attached to the surface of the positively charged PEI/pDNA complex to form a ternary complex. The zwitterionic PAMT-shielded complex exhibits rapid charge conversion when the pH decreases from 7.4 to 6.8. For the in vivo tumor inhibition experiment, PAMT/PEI/shVEGF injected intravenously shows a more significant inhibitory effect on tumor growth. The excellent results are mainly attributed to introduction of the zwitterionic copolymer PAMT, which can shield the positively charged PEI/shVEGF complex in physiological conditions, while the surface potential of the shielded complexes changes to a positive charge in the acidic tumor environment.

Engineered iron oxide nanoparticles to improve regenerative effects of mesenchymal stem cells

Abstract

Mesenchymal stem cells (MSCs) based therapies are a major field of regenerative medicine. However, the success of MSC therapy relies on the efficiency of its delivery and retention, differentiation, and secreting paracrine factors at the target sites. Recent studies show that superparamagnetic iron oxide nanoparticles (SPIONs) modulate the regenerative effects of MSCs. After interacting with the cell membrane of MSCs, SPIONs can enter the cells via the endocytic pathway. The physicochemical properties of nanoparticles, including size, surface charge (zeta-potential), and surface ligand, influence their interactions with MSC, such as cellular uptake, cytotoxicity, homing factors, and regenerative related factors (VEGF, TGF-β1). Therefore, in-depth knowledge of the physicochemical properties of SPIONs might be a promising lead in regenerative and anti-inflammation research using SPIONs mediated MSCs. In this review, recent research on SPIONs with MSCs and the various designs of SPIONs are examined and summarized.

Graphic abstract

A graphical abstract describes important parameters in the design of superparamagnetic iron oxide nanoparticles, affecting mesenchymal stem cells. These physicochemical properties are closely related to the mesenchymal stem cells to achieve improved cellular responses such as homing factors and cell uptake.

Selectively monitoring glutathione in human serum and growth-associated living cells using gold nanoclusters

Glutathione (GSH) plays a variety of vital functions in biological systems. Growth-associated change of GSH level in cells might be critical for cell survival and monitoring of GSH in living cells are of great significance for understanding the dynamic link between GSH and some diseases. In this work, chitason micelles templated gold nanoclusters (CM-Au NCs) emitting red fluorescence were prepared with a simple and rapid method, which shows interesting phenomenon of aggregation induced emission (AIE) affected by the size of the chitosan micelles. The unique CM-Au NCs can be used to develop turn-off fluorescent probe for detecting GSH in human serum and living cells based on the reverse process of AIE of CM-Au NCs, completely different from the principle of aggregation caused quenching (ACQ) effect, which can distinguish GSH from other biothiols (cysteine and homocysteine) and quantitatively detect GSH concentration of human serum in healthy people and cancer patients with high sensitivity. The practical application of fluorescent CM-Au NCs for cellular imaging and detecting GSH level indicates ultra-trace changes of GSH levels in normal and cancer cells could be monitored at different growth stages, which reveals that the levels of GSH in cancer cells was always higher than that of normal cells. Compared with commercial GSH assay kits for detection GSH in human serum and living cells, the proposed method was verified to be accuracy and precision. The results not only reflect the changes of GSH during cell growth at different stages, but also demonstrate the feasibility of reverse process of AIE of CM-Au NCs for detection GSH. This strategy would provide a platform to understand the dynamic link between GSH and disease to clarify the disease mechanism.

Kinetics of Poly-l-lysine Adsorption on Mica and Stability of Formed Monolayers: Theoretical and Experimental Studies

