Low molecular weight polyethylenimines linked by β-cyclodextrin for gene transfer into the nervous system

Cyclodextrin-conjugated low-molecular-weight polyethyleneimine as a macromolecular contrast agent for tumor-targeted magnetic resonance imaging

Macromolecular contrast agents (CAs) usually possess excellent contrast ability and tumor-targeting ability in comparison with small-molecule CAs, especially for early tumor detection. Herein, cyclodextrin-conjugated low-molecular-weight polyethyleneimine was synthesized as a macromolecular backbone. Afterward, a linear polymer with adamantane terminal and Gd chelates was synthesized, followed by conjugating with the backbone via host-guest interaction. Finally, folic acid was conjugated onto the as-prepared CAs through bioorthogonal chemistry, which endowed the CAs with the capability to accumulate into the tumor region. Compared to Magnevist (r1 = 4.25 mM-1 s-1) used in clinic, the PC/Ad-PEG2000-PLL(DTPA-Gd)-FA exhibited higher longitudinal relaxivity (r1 = 11.62 mM-1 s-1) with excellent biocompatibility. Furthermore, in vivo experiments demonstrated that PC/Ad-PEG2000-PLL(DTPA-Gd)-FA could effectively accumulate in the tumor region and produce a brighter image than that of Magnevist. The H&E staining and metabolic data further illustrated that this CA possessed excellent biocompatibility in vivo. Finally, these results above suggest that this macromolecular CA could be a potential candidate as a MRI CA for tumor-targeted diagnosis.

Polyethylenimine (PEI) in gene therapy: Current status and clinical applications

Polyethlyenimine (PEI) was introduced 1995 as a cationic polymer for nucleic acid delivery. PEI and its derivatives are extensively used in basic research and as reference formulations in the field of polymer-based gene delivery. Despite its widespread use, the number of clinical applications to date is limited. Thus, this review aims to consolidate the past applications of PEI in DNA delivery, elucidate the obstacles that hinder its transition to clinical use, and highlight potential prospects for novel iterations of PEI derivatives. The present review article is divided into three sections. The first section examines the mechanism of action employed by PEI, examining fundamental aspects of cellular delivery including uptake mechanisms, release from endosomes, and transport into the cell nucleus, along with potential strategies for enhancing these delivery phases. Moreover, an in-depth analysis is conducted concerning the mechanism underlying cellular toxicity, accompanied with approaches to overcome this major challenge. The second part is devoted to the in vivo performance of PEI and its application in various therapeutic indications. While systemic administration has proven to be challenging, alternative localized delivery routes hold promise, such as treatment of solid tumors, application as a vaccine, or serving as a therapeutic agent for pulmonary delivery. In the last section, the outcome of completed and ongoing clinical trials is summarized. Finally, an expert opinion is provided on the potential of PEI and its future applications. PEI-based formulations for nucleic acid delivery have a promising potential, it will be an important task for the years to come to introduce innovations that address PEI-associated shortcomings by introducing well-designed PEI formulations in combination with an appropriate route of administration.

Thermoreversible Gels Based on Chitosan Copolymers as "Intelligent" Drug Delivery System with Prolonged Action for Intramuscular Injection

Thermosensitive gels based on copolymers (PEG-chitosan, chitosan-polyethylenimine, chitosan-arginine and glycol-chitosan-spermine) are presented as promising polycations for the formation of DNA polyplexes and the potential for the development of drugs with prolonged release (up to 30 days). Being in liquid form at room temperature, such compounds can be injected into muscle tissue with rapid gel formation at human body temperature. An intramuscular depot is formed with a therapeutic agent that provides a gradual release of the drug, such as an antibacterial or cytostatic. The physico-chemical parameters of the formation of polyplexes between polycationic polymers of various compositions and molecular architecture and DNA were studied via FTIR, UV-vis and fluorescence spectroscopy using the dyes rhodamine 6G (R6G) and acridine orange (AO). The competitive displacement of AO from AO-DNA complexes showed that, with a ratio of N/P = 1, most of the DNA is bound to a polycation. During the formation of polyplexes, the DNA charge is neutralized by a polycation, which is reflected in electrophoretic immobility. The cationic polymers described in this work at a concentration of 1-4% are capable of forming gels, and the thermoreversible property is most characteristic of pegylated chitosan. BSA, as a model anionic molecule, is released by half in 5 days from the Chit5-PEG5 gel; full release is achieved in 18-20 days. At the same time, in 5 days, the gel is destroyed up to 30%, and in 20 days, by 90% (release of chitosan particles). For the first time, flow cytometry was used to study DNA polyplexes, which showed the existence of fluorescent particles in a much larger number in combination with free DNA. Thus, functional stimulus-sensitive polymers are potentially applicable for the creation of prolonged therapeutic formulations for gene delivery systems, which were obtained. The revealed regularities appear to be a platform for the design of polyplexes with controllable stability, in particular, fulfilling the requirements imposed for gene delivery vehicles.

