Reduced OxyR positively regulates the prodigiosin biosynthesis in Serratia marcescens FS14.

OxyR, a LysR family transcriptional regulator, plays vital roles in bacterial oxidative stress response. In this study, we found that the deletion of oxyR not only inhibited the antioxidant capacity of S. marcescens FS14, but also decreased the production of prodigiosin. Further study revealed that OxyR activated the prodigiosin biosynthesis at the transcriptional level. Complementary results showed that not only the wild-type OxyR but also the reduced form OxyRC199S could activate the prodigiosin biosynthesis. We further demonstrated that reduced form of wild type OxyR could bind to the promoter of pig gene cluster, and identified the binding sites which is different from oxidized OxyR binding sites in E. coli. Our results demonstrated that OxyR in FS14 uses oxidized form to regulate the expression of the antioxidant related genes and utilizes reduced form to activate prodigiosin production. Further in silico analysis suggested that the activation of prodigiosin biosynthesis by reduced OxyR should be general in S. marcesencs. To our knowledge, this is the first report to show that OxyR uses the reduced form to activate the gene's expression, therefore, our results provide a novel regulation mechanism of OxyR.

Mucus-penetrating PEGylated polysuccinimide-based nanocarrier for intravaginal delivery of siRNA battling sexually transmitted infections.

Intravaginal delivery of siRNA for prevention of sexually transmitted infections faces obstacles such as the acidic environment and vaginal mucus barrier. To achieve effective protection and delivery of siRNA, we developed a polysuccinimide (PSI)-based nanocarrier (PSI-PEG-API-PMA, PPAP) by conjugating methoxy polyethylene glycol amine (Me-PEG-NH2, Mw 5000), 1-(3-aminopropyl)imidazole (API), and 1-pyrenemethylamine hydrochloride (PMA) to PSI. PPAP demonstrated a spherical self-assembled nanostructure before and after encapsulation of a model siRNA. Variable electrostatic interaction between API and siRNA at acidic vs. neutral pH accomplished significantly lower burst release at pH 4.2 (4 ±â€¯1%) than pH 7.0 (26 ±â€¯5%) within 1 h. PEGylation enabled siRNA-PPAP to achieve higher mucus penetration efficiency (64 ±â€¯17%) than free siRNA (27 ±â€¯5%) for 24 h. Moreover, in vitro study showed minimal toxicity, successful internalization of siRNA-PPAP in HeLa cells and improved gene knockdown (97.5 ±â€¯0.4%). Overall, PPAP is promising for developing preventative treatments for battling sexually transmitted infections.

Reduction/Oxidation-Responsive Hierarchical Nanoparticles with Self-Driven Degradability for Enhanced Tumor Penetration and Precise Chemotherapy.

Deep tumor penetration, long blood circulation, rapid drug release, and sufficient stability are the most concerning dilemmas of nano-drug-delivery systems for efficient chemotherapy. Herein, we develop reduction/oxidation-responsive hierarchical nanoparticles co-encapsulating paclitaxel (PTX) and pH-stimulated hyaluronidase (pSH) to surmount the sequential biological barriers for precise cancer therapy. Poly(ethylene glycol) diamine (PEG-dia) is applied to collaboratively cross-link the shell of nanoparticles self-assembled by a hyaluronic acid-stearic acid conjugate linked via a disulfide bond (HA-SS-SA, HSS) to fabricate the hierarchical nanoparticles (PHSS). The PTX and pSH coloaded hierarchical nanoparticles (PTX/pSH-PHSS) enhance the stability in normal physiological conditions and accelerate drug release at tumorous pH, and highly reductive or oxidative environments. Functionalized with PEG and HA, the hierarchical nanoparticles preferentially prolong the circulation time, accumulate at the tumor site, and enter MDA-MB-231 cells via CD44-mediated endocytosis. Within the acidic tumor micro-environment, pSH would be partially reactivated to decompose the dense tumor extracellular matrix for deep tumor penetration. Interestingly, PTX/pSH-PHSS could be degraded apace by the completely activated pSH within endo/lysosomes and the intracellular redox micro-environment to facilitate drug release to produce the highest tumor inhibition (93.71%) in breast cancer models.

