Beyond nanoparticle-based oral drug delivery: transporter-mediated absorption and disease targeting.

Various strategies at the microscale/nanoscale have been developed to improve oral absorption of therapeutics. Among them, gastrointestinal (GI)-transporter/receptor-mediated nanosized drug delivery systems (NDDSs) have drawn attention due to their many benefits, such as improved water solubility, improved chemical/physical stability, improved oral absorption, and improved targetability of their payloads. Their therapeutic potential in disease animal models (e.g., solid tumors, virus-infected lungs, metastasis, diabetes, and so on) has been investigated, and could be expanded to disease targeting after systemic/lymphatic circulation, although the detailed paths and mechanisms of endocytosis, endosomal escape, intracellular trafficking, and exocytosis through the epithelial cell lining in the GI tract are still unclear. Thus, this review summarizes and discusses potential GI transporters/receptors, their absorption and distribution, in vivo studies, and potential sequential targeting (e.g., oral absorption and disease targeting in organs/tissues).

Beyond Nanoparticle-Based Intracellular Drug Delivery: Cytosol/Organelle-Targeted Drug Release and Therapeutic Synergism.

Nanoparticle (NP)-based drug delivery systems are conceived to solve poor water-solubility and chemical/physical instability, and their purpose expanded to target specific sites for maximizing therapeutic effects and minimizing unwanted events of payloads. Targeted sites are also narrowed from organs/tissues and cells to cytosol/organelles. Beyond specific site targeting, the particular release of payloads at the target sites is growing in importance. This review overviews various issues and their general strategies during multiple steps, from the preparation of drug-loaded NPs to their drug release at the target cytosol/organelles. In particular, this review focuses on current strategies for "first" delivery and "later" release of drugs to the cytosol or organelles of interest using specific stimuli in the target sites. Recognizing or distinguishing the presence/absence of stimuli or their differences in concentration/level/activity in one place from those in another is applied to stimuli-triggered release via bond cleavage or nanostructural transition. In addition, future directions on understanding the intracellular balance of stimuli and their counter-stimuli are demonstrated to synergize the therapeutic effects of payloads released from stimuli-sensitive NPs.

Efficient Combination Chemo-Sonodynamic Cancer Therapy Using Mitochondria-Targeting Sonosensitizer-Loaded Polysorbate-Based Micelles.

Sonodynamic therapy (SDT), utilizing ultrasound (US) and sonosensitizers, holds immense potential as a noninvasive and targeted treatment for a variety of deep-seated tumors. However, the clinical translation of SDT is hampered by several key limitations in sonosensitizers, especially their low aqueous stability and poor cellular uptake. In this study, non-ionic polysorbate (Tween 80, T80) was adopted to formulate effective nanocarriers for the safe and efficient delivery of sonosensitizers to cancer cells. Mitochondria-targeting triphenylphosphonium (TPP)-conjugated chlorin e6 (Ce6) sonosensitizer was loaded into T80-based micelles for efficient SDT. Pro-oxidant piperlongumine (PL) was co-encapsulated with TPP-conjugated Ce6 (T-Ce6) in T80 micelles to enable combination chemo-SDT. T80 micelles substantially enhanced the cellular internalization of T-Ce6. As a result, T80 micelles loaded with T-Ce6 and PL [T80(T-Ce6/PL)] significantly elevated intracellular reactive oxygen species (ROS) generation in MCF-7 human breast cancer cells upon US exposure. Moreover, T-Ce6 exhibited selective accumulation within the mitochondria, leading to efficient cell death under US irradiation. Importantly, T80(T-Ce6/PL) micelles caused cancer-specific cell death by selectively triggering apoptosis in cancer cells through PL. This study demonstrated the feasibility of using T80(T-Ce6/PL) micelles for efficient and cancer-specific combination chemo-SDT.

Brain endothelial cell-derived extracellular vesicles with a mitochondria-targeting photosensitizer effectively treat glioblastoma by hijacking the blood‒brain barrier.

