Effects of the Physicochemical, Colloidal, and Biological Characteristics of Different Polymer Structures between α-Poly(l-lysine) and ε-Poly(l-lysine) on Polymeric Gene Delivery.

Though α-poly(l-lysine) (APL) has been well-studied in gene delivery, ε-poly(l-lysine) (EPL) with same repeating unit of l-lysine but different structure has been rarely investigated. This study compared various effects of their different structures in gene delivery processes. EPL showed less cytotoxicity and more proton buffering capacity for endosomal release than APL. Also, EPL/pDNA polyplexes represented higher nucleus preference than APL/pDNA polyplexes. However, EPL had weaker affinities with pDNA than APL, leading to formation of larger EPL/pDNA complexes with less compactness and successively faster decomplexation. The resultant difference of their pDNA binding affinity caused lower cellular uptake and lower transfection efficiency of EPL/pDNA complexes than APL/pDNA complexes. Thus, this study confirmed that various effects of gene delivery processes are changed by chemical structure of polymeric gene carriers. Especially, despite the low transfection efficiency of EPL-based polyplexes, the study found potentials of EPL in cytocompatibility, endosomal release, and nuclear import.

Bioreducible Poly(ethylene glycol)-Triphenylphosphonium Conjugate as a Bioactivable Mitochondria-Targeting Nanocarrier.

Bioactivable nanocarrier systems have favorable characteristics such as high cellular uptake, target specificity, and an efficient intracellular release mechanism. In this study, we developed a bioreducible methoxy polyethylene glycol (mPEG)-triphenylphosphonium (TPP) conjugate (i.e., mPEG-(ss-TPP)2 conjugate) as a vehicle for mitochondrial drug delivery. A bioreducible linkage with two disulfide bond-containing end groups was used at one end of the hydrophilic mPEG for conjugation with lipophilic TPP molecules. The amphiphilic mPEG-(ss-TPP)2 self-assembled in aqueous media, which thereby formed core-shell structured nanoparticles (NPs) with good colloidal stability, and efficiently encapsulated the lipophilic anticancer drug doxorubicin (DOX). The DOX-loaded mPEG-(ss-TPP)2 NPs were characterized in terms of their physicochemical and morphological properties, drug-loading and release behaviors, in vitro anticancer effects, and mitochondria-targeting capacity. Our results suggest that bioreducible DOX-loaded mPEG-(ss-TPP)2 NPs can induce fast drug release with enhanced mitochondrial uptake and have a better therapeutic effect than nonbioreducible NPs.

Administration sequence- and formation-dependent vaccination using acid-degradable polymeric nanoparticles with high antigen encapsulation capability.

Vaccines aim to efficiently and specifically activate the immune system via a cascade of antigen uptake, processing, and presentation by antigen-presenting cells (APCs) to CD4 and CD8 T cells, which in turn drive humoral and cellular immune responses. The specific formulation of vaccine carriers can not only shield the antigens from premature sequestering before reaching APCs but also favorably promote intracellular antigen presentation and processing. This study compares two different acid-degradable polymeric nanoparticles that are capable of encapsulating a moderately immunogenic antigen, GFP, at nearly full efficacy via electrostatic interactions or molecular affinity between His tag and Ni-NTA-conjugated monomners. This resulted in GFP-encapsulating NPs composed of ketal monomers and crosslinkers (KMX/GFP NPs) and NTA-conjugated ketal monomers and crosslinkers (NKMX/GFP NPs), respectively. Encapsulated GFP was found to be released more rapidly from NKMX/GFP NPs (electrostatic encapsulation) than from KMX/GFP NPs (affinity-driven encapsulation). In vivo vaccination studies demonstrated that while repeated injections of either NP formulation resulted in poorer generation of anti-GFP antibodies than injections of the GFP antigen itself, sequential injections of NPs and GFP as prime and booster vaccines, respectively, restored the humoral response. We proposed that NPs primarily assist APCs in antigen presentation by T cells, and B cells need to be further stimulated by free protein antigens to produce antibodies. The findings of this study suggest that the immune response can be modulated by varying the chemistry of vaccine carriers and the sequences of vaccination with free antigens and antigen-encapsulating NPs.

Silver-Composited Polydopamine Nanoparticles: Antibacterial and Antioxidant Potential in Nanocomposite Hydrogels.

(1) Background: Infections of pathogenic microorganisms can be life-threatening due to delayed healing or even worsening conditions in tissue engineering and regenerative medicine. The excessive presence of reactive oxygen species in damaged and infected tissues causes a negative inflammatory response, resulting in failed healing. Thus, the development of hydrogels with antibacterial and antioxidant abilities for the treatment of infectious tissues is in high demand. (2) Methods: We herein describe the development of green-synthesized silver-composited polydopamine nanoparticles (AgNPs), which are fabricated by the self-assembly of dopamine as a reducing and antioxidant agent in the presence of silver ions. (3) Results: The facile and green-synthesized AgNPs have a nanoscale diameter with mostly spherical shapes, with various shapes coexisting. The particles are stable in an aqueous solution for up to 4 weeks. In addition, remarkable antibacterial activity against Gram-positive and -negative bacterial strains and antioxidant capabilities were evaluated by in vitro assays. When incorporated into biomaterial hydrogels at concentrations above 2 mg L-1, the hydrogels produced powerful antibacterial effects. (4) Conclusions: This study describes a biocompatible hydrogel with antibacterial and antioxidant activities from the introduction of facile and green-synthesized AgNPs as a safer tool for the treatment of damaged tissues.