Glucose-responsive mesoporous silica nanoparticles to generation of hydrogen peroxide for synergistic cancer starvation and chemistry therapy.

Background: The combination of novel starving therapy with chemotherapy is one of the most promising strategies to achieve an effective antitumor activity. Methods: Herein, we developed a multifunctional mesoporous silica nanoparticle (MSNs-GOx/PLL/HA) coated with poly (L-lysine) (PLL) and hyaluronic acid (HA) for co-delivery of glucose oxidase (GOx) and anticancer drug paclitaxel (PTX) for cancer treatment for the first time. Compared to single chemotherapy, introduction of GOx would not only selectively trigger the consumption of intracellular glucose, leading to the interruption of energy supply, but also elevat the endogenous H2O2 level, inducing stronger therapeutic effects. Results: The novel drug delivery system possessed desirable particle diameter of 40 nm and exhibited a pH-sensitive drug release behavior. An in vitro cellular uptake study indicated that MSNs-GOx/PLL/HA nanoparticles effectively enhanced the cellular uptake of drug in an apparently CD44 receptor-dependent manner, and delivered more cargo into cytoplasm via endolysosomal escape effect in presence of PLL. The nanoplatform has also demonstrated amplified synergistic therapeutic effects for remarkable tumor inhibition in a xenograft animal tumor model. Conclusion: Consequently, the developed synergistic starving-like/chemotherapy may provide a potential platform for next generation cancer therapy.

Hyaluronic acid-functionalized half-generation of sectorial dendrimers for anticancer drug delivery and enhanced biocompatibility.

Biocompatible, pH-sensitive and charge-conversion micelles derived from hyaluronic acid (HA), poly(lactide) (PLA) and half-generation of sectorial poly(amidoamine) dendrimers (sPA G4.5) were designed and fabricated to target delivery of docetaxel (DTX) to cancer cells. The novel micelles (HA-PALA-DTX) possessed stability against rat plasma and were capable of reversing surface zeta potential under acidic conditions in the presence of HAase. Moreover, the blank micelles demonstrated satisfactory biocompatibility and viability for biomedical applications. A cellular internalization experiment indicated that HA played an important role in increasing intracellular accumulation of DTX delivered by the micelles. Compared to Taxotere® and PALA-DTX, HA-PALA-DTX showed an enhanced anticancer activity in vivo, with a tumor growth inhibition rate of 72.32 ± 5.22%. Overall, the functionalized micelles could be utilized as an alternative carrier for effective targeted delivery of anticancer agents to improve therapeutic efficacy and minimize adverse effects.

Reduction-sensitive mixed micelles for selective intracellular drug delivery to tumor cells and reversal of multidrug resistance.

Stimuli-responsive nanocarriers have demonstrated their potentials in optimizing chemotherapeutics and anticancer efficacy. In this study, a mixed micelle system (THSP) was prepared by combining reduction-sensitive hyaluronic acid-poly(lactide) (HA-ss-PLA) conjugates and D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS), with objective to achieve multiple functionalities of selective intracellular rapid release, active targeting capability and multidrug resistance reversal. The mixed micelle possessed desirable particle diameter of 124.32 nm and high entrapment efficiency at 87.97%. Importantly, the THSP mixed micelles demonstrated good stability in systemic circulation and rapidly released PTX in intracellular reductive environment. In vitro cellular uptake study and cytotoxicity assay indicated that the mixed micelles effectively increased drug accumulation in A549 cells and Taxol resistant A549/Taxol cells, and inhibited growth of tumor cells. In addition, the redox-responsive THSP micelles preferentially accumulated to the tumor site and improved anticancer drug activity in vivo, with a TIR of 69.08%. It was concluded that redox-sensitive mixed micelles THSP provided a potential vehicle for efficient anticancer drug delivery and enhancement in treating MDR tumor in the future.

