Uptake by hepatocytes and biliary excretion of intravenously administered polystyrene microspheres in rats

Synthesis approaches of amphiphilic copolymers for spherical micelle preparation: application in drug delivery

The formation of polymeric micelles in aqueous environments through the self-assembly of amphiphilic polymers can provide a versatile platform to increase the solubility and permeability of hydrophobic drugs and pave the way for their administration. In comparison to various self-assembly-based vehicles, polymeric micelles commonly have a smaller size, spherical morphology, and simpler scale up process. The use of polymer-based micelles for the encapsulation and carrying of therapeutics to the site of action triggered a line of research on the synthesis of various amphiphilic polymers in the past few decades. The extended knowledge on polymers includes biocompatible smart amphiphilic copolymers for the formation of micelles, therapeutics loading and response to external stimuli, micelles with a tunable drug release pattern, etc. Different strategies such as ring-opening polymerization, atom transfer radical polymerization, reversible addition-fragmentation chain-transfer, nitroxide mediated polymerization, and a combination of these methods were employed to synthesize copolymers with diverse compositions and topologies with the proficiency of self-assembly into well-defined micellar structures. The current review provides a summary of the important polymerization techniques and recent achievements in the field of drug delivery using micellar systems. This review proposes new visions for the design and synthesis of innovative potent amphiphilic polymers in order to benefit from their application in drug delivery fields.

Pharmacokinetics and tumor delivery of nanoparticles

Nanoparticles (NPs) have been widely used in different areas, including consumer products and medicine. In terms of biomedical applications, NPs or NP-based drug formulations have been extensively investigated for cancer diagnostics and therapy in preclinical studies, but the clinical translation rate is low. Therefore, a thorough and comprehensive understanding of the pharmacokinetics of NPs, especially in drug delivery efficiency to the target therapeutic tissue tumor, is important to design more effective nanomedicines and for proper assessment of the safety and risk of NPs. This review article focuses on the pharmacokinetics of both organic and inorganic NPs and their tumor delivery efficiencies, as well as the associated mechanisms involved. We discuss the absorption, distribution, metabolism, and excretion (ADME) processes following different routes of exposure and the mechanisms involved. Many physicochemical properties and experimental factors, including particle type, size, surface charge, zeta potential, surface coating, protein binding, dose, exposure route, species, cancer type, and tumor size can affect NP pharmacokinetics and tumor delivery efficiency. NPs can be absorbed with varying degrees following different exposure routes and mainly accumulate in liver and spleen, but also distribute to other tissues such as heart, lung, kidney and tumor tissues; and subsequently get metabolized and/or excreted mainly through hepatobiliary and renal elimination. Passive and active targeting strategies are the two major mechanisms of tumor delivery, while active targeting tends to have less toxicity and higher delivery efficiency through direct interaction between ligands and receptors. We also discuss challenges and perspectives remaining in the field of pharmacokinetics and tumor delivery efficiency of NPs.

Uniquely sized nanogels via crosslinking polymerization

Nanogels are very promising carriers for nanomedicine, as they can be prepared in the favorable nanometer size regime, can be functionalized with targeting agents and are responsive to stimuli, i.e. temperature and pH. This induces shrinking or swelling, resulting in controlled release of a therapeutic cargo. Our interest lies in the controlled synthesis of functional nanogels, such as those containing epoxide moieties, that can be subsequently functionalized. Co-polymerization of glycidyl methacrylate and a bifunctional methacrylate crosslinker under dilute conditions gives rise to well-defined epoxide-functional nanogels, of which the sizes are controlled by the degree of polymerization. Nanogels with well-defined sizes (polydispersity of 0.2) ranging from 38 nm to 95 nm were prepared by means of controlled radical polymerization. The nanogels were characterized in detail by FT-IR, DLS, size exclusion chromatography, NMR spectroscopy, AFM and TEM. Nucleophilic attack with functional thiols or amines on the least hindered carbon of the epoxide provides water-soluble nanogels, without altering the backbone structure, while reaction with sodium azide provides handles for further functionalization via click chemistry.

Regulation of in vivo delivery of nanomedicines by herbal medicines

Nanomedicines are of increasing scrutiny due to their improved efficacy and/or mitigated side effects. They can be integrated with many other therapeutics to further boost the clinical benefits. Among those, herbal medicines are arousing great interest to be combined with nanomedicines to exert synergistic effects in multifaceted mechanisms. The in vivo performance of nanomedicines which determines the therapeutic efficacy and safety is believed to be heavily influenced by the physio-pathological characters of the body. Activation of multiple immune factors, e.g., complement system, phagocytic cells, lymphocytes, and among many others, can affect the fate of nanomedicines in blood circulation, biodistribution, interaction with single cells and intracellular transport. Immunomodulatory effects and metabolic regulation by herbal medicines have been widely witnessed during the past decades, which alter the physio-pathological conditions and dramatically affect in vivo delivery of nanomedicines. In this review, we summarize recent progress of understanding on the in vivo delivery process of nanomedicines and analyze the major affecting factors that regulate the interaction of nanomedicines with organisms. We discuss the immunomodulatory roles and metabolic regulation by herbal medicines and their effects on in vivo delivery process of nanomedicines, as well as the prospective clinical benefits from the combination of nanomedicines and herbal medicines.

