Redox Nanoparticles Research Articles

Silica-containing redox nanoparticles improve therapeutic efficacy for peritoneal dialysis

Event Abstract Back to Event Silica-containing redox nanoparticles improve therapeutic efficacy for peritoneal dialysis Yukio Nagasaki1, Tatsuya Yaguchi1*, Takuma Matsumura1*, Toru Yoshitomi1*, Yutaka Ikeda1*, Atsushi Ueda2 and Aki Hirayama3* 1 University of Tsukuba, Department of Materials Science, Master’s School of Medical Sciences and WPI-MANA Satellite,, Japan 2 University of Tsukuba, Tsukuba University Hospital Hitachi Medical Education and Research Center, Japan 3 Tsukuba University of Technology, Center for Integrative Medicine, Japan Introduction: Although hemodialysis (HD) substitutes for a portion of renal function, there still remain several issues such as (1) the continuous need for hospital attendance, (2) insufficient removal of medium molecular weight uremic toxins; and (3) cardiac overload and vascular damage. These issues increase the patient risk for several serious diseases such as stroke and myocardial infarction. In contrast, peritoneal dialysis (PD) has much potential to provide a high quality of life to patients because of (1) rehabilitation is easy, (2) it maintains renal function, and (3) the risk of stroke and myocardial dysfunction is low. However, the long-term outcome of PD is still poorer than that of HD. Two major reasons for this are (1) the insufficiency of dialysis due to the loss of peritoneal function, which thus increases often changes in dialysate; and (2) the occurrence of encapsulating peritoneal sclerosis (EPS), which is a fatal complication of PD. In order to improve PD efficiency, suppressing damage to peritoneal membrane, new silica-containing redox nanoparticle, siRNP was designed and used as an additive of dialysate. Methods: siRNP was prepared by RNP (see below) coupled with silica-nanoparticles. EPS model rats were prepared by injecting them daily with chlorhexidine gluconate (CH) i.p. for a week. siRNP was administered to the peritoneal cavity of the rats to evaluate protection against CH-induced inflammation. Renal failure mice were prepared by ischemic treatment of both kidneys and confirmed creatinine and blood urea nitrogen (BUN) levels after siRNP administration. Results and Discussion: We have previously developed novel redox nanoparticles (RNPs) containing nitroxide radicals as free radical scavengers. Typical characteristics of RNPs are: 1) Because nitroxide radicals are covalently conjugated to the nanoparticle backbone, they are not leaked to the outside; 2) the sizes of RNPs are ca. 40 nm and thus they are not internalized into healthy cells; and iii) RNPs do not interfere with normal redox reactions inside of cell. These characteristics help RNPs selectively scavenge over-produced ROS. We have so far confirmed the therapeutic effects of RNPs with respect to several disease models such as cerebral and renal ischemia reperfusion injuries, cerebral hemorrhage, cancer, ulcerative colitis, and NASH. The objective of this study was to apply RNPs as one of the components in dialysate to reduce oxidative stress. Porous silica nanoparticles were combined with RNPs to enhance the adsorption capacity of creatinine and other LMW wastes. siRNP thus prepared was confirmed to increase the adsorption capacity of uremic toxins in vivo. The CH-induced dysfunction of peritonitis such as disruption of the mesothelial cell layer and vascularity of the expanded submesothelial compact zone was not observed for the siRNPs treatments. These results show potential for siRNPs to be used as a new multi-functional nanomaterial in peritoneal dialysis. Conclusion: We have designed and developed a siRNP for treatment of EPS caused by peritoneal dialysis, reducing ureic toxins effectively. Our study indicates that the siRNP system is an innovative therapeutic material for the treatment of peritoneal dialysis. A Grant-in-Aid for Scientific Research S (25220203), the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan

Nitroxide radical containing nanoparticle as a potential candidate for redox therapeutics in breast cancer

