Polymer-based Non-viral Vectors for Gene Therapy in the Skin

Gene therapy has emerged as a versatile technique with the potential to treat a range of human diseases; however, examples of the topical application of gene therapy as a treatment...

Genetically-engineered "all-in-one" vaccine platform for cancer immunotherapy

An essential step for cancer vaccination is to break the immunosuppression and elicit a tumor-specific immunity. A major hurdle against cancer therapeutic vaccination is the insufficient immune stimulation of the cancer vaccines and lack of a safe and efficient adjuvant for human use. We discovered a novel cancer immunostimulant, trichosanthin (TCS), that is a clinically used protein drug in China, and developed a well-adaptable protein-engineering method for making recombinant protein vaccines by fusion of an antigenic peptide, TCS, and a cell-penetrating peptide (CPP), termed an “all-in-one” vaccine, for transcutaneous cancer immunization. The TCS adjuvant effect on antigen presentation was investigated and the antitumor immunity of the vaccines was investigated using the different tumor models. The vaccines were prepared via a facile recombinant method. The vaccines induced the maturation of DCs that subsequently primed CD8⁺ T cells. The TCS-based immunostimulation was associated with the STING pathway. The general applicability of this genetic engineering strategy was demonstrated with various tumor antigens (i.e., legumain and TRP2 antigenic peptides) and tumor models (i.e., colon tumor and melanoma). These findings represent a useful protocol for developing cancer vaccines at low cost and time-saving, and demonstrates the adjuvant application of TCS—an old drug for a new application.

Nanocarriers for Skin Applications: Where Do We Stand?

Skin penetration of active molecules for treatment of diverse diseases is a major field of research owing to the advantages associated with the skin like easy accessibility, reduced systemic‐derived side effects, and increased therapeutic efficacy. Despite these advantages, dermal drug delivery is generally challenging due to the low skin permeability of therapeutics. Although various methods have been developed to improve skin penetration and permeation of therapeutics, they are usually aggressive and could lead to irreversible damage to the stratum corneum. Nanosized carrier systems represent an alternative approach for current technologies, with minimal damage to the natural barrier function of skin. In this Review, the use of nanoparticles to deliver drug molecules, genetic material, and vaccines into the skin is discussed. In addition, nanotoxicology studies and the recent clinical development of nanoparticles are highlighted to shed light on their potential to undergo market translation.

Polymeric Delivery of Therapeutic Nucleic Acids

The advent of genome editing has transformed the therapeutic landscape for several debilitating diseases, and the clinical outlook for gene therapeutics has never been more promising. The therapeutic potential of nucleic acids has been limited by a reliance on engineered viral vectors for delivery. Chemically defined polymers can remediate technological, regulatory, and clinical challenges associated with viral modes of gene delivery. Because of their scalability, versatility, and exquisite tunability, polymers are ideal biomaterial platforms for delivering nucleic acid payloads efficiently while minimizing immune response and cellular toxicity. While polymeric gene delivery has progressed significantly in the past four decades, clinical translation of polymeric vehicles faces several formidable challenges. The aim of our Account is to illustrate diverse concepts in designing polymeric vectors towards meeting therapeutic goals of in vivo and ex vivo gene therapy. Here, we highlight several classes of polymers employed in gene delivery and summarize the recent work on understanding the contributions of chemical and architectural design parameters. We touch upon characterization methods used to visualize and understand events transpiring at the interfaces between polymer, nucleic acids, and the physiological environment. We conclude that interdisciplinary approaches and methodologies motivated by fundamental questions are key to designing high-performing polymeric vehicles for gene therapy.

Current and future technological advances in transdermal gene delivery

Transdermal gene delivery holds significant advantages as it is able to minimize the problems of systemic administration such as enzymatic degradation, systemic toxicity, and poor delivery to target tissues. This technology has the potential to transform the treatment and prevention of a range of diseases. However, the skin poses a great barrier for gene delivery because of the "bricks-and-mortar" structure of the stratum corneum and the tight junctions between keratinocytes in the epidermis. This review systematically summarizes the typical physical and chemical approaches to overcome these barriers and facilitate gene delivery via skin for applications in vaccination, wound healing, skin cancers and skin diseases. Next, the advantages and disadvantages of different approaches are discussed and the insights for future development are provided.