Theoretical elucidation of the energy conversion rate in organic photovoltaic cells of the fullerene nanostructure derivatives. A density functional theory study

A comparative theoretical study of the kinetics of the Diels–Alder (DA) reaction between empty fullerene (C[Formula: see text]) and lithium ion encapsulated fullerene ([Formula: see text]) with 1,3 cyclohexadiene (C[Formula: see text]H[Formula: see text]) was carried out. This reaction takes place in a photovoltaic cell. The effect of the encapsulated [Formula: see text] ion on the conversion rate of solar energy into electricity has been highlighted through calculations based on the density functional theory (DFT). In addition, a static study using the global conceptual DFT indices, as part of the demonstration of the significant electrophilic power of the fullerene nanostructure, was carried out to show the effect of encapsulating the [Formula: see text] ion in this nanoparticle on the electrophilic power of Li[Formula: see text]@C[Formula: see text] and therefore on the acceleration of the reaction. The relationship between the HOMOdonor–LUMOacceptor energy difference and the DA reaction acceleration, and therefore the acceleration of light conversion (a rapid conversion implies a small gap), has been thoroughly examined. Moreover, a mechanistic study of the kinetics of the DA reaction of the fullerene involved in an organic photovoltaic cell has been carried out. In this section, a concerted synchronous mechanism with no effect of [Formula: see text] encapsulation on the synchronicity of the reaction was observed. Finally, it was revealed that Li[Formula: see text]@C[Formula: see text] reacted approximately 2466 times faster than C[Formula: see text]. Moreover, the experimental results were found in good agreement with the computer calculations.

Electrospun Nanofibers for Drug Delivery and Biosensing

Early diagnosis and efficient treatment are of paramount importance to fighting cancers. Monitoring the foreign body response of a patient to treatment therapies also plays an important role in improving the care that cancer patients receive by their medical practitioners. As such, there is extensive research being conducted into ultrasensitive point-of-care detection systems and "smart" personalized anticancer drug delivery systems. Electrospun nanofibers have emerged as promising materials for the construction of nanoscale biosensors and therapeutic platforms because of their large surface areas, controllable surface conformation, good surface modification, complex pore structure, and high biocompatibility. Electrospun nanofibers are produced by electrospinning, which is a very powerful and economically viable method of synthesizing versatile and scalable assemblies from a wide array of raw materials. This review describes the theory of electrospinning, achievements, and problems currently faced in producing effective biosensors/drug delivery systems, in particular, for cancer diagnosis and treatment. Finally, insights into future prospects are discussed.

Co-disposition of chitosan nanoparticles by multi types of hepatic cells and their subsequent biological elimination: the mechanism and kinetic studies at the cellular and animal levels

Background: The clearance of nanomaterials (NMs) from the liver is essential for clinical safety, and their hepatic clearance is primarily determined by the co-disposition process of various types of hepatic cells. Studies of this process and the subsequent clearance routes are urgently needed for organic NMs, which are used as drug carriers more commonly than the inorganic ones. Materials and methods: In this study, the co-disposition of chitosan-based nanoparticles (CsNps) by macrophages and hepatocytes at both the cellular and animal levels as well as their subsequent biological elimination were investigated. RAW264.7 and Hepa1-6 cells were used as models of Kupffer cells and hepatocytes, respectively. Results: The cellular studies showed that CsNps released from RAW264.7 cells could enter Hepa1-6 cells through both clathrin- and caveolin-mediated endocytosis. The transport from Kupffer cells to hepatocytes was also studied in mice, and it was observed that most CsNps localized to the hepatocytes after intravenous injection. Following the distribution in hepatocytes, the hepatobiliary-fecal excretion route was shown to be the primary elimination route for CsNps, besides the kidney-urinary excretion route. The elimination of CsNps in mice was a lengthy process, with a half time of about 2 months. Conclusion: The demonstration in this study of the transport of CsNps from macrophages to hepatocytes and the subsequent hepatobiliary-fecal excretion provides basic information for the future development and clinical application of NMs.

Bioformulative concepts on intracellular organ specific bioavailability

Bioavailability is an ancient but effective terminology by which the entire therapeutic efficacy of a drug directly or indirectly relays. Despite considering general plasma bioavailability, specific organ/tissue bioavailability will pave the path to broad spectrum dose calculation. Clear knowledge and calculative vision on bioavailability can improve the research and organ-targeting phenomenon. This article comprises a detailed introduction on bioavailability along with regulatory aspects, kinetic data and novel bioformulative approaches to achieve improved organ specific bioavailability, which may not be readily related to blood plasma bioavailability.