Event Abstract Back to Event Nitroxide radical containing nanoparticle as a potential candidate for redox therapeutics in breast cancer Babita Shashni1 and Yukio Nagasaki1, 2, 3 1 Graduate School of Pure and Applied Sciences, University of Tsukuba, Department of Material Science, Japan 2 Graduate School of Comprehensive Human Sciences, University of Tsukuba, Master’s School of Medical Sciences, Japan 3 National Institute for Materials Science (NIMS), Satellite Laboratory, International Center for Materials Nanoarchitectonics (WPI-MANA), Japan Introduction: Elevated basal level of reactive oxygen species (ROS) is a hallmark for cancer cell phenotype. ROS, which is considered to be an oncogenic, has been reported to play a critical role in cancer development, progression and metastasis. Therefore ROS manipulating strategies in cancers may hold a great potential for cancer therapy. Henceforth, in this line we focused our study to investigate the therapeutic efficacy of our pH sensitive and non-sensitive ROS scavenging redox nanoparticle (RNP) [1],[2] (Figure 1) in breast cancer by specific inhibition of ROS regulated proteins associated with cancer metastasis and angiogenesis. Figure 1: Chemical structure representation of a) RNP(N): pH-sensitive and b) RNP(O): non-pH sensitive Materials and Methods: Therapeutic efficacy of RNPs was evaluated by in vitro and in vivo assays. In vitro anti-proliferative, -metastatic and -angiogenic activities were confirmed by cell viability, migration and endothelial migration and tube cell formation assays, respectively, whereas in in vivo the efficacy was investigated in breast cancer mice models by biochemical assays. The mechanisms of anti -metastatic and -angiogenic activities were investigated by expression studies. Results: We confirmed that RNPs significantly restricts proliferation, migration and angiogenesis in breast cancer. Furthermore, we also confirmed RNP directed suppression of ROS regulated migration (NF-kβ and metallo matrix proteases (MMPs)) and angiogenesis (vascular endothelial growth factor (VEGF)) promoting proteins. Anti-metastatic tendency was also confirmed in in vivo breast cancer mice models. Discussion: ROS plays a critical role in cancer cell survival. Considering the dependence of cancer cells on ROS-induced molecular signaling pathways, ROS can thus represent a vulnerable specific target for redox cancer therapeutics. In this study we specifically inhibited the ROS induced metastasis and angiogenesis promoting characteristics of breast cancer cells by down-regulating transcriptional factor NF-kB, MMPs and VEGF (Figure 2). This preclinical evaluation study will thus establish RNP as a potential candidate for breast cancer therapeutics. Figure 2: Schematic representation of mechanism of RNP directed restriction of metastasis and angiogenesis in breast cancer Conclusion: We provide the first molecular evidence of anti-metastatic and anti-angiogenic activities of RNP. This report thus strengthens the role of ROS scavenging nanoparticles as potential candidates for breast cancer therapeutics.