Glioblastoma (GBM) is the most aggressive malignant brain tumor and has a high mortality rate. Photodynamic therapy (PDT) has emerged as a promising approach for the treatment of malignant brain tumors. However, the use of PDT for the treatment of GBM has been limited by its low blood‒brain barrier (BBB) permeability and lack of cancer-targeting ability. Herein, brain endothelial cell-derived extracellular vesicles (bEVs) were used as a biocompatible nanoplatform to transport photosensitizers into brain tumors across the BBB. To enhance PDT efficacy, the photosensitizer chlorin e6 (Ce6) was linked to mitochondria-targeting triphenylphosphonium (TPP) and entrapped into bEVs. TPP-conjugated Ce6 (TPP-Ce6) selectively accumulated in the mitochondria, which rendered brain tumor cells more susceptible to reactive oxygen species-induced apoptosis under light irradiation. Moreover, the encapsulation of TPP-Ce6 into bEVs markedly improved the aqueous stability and cellular internalization of TPP-Ce6, leading to significantly enhanced PDT efficacy in U87MG GBM cells. An in vivo biodistribution study using orthotopic GBM-xenografted mice showed that bEVs containing TPP-Ce6 [bEV(TPP-Ce6)] substantially accumulated in brain tumors after BBB penetration via transferrin receptor-mediated transcytosis. As such, bEV(TPP-Ce6)-mediated PDT considerably inhibited the growth of GBM without causing adverse systemic toxicity, suggesting that mitochondria are an effective target for photodynamic GBM therapy.

Bioreducible exosomes encapsulating glycolysis inhibitors potentiate mitochondria-targeted sonodynamic cancer therapy via cancer-targeted drug release and cellular energy depletion.

Nanocarrier-assisted sonodynamic therapy (SDT) has shown great potential for the effective and targeted treatment of deep-seated tumors by overcoming the critical limitations of sonosensitizers. However, in vivo SDT using nanocarriers is still constrained by their intrinsic toxicity and nonspecific cargo release. In this study, we developed bioreducible exosomes for the safe and tumor-specific delivery of mitochondria-targeting sonosensitizers [triphenylphosphonium-conjugated chlorin e6 (T-Ce6)] and glycolysis inhibitors (FX11). Redox-cleavable diselenide linker-bearing lipids were embedded into exosomes to trigger drug release in response to overexpressed glutathione in the tumor microenvironment. Bioreducible exosomes facilitate the cytoplasmic release of their payload in the reducing environment of tumor cells. They significantly enhance drug release and sonodynamic effects when irradiated with ultrasound (US). The mitochondria-targeted accumulation of T-Ce6 efficiently damaged the mitochondria of the cells under US irradiation, accelerating apoptotic cell death. FX11 substantially inhibited cellular energy metabolism, potentiating the antitumor efficacy of mitochondria-targeted SDT. Bioreducible exosomes effectively suppressed tumor growth in mice without significant systemic toxicity, via a combination of mitochondria-targeted SDT and energy metabolism-targeted therapy. This study offers new insights into the use of dual stimuli-responsive exosomes encapsulating sonosensitizers for safe and targeted sonodynamic cancer therapy.

Piezocatalytic 2D WS2 Nanosheets for Ultrasound-Triggered and Mitochondria-Targeted Piezodynamic Cancer Therapy Synergized with Energy Metabolism-Targeted Chemotherapy.

Piezoelectric nanomaterials that can generate reactive oxygen species (ROS) by piezoelectric polarization under an external mechanical force have emerged as an effective platform for cancer therapy. In this study, piezoelectric 2D WS2 nanosheets are functionalized with mitochondria-targeting triphenylphosphonium (TPP) for ultrasound (US)-triggered, mitochondria-targeted piezodynamic cancer therapy. In addition, a glycolysis inhibitor (FX11) that can inhibit cellular energy metabolism is loaded into TPP- and poly(ethylene glycol) (PEG)-conjugated WS2 nanosheet (TPEG-WS2 ) to potentiate its therapeutic efficacy. Upon US irradiation, the sono-excited electrons and holes generated in the WS2 are efficiently separated by piezoelectric polarization, which subsequently promotes the production of ROS. FX11-loaded TPEG-WS2 (FX11@TPEG-WS2 ) selectively accumulates in the mitochondria of human breast cancer cells. In addition, FX11@TPEG-WS2 effectively inhibits the production of adenosine triphosphate . Thus, FX11@TPEG-WS2 exhibits outstanding anticancer effects under US irradiation. An in vivo study using tumor-xenograft mice demonstrates that FX11@TPEG-WS2 effectively accumulated in the tumors. Its tumor accumulation is visualized using in vivo computed tomography . Notably, FX11@TPEG-WS2 with US irradiation remarkably suppresses the tumor growth of mice without systemic toxicity. This study demonstrates that the combination of piezodynamic therapy and energy metabolism-targeted chemotherapy using mitochondria-targeting 2D WS2 is a novel strategy for the selective and effective treatment of tumors.