Mannosylated Systems for Targeted Delivery of Antibacterial Drugs to Activated Macrophages

Macrophages are a promising target for drug delivery to influence macrophage-associated processes in the body, namely due to the presence of resistant microorganisms in macrophages. In this work, a series of mannosylated carriers based on mannan, polyethylenimine (PEI) and cyclodextrin (CD) was synthesized. The molecular architecture was studied using FTIR and ¹H NMR spectroscopy. The particle size, from small 10-50 nm to large 500 nm, depending on the type of carrier, is potentially applicable for the creation of various medicinal forms: intravenous, oral and inhalation. Non-specific capture by cells with a simultaneous increase in selectivity to CD206+ macrophages was achieved. ConA was used as a model mannose receptor, binding galactosylated (CD206 non-specific) carriers with constants of the order of 10⁴ M^-1 and mannosylated conjugates of 10⁶-10⁷ M^-1. The results of such primary "ConA-screening" of ligands are in a good agreement in terms of the comparative effectiveness of the interaction of ligands with the CD206+ macrophages: non-specific (up to 10%) absorption of highly charged and small particles; weakly specific uptake of galactosylated polymers (up to 50%); and high affine capture (more than 70-80%) of the ligands with grafted trimannoside was demonstrated using the cytometry method. Double and multi-complexes of antibacterials (moxifloxacin with its adjuvants from the class of terpenoids) were proposed as enhanced forms against resistant pathogens. In vivo pharmacokinetic experiments have shown that polymeric carriers significantly improve the efficiency of the antibiotic: the half-life of moxifloxacin is increased by 2-3 times in conjugate-loaded forms, bio-distribution to the lungs in the first hours after administration of the drug is noticeably greater, and, after 4 h of observation, free moxifloxacin was practically removed from the lungs of rats. Although, in polymer systems, its content is significant-1.2 µg/g. Moreover, the importance of the covalent crosslinking carrier with mannose label was demonstrated. Thus, this paper describes experimental, scientifically based methods of targeted drug delivery to macrophages to create enhanced medicinal forms.

Mannosylated Polymeric Ligands for Targeted Delivery of Antibacterials and Their Adjuvants to Macrophages for the Enhancement of the Drug Efficiency

Bacterial infections and especially resistant strains of pathogens localized in macrophages and granulomas are intractable diseases that pose a threat to millions of people. In this paper, the theoretical and experimental foundations for solving this problem are proposed due to two key aspects. The first is the use of a three-component polymer system for delivering fluoroquinolones to macrophages due to high-affinity interaction with mannose receptors (CD206). Cytometry assay determined that 95.5% macrophage-like cells were FITC-positive after adding high-affine to CD206 trimannoside conjugate HPCD-PEI1.8-triMan, and 61.7% were FITC-positive after adding medium-affine ligand with linear mannose label HPCD-PEI1.8-Man. The second aspect is the use of adjuvants, which are synergists for antibiotics. Using FTIR and NMR spectroscopy, it was shown that molecular containers, namely mannosylated polyethyleneimines (PEIs) and cyclodextrins (CDs), load moxifloxacin (MF) with dissociation constants of the order of 10⁻⁴–10⁻⁶ M; moreover, due to prolonged release and adsorption on the cell membrane, they enhance the effect of MF. Using CLSM, it was shown that eugenol (EG) increases the penetration of doxorubicin (Dox) into cells by an order of magnitude due to the creation of defects in the bacterial wall and the inhibition of efflux proteins. Fluorescence spectroscopy showed that 0.5% EG penetrates into bacteria and inhibits efflux proteins, which makes it possible to increase the maximum concentration of the antibiotic by 60% and maintain it for several hours until the pathogens are completely neutralized. Regulation of efflux is a possible way to overcome multiple drug resistance of both pathogens and cancer cells.

Therapeutic nanotechnologies for Alzheimer's disease: a critical analysis of recent trends and findings

Alzheimer's Disease (AD) is an irreversible neurodegenerative disease for which no disease modifying therapies are presently available. Besides the identification of pathological targets, AD presents numerous clinical and pharmacological challenges such as efficient active delivery to the central nervous system, cell targeting, and long-term dosing. Nanoparticles have been explored to overcome some of these challenges as drug delivery vehicles or drugs themselves. However, early promises have failed to materialize as no nanotechnology-based product has been able to reach the market and very few have moved past preclinical stages. In this review, we perform a critical analysis of the past decade's research on nanomedicine-based therapies for AD at the preclinical and clinical stages. The main obstacles to nanotechnology products and the most promising approaches were also identified, including renewed promise with gene editing, gene modulation, and vaccines.

Spectroscopy Approach for Highly-Efficient Screening of Lectin-Ligand Interactions in Application for Mannose Receptor and Molecular Containers for Antibacterial Drugs

Rational search of a ligand for a specific receptor is a cornerstone of a typical drug discovery process. However, to make it more “rational” one would appreciate having detailed information on the functional groups involved in ligand-receptor interaction. Typically, the 3D structure of a ligand-receptor complex can be built on the basis of time-consuming X-ray crystallography data. Here, a combination of FTIR and fluorescence methods, together with appropriate processing, yields valuable information about the functional groups of both the ligand and receptor involved in the interaction, with the simplicity of conventional spectrophotometry. We have synthesized the “molecular containers” based on cyclodextrins, polyethyleneimines (PEI) or spermine with mannose-rich side-chains of different molecular architecture (reticulated, star-shaped and branched) with variable parameters to facilitate delivery to alveolar macrophages. We have shown that synthetic mannose-rich conjugates are highly affine to the model mannose receptor ConA: K_d ≈ 10⁻⁵–10⁻⁷ M vs. natural ligand trimannoside (10⁻⁵ M). Further, it was shown that molecular containers effectively load levofloxacin (dissociation constants are 5·10⁻⁴–5·10⁻⁶ M) and the eugenol adjuvant (up to 15–80 drug molecules for each conjugate molecule) by including them in the cyclodextrins cavities, as well as by interacting with polymer chains. Promising formulations of levofloxacin and its enhancer (eugenol) in star-shaped and polymer conjugates of high capacity were obtained. UV spectroscopy demonstrated a doubling of the release time of levofloxacin into the external solution from the complexes with conjugates, and the effective action time (time of 80% release) was increased from 0.5 to 20–70 h. The synergy effect of antibacterial activity of levofloxacin and its adjuvants eugenol and apiol on Escherichia coli was demonstrated: the minimum effective concentration of the antibiotic was approximately halved.