Various physicochemical parameters of poly-l-lysine (PLL) solutions comprising the diffusion coefficient, the electrophoretic mobility, the density, and the intrinsic viscosity were determined for the pH range 3.0-9.2. This allowed us to calculate derivative parameters characterizing the PLL molecule such as: zeta potential, the number of electrokinetic charges, ionization degree, contour length, and cross section area. These data were exploited in theoretical calculations of PLL adsorption kinetics on solid substrates under diffusion transport. A hybrid approach was used comprising a blocking function derived from the random sequential adsorption (RSA) model. In experiments, the PLL adsorption on mica was studied using the streaming potential measurements and interpreted in terms of a general electrokinetic model. This confirmed a side-on adsorption mechanism of the macroion molecules at the examined pH range. Additionally, using this method, the stability of PLL monolayers was determined performing in situ desorption kinetic experiments. In this way, the equilibrium adsorption constant and the energy minimum depth were determined. It was confirmed that the monolayer stability decreases with pH following the decrease in the number of electrokinetic charges per molecule. This confirmed the electrostatic interaction driven adsorption mechanism of PLL. It is also predicted that at pH 5.7-7.4 the monolayers were stable under diffusion-controlled desorption over the time exceeding 100 h. In addition to their significance for basic science, the results obtained in this work can be exploited for developing procedures for preparing stable PLL monolayers of well controlled coverage and electrokinetic properties.

Molecular Insights into Dipole Relaxation Processes in Water-Lysine Mixtures

Dielectric spectroscopy is a robust method to investigate relaxations of molecular dipoles. It is particularly useful for studies of biological solutions because of the potential of this method to cover a broad range of dynamical time scales typical for such systems. However, this technique does not provide any information about the nature of the molecular motions, which leads to a certain underemployment of dielectric spectroscopy for gaining microscopic understanding of material properties. For such detailed understanding, computer simulations are valuable tools because they can provide information about the nature of molecular motions observed by, for example, dielectric spectroscopy and to further complement them with structural information. In this work, we acquire information about the nature of dipole relaxation, in n-lysine solutions by means of molecular dynamics simulations. Our results indicate that the experimentally observed main relaxation process of n-lysine has different origins for the single monomer and the polypeptide chains. The relaxation of 1-lysine is due to the motions of whole molecules, whereas the experimentally observed relaxation of 3-lysine and 4-lysine is due to the motions of the residues, which, in turn, are promoted by water relaxation. Furthermore, we propose a new structural model of the lysine amino acids, which can quantitatively account for the experimental dielectric relaxation data. Hydrogen bonding and the structure of water are also discussed in terms of their influence on relaxation processes.

Lipid- and polymer-based plexes as therapeutic carriers for bioactive molecules

Recently, promising strategies of plexes include the complexation of nucleic acids with lipids (lipoplexes) and different kinds of polymers (polyplexes) for delivery of actives and genetic material in abnormal conditions like cancer, cystic fibrosis and genetic disorders. The present review article focuses on the comparative aspects of lipoplexes and polyplexes associated with molecular structure, cellular transportation and formulation aspects. The major advantages of lipoplexes and polyplexes over conventional liposomes involve non-immunogenic viral gene transfer, facile manufacturing and preservation of genetic material encapsulated within the nanocarriers. Lipoplexes and polyplexes enhance the transfection of DNA into the cell by stepwise electrostatic cationic-anionic interaction with DNA backbones. The ease and cost-effective formation of complexes extend their applications in the treatment of cancer and genetic disorders. Lipoplexes and polyplexes necessitate intensive research in the fields of quality, toxicity and methods of preparation for commercialization.

Strategies to overcome the polycation dilemma in drug delivery

Because of polycationic auxiliary agents such as chitosan, polyethyleneimine and cell penetrating peptides as well as cationic lipids assembling to polycationic systems, drug carriers can tightly interact with cell membranes exhibiting a high-density anionic charge. Because of these interactions the cell membrane is depolarized and becomes vulnerable to various uptake mechanisms. On their way to the target site, however, the polycationic character of all these drug carriers is eliminated by polyanionic macromolecules such as mucus glycoproteins, serum proteins, proteoglycans of the extracellular matrix (ECM) and polyanionic surface substructures of non-target cells such as red blood cells. Strategies to overcome this polycation dilemma are focusing on a pH-, redox- or enzyme-triggered charge conversion at the target site. The pH-triggered systems are making use of a slight acidic environment at the target site such as in case of solid tumors, inflammatory tissue and ischemic tissue. Due to a pH shift from 7.2 to slightly acidic mainly amino substructures of polymeric excipients are protonated or shielding groups such as 2,3 dimethylmaleic acid are cleaved off unleashing the underlying cationic character. Redox-triggered systems are utilizing disulfide linkages to bulky side chains such as PEGs masking the polycationic character. Under mild reducing conditions such as in the tumor microenvironment these disulfide bonds are cleaved. Enzyme-triggered systems are targeting enzymes such as alkaline phosphatase, matrix metalloproteinases or hyaluronidase in order to eliminate anionic moieties via enzymatic cleavage resulting in a charge conversion from negative to positive. Within this review an overview about the pros and cons of these systems is provided.