Mitochondria-targeting sonosensitizer-loaded extracellular vesicles for chemo-sonodynamic therapy.

Sonodynamic therapy (SDT) has emerged as an effective therapeutic modality as it employs ultrasound (US) to eradicate deep-seated tumors noninvasively. However, the therapeutic efficacy of SDT in clinical settings remains limited owing to the low aqueous stability and poor pharmacokinetic properties of sonosensitizers. In this study, extracellular vesicles (EVs), which have low systemic toxicity, were used as clinically available nanocarriers to effectively transfer a sonosensitizer to cancer cells. Chlorin e6 (Ce6), a sonosensitizer, was conjugated to a mitochondria-targeting triphenylphosphonium (TPP) moiety and loaded into EVs to enhance the efficacy of SDT, because mitochondria are critical subcellular organelles that regulate cell survival and death. Additionally, piperlongumine (PL), a pro-oxidant and cancer-specific chemotherapeutic agent, was co-encapsulated into EVs to achieve efficient and selective anticancer activity. The EVs substantially amplified the cellular internalization of TPP-conjugated Ce6 (TPP-Ce6), resulting in the enhanced generation of intracellular reactive oxygen species (ROS) in MCF-7 human breast cancer cells upon US exposure. Importantly, EVs encapsulating TPP-Ce6 effectively destroyed the mitochondria under irradiation with US, leading to efficient anticancer activity. The co-encapsulation of pro-oxidant PL into EVs significantly enhanced the SDT efficacy in MCF-7 cells through the excessive generation of ROS. Moreover, the EV co-encapsulating TPP-Ce6 and PL [EV(TPP-Ce6/PL)] exhibited cancer-specific cell death owing to the cancer-selective apoptosis triggered by PL. In vivo study using MCF-7 tumor-xenograft mice revealed that EV(TPP-Ce6/PL) effectively accumulated in tumors after intravenous injection. Notably, treatment with EV(TPP-Ce6/PL) and US inhibited tumor growth significantly without causing systemic toxicity. This study demonstrated the feasibility of using EV(TPP-Ce6/PL) for biocompatible and cancer-specific chemo-SDT.

Extracellular vesicles with high dual drug loading for safe and efficient combination chemo-phototherapy.

Extracellular vesicles (EVs) have emerged as biocompatible nanocarriers for efficient delivery of various therapeutic agents, with intrinsic long-term blood circulatory capability and low immunogenicity. Here, indocyanine green (ICG)- and paclitaxel (PTX)-loaded EVs [EV(ICG/PTX)] were developed as a biocompatible nanoplatform for safe and efficient cancer treatment through near-infrared (NIR) light-triggered combination chemo/photothermal/photodynamic therapy. High dual drug encapsulation in EVs was achieved for both the hydrophilic ICG and hydrophobic PTX by simple incubation. The EVs substantially improved the photostability and cellular internalization of ICG, thereby augmenting the photothermal effects and reactive oxygen species production in breast cancer cells upon NIR light irradiation. Hence, ICG-loaded EVs activated by NIR light irradiation showed greater cytotoxic effects than free ICG. EV(ICG/PTX) showed the highest anticancer activity owing to the simultaneous chemo/photothermal/photodynamic therapy when compared with EV(ICG) and free ICG. In vivo study revealed that EV(ICG/PTX) had higher accumulation in tumors and improved pharmacokinetics compared to free ICG and PTX. In addition, a single intravenous administration of EV(ICG/PTX) exhibited a considerable inhibition of tumor proliferation with negligible systemic toxicity. Thus, this study demonstrates the potential of EV(ICG/PTX) for clinical translation of combination chemo-phototherapy.