Bio-inspired drug delivery systems: an emerging platform for targeted cancer therapy.

The quest for an ideal cancer treatment has led to the exploration of a variety of platforms to facilitate highly desirable and efficient drug delivery. As most anticancer drugs possess therapeutic potency to destroy tumor cells, there is a need to steer the compounds to their required sites using site-specific drug delivery vehicles. This has inspired the investigation of various natural particulates and biomaterials for the purpose. Bio-inspired platforms that directly mimic natural components in the body have demonstrated their ability to serve as one of the most versatile and innovative drug delivery systems in cancer therapy and diagnosis. The primary advantage of this innovation lies in the fundamental changes in systemic biodistribution that non-native drug delivery does not possess. This review will try to provide a comprehensive understanding and a succinct evaluation of various intelligent bio-inspired delivery platforms, which have become prominent in recent studies. Recent innovative examples and their advantages and limitations as well as future clinical potential will also be thoroughly discussed.

Nanostructured Peptidotoxins as Natural Pro-Oxidants Induced Cancer Cell Death via Amplification of Oxidative Stress.

Melittin (Mel), one of the host defense peptides derived from the venom of honeybees, demonstrates substantial anticancer properties, which is attributed to augmenting reactive oxygen species (ROS) generation. However, little has been reported on its pro-oxidation capacity in cancer oxidation therapy. In this study, an ROS amplifying nanodevice was fabricated through direct complexation of two natural pro-oxidants, Mel and condensed epigallocatechin gallate (pEGCG). The obtained nanocomplex (NC) was further covered with phenylboronic acid derivatized hyaluronic acid (pHA) through the ROS-responsive boronate ester coordination bond to produce pHA-NC. Upon undergoing receptor-mediated endocytosis into cancer cells, the inner cores of pHA-NC will be partially uncovered once pHA corona is degraded by hyaluronidase and will then escape from the lysosome by virtue of cytolytic Mel. The elevated ROS level in the tumor cytoplasm can disrupt the boronate ester bond to facilitate drug release. Both Mel and pEGCG could synergistically amplify oxidative stress and prolong ROS retention in cancer cells, leading to enhanced anticancer efficacy. This ROS cascade amplifier based on selective coordination bond and inherent pro-oxidation properties of natural ingredients could detect and elevate intracellular ROS signals, potentiating to move the tumor away from its homeostasis and make the tumor vulnerable. Compared to previously reported chemosynthetic pro-oxidants, the ROS self-sufficient system, fully composed of natural medicine, from this study provides a new insight in developing cancer oxidation therapy.

Bromelain Loading and Release from a Hydrogel Formulated Using Alginate and Arabic Gum.

An ideal wound dressing ensures a moist environment around the wound area and absorbs exudates from the wound surface. Topical application of bromelain to incised wounds has been shown to reprogram the wound microenvironment to promote effective tissue repair. Combining the characteristics of hydrogels and bromelain is therefore of great interest. Herein, we describe the development of a hydrogel, formulated using alginate and Arabic gum, for bromelain loading and release. The hydrogel formulation was evaluated using response surface methodology, considering the pH value and the concentration of alginate and Arabic gum. Bromelain loading and release were evaluated based on passive diffusion. Differential scanning calorimetry and Fourier transform infrared spectroscopy were performed to confirm bromelain immobilization in the hydrogel. The final hydrogel formulation had a swelling ratio of 227 % and incorporated 19 % of bromelain from a bromelain solution. Bromelain immobilization in the hydrogel was the result of hydrogen bond formation and was optimal at 4 °C after 4 h of contact. This evidence suggests that bromelain entrapment into a hydrogel is a promising strategy for the development of wound dressings that support the debridement of burns and wounds.

Simultaneous quantification of reparixin and paclitaxel in plasma and urine using ultra performance liquid chromatography-tandem mass spectroscopy (UHPLC-MS/MS): Application to a preclinical pharmacokinetic study in rats.