Arginine-based poly(ester amide) nanoparticle platform: From structure-property relationship to nucleic acid delivery

Many different types of polycations have been vigorously studied for nucleic acid delivery, but a systematical investigation of the structure-property relationships of polycations for nucleic acid delivery is still lacking. In this study, a new library of biodegradable and biocompatible arginine-based poly(ester amide) (Arg-PEA) biomaterials was designed and synthesized with a tunable structure for such a comprehensive structure-property research. Nanoparticle (NP) complexes were formed through the electrostatic interactions between the polycationic Arg-PEAs and anionic nucleic acids. The following structure effects of the Arg-PEAs on the transfection efficiency of nucleic acids were investigated: 1) the linker/spacer length (length effect and odd-even effect); 2) salt type of arginine; 3) the side chain; 4) chain stiffness; 5) molecular weight (MW). The data obtained revealed that a slight change in the Arg-PEA structure could finely tune its physicochemical property such as hydrophobicity, and this could subsequently affect the nanoparticle size and zeta potential, which, in turn, regulate the transfection efficiency and silencing outcomes. A further study of the Arg-PEA/CpG oligodeoxynucleotide NP complexes indicated that the polymer structure could precisily regulate the immune response of CpG, thus providing a new potential nano-immunotherapy strategy. The in vitro data have further confirmed that the Arg-PEA NPs showed a satisfactory delivery performance for a variety of nucleic acids. Therefore, the data from the current study provide comprehensive information about the Arg-PEA structure-transfection property relationship; the tunable property of the library of Arg-PEA biomaterials can be one of the promising candidates for nucleic acid delivery and other biomedical applications.

STATEMENT OF SIGNIFICANCE

Polycations have being intensive utilized for nucleic acid delivery. However, there has not been elucidated about the relationship between polycation's structure and the physicochemical properties/biological function. In this timely report, an arginine based poly(ester amide) (Arg-PEA) library was prepared with finely tunable structure to systematically investigate the structure-property relationships of polycations for nucleic acid delivery. The results revealed that slight change of Arg-PEA structure could finely tune the physicochemical property (such as hydrophobicity), which subsequently affect the size and zeta potential of Arg-PEA/nucleic acid nanoparticles(NPs), and finally regulate the resulting transfection or silencing outcomes. Further study of Arg-PEA/CpG NPs indicated that the polymer structure could precisely regulate immuno response of CpG, providing new potential nano-immunotherapy strategy. In vitro evaluations confirmed that the NPs showed satisfied delivery performance for a variety types of nucleic acids. Therefore, these studies provide comprehensive information of Arg-PEA structure-property relationship, and the tunable properties of Arg-PEAs make them promising candidates for nucleic acid delivery and other biomedical applications. Overall, we have shown enough significance and novelty in terms of nucleic acid delivery, biomaterials, pharmaceutical science and nanomedicine.

Impact of Cationic Charge Density and PEGylated Poly(amino acid) Tercopolymer Architecture on Their Use as Gene Delivery Vehicles. Part 1: Synthesis, Self-Assembly, and DNA Complexation