Engineered extracellular vesicle-based sonotheranostics for dual stimuli-sensitive drug release and photoacoustic imaging-guided chemo-sonodynamic cancer therapy.

Sonodynamic therapy has shown promise as an effective alternative to conventional photodynamic therapy owing to its ability to treat deep-seated tumors. However, the development of stimuli-responsive sonosensitizers with high biocompatibility faces a significant challenge. Methods: In this study, we developed dual stimuli-responsive sonosensitizers with desirable biosafety using extracellular vesicles (EVs), a class of naturally occurring nanoparticles. Indocyanine green (ICG), which functions as both a sonosensitizer and photoacoustic (PA) imaging agent, was loaded into EVs, together with paclitaxel (PTX) and sodium bicarbonate (SBC), to achieve pH-responsive PA imaging-guided chemo-sonodynamic combination therapy. Results: The EVs significantly improved the cellular uptake of ICG, thus triggering enhanced sonodynamic effects in breast cancer cells. SBC-, ICG-, and PTX-loaded EV [SBC-EV(ICG/PTX)] efficiently released the PTX in response to acidic pH in the endo/lysosomes because CO2 bubbles generated from the SBC caused the EV membranes to burst. The drug release was further facilitated by ultrasound (US) treatment, demonstrating dual pH/US-responsive drug release. The ICG- and PTX-loaded EVs exhibited efficient anticancer activity against breast tumor cells owing to the combination of chemo-sonodynamic therapy. High-resolution PA imaging visualized the preferential tumor accumulation of SBC-EV(ICG/PTX) in tumor-bearing mice. Notably, a single intravenous injection of SBC-EV(ICG/PTX) with US irradiation significantly suppressed tumor growth in mice without systemic toxicity. Conclusions: Our findings demonstrate that dual stimuli-responsive SBC-EV(ICG/PTX) are promising sonotheranostic nanoplatforms for safe and efficient chemo-sonodynamic combination cancer therapy and photoacoustic imaging.

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.

Pro-oxidant drug-loaded porphyrinic zirconium metal-organic-frameworks for cancer-specific sonodynamic therapy.

Sonodynamic therapy, which utilizes ultrasound (US) to produce cytotoxic reactive oxygen species (ROS), can overcome the critical drawbacks of photodynamic therapy, such as limited tissue penetration depth. However, the development of sonosensitizers having superior sonodynamic effects and desirable biocompatibility remains a major challenge. In this study, nanoscale zirconium-based porphyrinic metal organic frameworks (MOFs) (PCN-222) were developed as safe and effective nanosonosensitizers. Polyethylene glycol (PEG)-coated PCN-222 (PEG-PCN) was loaded with a pro-oxidant drug, piperlongumine (PL), to enable tumor-specific chemo-photodynamic combination therapy. Both PEG-PCN and PL-incorporated PEG-PCN (PL-PEG-PCN) showed high colloidal stability in biological media. In addition, nanoscale PL-PEG-PCN was efficiently internalized by breast cancer cells, leading to substantially increased ROS generation under US exposure. The effective intracellular delivery of PL by PEG-PCN further elevated the level of intracellular ROS in breast cancer cells owing to the pro-oxidative activity of PL. Therefore, PL-PEG-PCN revealed significantly higher sonotoxicity than free PL and PEG-PCN. Owing to the cancer-specific apoptosis triggered by PL, PL-PEG-PCN showed cancer-selective cell death in breast cancer cells compared with normal fibroblast cells. This study demonstrates that pro-oxidant drug-loaded porphyrinic MOFs are biocompatible and effective sonosensitizers for cancer-targeted chemo-sonodynamic combination therapy.

Metformin and Dichloroacetate Suppress Proliferation of Liver Cancer Cells by Inhibiting mTOR Complex 1.