Combination of chemotherapeutics with redox nanoparticles for colon cancer

Event Abstract Back to Event Combination of chemotherapeutics with redox nanoparticles for colon cancer Long Vong1*, Toru Yoshitomi1*, Hirofumi Matsui2, 3* and Yukio Nagasaki1, 2, 4* 1 University of Tsukuba, Department of Materials Science, Graduate School of Pure and Applied Sciences, Japan 2 University of Tsukuba, Master’s School of Medical Sciences, Graduate School of Comprehensive Human Sciences, Japan 3 University of Tsukuba, Division of Gastroenterology, Graduate School of Comprehensive Human Sciences, Japan 4 National Institute for Materials Science, Satellite Laboratory, International Center of Materials Nanoarchitectonics, Japan Conventional chemotherapeutic drugs such as doxorubicin (DOX) and irrinotecan (IRI) cause severe adverse effects to healthy tissues due to excessive generation of reactive oxygen species (ROS). ROS are also reported to induce drug resistance in cancer cells. Antioxidant compounds and free radical scavengers have been used to improve anticancer efficacy of chemotherapy and minimize the adverse effect in vitro. However, these low-molecular-weight (LMW) antioxidants have failed so miserably in clinical practice due to low stability and non-specific distribution in vivo environments. Moreover, LMW compounds facilely internalize into the healthy cells to disturb the important redox reactions in mitochondrial respiratory chain, leading to cellular dysfunctions and adverse effects. In order to prevent the nonspecific accumulation of LMW antioxidant to healthy tissues, we have recently developed a core–shell-type redox nanoparticles (RNP) covalently conjugating nitroxide radicals (TEMPO) as ROS scavengers in the core of nanoparticle with 40 nm in diameter [1]. It was confirmed that RNP does not internalize into healthy cells, resulting in an extremely low adverse effects to healthy tissues on models of mice and zebra fish as compared to LWM nitroxide radicals. RNP exhibited long blood circulation via intravenous administration, while it accumulates in gastrointestinal tract after oral administration due to its high colloidal stability as compared to LMW nitroxide radical (TEMPOL) [1],[2]. We investigated that RNP enhances the anticancer drug uptake in cancer cells by scavenging overproduced ROS in inflamed and cancer sites, significantly improving anticancer efficacies of DOX and IRI in colitis-associated colon cancer mice [3],[4]. In addition, RNP effectively suppressed DOX-induced cardiotoxicity and IRI-induced intestinal injury. Based on these results, RNP is a promising antioxidant nanotherapeutics to improve cancer chemotherapy with minimal adverse effects. A part of this work was supported by Grant-in-Aid for Scientific Research S (25220203) and the World Premier International Research Center Initiative (WPI Initiative) on Materials Nanoarchitronics of the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan; Long B. Vong would like to express his sincere appreciation for the Research Fellowship of the Japan Society for the Promotion of Science (JSPS) for Young Scientists.

Redox Nanoparticle Therapeutics for Acetaminophen-Induced Hepatotoxicity in Mice.

The purpose of this study was to evaluate the hepatoprotective effect of an antioxidative nanoparticle (RNPN) recently developed against APAP-induced hepatotoxicity in mice. The effects of oral administration of RNPN to APAP-treated mice were assessed for various biochemical liver function parameters: alanine transaminase (ALT) activity, aspartate transaminase (AST) activity, alkaline phosphatase (ALP) activity, prothrombin time, and serum albumin (ALB) level. The treatment effects were assessed in terms of free radical parameters: malondialdehyde (MDA) accumulation, glutathione peroxidase (GPx) activity, % inhibition of superoxide anion (O2 −∙), and histopathological examination. The N-acetylcysteine (NAC)-treated group exhibited an enhanced prothrombin time relative to the control group, while RNPN did not prolong prothrombin time. The RNPN-treated animals exhibited lower levels of ALT, AST, and ALP, while increased ALB levels were measured in these animals compared to those in the other groups. The RNPN-treated animals furthermore exhibited improved MDA levels, GPx activity, and % inhibition of O2 −∙, which relate to oxidative damage. Histological staining of liver tissues from RNPN-treated animals did not reveal any microscopic changes relative to the other groups. The findings of this study suggest that RNPN possesses effective hepatoprotective properties and does not exhibit the notable adverse effects associated with NAC treatment.

Redox nanoparticles as a novel treatment approach for inflammation and fibrosis associated with nonalcoholic steatohepatitis.

Oxidative stress (OS) is largely thought to be a central mechanism responsible for liver damage, inflammation and fibrosis in nonalcoholic steatohepatitis (NASH). Our aim was to investigate whether suppression of OS in the liver via redox nanoparticles (RNPs) reduces liver damage in a mouse model of NASH. RNPs were prepared by self-assembly of redox polymers possessing antioxidant nitroxide radicals and were orally administered by daily gavage for 4 weeks. The redox polymer was delivered to the liver after disintegration of nanoparticle in the stomach. RNP treatment in NASH mice via gavage led to a reduction of liver OS, improvement of fibrosis, and significant reduction of inflammation. These findings uncover RNP as a novel potential NASH therapy.