Spatiotemporal Developmental Upregulation of Prestin Correlates With the Severity and Location of Cyclodextrin-Induced Outer Hair Cell Loss and Hearing Loss

2-Hyroxypropyl-beta-cyclodextrin (HPβCD) is being used to treat Niemann-Pick C1, a fatal neurodegenerative disease caused by abnormal cholesterol metabolism. HPβCD slows disease progression, but unfortunately causes severe, rapid onset hearing loss by destroying the outer hair cells (OHC). HPβCD-induced damage is believed to be related to the expression of prestin in OHCs. Because prestin is postnatally upregulated from the cochlear base toward the apex, we hypothesized that HPβCD ototoxicity would spread from the high-frequency base toward the low-frequency apex of the cochlea. Consistent with this hypothesis, cochlear hearing impairments and OHC loss rapidly spread from the high-frequency base toward the low-frequency apex of the cochlea when HPβCD administration shifted from postnatal day 3 (P3) to P28. HPβCD-induced histopathologies were initially confined to the OHCs, but between 4- and 6-weeks post-treatment, there was an unexpected, rapid and massive expansion of the lesion to include most inner hair cells (IHC), pillar cells (PC), peripheral auditory nerve fibers, and spiral ganglion neurons at location where OHCs were missing. The magnitude and spatial extent of HPβCD-induced OHC death was tightly correlated with the postnatal day when HPβCD was administered which coincided with the spatiotemporal upregulation of prestin in OHCs. A second, massive wave of degeneration involving IHCs, PC, auditory nerve fibers and spiral ganglion neurons abruptly emerged 4–6 weeks post-HPβCD treatment. This secondary wave of degeneration combined with the initial OHC loss results in a profound, irreversible hearing loss.

Human-derived NLS enhance the gene transfer efficiency of chitosan

Nuclear import is considered as one of the major limitations for non-viral gene delivery systems and the incorporation of nuclear localization signals (NLS) that mediate nuclear intake can be used as a strategy to enhance internalization of exogenous DNA.

In this work, human-derived endogenous NLS peptides based on insulin growth factor binding proteins (IGFBP), namely IGFBP-3 and IGFBP-5, were tested for their ability to improve nuclear translocation of genetic material by non-viral vectors. Several strategies were tested to determine their effect on chitosan mediated transfection efficiency: co-administration with polyplexes, co-complexation at the time of polyplex formation, and covalent ligation to chitosan. Our results show that co-complexation and covalent ligation of the NLS peptide derived from IGFBP-3 to chitosan polyplexes yields a 2-fold increase in transfection efficiency, which was not observed for NLS peptide derived from IGFBP-5.

These results indicate that the integration of IGFBP-NLS-3 peptides into polyplexes has potential as a strategy to enhance the efficiency of non-viral vectors.

Cochlear spiral ganglion neuron degeneration following cyclodextrin-induced hearing loss

Because cyclodextrins are capable of removing cholesterol from cell membranes, there is growing interest in using these compounds to treat diseases linked to aberrant cholesterol metabolism. One compound, 2-hydroxypropyl-beta-cyclodextrin (HPβCD), is currently being evaluated as a treatment for Niemann-Pick Type C1 disease, a rare, fatal neurodegenerative disease caused by the buildup of lipids in endosomes and lysosomes. HPβCD can reduce some debilitating symptoms and extend life span, but the therapeutic doses used to treat the disease cause hearing loss. Initial studies in rodents suggested that HPβCD selectively damaged only cochlear outer hair cells during the first week post-treatment. However, our recent in vivo and in vitro studies suggested that the damage could become progressively worse and more extensive over time. To test this hypothesis, we treated rats subcutaneously with 1, 2, 3 or 4 g/kg of HPβCD and waited for 8-weeks to assess the long-term histological consequences. Our new results indicate that the two highest doses of HPβCD caused extensive damage not only to OHC, but also to inner hair cells, pillar cells and other support cells resulting in the collapse and flattening of the sensory epithelium. The 4 g/kg dose destroyed all the outer hair cells and three-fourths of the inner hair cells over the basal two-thirds of the cochlea and more than 85% of the nerve fibers in the habenula perforata and more than 80% of spiral ganglion neurons in the middle of basal turn of the cochlea. The mechanisms that lead to the delayed degeneration of inner hair cells, pillar cells, nerve fibers and spiral ganglion neurons remain poorly understood, but may be related to the loss of trophic support caused by the degeneration of sensory and/or support cells in the organ of Corti. Despite the massive damage to the cochlear sensory epithelium, the blood vessels in the stria vascularis and the vestibular hair cells in the utricle and saccule remained normal.