The Warburg effect is important for cancer cell proliferation. This phenomenon can be flexible by interaction between glycolysis and mitochondrial oxidation for energy production. We aimed to investigate the anticancer effects of the pyruvate dehydrogenase kinase inhibitor, dichloroacetate (DCA) and the mitochondrial respiratory complex I inhibitor metformin in liver cancer cells. The anticancer effect of DCA and/or metformin on HepG2, PLC/PRF5 human liver cancer cell lines, MH-134 murine hepatoma cell lines, and primary normal hepatocytes using MTT assay. Inhibition of lactate/ATP production and intracellular reactive oxygen species generation by DCA and metformin was investigated. Inhibition of PI3K/Akt/mTOR complex I was evaluated to see whether it occurred through AMPK signaling. Anticancer effects of a combination treatment of DCA and metformin were evaluated in HCC murine model. The results showed that metformin and DCA effectively induced apoptosis in liver cancer cells. A combination treatment of metformin and DCA did not affect viability of primary normal hepatocytes. Metformin upregulated glycolysis in liver cancer cells, thereby increasing sensitivity to the DCA treatment. Metformin and DCA inhibited mTOR complex I signaling through upregulated AMPK-independent REDD1. In addition, metformin and DCA increased reactive oxygen species levels in liver cancer cells, which induced apoptosis. A combination treatment of metformin and DCA significantly suppressed the tumor growth of liver cancer cells using in vivo xenograft model. Taken together, the combined treatment of metformin and DCA suppressed the growth of liver cancer cells. This strategy may be effective for patients with advanced liver cancer.

Safe and Targeted Sonodynamic Cancer Therapy Using Biocompatible Exosome-Based Nanosonosensitizers.

Sonodynamic therapy (SDT), wherein sonosensitizers irradiated with ultrasound (US) produce cytotoxic reactive oxygen species (ROS), has garnered great attention as a promising alternative to photodynamic therapy owing to the significantly increased depth of tissue penetration. The development of nanocarriers that can selectively deposit sonosensitizers into tumor tissues without systemic toxicity is crucial to facilitate the translation of SDT to clinical use. In this study, exosomes, a class of naturally occurring nanoparticles, were utilized as nanocarriers for safe and cancer-targeted delivery of a sonosensitizer, indocyanine green (ICG). The exosomes were surface-engineered with an active cancer-targeting ligand, folic acid (FA), to increase the cancer specificity of the ICG-loaded exosomes (ExoICG). The FA-conjugated, ICG-loaded exosomes (FA-ExoICG) greatly improved aqueous stability and cellular uptake of ICG, resulting in significantly increased ROS generation in breast cancer cells. As a result, the FA-ExoICG demonstrated greater sonotoxicity against cancer cells than ExoICG and free ICG. The in vivo study revealed that compared to ExoICG, more FA-ExoICG accumulated in tumors, and their pharmacokinetic properties were superior. Notably, tumor growth in mice was significantly suppressed, without systemic toxicity, by a single intravenous injection of the FA-ExoICG and subsequent US irradiation. Therefore, this study demonstrated that active cancer-targeted FA-ExoICG could serve as effective nanosonosensitizers for safe and targeted cancer treatment.

Solvent-driven, self-assembled acid-responsive poly(ketalized serine)/siRNA complexes for RNA interference.

Advances in bionanotechnology aim to develop smart nucleic acid delivery carriers with stimuli-responsive features to overcome challenges such as non-biodegradability, rapid clearance, immune response, and reaching intracellular targets. Peptide-based nanomaterials have become widely used in the field of gene and drug delivery due to their structural versatility and biomimetic properties. Particularly, polypeptide gene vectors that respond to biological stimuli, such as acidic intracellular environments, have promising applications in mediating efficient endosomal escape and drug release. Unfortunately, synthesis strategies for efficient polymerization of acid-labile peptides have been limited due to conditions that fail to preserve acid-degradable functional groups. Stable urethane derivatives of the acid-labile amino acid ketalized serine (kSer) were synthesized and polymerized to a high molecular weight under permissive conditions independent of elevated temperature, restrictive solvents, or an inert atmosphere. A new formulation strategy utilizing solvent-driven self-assembly of poly(kSer) peptides with small interfering RNA (siRNA) was developed, and the resulting poly(kSer)/siRNA complexes were further cross-linked for reinforced stability under physiological conditions. The complexes were highly monodisperse and precisely spherical in morphology, which has significant clinical implications in definitive biodistribution, cellular internalization, and intracellular trafficking patterns. Self-assembled, cross-linked poly(kSer)/siRNA complexes demonstrated efficient nucleic acid encapsulation, internalization, endosomal escape, and acid-triggered cargo release, tackling multiple hurdles in siRNA delivery. The acid-responsive polypeptides and solvent-driven self-assembly strategies demonstrated in this study could be applicable to developing other efficient and safe delivery systems for gene and drug delivery.