Specific accumulation of orally administered redox nanotherapeutics in the inflamed colon reducing inflammation with dose–response efficacy

Although current medications for ulcerative colitis (UC) are effective to some extent, there are still some limitation of their use due to the non-specific distribution, drug metabolism in the gastrointestinal tract, and severe adverse effects. In our previous studies, we developed oral redox nanoparticles (RNPO) that specifically accumulated and scavenged overproduced reactive oxygen species (ROS) in an inflamed colon. However, the mechanism leading to specific accumulation of RNPO in an inflamed colon is still unclear. In this study, we investigated the cellular uptake of RNPO into ROS-treated epithelial colonic cells in vitro, and compared to the untreated cells, found a significantly increased uptake in ROS-treated cells. In vivo, we discovered that orally administered RNPO were not internalized into the cells of a normal colon. A significant amount of disintegrated RNPO was detected in the cells of an inflamed colon of dextran sodium sulfate (DSS)-induced colitis mice, resulting in scavenging of ROS and suppression of inflammation with low adverse effects. Furthermore, we confirmed a significant reduction of disease activity and a robust dose response efficacy following RNPO treatment in acute DSS-induced colitis mice, outperforming the positive control 5-aminosalicylic acid. Oral administration of RNPO is a promising approach to develop a new therapy for UC disease.

Recovery of Cognitive Dysfunction via Orally Administered Redox-Polymer Nanotherapeutics in SAMP8 Mice

Excessively generated reactive oxygen species are associated with age-related neurodegenerative diseases. We investigated whether scavenging of reactive oxygen species in the brain by orally administered redox nanoparticles, prepared by self-assembly of redox polymers possessing antioxidant nitroxide radicals, facilitates the recovery of cognition in 17-week-old senescence-accelerated prone (SAMP8) mice. The redox polymer was delivered to the brain after oral administration of redox nanoparticles via a disintegration of the nanoparticles in the stomach and absorption of the redox polymer at small intestine to the blood. After treatment for one month, levels of oxidative stress in the brain of SAMP8 mice were remarkably reduced by treatment with redox nanoparticles, compared to that observed with low-molecular-weight nitroxide radicals, resulting in the amelioration of cognitive impairment with increased numbers of surviving neurons. Additionally, treatment by redox nanoparticles did not show any detectable toxicity. These findings indicate the potential of redox polymer nanotherapeutics for treatment of the neurodegenerative diseases.

Redox nanoparticles inhibit curcumin oxidative degradation and enhance its therapeutic effect on prostate cancer

Curcumin is a phytochemical with diverse molecular targets and is well known for its anti-tumor potential. However, it has limited application in cancer therapy because curcumin undergoes rapid oxidative degradation at physiological conditions resulting in poor stability and bio-availability. In this study, we were able to suppress curcumin's oxidative degradation by encapsulating it in a nanoparticle that also acts as a radical scavenger. We prepared curcumin-loaded pH-sensitive redox nanoparticles (RNPN) by self-assembling amphiphilic block copolymers conjugated with reactive oxygen species (ROS) scavenging nitroxide radicals to ensure the delivery of minimally degraded curcumin to target regions. In vitro analysis confirmed that the entrapment of both curcumin and nitroxide radicals in the hydrophobic core of RNPN suppressed curcumin degradation in conditions mimicking the physiological environment. Evaluation of apoptosis-related molecules in the cells, such as ceramides, caspases, apoptosis-inducing factor, and acid ceramidase revealed that curcumin loaded RNPN induced strong apoptosis compared to free curcumin. Lastly, intravenous injection of curcumin loaded RNPN suppressed tumor growth in vivo, which is due to the increased bio-availability and significant ROS scavenging at tumor sites. These results demonstrated that RNPN is a promising drug carrier with unique ROS-scavenging abilities, and it is able to overcome the crucial hurdle of curcumin's limitations to enhance its therapeutic potential.