Nanocomplexes of doxorubicin and DNA fragments for efficient and safe cancer chemotherapy.

Cancer-targeted therapy by a chemotherapeutic agent formulated in a nanoscale platform has been challenged by complex and inefficient manufacturing, low drug loading, difficult characterization, and marginally improved therapeutic efficacy. This study investigated facile-to-produce nanocomplexes of doxorubicin (DOX), a widely used cancer drug, and clinically approved DNA fragments that are extracted from a natural source. DOX was found to self-assemble DNA fragments into relatively monodispersed nanocomplexes with a diameter of ∼70 nm at 14.3% (w/w) drug loading by simple and scalable mixing. The resulting DOX/DNA nanocomplexes showed sustained DOX release, unlike overly stable Doxil®, cellular uptake via multiple endocytosis pathways, and high hematological and immunological compatibility. DOX/DNA nanocomplexes eradicated EL4 T lymphoma cells in a time-dependent manner, eventually surpassing free DOX. Extended circulation of DOX/DNA nanocomplexes, while avoiding off-target accumulation in the lung and being cleared from the liver, resulted in rapid accumulation in tumor and lowered cardio toxicity. Finally, tumor growth of EL4-challenged C57BL/6 mice (syngeneic model) and OPM2-challenged NSG mice (human xenograft model) were efficiently inhibited by DOX/DNA nanocomplexes with enhanced overall survival, in comparison with free DOX and Doxil®, especially upon repeated administrations. DOX/DNA nanocomplexes are a promising chemotherapeutics delivery platform for their ease of manufacturing, high biocompatibility, desired drug release and accumulation, efficient tumor eradication with improved safety, and further engineering versatility for extended therapeutic applications.

Beyond hydrophilic polymers in amphiphilic polymer-based self-assembled NanoCarriers: Small hydrophilic carboxylate-capped disulfide drug delivery system and its multifunctionality and multispatial targetability.

Due to increasing safety and intracellular delivery concerns about hydrophilic polymers in amphiphilic polymer-based nanoparticles (NPs), this study investigates small hydrophilic molecule-stabilized NPs for effective intracellular delivery with multiorganelle targetability and dual responsiveness to acidic pH/glutathione (GSH). In the construction of small hydrophilic molecule-stabilized NP (MSPCL-NP), the A-B-A-type amphiphilic polymer (MSPCL-P) is composed of two short hydrophilic carboxylate-capped disulfide derivatives (A) that replace hydrophilic polymers and assist in providing colloidal stability and preventing antibody (e.g., at least anti-PEG antibody)-mediated specific interactions and complement activation in the plasma and a hydrophobic multiple disulfide-containing poly(ε-caprolactone) block (B) that carries hydrophobic drugs. The carboxylates on the surface of MSPCL-NP target the acidic extratumoral/endolysosomal milieu by sensing and buffering acidic pH values, and the hydrophobic carboxylic acids improve adsorptive endocytosis and effective endosomal escape. Multiple disulfide linkages selectively target cytosolic GSH, resulting in rapid drug release from the destroyed MSPCL-NP via the cleavage of disulfide bonds in MSPCL-P. Doxorubicin (DOX)-loaded NP (DOX@MSPCL-NP) exerts strong effects on killing cells in vitro and inhibits tumor growth in HCT116 xenograft tumor-bearing mice. In conclusion, the multifunctionality and multispatial targetability of MSPCL-NP might effectively overcome various sequential drug delivery hurdles, ranging from blood circulation to drug release. Furthermore, the introduction of small hydrophilic molecules represents a potential strategy to make self-assembled NPs without the use of hydrophilic polymers.

Mitochondria-targeting drug conjugates for cytotoxic, anti-oxidizing and sensing purposes: current strategies and future perspectives.

Mitochondrial targeting is a promising approach for solving current issues in clinical application of chemotherapy and diagnosis of several disorders. Here, we discuss direct conjugation of mitochondrial-targeting moieties to anticancer drugs, antioxidants and sensor molecules. Among them, the most widely applied mitochondrial targeting moiety is triphenylphosphonium (TPP), which is a delocalized cationic lipid that readily accumulates and penetrates through the mitochondrial membrane due to the highly negative mitochondrial membrane potential. Other moieties, including short peptides, dequalinium, guanidine, rhodamine, and F16, are also known to be promising mitochondrial targeting agents. Direct conjugation of mitochondrial targeting moieties to anticancer drugs, antioxidants and sensors results in increased cytotoxicity, anti-oxidizing activity and sensing activity, respectively, compared with their non-targeting counterparts, especially in drug-resistant cells. Although many mitochondria-targeted anticancer drug conjugates have been investigated in vitro and in vivo, further clinical studies are still needed. On the other hand, several mitochondria-targeting antioxidants have been analyzed in clinical phases I, II and III trials, and one conjugate has been approved for treating eye disease in Russia. There are numerous ongoing studies of mitochondria-targeted sensors.