Effects of Decomplexation Rates on Ternary Gene Complex Transfection with α-Poly(l-Lysine) or ε-Poly(l-Lysine) as a Decomplexation Controller in An Easy-To-Transfect Cell or A Hard-To-Transfect Cell.

The tight binding of pDNA with a cationic polymer is the crucial requirement that prevents DNA degradation from undesired DNase attack to safely deliver the pDNA to its target site. However, cationic polymer-mediated strong gene holding limits pDNA dissociation from the gene complex, resulting in a reduction in transfection efficiency. In this study, to control the decomplexation rate of pDNA from the gene complex in a hard-to-transfect cell or an easy-to-transfect cell, either α-poly(l-lysine) (APL) or ε-poly(l-lysine) (EPL) was incorporated into branched polyethylenimine (bPEI)-based nanocomplexes (NCs). Compared to bPEI/pDNA NCs, the addition of APL or EPL formed smaller bPEI-APL/pDNA NCs with similar zeta potentials or larger bPEI-EPL/pDNA NCs with reduced zeta potentials, respectively, due to the different characteristics of the primary amines in the two poly(l-lysine)s (PLs). Interestingly, although both bPEI-APL/pDNA NCs and bPEI-EPL/pDNA NCs showed similar pDNA compactness to bPEI/pDNA NCs, the addition of APL or EPL resulted in slower or faster pDNA release, respectively, from the bPEI-PL/pDNA NCs than from the bPEI/pDNA NCs. bPEI-EPL/pDNA NCs with a decomplexation enhancer (i.e., EPL) improved the transfection efficiency (TE) in both a hard-to-transfect HepG2 cell and an easy-to-transfect HEK293 cell. However, although a decomplexation inhibitor (i.e., APL) reduced the TE of bPEI-APL/pDNA NCs in both cells, the degree of reduction in the TE could be compensated by PL-mediated enhanced nuclear delivery, particularly in HepG2 cells but not HEK293 cells, because both PLs facilitate nuclear localization of the gene complex per its cellular uptake. In conclusion, a decomplexation rate controller could be a potential factor to establish a high TE and design clinically available gene complex systems.

Mitochondria-targeted drug delivery in cancers.

Mitochondria are considered one of the most important subcellular organelles for targeting and delivering drugs because mitochondria are the main location for various cellular functions and energy (i.e., ATP) production, and mitochondrial dysfunctions and malfunctions cause diverse diseases such as neurodegenerative disorders, cardiovascular disorders, metabolic disorders, and cancers. In particular, unique mitochondrial characteristics (e.g., negatively polarized membrane potential, alkaline pH, high reactive oxygen species level, high glutathione level, high temperature, and paradoxical mitochondrial dynamics) in pathological cancers have been used as targets, signals, triggers, or driving forces for specific sensing/diagnosing/imaging of characteristic changes in mitochondria, targeted drug delivery on mitochondria, targeted drug delivery/accumulation into mitochondria, or stimuli-triggered drug release in mitochondria. In this review, we describe the distinctive structures, functions, and physiological properties of cancer mitochondria and discuss recent technologies of mitochondria-specific "key characteristic" sensing systems, mitochondria-targeted "drug delivery" systems, and mitochondrial stimuli-specific "drug release" systems as well as their strengths and weaknesses.

Controlling complexation/decomplexation and sizes of polymer-based electrostatic pDNA polyplexes is one of the key factors in effective transfection.