A liquid chromatography-tandem mass spectroscopy (LC-MS/MS) assay was developed and validated to simultaneously quantify anticancer drugs reparixin and paclitaxel in this study. The compounds were extracted from plasma and urine samples by protein precipitation with acetone (supplemented with 0.1% formic acid). Chromatographic separation was achieved using a C18 column, and drug molecules were ionized using dual ion source electrospray and atmospheric pressure chemical ionization (DUIS: ESI-APCI). Reparixin and paclitaxel were quantified using negative and positive multiple reaction monitoring (MRM) mode, respectively. Stable isotope palcitaxel-D5 was used as the internal standard (IS). The assay was validated for specificity, recovery, carryover and sample stability under various storage conditions; it was also successfully applied to measure drug concentrations collected from a pharmacokinetic study in rats. The results confirmed that the assay was accurate and simple in quantifying both reparixin and paclitaxel in plasma and urine with minimal sample pretreatment.

Green design "bioinspired disassembly-reassembly strategy" applied for improved tumor-targeted anticancer drug delivery.

In this study, a simple and green approach 'bioinspired disassembly-reassembly strategy' was employed to reconstitute lipoprotein nanoparticles (RLNs) using whole-components of endogenous ones (contained dehydrated human lipids and native apolipoproteins). These RLNs were engineered to mimic the configuration and properties of natural lipoproteins for efficient drug delivery. In testing therapeutic targeting to microtubules, paclitaxel (PTX) was reassembled into RLNs to achieve improved targeted anti-carcinoma treatment and minimize adverse effects, demonstrating ultimately more applicable than HDL-like particles which are based on exogenous lipid sources. We have characterized that apolipoprotein-decoration of PTX-loaded RLNs (RLNs-PTX) led to favoring uniformly dispersed distribution, increasing PTX-encapsulation with a sustained-release pattern, while enhancing biostability during blood circulation. The innate biological RLNs induced efficient intracellular trafficking of cargos in situ via multi-targeting mechanisms, including scavenger receptor class B type I (SR-BI)-mediated direct transmembrane delivery, as well as other lipoprotein-receptors associated endocytic pathways. The resulting anticancer treatment from RLNs-PTX was demonstrated a half-maximal inhibitory concentration of 0.20µg/mL, cell apoptosis of 18.04% 24h post-incubation mainly arresting G2/M cell cycle in vitro, and tumor weight inhibition of 70.51% in vivo. Collectively, green-step assembly-based RLNs provided an efficient strategy for mediating tumor-targeted accumulation of PTX and enhanced anticancer efficacy.

Intracellular delivery and antitumor effects of a redox-responsive polymeric paclitaxel conjugate based on hyaluronic acid.

Polymer-drug conjugates have demonstrated application potentials in optimizing chemotherapeutics. In this study a new bioconjugate, HA-ss-PTX, was designed and synthesized with cooperative dual characteristics of active tumor targeting and selective intracellular drug release. Paclitaxel (PTX) was covalently attached to hyaluronic acid (HA) with various sizes (MW 9.5, 35, 770 kDa); a cross-linker containing disulfide bond was also used to shield drug leakage in blood circulation and to achieve rapid drug release in tumor cells in response to glutathione. Incorporation of HA to the conjugate enhanced the capabilities of drug loading, intracellular endocytosis and tumor targeting of micelles in comparison to mPEG. HA molecular weight showed significant effect on properties and antitumor efficacy of the synthesized conjugates. Intracellular uptake of HA-ss-PTX toward MCF-7 cells was mediated by CD44-caveolae-mediated endocytosis. Compared to Taxol and mPEG-ss-PTX, HA9.5-ss-PTX demonstrated improved tumor growth inhibition in vivo with a TIR of 83.27 ± 5.20%. It was concluded that HA9.5-ss-PTX achieved rapid intracellular release of PTX and enhanced its therapeutic efficacy, thus providing a platform for specific drug targeting and controlled intracellular release in chemotherapeutics. STATEMENT OF SIGNIFICANCE: Polymer-drug conjugates, promising nanomedicines, still face some technical challenges including a lack of specific targeting and rapid intracellular drug release at the target site. In this manuscript we designed and constructed a novel bioconjugate HA-ss-PTX, which possessed coordinated dual characteristics of active tumor targeting and selective intracellular drug release. Redox-responsive disulfide bond was introduced to the conjugate to shield drug leakage in blood circulation and to achieve rapid drug release at tumor site in response to reductant like glutathione. Paclitaxel was selected as a model drug to be covalently attached to hyaluronic acid (HA) with various sizes to elucidate the structure-activity relationship and to address whether HA could substitute PEG as a carrier for polymeric conjugates. Based on a series of in vitro and in vivo experiments, HA-ss-PTX performed well in drug loading, cellular internalization, tumor targeting by entering tumor cells via CD44-caveolae-mediated endocytosis and rapidly release drug at target in the presence of GSH. One of the key issues in clinical oncology is to enhance drug delivery efficacy while minimizing side effects. The study indicated that this new polymeric conjugate system would be useful in delivering anticancer agents to improve therapeutic efficacy and to minimize adverse effects, thus providing a platform for specific drug targeting and controlled intracellular release in chemotherapeutics.