Intrathecal drug delivery in the era of nanomedicine

Administration of substances directly into the cerebrospinal fluid (CSF) that surrounds the brain and spinal cord is one approach that can circumvent the blood-brain barrier to enable drug delivery to the central nervous system (CNS). However, molecules that have been administered by intrathecal injection, which includes intraventricular, intracisternal, or lumbar locations, encounter new barriers within the subarachnoid space. These barriers include relatively high rates of turnover as CSF clears and potentially inadequate delivery to tissue or cellular targets. Nanomedicine could offer a solution. In contrast to the fate of freely administered drugs, nanomedicine systems can navigate the subarachnoid space to sustain delivery of therapeutic molecules, genes, and imaging agents within the CNS. Some evidence suggests that certain nanomedicine agents can reach the parenchyma following intrathecal administration. Here, we will address the preclinical and clinical use of intrathecal nanomedicine, including nanoparticles, microparticles, dendrimers, micelles, liposomes, polyplexes, and other colloidalal materials that function to alter the distribution of molecules in tissue. Our review forms a foundational understanding of drug delivery to the CSF that can be built upon to better engineer nanomedicine for intrathecal treatment of disease.

Facile Fabrication of Self-Healable and Antibacterial Soy Protein-Based Films with High Mechanical Strength

Soy protein isolate (SPI), a ubiquitous and readily available biopolymer, has drawn increasing attention because of its sustainability, abundance, and low price. However, the poor mechanical properties, tedious performance adjustments, irreversible damage, and weak microorganism resistance have limited its applications. In this study, a facile but delicate strategy is proposed to fabricate an excellently self-healable and remarkably antibacterial SPI-based material with high mechanical strength by integrating polyethyleneimine (PEI) and metal ions (Cu(II) or Zn(II)). The tensile strengths of the SPI/PEI-Cu-0.750 and SPI/PEI-Zn-0.750 films reach up to 10.46 ± 0.50 and 9.06 ± 0.62 MPa, which is 367.06 and 306.28% strength increase compared to that of neat SPI film, respectively. Due to abundant non-covalent bonds and low glass transition temperature of the network, both SPI/PEI-Cu and SPI/PEI-Zn films exhibit a satisfactory self-healing behavior even at room temperature. Furthermore, SPI/PEI-Cu and SPI/PEI-Zn films demonstrate high bacterial resistance against Escherichia coli and Staphylococcus aureus. This facile strategy of establishing dynamic networks in a biomaterial with numerous excellent properties will enormously expand the scope of its applications, especially in the field of recyclable and durable materials.

ATP-Responsive Low-Molecular-Weight Polyethylenimine-Based Supramolecular Assembly via Host-Guest Interaction for Gene Delivery

In this work, we report on an ATP-responsive low-molecular-weight polyethylenimine (LMW-PEI)-based supramolecular assembly. It formed via host-guest interaction between PEI (MW = 1.8 kDa)-α-cyclodextrin (α-CD) conjugates and PEI_1.8k-phenylboronic acid (PBA) conjugates. The host-guest interaction between PEI_1.8k-α-CD and PEI_1.8k-PBA was confirmed by the 2D-NOESY chromatogram experiment and competition test. The ATP-responsive property of the supramolecular assembly was evaluated by a series of ATP-triggered degradation and siRNA release studies in terms of fluorescence resonance energy transfer, agarose gel electrophoresis assay, and the time course monitoring of the particle size and morphology. Confocal laser scanning microscopy confirmed the intracellular disassembly of the supramolecular polymer and the release of siRNA. The supramolecular assembly showed high buffering capability and was capable of protecting siRNA from RNase degradation. It had high cytocompatibility according to in vitro cytotoxicity and hemolysis assays. LMW-PEI-based supramolecular assembly facilitated cellular entry of siRNA via energy-dependent endocytosis. Moreover, the assembly/SR-A siRNA polyplexes at N/P ratio of 30 was most effective in knocking down SR-A mRNA and inhibiting uptake of modified LDL. Taken together, this work shows that ATP-responsive LMW-PEI-based supramolecular assembly is a promising gene vector and has potential application in treating atherosclerosis.

Pancreatic Cancer Gene Therapy Delivered by Nanoparticles

Pancreatic cancer is one of the most lethal forms of cancer and has proven to be difficult to treat through conventional methods, including surgery and chemotherapy. Gene therapy serves as a potential novel treatment to interfere with genes that make this cancer so aggressive, but free nucleic acids have low cell uptake due to their negative charge and are unstable in circulation. Nanoparticles can serve as an effective carrier for a wide variety of gene therapies for pancreatic cancer as they can improve the circulation time, decrease the recognition by the immune system, and be functionalized to target specific surface proteins. In this review, we focus on therapeutic strategies using nanoparticles as carriers of small interfering RNA (siRNA), microRNA (miRNA), and gene augmentation (DNA) therapies in the context of pancreatic cancer. Lastly, we discuss the future outlook of nanoparticle-based therapies, including challenges in the clinical setting.