Co-Delivery of Trichosanthin and Albendazole by Nano-Self-Assembly for Overcoming Tumor Multidrug-Resistance and Metastasis

Multidrug resistance (MDR) and metastasis are the major obstacles in cancer chemotherapy. Nanotechnology-based combination therapy is a useful strategy. Recently, the combination of biologics and small drugs has attracted much attention in cancer therapy. Yet, the treatment outcomes are often compromised by the different pharmacokinetic profiles of the co-administered drugs thus leading to inconsistent drug uptake and suboptimal drug combination at the tumor sites. Nanotechnology-based co-delivery offers a promising method to address this problem, which is well demonstrated in the use of small drug combinations. However, co-delivery of the drugs bearing different physicochemical properties (e.g., proteins and small drugs) remains a formidable challenge. Herein, we developed a self-assembled nanosystem for co-delivery of trichosanthin (TCS) protein and albendazole (ABZ) as a combination therapy for overcoming MDR and metastasis. TCS is a ribosome-inactivating protein with high antitumor activity. However, the druggability of TCS is poor due to its short half-life, lack of tumor-specific action, and low cell uptake. ABZ is a clinically used antihelmintic drug, which can also inhibit tubulin polymerization and thus serve as a potential antitumor drug. In our work, ABZ was encapsulated in the albumin-coated silver nanoparticles (termed ABZ@BSA/Ag NP). The thus-formed NPs were negatively charged and could tightly bind with the cationic TCS that was modified with a cell-penetrating peptide (CPP) low-molecular-weight protamine (termed rTL). Via the stable charge interaction, the nanosystem (rTL/ABZ@BSA/Ag NP) was self-assembled, and featured by the TCS corona. The co-delivery system efficiently inhibited the proliferation of the drug-resistant tumor cells (A549/T and HCT8/ADR) by impairing the cytoskeleton, arresting the cell cycle, and enhancing apoptosis. In addition, the migration and invasion of tumor cells were inhibited presumably due to the impeded cytoskeleton functions. The anti-MDR effect was further confirmed by the in vivo studies with the subcutaneous A549/T tumor mouse model. More importantly, the co-delivery system was demonstrated to be able to inhibit metastasis. The co-delivery system of TCS/ABZ provided a potential strategy for both overcoming drug resistance and inhibiting tumor metastasis.

Nanoparticles and targeted drug delivery in cancer therapy

Surgery, chemotherapy, radiotherapy, and hormone therapy are the main common anti-tumor therapeutic approaches. However, the non-specific targeting of cancer cells has made these approaches non-effective in the significant number of patients. Non-specific targeting of malignant cells also makes indispensable the application of the higher doses of drugs to reach the tumor region. Therefore, there are two main barriers in the way to reach the tumor area with maximum efficacy. The first, inhibition of drug delivery to healthy non-cancer cells and the second, the direct conduction of drugs into tumor site. Nanoparticles (NPs) are the new identified tools by which we can deliver drugs into tumor cells with minimum drug leakage into normal cells. Conjugation of NPs with ligands of cancer specific tumor biomarkers is a potent therapeutic approach to treat cancer diseases with the high efficacy. It has been shown that conjugation of nanocarriers with molecules such as antibodies and their variable fragments, peptides, nucleic aptamers, vitamins, and carbohydrates can lead to effective targeted drug delivery to cancer cells and thereby cancer attenuation. In this review, we will discuss on the efficacy of the different targeting approaches used for targeted drug delivery to malignant cells by NPs.