Preparation of Hollow N-Chloramine-Functionalized Hemispherical Silica Particles with Enhanced Efficacy against Bacteria in the Presence of Organic Load: Synthesis, Characterization, and Antibacterial Activity.

The fabrication of highly effective antimicrobial materials is an important strategy for coping with the growing concern of bacterial resistance. In this study, N-chloramine-functionalized hollow hemispherical structures were designed and prepared to examine possible enhancement of antimicrobial performance. Antimicrobial testing was carried out on Gram-negative (Escherichia coli) and Gram-positive (Baccilus Cereus) bacteria in the presence and absence of biological medium. The efficacy of the hollow hemispherical particles functionalized with various N-chloramines in killing bacteria was compared among themselves with that of small organic molecules and spherical particles to investigate the effect of the surface charge, chemical structure, and shape of the particles. Results demonstrated that quaternary ammonium salt or amine functions in the chemical structure enhanced the antimicrobial activity of the particles and made the particles more effective than the small molecules in the presence of biological medium. The importance of particle shape in the killing tests was also confirmed.

Nanocarrier-mediated drugs targeting cancer stem cells: an emerging delivery approach.

INTRODUCTION: Cancer stem cells (CSCs) play an important role in the development of drug resistance, metastasis and recurrence. Current conventional therapies do not commonly target CSCs. Nanocarrier-based delivery systems targeting cancer cells have entered a new era of treatment, where specific targeting to CSCs may offer superior outcomes to efficient cancer therapies. AREAS COVERED: This review discusses the involvement of CSCs in tumor progression and relevant mechanisms associated with CSCs resistance to conventional chemo- and radio-therapies. It highlights CSCs-targeted strategies that are either under evaluation or could be explored in the near future, with a focus on various nanocarrier-based delivery systems of drugs and nucleic acids to CSCs. Novel nanocarriers targeting CSCs are presented in a cancer-specific way to provide a current perspective on anti-CSCs therapeutics. EXPERT OPINION: The field of CSCs-targeted therapeutics is still emerging with a few small molecules and macromolecules currently proving efficacy in clinical trials. However considering the complexities of CSCs and existing delivery difficulties in conventional anticancer therapies, CSC-specific delivery systems would face tremendous technical and clinical challenges. Nanocarrier-based approaches have demonstrated significant potential in specific drug delivery and targeting; their success in CSCs-targeted drug delivery would not only significantly enhance anticancer treatment but also address current difficulties associated with cancer resistance, metastasis and recurrence.

Sorption characteristics of phenanthrene and pyrene to surfactant-modified peat from aqueous solution: the contribution of partition and adsorption.