The delivery of plasmid DNA (pDNA) using polycations has been investigated for several decades; however, obstacles that limit efficient gene delivery still hinder the clinical application of gene therapy. One of the major limiting factors is controlling pDNA binding affinity with polymers to control the complexation and decomplexation of polyplexes. To address this challenge, polycations of α-poly(L-lysine) (APL) and ε-poly(L-lysine) (EPL) were used to prepare variable complexation/decomplexation polyplexes with binding affinities ranging from too tight to too loose and sizes ranging from small to large. APL-EPL/ATP-pDNA polyplexes were also prepared to compare the effects of endosomolytic ATP on complexation/decomplexation and the sizes of polyplexes. The results showed that smaller and tighter polyplexes delivered more pDNA into the cells and into the nucleus than the larger and looser polyplexes. Larger polyplexes exhibited slower cytosolic transport and consequently less nuclear delivery of pDNA than smaller polyplexes. Tighter polyplexes exhibited poor pDNA release in the nucleus, leading to no improvement in transfection efficiency. Thus, polyplexes should maintain a balance between complexation and decomplexation and should have optimal sizes for effective cellular uptake, cytosolic transport, nuclear import, and gene expression. Understanding the effects of complexation/decomplexation and size is important when designing effective polymer-based electrostatic gene carriers.

Selective Anticancer Therapy Using Pro-Oxidant Drug-Loaded Chitosan-Fucoidan Nanoparticles.

Pro-oxidant therapy exploiting pro-oxidant drugs that can trigger cytotoxic oxidative stress in cancer cells has emerged as an innovative strategy for cancer-specific therapy. Piperlongumine (PL) has gained great interest as a novel pro-oxidant agent, because it has an ability to trigger cancer-specific apoptosis through the increase of oxidative stress in cancer cells. However, the use of PL is limited in the clinic because of its hydrophobic nature. In this study, chitosan- and fucoidan-based nanoparticles were prepared for the effective intracellular delivery of PL into cancer cells. Chitosan and fucoidan formed nanoparticles by ionic gelation. The chitosan- and fucoidan-based nanoparticles (CS-F NPs) effectively encapsulated PL, and increased its water solubility and bioavailability. CS-F NPs showed very low cytotoxicity in human prostate cancer cells, demonstrating its high potential for in vivo applications. The PL-loaded chitosan-fucoidan nanoparticles (PL-CS-F NPs) efficiently killed human prostate cancer cells via PL-induced intracellular reactive oxygen species (ROS) generation. This study demonstrates that CS-F NPs are promising natural polymer-based drug carriers for safe and effective PL delivery.

Targeted siRNA delivery using aptamer-siRNA chimeras and aptamer-conjugated nanoparticles.

The sequence-specific gene-silencing ability of small interfering RNA (siRNA) has been exploited as a new therapeutic approach for the treatment of a variety of diseases. However, efficient and safe delivery of siRNA into target cells is still a challenge in the clinical development of siRNA-based therapeutics. Recently, nucleic acid-based aptamers that target cell surface proteins have emerged as a new class of targeting moieties due to their high specificity and avidity. To date, various aptamer-mediated siRNA delivery systems have been developed to enhance the RNA interference (RNAi) efficacy of siRNA via targeted delivery. In this review, we summarize recent advances in developing aptamer-mediated siRNA delivery systems for RNAi therapeutics, mainly aptamer-siRNA chimeras and aptamer-functionalized nanocarriers incorporating siRNA, with a focus on their molecular designs and formulations. In addition, the challenges and engineering strategies of aptamer-mediated siRNA delivery systems for clinical translation are discussed. This article is categorized under: Biology-Inspired Nanomaterials > Nucleic Acid-Based Structures Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Glycol chitosan-coated near-infrared photosensitizer-encapsulated gold nanocages for glioblastoma phototherapy.

Photodynamic therapy is a clinically approved treatment approach for cancer. However, it has limited applications owing to poor water solubility and the short wavelength absorption of the photosensitizer (PS). We selected a near-infrared photosensitizer, SiNC, and encapsulated into a gold nanocage (AuNC) in the presence of phase-changing material. Then, the PS-encapsulated nanocage was coated with glycol chitosan (GC) with a cleavable peptide linkage or stable cysteine linkage to protect the PS from premature release and to improve the biocompatibility of the nanocage. We obtained particles of GC-coated SiNC-encapsulated AuNC with a neutral surface charge and approximately 160 nm in size. The enzyme-cleavable peptide-linked GC formulation (GC-pep@SiNC-AuNC) showed stronger phototoxicity and tumor suppression efficacy in a glioblastoma model compared with free NIR-PS and stable cysteine-linked GC-AuNC (GC-cys@SiNC-AuNC). This polymer-coated SiNC-AuNC may be a promising agent for brain cancer phototherapy.