Water-Soluble Polymer Assists N-Methyl-D-Aspartic Acid Receptor 2B siRNA Delivery to Relieve Chronic Inflammatory Pain In Vitro and In Vivo

We constructed a water-soluble lipopolymer (WSLP) as a nonviral gene carrier to deliver siRNA targeting NR2B. The cytotoxicity and serum stability of WSLP loaded with siRNA were evaluated, and the knockdown efficiency of WSLP/NR2B-siRNA in PC12 cells was examined. The results showed that WSLP could protect the loading siRNAs from enzymatic degradation in serum and exhibit low cytotoxicity to cells. After transfection, WSLP/NR2B-siRNA complexes reduced the NR2B transcriptional level by 50% and protein level by 55% compared to control siRNA. Moreover, 3 days after intrathecal injection of WSLP/NR2B-siRNA complexes into rats, the NR2B protein expression decreased significantly to 58%, compared to control treatment (p < 0.01). Injection of WSLP with scrambled siRNA or of polyethylenimine (PEI) with NR2B-siRNA did not show this inhibitory effect. Additionally, injection of WSLP/NR2B-siRNA complexes significantly relieved inflammatory pain in rats at 3, 4, and 5 days with reduced MWT and decreased TWL scores, while injection of WSLP with scrambled siRNA or of PEI with NR2B-siRNA did not. These results demonstrated that WSLP can efficiently deliver siRNA targeting NR2B to PC12 cells and relieve pain in rats with chronic inflammatory pain.

Engineering intranasal mRNA vaccines to enhance lymph node trafficking and immune responses

Intranasal mRNA vaccination provides immediate immune protection against pandemic diseases. Recent studies have shown that diverse forms of polyethyleneimine (PEI) have potent mucosal adjuvant activity, which could significantly facilitate the delivery of intranasal mRNA vaccines. Nevertheless, optimizing the chemical structure of PEI to maximize its adjuvanticity and decrease its toxicity remains a challenge. Here we show that the chemical structure of PEI strongly influences how well nanocomplexes of PEI and mRNA migrate to the lymph nodes and elicit immune responses. Conjugating cyclodextrin (CD) with PEI600 or PEI2k yielded CP (CD-PEI) polymers with different CD/PEI ratios. We analyzed the delivery efficacy of CP600, CP2k, and PEI25k as intranasal mRNA vaccine carriers by evaluating the lymph nodes migration and immune responses. Among these polymers, CP2k/mRNA showed significantly higher in vitro transfection efficiency, stronger abilities to migrate to lymph nodes and stimulate dendritic cells maturation in vivo, which further led to potent humoral and cellular immune responses, and showed lower local and systemic toxicity than PEI25k/mRNA. These results demonstrate the potential of CD-PEI2k/mRNA nanocomplex as a self-adjuvanting vaccine delivery vehicle that traffics to lymph nodes with high efficiency.

STATEMENT OF SIGNIFICANCE

As we face outbreaks of pandemic diseases such as Zika virus, intranasal mRNA vaccination provides instant massive protection against highly variant viruses. Various polymer-based delivery systems have been successfully applied in intranasal vaccine delivery. However, the influence of molecular structure of the polymeric carriers on the lymph node trafficking and dendritic cell maturation is seldom studied for intranasal vaccination. Therefore, engineering polymer-based vaccine delivery system and elucidating the relationship between molecular structure and the intranasal delivery efficiency are essential for maximizing the immune responses. We hereby construct self-adjuvanting polymer-based intranasal mRNA vaccines to enhance lymph node trafficking and further improve immune responses.

Polymeric Nanoparticles Induce NLRP3 Inflammasome Activation and Promote Breast Cancer Metastasis

Polymeric nanoparticles gain enormous interests in cancer therapy. Polyethylenimine (PEI) 25 kD is well known for its high transfection efficiency and cytotoxicity. PEI-CyD (PC) was previously synthesized by conjugating low molecular PEI (M _w 600) with β-cyclodextrin (β-CyD), which is shown to induce lower cytotoxicity than PEI 25 kD. In the current study, the in vivo immune response of branched PEI 25 kD and PC is investigated. Compared to PC/pDNA, exposure of PEI 25kD/pDNA induces higher level of immune-stimulation evidenced by the increased spleen weight, phagocytic capacity of peritoneal macrophage, and proinflammatory cytokines in serum and liver. Importantly, administration of PEI 25 kD can greatly promote breast cancer metastasis in liver and lung tissues, which correlates with its ability to induce high oxidative stress and NLRP3-inflammasome activation. These results suggest that polymeric nanocarriers have the potential to induce immune-stimulation and cancer metastasis, which may affect their efficiency for cancer therapy.

Targeting Wall Teichoic Acid in Situ with Branched Polyethylenimine Potentiates β-Lactam Efficacy against MRSA

Methicillin-resistant Staphylococcus aureus (MRSA) is a medical concern. Here, we show that branched polyethylenimine (BPEI), a nontoxic, cationic polymer, restores MRSA's susceptibility to β-lactam antibiotics. Checkerboard assays with MRSA demonstrated synergy between BPEI and β-lactam antibiotics. A time-killing curve showed BPEI to be bactericidal in combination with oxacillin. BPEI did not potentiate efficacy with vancomycin, chloramphenicol, or linezolid. When exposed to BPEI, MRSA increased in size and had difficulty forming septa. BPEI electrostatically binds to wall teichoic acid (WTA), a cell wall anionic polymer of Gram-positive bacteria that is important for localization of certain cell wall proteins. Lack of potentiation in a WTA knockout mutant supports the WTA-based mechanism. These data suggest that BPEI may prevent proper localization of cell wall machinery by binding to WTA; leading to cell death when administered in combination with β-lactam antibiotics. Negligible in vitro toxicity suggests the combination could be a viable treatment option.