In this paper, the sorption characteristics and mechanisms of phenanthrene and pyrene onto peat (PT) and surfactant-modified peat (MPT) were investigated. Sorption results fit closely to the Partition model and Freundlich model, the coefficient of determination (R²) were higher than 0.98 and 0.99, respectively. The contributions of partition and adsorption to the total sorption of phenanthrene and pyrene by PT and MPT were analyzed quantitatively. Results indicate that the sorption process is a combination of partition and adsorption, and partition plays a major role in the sorption process. The contribution of partition increased with the increasing of initial concentrations of polycyclic aromatic hydrocarbons. The sorption ability of phenanthrene and pyrene by PT and MPT followed the order of pyrene > phenanthrene. MPT has demonstrated potential as a promising new class of materials for environmental remediation of organic pollutants.

Direct cytosolic siRNA delivery by reconstituted high density lipoprotein for target-specific therapy of tumor angiogenesis.

We described here the mechanisms by which small interfering RNA (siRNA) molecules incorporated in reconstituted high density lipoprotein (rHDL) were efficiently transferred into the cytoplasm of cells to perform target-specific therapy of tumor angiogenesis. Using fluorescent-tagged apolipoprotein A-I (apoA-I) and cholesterol-conjugated siRNA (Chol-siRNA), it was confirmed with FACS and confocal microscopic measurements that Chol-siRNA-loaded rHDL nanoparticles (rHDL/Chol-siRNA complexes) were successfully established and apoA-I certainly was attached to the surface of Chol-siRNA-loaded lipoplexes (Lipos/Chol-siRNA complexes). Stably assembled rHDL/Chol-siRNA complexes demonstrated proper nanosize, quasi-spherical shape and improved nuclease protection over naked Chol-siRNA. It was also interesting to note that rHDL provided a highly effective approach to transfer Chol-siRNA across the membrane directly into the cytoplasm via the scavenger receptor BI (SR-BI)-mediated non-endocytotic mechanism, thereby bypassing endo-lysosomal trapping. We also showed clear evidence that the in vitro implementation of rHDL for Chol-siRNA-VEGF (Chol-siRNA targeting vascular endothelial growth factor gene) delivery markedly promoted RNA interference (RNAi)-mediated degradation of VEGF mRNA, resulting in down-regulation of secreted VEGF protein. In vivo fluorescence imaging indicated that near-infrared (NIR) dye Cy5 labeled Chol-siRNA-loaded rHDL nanoparticles (rHDL/Cy5-Chol-siRNA complexes) displayed long circulation time, SR-BI positive tumor-selective targeting, and efficient cytosolic delivery capabilities. Furthermore, intravenous administration of Chol-siRNA-VEGF-loaded rHDL nanoparticles (rHDL/Chol-siRNA-VEGF complexes) significantly enhanced anti-tumor efficacy against breast cancer, decreased VEGF expression level, and inhibited formation of intratumoral microvessels at the tumor tissue. It was concluded that rHDL possessed therapeutic potential and versatility in mediating Chol-siRNA-VEGF direct cytosolic delivery for target-specific anti-angiogenic therapy in breast cancer.

Kidney-specific drug delivery system for renal fibrosis based on coordination-driven assembly of catechol-derived chitosan.

Renal fibrosis is a common progressive kidney disease, and there is a lack of efficient treatment for the condition. In this study, we designed a kidney-specific nanocomplex by forming coordination-driven assembly from catechol-derived low molecular weight chitosan (HCA-Chi), metal ions and active drug molecules. The coordination activities of various metals and ligands, cytotoxicity, immunogenicity and biodistribution of HCA-Chi were investigated. Autofluorescent doxorubicin (DOX) was selected to fabricate HCA-Chi-Cu-DOX ternary nanocomplex for investigating cellular uptake behavior, transmembrane and targeting properties. The nanodevice demonstrated satisfactory stability under normal physiological conditions and pH-responsive drug release in acidic environments. Uptake of HCA-Chi-Cu-DOX by HK-2 cells was dependent on exposure time, concentration, and temperature, and was inhibited by blockers of megalin receptor. Tissue distribution showed that HCA-Chi-Cu-DOX nanocomplex was specifically accumulated in kidney with a renal relative uptake rate (r(e)) of 25.6. When active anti-fibrosis compound emodin was installed in HCA-Chi-Zn-emodin and intravenously injected to the ureter obstructed mice, obvious attenuation of fibrotic progression was exhibited. It was concluded that HCA-Chi coordination-driven nanocomplex showed special renal targeting capacity and could be utilized to develop drug delivery systems for treating renal fibrosis.