Photosensitizer-mediated mitochondria-targeting nanosized drug carriers: Subcellular targeting, therapeutic, and imaging potentials.

Mitochondria-targeting drug carriers have considerable potential because of the presence of many molecular drug targets in the mitochondria and their pivotal roles in cellular viability, metabolism, maintenance, and death. To compare the mitochondria-targeting abilities of triphenylphosphonium (TPP) and pheophorbide a (PhA) in nanoparticles (NPs), this study prepared mitochondria-targeting NPs using mixtures of methoxy poly(ethylene glycol)-(SS-PhA)2 [mPEG-(SS-PhA)2 or PPA] and TPP-b-poly(ε-caprolactone)-b-TPP [TPP-b-PCL-b-TPP or TPCL], which were designated PPAn-TPCL4-n (0≤n≤4) NPs. With increasing TPCL content, the formed PPAn-TPCL4-n NPs decreased in size from 33nm to 18nm and increased in terms of positive zeta-potentials from -12mV to 33mV. Although the increased TPCL content caused some dark toxicity of the PPAn-TPCL4-n NPs due to the intrinsic positive character of TPCL, the NPs showed strong light-induced killing effects in tumor cells. In addition, the mitochondrial distribution of the PPAn-TPCL4-n NPs was analyzed and imaged by flow cytometry and confocal microscopy, respectively. Thus, the PhA-containing NPs specifically targeted the mitochondria, and light stimulation caused PhA-mediated therapeutic effects and imaging functions. Expanding the capabilities of these nanocarriers by incorporating other drugs should enable multiple potential applications (e.g., targeting, therapy, and imaging) for combination and synergistic treatments.

Enhanced cell survival of pH-sensitive bioenergetic nucleotide nanoparticles in energy/oxygen-depleted cells and their intranasal delivery for reduced brain infarction.

UNLABELLED: Nucleotides (NTs) (e.g., adenosine triphosphate) are very important molecules in the body. They generate bioenergy through phosphate group release, are involved in various biological processes, and are used to treat various diseases that involve energy depletion. However, their highly anionic characteristics might limit delivery of exogenous NTs into the cell, which is required to realize their functions as bioenergy sources. In this study, ionic complexation between Ca(2+) and NT phosphates was used to form Ca(2+)/NT nanocomplexes (NCs), and branched polyethyleneimine (bPEI1.8kDa) was coated on the surface of Ca(2+)/NT NCs via a simple electrostatic coating. The resultant Ca(2+)/NT/bPEI1.8kDa NCs were approximately 10-25nm in size and had positive zeta-potentials, and their NT loading efficiency and content were approximately 60-75% and 10-20 wt%, respectively. Faster NT release from Ca(2+)/NT/bPEI1.8kDa NCs was induced by lower pH and by NTs with fewer phosphates. Reductions in cell viability in response to low temperature, serum deprivation, or hypoxia were recovered by NT delivery in Ca(2+)/NT/bPEI1.8kDa NCs. In a middle cerebral artery occlusion (MCAO)-induced post-ischemic rat model, the BBB (blood brain barrier)-detoured intranasal administration of Ca(2+)/ATP/bPEI1.8kDa NCs induced a better reduction in infarct volume and neurological deficits than did free ATP. In conclusion, intracellular NT delivery using Ca(2+)/NT/bPEI1.8kDa NCs might potentially enhance cell survival and reduce infarction in energy-/oxygen-depleted environments. STATEMENT OF SIGNIFICANCE: This study describes bioenergetic nucleotide delivery systems and their preparation, physicochemical characterization, and biological characterization both in vitro and in vivo. Nucleotides, such as adenosine triphosphate (ATP) and guanosine triphosphate (GTP), are very important signaling and energy molecules in the body. However, research on these nucleotides using nanosized carriers has been very limited. Liposomal ATP delivery has been reported in heart and renal ischemia studies. Notably, although this delivery system has potential in energy-depleted environments (e.g., low temperature, serum deprivation, and hypoxia) and in brain ischemia, studies are lacking regarding these systems. Thus, we designed polycation-shielded Ca(2+)/nucleotide nanocomplexes using simple mixing, which produced 10- to 25-nm-sized particles. The nanocomplexes released nucleotides in response to acidic pH, and they enhanced cell survival rates under conditions of low temperature, serum deprivation, or hypoxia. Importantly, the nanocomplexes reduced cerebral infarct volumes in a post-ischemic rat model. Thus, our study demonstrates that a novel nucleotide nanocomplex could have potential for preventing or treating diseases that involve energy depletion, such as cardiac, cerebral, and retinal ischemia, and liver failure.