Development of an oral nanotherapeutics using redox nanoparticles for treatment of colitis-associated colon cancer

Oral chemotherapy is the preferred treatment for colon cancer. However, this strategy faces many challenges, including instability in the gastrointestinal (GI) tract, insufficient bioavailability, low tumor targeting, and severe adverse effects. In this study, we designed a novel redox nanoparticle (RNPO) that is an ideal oral therapeutics for colitis-associated colon cancer treatment. RNPO possesses nitroxide radicals in the core, which act as reactive oxygen species (ROS) scavengers. Orally administered RNPO highly accumulated in colonic mucosa, and specifically internalized in cancer tissues, but less in normal tissues. Despite of long-term oral administration of RNPO, no noticeable toxicities were observed in major organs of mice. Because RNPO effectively scavenged ROS, it significantly suppressed tumor growth after accumulation at tumor sites. Combination of RNPO with the conventional chemotherapy, irinotecan, led to remarkably improved therapeutic efficacy and effectively suppressed its adverse effects on GI tract. Therefore, RNPO is promising oral nanotherapeutics for cancer therapies.

Development of silica-containing redox nanoparticles for medical applications.

Silica-containing redox nanoparticles (siRNP) are nanocomposites consisting of silica nanoparticles and amphiphilic block copolymers with nitroxide radicals as reactive oxygen species (ROS) scavengers. Electrostatic interactions between the cationic segment of a polymer in the core and the entrapped silica nanoparticles form a crosslinking structure that provides siRNP stability in vivo, even under harsh conditions in the gastrointestinal tract. Due to the adsorption character of silica nanoparticles in the nanocomposite, siRNP can be applied not only for adsorbents of body wastes but also for drug carriers with high loading capacity. The ROS-scavenging character of siRNP significantly improves their performance for medical applications. Here, we describe the development of siRNP and provide two examples of their medical applications as (1) novel nano-sized adsorbents for peritoneal dialysis, and (2) orally administrable drug carriers for the treatment of gastrointestinal inflammation.

Silica-installed redox nanoparticles for novel oral nanotherapeutics – improvement in intestinal delivery with anti-inflammatory effects

Silica nanoparticles were synthesized via a sol–gel method in which tetraethyl orthosilicate was hydrolyzed by the alkaline core of the nitroxide radical-containing nanoparticle (RNP). The silica nanoparticles were successively captured in the RNP core to obtain silica/RNP nanocomposite (siRNP). Alternatively, siRNP was prepared using commercially available silica nanoparticles. The amount of elemental Si present in the siRNPs was controlled from 3 wt% to 12 wt%. Notably, the obtained siRNPs were stable in acidic media, whereas the starting RNP disintegrated immediately. Crosslinking of the RNP by the entrapped silica might improve stability of the siRNPs under such acidic conditions. Rebamipide was found to be stably encapsulated in the cores of the prepared siRNPs even under acidic conditions, probably due to the both basic environment of the cores and absorption tendencies of the entrapped silica. Under neutral to alkaline conditions, release of the rebamipide is accelerated, which is probably due to the repulsion between the anionic silica surface and the anionic rebamipide. Rebamipide-loaded siRNPs (rebamipide@siRNP) were orally administered to mice, and the plasma level of rebamipide was checked at predetermined time intervals, showing a significantly higher uptake of rebamipide in the plasma when compared to orally-administered free rebamipide. Because siRNP possesses nitroxide radicals in the core, it is confirmed that dextran sodium sulfate-induced colon inflammation was effectively suppressed by the oral administration of rebamipide@siRNP in mice.