Evaluation of percutaneous permeation of repellent DEET and sunscreen oxybenzone from emulsion-based formulations in artificial membrane and human skin.

Insect repellent DEET and sunscreen ingredient oxybenzone play an essential role in minimizing vector-borne diseases and skin cancers. The purpose of this study was to investigate the effects of emulsion type, addition of thickening agent and droplet size in three emulsion-based lotions on percutaneous permeation of DEET and oxybenzone using in vitro diffusion experiments, in order to minimize overall systemic permeation of the substances. Formulation C (water-in-oil emulsion) significantly increased overall permeation of DEET through human skin (56%) compared to Formulation A (oil-in-water emulsion). Formulation B (oil-in-water emulsion with thickening agent xanthan gum) significantly decreased the size of oil droplet containing DEET (16%), but no effect on oil droplets containing oxybenzone. Adding xanthan gum also increased overall permeation of DEET and oxybenzone (21% and 150%) when compared to Formulation A; presence of both ingredients in Formulation B further increased their permeation (36% and 23%) in comparison to its single counterparts. Overall permeation of oxybenzone through LDPE was significantly higher by 26%-628% than that through human skin; overall permeation of DEET through human skin was significantly higher by 64%-338% than that through LDPE.

pH-dependent stability of creatine ethyl ester: relevance to oral absorption.

Creatine ethyl ester hydrochloride (CEE) was synthesized as a prodrug of creatine (CRT) to improve aqueous solubility, gastrointestinal permeability, and ultimately the pharmacodynamics of CRT. We used high-performance liquid chromatography (HPLC) and proton nuclear magnetic resonance (NMR) to characterize the pH-dependent stability of CEE in aqueous solution and compared the permeability of CEE to CRT and creatinine (CRN) across Caco-2 human epithelial cell monolayers and transdermal permeability across porcine skin. CEE was most stable in a strongly acidic condition (half-life = 570 hours at pH 1.0) where it undergoes ester hydrolysis to CRT and ethanol. At pH ≥ 1.0, CEE cyclizes to CRN with the logarithm of the first order rate constant increasing linearly with pH. Above pH 8.0 (half-life = 23 sec) the rate of degradation was too rapid to be determined. The rate of degradation of CEE in cell culture media and simulated intestinal fluid (SIF) was a function of pH and correlated well with the stability in aqueous buffered solutions. The permeability of CEE across Caco-2 monolayers and porcine skin was significantly greater than that of CRT or CRN. The stability of CEE in acidic media together with its improved permeability suggests that CEE has potential for improved oral absorption compared to CRT.

Synthesis and characterization of multi-functional linear-dendritic block copolymer for intracellular delivery of antitumor drugs.

A novel amphiphilic linear-dendritic block copolymer, semi-polyamidoamine-b-poly(D,L-lactic acid) (PALA) was synthesized and evaluated for its potential as a drug delivery system in this study. PALA was self-assembled in aqueous solution to form nanomicelles with low critical micelle concentration; antitumor drug docetaxel (DTX) was successfully encapsulated into micelles. The prepared micelles demonstrated pH-induced charge conversion and dimension changes. In vitro drug release suggested susceptibility of DTX-loaded micelles to acidic microenvironment. Hemolysis and cytotoxicity testing also indicated in vitro biocompatibility of PALA. Pharmacokinetic study in rats proved that DTX-loaded PALA micelles enhanced the AUC of DTX and prolonged drug clearance in comparison to conventional DTX injection (Taxotere(®)). It was concluded that self-assembled micelles from linear-dendritic block copolymer PALA demonstrated potential for intracellular delivery of anticancer molecules, and that its safety and efficacy in chemotherapy should be further studied.