Combined delivery of a TGF-β inhibitor and an adenoviral vector expressing interleukin-12 potentiates cancer immunotherapy

Cancer immunotherapy appears to have a promising future, but it can be thwarted by secretion of immunosuppressive factors, such as transforming growth factor-β (TGF-β), which inhibits local immune responses to tumors. To weaken immune resistance of tumors and simultaneously strengthen immune responses, we developed a multifunctional polymer that could co-deliver hydrophobic TGF-β inhibitor and an adenovirus gene vector to tumor sites. This co-delivery system sustainably released TGF-β inhibitor SB-505124 and effectively transferred the adenovirus vector carrying the interleukin-12 gene. In addition, it significantly delayed growth of B16 melanoma xenografts in mice and increased animal survival. Mechanistic studies showed that this combination therapy enhanced anti-tumor immune response by activating CD4⁺ and CD8⁺ T cells, natural killer cells and interferon-γ secretion in the tumor microenvironment.

STATEMENT OF SIGNIFICANCE

To weaken immune resistance of tumors and simultaneously strengthen tumors' immune responses, we synthesized a structurally simple, low-toxic but functional polymer β-cyclodextrin-PEI to encapsulate a hydrophobic TGF-β inhibitor SB-505124 and to complex adenovirus vectors expressing IL-12. This is the first report demonstrating that combining TGF-β inhibitor with IL-12 could provide effective immunotherapy against melanoma by the sustainable release of SB-505124 and the effectible transduction of IL-12 gene in tumor cells. The rational delivery system presented a comprehensive and valued platform to be a candidate vector for co-delivering hydrophobic small-molecule drugs and therapeutic genes for treating cancer, providing a new approach for cancer immunotherapy.

Linear polymers of β and γ cyclodextrins with a polyglutamic acid backbone as carriers for doxorubicin

Cyclodextrins have been used to encapsulate drugs improving their stability and efficiently regulating their release. Polymeric nanoparticles containing cyclodextrins are currently undergoing clinical trials as nanotherapeutics. In this context, we have synthesized new linear polymers based on polyglutamic acid with pendant β- or γ-cyclodextrins, using a high yield reaction route. The new polymers with an average number of about 17 cyclodextrin cavities were characterized (NMR, MALDI-MS, DLS) and tested as carriers of doxorubicin in human tumor cells. They can include doxorubicin, and the inclusion complexes show antiproliferative activity in human tumor cells.

Investigation of the Sequential Actions of Doxorubicin and p53 on Tumor Cell Growth Via Branched Polyethylenimine-β-cyclodextrin Conjugates

The combination of gene therapy and chemotherapy has showed increased therapeutic efficacy in the treatment of cancers, but it is not well investigated about the actual coordination pattern between therapeutic gene and chemical drug. In this work, p53/BPEI-β-CD/AD-dox complex was fabricated and employed to investigate the interaction manner between p53 and doxorubicin (Dox). Briefly, branched polyethylenimine (BPEI) was conjugated with β-cyclodextrin hydrate (β-CD) to form BPEI-β-CD backbone, and p53 plasmid was condensed by positively charged BPEI via electrostatic interaction, while Dox was first conjugated with adamantine (AD) and then assembled with BPEI-β-CD backbone via the host-guest interaction. It was found that the BPEI-β-CD backbone possessed high endocytosis efficiency but low cytotoxicity. Moreover, p53/BPEI-β-CD/AD-dox complex released Dox and enabled the expression of p53 gene in a sequential manner, and the released Dox and expressed p53 gene showed successive inhibition of the growth of HeLa cells in vitro. With the ability to co-deliver chemical drug and therapeutic gene and exert their inhibitory actions on tumor cell growth in a sequential manner, this DNA/BPEI-β-CD/AD-drug complex via electrostatic interaction and host-guest assembly not only achieved long-term efficacy in inhibiting tumor cell growth but also can be employed as a platform to investigate the coordination pattern between chemical drugs and therapeutic genes for other purposes.

Synergistic effects of A-B-C-type amphiphilic copolymer on reversal of drug resistance in MCF-7/ADR breast carcinoma

P-glycoprotein (P-gp) overexpression has become the most common cause of occurrence of multidrug resistance in clinical settings. We aimed to construct a micellar polymer carrier to sensitize drug-resistant tumors to doxorubicin (DOX). This A-B-C-type amphiphilic copolymer was prepared by the sequential linkage of β-cyclodextrin, hydrophobic poly(d,l-lactide), and hydrophilic poly(ethylene glycol). Upon incubation of the DOX-loaded micelles with DOX-resistant human breast carcinoma MCF-7/ADR cells, significantly enhanced cytotoxicity and apoptosis were achieved. A series of studies on the action mechanism showed that the polymer components such as β-cyclodextrin, hydrophobic poly(d,l-lactide) segment, and poly(ethylene glycol) coordinatively contributed to the improved intracellular ATP depletion and ATPase activity, increased intracellular uptake of P-gp substrates via competitive binding to P-gp, and decreased P-gp expression in MCF-7/ADR cells. More interestingly, a similar phenomenon was observed in the zebrafish xenograft model, resulting in ~64% inhibition of MCF-7/ADR tumor growth. These results implied that the polymeric micelles displayed great potentials as P-gp modulators to reverse DOX resistance in MCF-7/ADR breast carcinoma.