The interaction of PEGylated poly(amino acid)s with their biological targets depends on their chemical nature and spatial arrangement of their building blocks. The synthesis, self-assembly, and DNA complexation of ABC terblock copolymers consisting of poly(ethylene glycol), (PEG), poly(l-lysine), and poly(l-leucine), are reported. Block copolymers are produced by a metal-free, living ring-opening polymerization of respective amino acid N-carboxyanhydrides using amino-terminated PEG as macroinitiator: (PEG-b-p(l-Lys)_x -b-p(l-Leu)_y , PEG-b-p(l-Leu)_x -b-p(l-Lys)_y , and PEG-b-p((l-Lys)_x -co-p(l-Leu)_y ). Sizes of self-assembled nanoparticles depend on the formation method. The nanoprecipitation method proves useful for copolymers with the poly(l-lysine) block protected as trifluoroacetate, effective diameters range between 92 and 132 nm, while direct dissolution in distilled water is suitable for the deprotected copolymers, yielding effective diameters between 52 and 173 nm. Critical micelle concentration (CMC) analyses corroborate particle size analyses and show a distinct impact of the molecular architecture; the lowest CMC (8 µg mL^-1 ) is observed when the poly(l-leucine) segment forms the C-block and the hydrophilic, disassembly driving poly(l-lysine) segment is short. DNA complexation, evaluated by gel motility and RiboGreen analyses, depends strongly on the molecular architecture. A more efficient DNA complexation is observed when poly(l-lysine) and poly(l-leucine) form individual blocks as opposed to them forming a copolymer.

Targeted multifunctional redox-sensitive micelle co-delivery of DNA and doxorubicin for the treatment of breast cancer

Drug/gene co-delivery carriers are a promising strategy for cancer treatment. Thus, herein, T7-conjugated redox-sensitive amphiphilic polyethylene glycol-polyethyleneimine-poly(caprolactone)-SS-poly(caprolactone)-polyethyleneimine-polyethylene glycol (PEG-PEI-PCL-SS-PCL-PEG) (PPPT) is designed to realize the co-delivery of pORF-hTRAIL and DOX efficiently into tumor cells. PPPT is synthesized via the ring opening polymerization (ROP) of ε-caprolactone followed by Michael addition polymerization and atom transfer radical polymerization (ATRP) of the maleic imide group of MAL-PEG-NHS. The PPPT micelles present a spherical or ellipsoidal geometry with a mean diameter of approximately 100-120 nm. Meanwhile, they also exhibit a redox-responsive drug release profile in vitro. The blood compatibility and complement activation tests reveal that the PPPT micelles do not induce blood hemolysis, blood clotting, or complement activation. The T7-modified co-delivery system shows a higher cellular uptake efficiency than the unmodified co-delivery system in human breast cancer MCF-7 cells and is accumulated in tumor more efficiently in vivo. These results suggest that the T7-targeted codelivery system of DOX and pORF-hTRAIL is a combined delivery platform that can significantly improve the treatment of breast cancer.

ε-Poly-l-Lysine/plasmid DNA nanoplexes for efficient gene delivery in vivo

The present work addresses the development and characterization of ε-Poly-l-Lysine/pDNA polyplexes and evaluation for their improved transfection efficacy and safety as compared to polyplexes prepared using Poly-l-Lysine and SuperFect®. Self-assembling polyplexes were prepared by varying the N/P ratio to obtain the optimum size, a net positive zeta potential and gel retardation. The stability in presence of DNase I and serum was assured using gel retardation assay. Their appreciable uptake in MCF-7 and 3.5, 3.79 and 4.79-fold higher transfection compared to PLL/pDNA polyplexes and 1.60, 1.53 and 1.79-fold higher transfection compared to SuperFect®/pDNA polyplexes in MCF-7, HeLa and HEK-293 cell lines respectively, affirmed the enhanced transfection of ε-PLL/pDNA polyplexes which was well supported with in vivo transfection and gene expression studies. The <8% in vitro hemolysis and >98% viability of MCF-7, HeLa and HEK-293 cells in presence of ε-PLL/pDNA polyplexes addressed their safety, which was also ensured using in vivo toxicity studies, where hemocompatibility, unaltered levels of biochemical markers and histology of vital organs confirmed ε-PLL to be an effective and safer alternative for non-viral genetic vectors.

The great escape: how cationic polyplexes overcome the endosomal barrier

Endo-lysosomal escape strategies of cationic polymer-mediated gene delivery at a glance.

Dendritic phospholipid-based drug delivery systems

A class of new dendritic phospholipid compounds with different hydrophilic dendritic poly(l-lysine) peripheries from generations 1 (G1) to 3 (G3) (DPL-1 to DPL-3) were synthesised and nano-drug delivery systems based on these compounds were prepared (DPN-2 and DPN-3).