Evaluation of the in vivo antioxidative activity of redox nanoparticles by using a developing chicken egg as an alternative animal model

Antioxidants have been demonstrated to exert beneficial effects as pharmacotherapies for cardiovascular diseases. The in vitro systems generally employed to evaluate antioxidants, however, are limited by having no appreciable in vivo redox status of the antioxidants. Therefore, we used our developing chicken egg model to evaluate the in vivo antioxidative activity of a redox nanoparticle possessing 2,2,6,6-tetramethylpiperidine-1-oxyl (RNPO). The 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AAPH) elicited strong oxidative stress and its LD50 value for chick embryos was 3.5±0.9mg/egg. The low molecular weight nitroxide compound, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL), which is known to have the highest level of antioxidant activity, showed no significant protective effect against AAPH-induced embryo lethality. On the contrary, RNPO had potent protective effects against AAPH-induced embryo lethality. Moreover, RNPO could significantly suppress the production of lipid peroxides in chick serum induced by hydrocortisone. Since RNPO has a longer retention time in blood than TEMPOL, RNPO may protect the embryo against lethal oxidative stress by suppressing lipid peroxidation. The validity of in vivo experiments using developing chicken eggs was supported by our data, where RNPO was determined to elicit strong antioxidative activity in vivo, irrespective of the lack of a significant difference in the in vitro activity between low-molecular weight TEMPOL and RNPO. Our results support the use of the developing chicken egg model to evaluate the potential in vivo antioxidative activity of RNPO.

Reactive Oxygen Species‐Scavenging Nanomedicines for the Treatment of Oxidative Stress Injuries

This Progress Report describes a development of two types of reactive oxygen species (ROS)-scavenging nanomedicines for the treatment of oxidative stress injuries, referred to as pH-sensitive redox nanoparticle (RNP(N) ) and pH-insensitive redox nanoparticle (RNP(O) ), which are prepared by self-assembling amphiphilic block copolymers possessing nitroxide radicals as a side chain of hydrophobic segment via amine and ether linkages, respectively. Due to a protonation of amino groups in hydrophobic core, RNP(N) disintegrates in low pH environments such as ischemic, inflamed, and tumor tissues, resulting in increased ROS-scavenging activity because of the exposed nitroxide radicals from the core. Utilizing pH-responsiveness of RNP(N) , it shows remarkable therapeutic effects on oxidative stress injuries such as renal and cerebral ischemia-reperfusion injuries after intravenous administration. Moreover, RNP(N) shows an enhancement of the activity of anticancer drugs by suppression of activation of transcription factors in tumor due to the ROS scavenging. On the other hand, orally administered RNP(O) has notable characteristics such as preferential accumulation in mucosa and inflamed area of gastrointestinal tract and no uptake into blood stream. Based on these characters, RNP(O) shows a remarkable therapeutic effect for the gastrointestinal inflammation without any adverse effects. Thus, ROS-scavenging nanomedicines have therapeutic efficacy in numerous oxidative stress diseases.

The behavior of ROS-scavenging nanoparticles in blood

Here, we report an interaction between blood and redox nanoparticles, prepared by self-assembly of amphiphilic block copolymers possessing 2,2,6,6-tetramethylpiperidine-N-oxyls as a side chain of hydrophobic segment. When 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl was added to rat whole blood, its electron spin resonance signal disappeared rapidly. In contrast, the signal from redox nanoparticles remained for a long period of time, indicating that nitroxide radicals were protected in the blood by their compartmentalization in the core of nanoparticle. Although most 2,2,6,6-tetramethylpiperidine-N-oxyls were located in the nanoparticle core, reactive oxygen species-scavenging activity was found outside of blood cells. For example, redox nanoparticles suppressed superoxide anion-induced hemolysis effectively, while 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl did not. It was revealed that redox nanoparticles were not internalized into the healthy blood cells, which was in sharp contrast to 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl. Due to its internalization into healthy platelets, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl induced mitochondrial dysfunction, while redox nanoparticles did not. Redox nanoparticles suppressed platelet adhesion and extended blood coagulation time, in contrast to 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl. These results indicate that redox nanoparticles scavenge reactive oxygen species outside of cells, but do not interfere with normal redox reactions inside of the cell. Based on these results, we determine that an anti-oxidative strategy based on nanotechnology is a rational and safe therapeutic approach.