Microneedle-Assisted, DC-Targeted Codelivery of pTRP-2 and Adjuvant of Paclitaxel for Transcutaneous Immunotherapy

This work aims at developing an immunotherapeutic strategy to deliver a cancer DNA vaccine targeting dendritic cells (DCs), to trigger their maturation and antitumor function, and reduce immune escape using a polymeric nanocomplex of paclitaxel (PTX)-encapsulated sulfobutylether-β-cyclodextrin (SBE)/mannosylated N,N,N-trimethylchitosan (mTMC)/DNA. To enhance DC-targeting and revoke immunosuppression is the major challenge for eliciting effective antitumor immunity. This codelivery system is characterized by using low-dose PTX as an adjuvant that is included inside SBE, and the PTX/SBE further serves as an anionic crosslinker to self-assemble with the cationic mTMC/DNA polyplexes. This system is used in combination with a microneedle for transcutaneous vaccination. Once penetrating into the epidermis, the mannosylated nanocomplexes would preferentially deliver the pTRP-2 DNA vaccine inside the DCs. Phenotypic maturation is demonstrated by the increased expression of costimulatory molecules of CD80 and CD86, and the elevated secretion of IL-12p70. The mixed leucocyte reactions reveal that the PTX/SBE-mTMC/DNA nanocomplexes enhance the proliferation of CD4+ and CD8+ T cells, and inhibit the generation of immune-suppressive FoxP3+ T cells. The system shows high antitumor efficacy in vivo. The PTX/SBE-mTMC/DNA nanocomplexes for DC-targeted codelivery of DNA vaccine and adjuvant PTX yield synergistic effects on the DC maturation and its presenting functions, thus increasing immune stimulation and reducing immune escape.

A mannosylated PEI–CPP hybrid for TRAIL gene targeting delivery for colorectal cancer therapy

A mannosylated, bioreducible Man-PEI_5k–CPP/pTRAIL system was developed for treating colon cancer.

Poly-γ-glutamic acid-based GGT-targeting and surface camouflage strategy for improving cervical cancer gene therapy

A γ-PGA-based GGT-targeting and surface camouflage strategy for constructing a ternary layer-by-layer self-assembly gene delivery system.

Intein-mediated site-specific synthesis of tumor-targeting protein delivery system: Turning PEG dilemma into prodrug-like feature

Poor tumor-targeted and cytoplasmic delivery is a bottleneck for protein toxin-based cancer therapy. Ideally, a protein toxin drug should remain stealthy in circulation for prolonged half-life and reduced side toxicity, but turn activated at tumor. PEGylation is a solution to achieve the first goal, but creates a hurdle for the second because PEG rejects interaction between the drugs and tumor cells therein. Such PEG dilemma is an unsolved problem in protein delivery. Herein proposed is a concept of turning PEG dilemma into prodrug-like feature. A site-selectively PEGylated, gelatinase-triggered cell-penetrating trichosanthin protein delivery system is developed with three specific aims. The first is to develop an intein-based ligation method for achieving site-specific modification of protein toxins. The second is to develop a prodrug feature that renders protein toxins remaining stealthy in blood for reduced side toxicity and improved EPR effect. The third is to develop a gelatinase activatable cell-penetration strategy for enhanced tumor targeting and cytoplasmic delivery. Of note, site-specific modification is a big challenge in protein drug research, especially for such a complicated, multifunctional protein delivery system. We successfully develop a protocol for constructing a macromolecular prodrug system with intein-mediated ligation synthesis. With an on-column process of purification and intein-mediated cleavage, the site-specific PEGylation then can be readily achieved by conjugation with the activated C-terminus, thus constructing a PEG-capped, cell-penetrating trichosanthin system with a gelatinase-cleavable linker that enables tumor-specific activation of cytoplasmic delivery. It provides a promising method to address the PEG dilemma for enhanced protein drug delivery, and importantly, a facile protocol for site-specific modification of such a class of protein drugs for improving their druggability and industrial translation.