Efficacy of ampicillin against methicillin-resistant Staphylococcus aureus restored through synergy with branched poly(ethylenimine)

Beta-lactam antibiotics kill Staphylococcus aureus bacteria by inhibiting the function of cell-wall penicillin binding proteins (PBPs) 1 and 3. However, β-lactams are ineffective against PBP2a, used by methicillin-resistant Staphylococcus aureus (MRSA) to perform essential cell wall crosslinking functions. PBP2a requires teichoic acid to properly locate and orient the enzyme, and thus MRSA is susceptible to antibiotics that prevent teichoic acid synthesis in the bacterial cytoplasm. As an alternative, we have used branched poly(ethylenimine), BPEI, to target teichoic acid in the bacterial cell wall. The result is restoration of MRSA susceptibility to the β-lactam antibiotic ampicillin with a MIC of 1 μg/mL, superior to that of vancomycin (MIC = 3.7 μg/mL). A checkerboard assay shows synergy of BPEI and ampicillin. Nuclear magnetic resonance (NMR) data show that BPEI alters the teichoic acid chemical environment. Laser scanning confocal microscopy (LSCM) images show BPEI residing on the bacterial cell wall where teichoic acids and PBPs are located.

Nanoparticle delivery systems for siRNA-based therapeutics

RNA interference (RNAi) is a naturally occurring endogenous regulatory process in which the short double-stranded RNA causes sequence-specific post-transcriptional gene silencing.

Bio-inspired polymer envelopes around adenoviral vectors to reduce immunogenicity and improve in vivo kinetics

Adenoviral vectors have attracted substantial interest for systemic tumor gene therapy, but further work is needed to reduce their immunogenicity and alter their biodistribution before they can be used in the clinic. Here we describe a bio-inspired, cleavable PEGylated β-cyclodextrin-polyethyleneimine conjugate (CDPCP) that spontaneously coats adenovirus in solution. This cleavable PEG coating reduces the innate and adaptive immunogenicity of adenovirus particles, as well as improves their biodistribution away from the liver and into the tumor. Insertion of a matrix metalloproteinase substrate sequence into the conjugate allows PEG cleavage at the tumor site, simultaneously reducing liver biodistribution and increasing transgene expression in tumors, thereby avoiding the "PEG dilemma". Cationic β-cyclodextrin-PEI not only provides electrostatic attraction to promote envelope attachment to the viral capsid, but it also improves vector internalization and transduction after PEG cleavage. These results suggest that CDPCP may help expand the use of adenoviral vectors in cancer gene therapy.

STATEMENT OF SIGNIFICANCE

The synthesized β-cyclodextrin-PEI-MMP-cleavable-PEG polymer (CDPCP), held great potential for gene therapy when applied for adenovirus coating. The β-cyclodextrin-PEI provided a powerful electrostatic attraction to attach the whole polymer onto the viral capsid, while the MMPs-cleavable PEG reduced innate and adaptive immunogenicity and improved the biodistribution of adenovirus vectors due to the tumor-specific enzyme triggered PEG cleavage. More importantly, an ingenious cooperation between the two components could solve the PEG dilemma. The CDPCP/Ad complexes exhibited a comprehensive and valued profile to be a candidate vector for future tumor gene therapy, we believe the current investigation on this kind of biomaterial may be of particular interest to the readership of Acta biomaterialia.

Pulmonary Codelivery of Doxorubicin and siRNA by pH-Sensitive Nanoparticles for Therapy of Metastatic Lung Cancer

A pulmonary codelivery system that can simultaneously deliver doxorubicin (DOX) and Bcl2 siRNA to the lungs provides a promising local treatment strategy for lung cancers. In this study, DOX is conjugated onto polyethylenimine (PEI) by using cis-aconitic anhydride (CA, a pH-sensitive linker) to obtain PEI-CA-DOX conjugates. The PEI-CA-DOX/siRNA complex nanoparticles are formed spontaneously via electrostatic interaction between cationic PEI-CA-DOX and anionic siRNA. The drug release experiment shows that DOX releases faster at acidic pH than at pH 7.4. Moreover, PEI-CA-DOX/Bcl2 siRNA complex nanoparticles show higher cytotoxicity and apoptosis induction in B16F10 cells than those treated with either DOX or Bcl2 siRNA alone. When the codelivery systems are directly sprayed into the lungs of B16F10 melanoma-bearing mice, the PEI-CA-DOX/Bcl2 siRNA complex nanoparticles exhibit enhanced antitumor efficacy compared with the single delivery of DOX or Bcl2 siRNA. Compared with systemic delivery, most drug and siRNA show a long-term retention in the lungs via pulmonary delivery, and a considerable number of the drug and siRNA accumulate in tumor tissues of lungs, but rarely in normal lung tissues. The PEI-CA-DOX/Bcl2 siRNA complex nanoparticles are promising for the treatment of metastatic lung cancer by pulmonary delivery with low side effects on the normal tissues.