Design and use of silica-containing redox nanoparticles, siRNPs, for high-performance peritoneal dialysis.

The prevention of encapsulating peritoneal sclerosis (EPS) and the enhancement of dialysis efficiency are two important strategies that can improve the quality of life of patients undergoing peritoneal dialysis. We have thus far developed bionanoparticles that effectively scavenge reactive oxygen species (redox nanoparticles; RNPs). The objective of this study was to apply RNPs as a component of dialysate to reduce oxidative stress. Porous silica nanoparticles were combined with RNPs to enhance the effective adsorption capacity of low-molecular weight (LMW) compounds. The silica-containing RNPs (siRNPs) were confirmed to statistically decrease the level of creatinine and blood urea nitrogen in vivo. EPS model rats that underwent an intraperitoneal injection of chlorhexidine gluconate exhibited dysfunction of the peritoneal membrane. siRNP administration did not result in dysfunction of the peritoneal membrane. An LMW nitroxide compound, TEMPOL, also showed a weak peritoneal protective effect, although its efficiency was limited. No blood uptake of siRNPs was observed when they were administered into the peritoneal cavity. However, LMW-TEMPOL diffused into the blood stream, which might have decreased its effective concentration in the peritoneal cavity and led to adverse effects across the entire body. Considering these results, siRNPs are expected to be a new multi-functional nanomaterial for high performance peritoneal dialysis.

Indomethacin-Loaded Redox Nanoparticles Improve Oral Bioavailability of Indomethacin and Suppress Its Small Intestinal Inflammation

Continuous administration of low-dose nonsteroidal anti-inflammatory drugs such as indomethacin (IND) is associated with an increased risk of gastrointestinal damage. In this study, the authors developed IND-loaded redox nanoparticles (IND@RNP(O)) with core-shell-type polymeric micelles possessing nitroxide radicals as reactive oxygen species scavengers. Orally administered IND@RNP(O) significantly accumulated in the intestinal mucosa and improved blood uptake of IND. Because of the reactive oxygen species-scavenging effect, IND@RNP(O) did not cause severe inflammation in the small intestine; this effect sharply contrasted with those of orally administered free-IND and IND-loaded polymeric micelles that do not possess reactive oxygen species scavengers. Oral IND@RNP(O) administration is a useful approach for improving the oral bioavailability of IND and suppressing its adverse effects.

Redox nanoparticle therapeutics to cancer — increase in therapeutic effect of doxorubicin, suppressing its adverse effect

The ultimate goal of cancer chemotherapy is to achieve a cure without causing any adverse effects. We have developed a pH-sensitive redox nanoparticle (RNPN), which disintegrates under acidic conditions and exposes nitroxide radicals, leading to strongly scavenging reactive oxygen species (ROS). After intravenous administration of RNPN to tumor bearing mice, it effectively accumulated in tumors due to the leaky neovascular and immature lymphatic system and scavenged ROS, resulting in suppression of inflammation and activation of NF-кB, after disintegration of RNPN in the tumors. Pre-administration of RNPN prior to treatments with anticancer agents, doxorubicin, to tumor-bearing mice significantly suppressed the progression of tumor size, compared to low-molecular weight 4-hydroxy-TEMPO. Interestingly, the administration of RNPN suppressed adverse effects of doxorubicin to normal organs due to the scavenging ROS and suppression of inflammation, which was confirmed by reduction in lactate dehydrogenase and creatine phosphokinase activities in plasma. RNPN is thus anticipated as a novel and ideal adjuvant for cancer chemotherapy.