Blood-Brain-Barrier-Penetrating Albumin Nanoparticles for Biomimetic Drug Delivery via Albumin-Binding Protein Pathways for Antiglioma Therapy

Nutrient transporters have been explored for biomimetic delivery targeting the brain. The albumin-binding proteins (e.g., SPARC and gp60) are overexpressed in many tumors for transport of albumin as an amino acid and an energy source for fast-growing cancer cells. However, their application in brain delivery has rarely been investigated. In this work, SPARC and gp60 overexpression was found on glioma and tumor vessel endothelium; therefore, such pathways were explored for use in brain-targeting biomimetic delivery. We developed a green method for blood-brain barrier (BBB)-penetrating albumin nanoparticle synthesis, with the capacity to coencapsulate different drugs and no need for cross-linkers. The hydrophobic drugs (i.e., paclitaxel and fenretinide) yield synergistic effects to induce albumin self-assembly, forming dual drug-loaded nanoparticles. The albumin nanoparticles can penetrate the BBB and target glioma cells via the mechanisms of SPARC- and gp60-mediated biomimetic transport. Importantly, by modification with the cell-penetrating peptide LMWP, the albumin nanoparticles display enhanced BBB penetration, intratumoral infiltration, and cellular uptake. The LMWP-modified nanoparticles exhibited improved treatment outcomes in both subcutaneous and intracranial glioma models, with reduced toxic side effects. The therapeutic mechanisms were associated with induction of apoptosis, antiangiogenesis, and tumor immune microenvironment regulation. It provides a facile method for dual drug-loaded albumin nanoparticle preparation and a promising avenue for biomimetic delivery targeting the brain tumor based on combination therapy.

Low-molecular-weight protamine-modified PLGA nanoparticles for overcoming drug-resistant breast cancer

Multidrug resistance (MDR) is a major challenge for cancer therapy. Herein, we report a simple yet effective system, cell-penetrating peptide (CPP)-assisted poly(lactic-co-glycolic acid nanoparticles (PLGA NPs), for improving doxorubicin (DOX) delivery and overcoming MDR cancer. We selected the naturally derived CPP low-molecular-weight protamine (LMWP) to modify PLGA NP for enhanced drug delivery. We demonstrated that multiple mechanisms ("synergistic multipronged delivery") were responsible for the anti-MDR effects of LMWP/PLGA NP. This delivery system could boost intracellular and intranuclear delivery, thereby circumventing drug efflux. Use of a P-glycoprotein inhibitor did not further increase the efficiency of intracellular delivery of LMWP/PLGA/DOX NP, suggesting that delivery of LMWP-based NP was not affected by transporter-mediated drug efflux. Importantly, enhanced uptake and penetration within the tumor was found in mice given LMWP-based NP. LMWP/PLGA NP effectively arrested tumor growth in mice harboring drug-resistant breast tumors, thereby improving treatment outcomes without detectable toxicities. These data suggest that our system could provide effective yet safe anti-MDR cancer therapy based on a synergistic, multipronged drug-delivery strategy.

Antheraea pernyi silk fibroin-coated PEI/DNA complexes for targeted gene delivery in HEK 293 and HCT 116 cells

Polyethylenimine (PEI) has attracted much attention as a DNA condenser, but its toxicity and non-specific targeting limit its potential. To overcome these limitations, Antheraea pernyi silk fibroin (ASF), a natural protein rich in arginyl-glycyl-aspartic acid (RGD) peptides that contains negative surface charges in a neutral aqueous solution, was used to coat PEI/DNA complexes to form ASF/PEI/DNA ternary complexes. Coating these complexes with ASF caused fewer surface charges and greater size compared with the PEI/DNA complexes alone. In vitro transfection studies revealed that incorporation of ASF led to greater transfection efficiencies in both HEK (human embryonic kidney) 293 and HCT (human colorectal carcinoma) 116 cells, albeit with less electrostatic binding affinity for the cells. Moreover, the transfection efficiency in the HCT 116 cells was higher than that in the HEK 293 cells under the same conditions, which may be due to the target bonding affinity of the RGD peptides in ASF for integrins on the HCT 116 cell surface. This result indicated that the RGD binding affinity in ASF for integrins can enhance the specific targeting affinity to compensate for the reduction in electrostatic binding between ASF-coated PEI carriers and cells. Cell viability measurements showed higher cell viability after transfection of ASF/PEI/DNA ternary complexes than after transfection of PEI/DNA binary complexes alone. Lactate dehydrogenase (LDH) release studies further confirmed the improvement in the targeting effect of ASF/PEI/DNA ternary complexes to cells. These results suggest that ASF-coated PEI is a preferred transfection reagent and useful for improving both the transfection efficiency and cell viability of PEI-based nonviral vectors.