Chemotherapeutic Drugs Interfere with Gene Delivery Mediated by Chitosan-Graft-Poly(ethylenimine)

Combined chemo-gene therapy is one of the treatment modalities that have attracted extensive research interests; however, there is little information regarding the influence of drug application on gene transfer. This study bridges this gap by examining how chemotherapeutic drugs (teniposide, cis-diamminedichloroplatinum(II) and temozolomide) interfere with polyplex formation and transfection of chitosan-graft-poly(ethylenimine). Our results indicate that the degree of drug interference varies with the mechanism of drug action, with the transgene expression being severely suppressed when the plasmid is co-delivered with cis-diamminedichloroplatinum(II) or teniposide but not temozolomide. In addition, the interference with transfection by drugs varies with different gene/drug co-formulations. This is the first study to evidence that, though combined chemo-gene therapy has therapeutic potential, some chemotherapeutic drugs may reduce the treatment efficiency of gene therapy.

Engineering nanoparticle-coated bacteria as oral DNA vaccines for cancer immunotherapy

Live attenuated bacteria are of increasing importance in biotechnology and medicine in the emerging field of cancer immunotherapy. Oral DNA vaccination mediated by live attenuated bacteria often suffers from low infection efficiency due to various biological barriers during the infection process. To this end, we herein report, for the first time, a new strategy to engineer cationic nanoparticle-coated bacterial vectors that can efficiently deliver oral DNA vaccine for efficacious cancer immunotherapy. By coating live attenuated bacteria with synthetic nanoparticles self-assembled from cationic polymers and plasmid DNA, the protective nanoparticle coating layer is able to facilitate bacteria to effectively escape phagosomes, significantly enhance the acid tolerance of bacteria in stomach and intestines, and greatly promote dissemination of bacteria into blood circulation after oral administration. Most importantly, oral delivery of DNA vaccines encoding autologous vascular endothelial growth factor receptor 2 (VEGFR2) by this hybrid vector showed remarkable T cell activation and cytokine production. Successful inhibition of tumor growth was also achieved by efficient oral delivery of VEGFR2 with nanoparticle-coated bacterial vectors due to angiogenesis suppression in the tumor vasculature and tumor necrosis. This proof-of-concept work demonstrates that coating live bacterial cells with synthetic nanoparticles represents a promising strategy to engineer efficient and versatile DNA vaccines for the era of immunotherapy.

Smart polymeric nanoparticles for cancer gene delivery

The massive amount of human genetic information already available has accelerated the identification of target genes, making gene and nucleic acid therapy the next generation of medicine. Nanoparticle (NP)-based anticancer gene therapy treatment has received significant interest in this evolving field. Recent advances in vector technology have improved gene transfection efficiencies of nonviral vectors to a level similar to viruses. This review serves as an introduction to surface modifications of NPs based on polymeric structural improvements and target moieties. A discussion regarding the future perspective of multifunctional NPs in cancer therapy is also included.

Engineering and functionalization of biomaterials via surface modification

Recent progress pertaining to the surface treatment of implantable macro-scale biomaterials and using micro- and nano-biomaterials for disease diagnosis and drug/gene delivery is reviewed.

Cationic star copolymers based on β-cyclodextrins for efficient gene delivery to mouse embryonic stem cell colonies

A cationic star copolymer with a β-cyclodextrin core was developed for nonviral gene transfer to mouse embryonic stem cells (mESCs).

Aminated β-Cyclodextrin-Modified-Carboxylated Magnetic Cobalt/Nanocellulose Composite for Tumor-Targeted Gene Delivery

Gene therapy is a new kind of medicine, which uses genes as drugs in order to treat life threatening diseases. In the present work, a nonviral vector, aminated β-cyclodextrin-modified-carboxylated magnetic cobalt/nanocellulose composite (ACDC-Co/NCC), was synthesized for efficient transfection of genes into tumour cells. The synthesized ACDC-Co/NCC was characterized by means of FTIR, XRD, SEM, and ESR techniques. DNA condensing ability of ACDC-Co/NCC was found to be increased with increase in amount of ACDC-Co/NCC and 84.9% of DNA (1.0 μg/mL) inclusion was observed with 6.0 μg/mL of ACDC-Co/NCC. The cytotoxicity of ACDC-Co/NCC was observed to be minimal, even at higher concentration, with respect to the model transfecting agent, poly(ethyleneimine) (PEI). 88.2% of the gene was transfected at high dose of DNA, as indicated by the highest luciferase expression. These results indicated that ACDC-Co/NCC might be a promising candidate for gene delivery with the characteristics of good biocompatibility, potential biodegradability, minimal cytotoxicity, and relatively high gene transfection efficiency.

Intrathecal injection of a therapeutic gene-containing polyplex to treat spinal cord injury

Spinal cord injury (SCI) is a serious clinical problem that suddenly deprives patients of neurologic function and drastically diminishes their quality of life. Gene introduction has the potential to be effective for various pathological states of SCI because various proteins can be produced just by modifying nucleic acid sequences. In addition, the sustainable protein expression allows to maintain its concentration at an effective level at the target site in the spinal cord. Here we propose an approach using a polyplex system composed of plasmid DNA (pDNA) and a cationic polymer, poly{N'-[N-(2-aminoethyl)-2-aminoethyl]aspartamide} [PAsp(DET)], that has high capacity to promote endosome escape and the long-term safety by self-catalytically degrading within a few days. We applied brain-derived neurotrophic factor (BDNF)-expressing pDNA for SCI treatment by intrathecal injection of PAsp(DET)/pDNA polyplex. A single administration of polyplex for experimental SCI provided sufficient therapeutic effects including prevention of neural cell death and enhancement of motor function recovery. This lasted for a few weeks after SCI, demonstrating the capability of this system to express BDNF in a safe and responsible manner for treatment of various pathological states in SCI.