Suppression of NSAID-induced small intestinal inflammation by orally administered redox nanoparticles

Patients regularly taking non-steroidal anti-inflammatory drugs (NSAIDs) such as indomethacin (IND) have a risk of small intestinal injuries. In this study, we have developed an oral nanotherapeutics by using a redox nanoparticle (RNPO), which is prepared by self-assembly of an amphiphilic block copolymer that possesses nitroxide radicals as side chains of hydrophobic segment via ether linkage, to reduce inflammation in mice with IND-induced small intestinal injury. The localization and accumulation of RNPO in the small intestine were determined using fluorescent-labeled RNPO and electron spin resonance. After oral administration, the accumulation of RNPO in both the jejunum and ileum tissues was about 40 times higher than those of low-molecular-weight nitroxide radical compounds, and RNPO was not absorbed into the bloodstream via the mesentery, thereby avoiding the adverse effects of nitroxide radicals in the entire body. RNPO remarkably suppressed inflammatory mediators such as myeloperoxidase, superoxide anion, and malondialdehyde in the small intestines of IND-treated mice. Compared to low-molecular-weight nitroxide radical compounds, RNPO also significantly increased the survival rate of mice treated daily with IND. On the basis of these results, RNPO is promising as a nanotherapeutics for treatment of inflammation in the small intestine of patients receiving NSAIDs.

Oral nanotherapeutics: effect of redox nanoparticle on microflora in mice with dextran sodium sulfate-induced colitis

Patients with ulcerative colitis (UC) exhibit overproduction of reactive oxygen species (ROS) and imbalance of colonic microflora. We previously developed a novel redox nanoparticle (RNP(O)), which effectively scavenged ROS in the inflamed mucosa of mice with dextran sodium sulfate (DSS)-induced colitis after oral administration. The objective of this study was to examine whether the orally administered RNP(O) changed the colonic microflora in healthy mice and those with colitis. RNP(O) was synthesized by self-assembly of an amphiphilic block copolymer that contains stable nitroxide radicals in hydrophobic side chain via ether linkage. Colitis was induced in mice by supplementing DSS in drinking water for 7days, and RNP(O) was orally administered daily during DSS treatment. The alterations of fecal microflora during treatment of DSS and RNP(O) were investigated using microbiological assays. We investigated that RNP(O) did not result in significant changes to the fecal microflora in healthy mice. Although total aerobic and anaerobic bacteria were not significantly different between experimental groups, a remarkable increase in commensal bacteria (Escherichia coli and Staphylococcus sp.) was observed in mice with DSS-induced colitis. Interestingly, orally administered RNP(O) remarkably reduced the rate of increase of these commensal bacteria in mice with colitis. On the basis of the obtained results, it was confirmed that the oral administration of RNP(O) did not change any composition of bacteria in feces, which strongly suggests a protective effect of RNP(O) on healthy environments in intestinal microflora. RNP(O) may become an effective and safe medication for treatment of UC.

Electrochemistry and Current Control in Surface Films Based on Silica-Azure Redox Nanoparticles, Carbon Nanotubes, Enzymes, and Polyelectrolytes

The redox active nanoparticles were developed by covalently attaching redox dye Azure C (AZU) to commercial silica nanoparticles (SN) via the silylated amine and glutaric dialdehyde links. The SN-AZU nanoparticles were studied as redox mediators for the oxidation of reduced β-nicotinamide adenine dinucleotide (NADH) in two polymeric films. The first film (F1) was composed of SN-AZU, carbon nanotubes, and cationic polyelectrolyte chitosan. The second film (F2) contained also added enzyme glucose dehydrogenase and its cofactor β-nicotinamide adenine dinucleotide (NAD(+)). The films F1 and F2 were cast on the glassy carbon electrodes, covered with an anionic polyelectrolyte Nafion, and their electrochemical properties were probed with NADH and glucose, respectively, using voltammetry, amperometry, and potentiometry. The Nafion overcoat reduced the sensitivity of F1/Nafion film electrodes to NADH by >98%. In contrast, depending on the concentration of Nafion, the sensitivity of the F2/Nafion film electrodes (reagentless biosensors) to glucose increased by up to 340%. The amplification of glucose signal was ascribed to the Donnan exclusion and ensuing Nafion-gated ionic fluxes, which enhanced enzyme activity in films F2. The proposed model predicts that such signal amplification should be also feasible in the case of other enzyme-based biosensors.