Curb challenges of the "Trojan Horse" approach: smart strategies in achieving effective yet safe cell-penetrating peptide-based drug delivery

Cell-penetrating peptide (CPP)-mediated intracellular drug delivery system, often specifically termed as "the Trojan horse approach", has become the "holy grail" in achieving effective delivery of macromolecular compounds such as proteins, DNA, siRNAs, and drug carriers. It is characterized by the unique cell- (or receptor-), temperature-, and payload-independent mechanisms, therefore offering potent means to improve poor cellular uptake of a variety of macromolecular drugs. Nevertheless, this "Trojan horse" approach also acts like a double-edged sword, causing serious safety and toxicity concerns to normal tissues or organs for in vivo application, due to lack of target selectivity of the powerful cell penetrating activity. To overcome this problem of potent yet non-selective penetration vs. targeting delivery, a number of "smart" strategies have been developed in recent years, including controllable CPP-based drug delivery systems based on various stimuli-responsive mechanisms. This review article provides a fundamental understanding of these smart systems, as well as a discussion of their real-time in vivo applicability.

Layer-by-layer assembly of ferrocene-modified linear polyethylenimine redox polymer films

Herein, both electrostatic and covalent layer-by-layer assembly were used for the construction of multicomposite thin films using a ferrocene-modified linear poly(ethylenimine) redox polymer (Fc-C6-LPEI) as the cationic polyelectrolye, and poly(acrylic acid) (PAA), poly(glutamic acid) (PGA), or glucose oxidase (GOX) as the negative polyelectrolyte. The assembly of the multilayer films was characterized by cyclic voltammetry (CV), UV/Vis spectroscopy, and ellipsometry with the enzymatic response of the films containing GOX being characterized via constant potential amperometry. CV measurements suggested that the successful buildup of multilayer films was dependent upon the nature of the anionic polyelectrolyte used. Electrostatic assembly of films composed of Fc-C6-LPEI and either PAA or PGA produced large oxidation peak current densities of 630 and 670 μA cm(-2), respectively, during cyclic voltammetry. Increased measured absorbance by UV/Vis spectroscopy and increased measured film thicknesses (400-600 nm) by ellipsometry provided additional evidence of successful film formation. In contrast, the films incorporating GOX that were electrostatically assembled surprisingly produced significantly lower electrochemical responses (12 μA cm(-2)), low absorbance values, and reduced film thicknesses (~15 nm), and glucose electro-oxidation current densities less than 1 μA cm(-2), which all suggested unstable or minimal film formation. Subsequently, we developed a covalent layer-by-layer approach to fabricate films of Fc-C6-LPEI/GOX by covalently linking the amine groups of Fc-C6-LPEI to the aldehyde groups of periodate-oxidized glucose oxidase. Covalent assembly of the Fc-C6-LPEI/GOX films produced oxidation peak current densities during cyclic voltammetry of 40 μA cm(-2) and glucose electro-oxidation current densities of 220 μA cm(-2). These films also showed an increase in their thicknesses (~140 nm) relative to the electrostatic GOX films. For the films containing either PAA or PGA, the pH of the polymer solutions used for construction was found to have a significant effect on the response of the multilayer films, and the electrochemical response of the Fc-C6-LPEI/PAA, Fc-C6-LPEI/PGA, or covalently assembled Fc-C6-LPEI/GOX films could be tuned by varying the number of bilayers (n=1-16) in the film. These results are important because this is the first report of the use of the novel Fc-C6-LPEI redox polymer in the successful development of multicomposite layer-by-layer films. The electrochemical response achieved with the covalently assembled Fc-C6-LPEI/GOX films demonstrates that this redox polymer and layer-by-layer assembly technique can be used for possible biosensor and biofuel applications, and the success of multiple anionic polyelectrolytes could lead to additional applications with other enzyme systems.