Elimination Pathways of Nanoparticles

Understanding how nanoparticles are eliminated from the body is required for their successful clinical translation. Many promising nanoparticle formulations for in vivo medical applications are large (>5.5 nm) and nonbiodegradable, so they cannot be eliminated renally. A proposed pathway for these nanoparticles is hepatobiliary elimination, but their transport has not been well-studied. Here, we explored the barriers that determined the elimination of nanoparticles through the hepatobiliary route. The route of hepatobiliary elimination is usually through the following pathway: (1) liver sinusoid, (2) space of Disse, (3) hepatocytes, (4) bile ducts, (5) intestines, and (6) out of the body. We discovered that the interaction of nanoparticles with liver nonparenchymal cells ( e. g., Kupffer cells and liver sinusoidal endothelial cells) determines the elimination fate. Each step in the route contains cells that can sequester and chemically or physically alter the nanoparticles, which influences their fecal elimination. We showed that the removal of Kupffer cells increased fecal elimination by >10 times. Combining our results with those of prior studies, we can start to build a systematic view of nanoparticle elimination pathways as it relates to particle size and other design parameters. This is critical to engineering medically useful and translatable nanotechnologies.

Nanotechnology, from quantum mechanical calculations up to drug delivery

There are several reasons why nanotechnology is currently considered as the leader among the most intensively developing research trends. Nanomatter often exhibits new properties, other than those of the morphology of a continuous solid. Also, new phenomena appear at the nanoscale, which are unknown in the case of microcrystalline objects. For this reason, nanomaterials have already found numerous applications that are described in this review. However, among intensively developed various branches of nanotechnology, nanomedicine and pharmacology stand out particularly, which opens new possibilities for the development of these disciplines, gives great hope for the creation of new drugs in which toxicological properties are reduced to a minimum, reduces the doses of medicines, offers targeted treatment and increases diagnostic possibilities. Nanotechnology is the source of a great revolution in medicine. It gives great hope for better and faster treatment of many diseases and gives hope for a better tomorrow. However, the creation of new "nanodrugs" requires a special understanding of the properties of nanoparticles. This article is a review work which determines and describes the way of creating new nanodrugs from ab initio calculations by docking and molecular dynamic applications up to a new medicinal product, as a proposal for the personalized medicine, in the early future.

From Batch to Continuous Precipitation Polymerization of Thermoresponsive Microgels

Microgels are commonly synthesized in batch experiments, yielding quantities sufficient to perform characterization experiments for physical property studies. With increasing attention on the application potential of microgels, little attention is yet paid to the questions (a) whether they can be produced continuously on a larger scale, (b) whether synthesis routes can be easily transferred from batch to continuous synthesis, and (c) whether their properties can be precisely controlled as a function of synthesis parameters under continuous flow reaction conditions. We present a new continuous synthesis process of two typical but different microgel systems. Their size, size distribution, and temperature-responsive behavior are compared in depth to those of microgels synthesized using batch processes, and the influence of premixing and surfactant is also investigated. For the surfactant-free poly( N-vinylcaprolactam) and poly( N-isopropylacrylamide) systems, microgels are systematically smaller, while the actual size is depending on the premixing of the reaction solutions. However, by the use of a surfactant, the size difference between batch and continuous preparation diminishes, resulting in equal-sized microgels. Temperature-induced swelling-deswelling of microgels synthesized under continuous flow conditions was similar to that of their analogues synthesized using the batch polymerization process. Additionally, investigation of the internal microgel structure using static light scattering showed no significant changes between microgels prepared under batch and continuous conditions. The work encourages synthesis concepts of sequential chemical conditions in continuous flow reactors to prepare precisely tuned new microgel systems.

Tumor cell responses to carbon dots derived from chondroitin sulfate

Photoluminescent carbon dots (CDs) derived from chondroitin sulfate (CS) showing multifunctional behavior: cell imaging and cell proliferative responses.

Exploring uptake mechanisms of oral nanomedicines using multimodal nonlinear optical microscopy

Advances in pharmaceutical nanotechnology have yielded ever increasingly sophisticated nanoparticles for medicine delivery. When administered via oral, intravenous, ocular and transcutaneous delivery routes, these nanoparticles can elicit enhanced drug performance. In spite of this, little is known about the mechanistic processes underlying interactions between nanoparticles and tissues, or how these correlate with improved pharmaceutical effects. These mechanisms must be fully understood before nanomedicines can be rationally engineered to optimise their performance. Methods to directly visualise these particulates within tissue samples have traditionally involved imaging modalities requiring covalent labelling of fluorescent or radioisotope contrast agents. We present CARS, second harmonic generation and two photon fluorescence microscopy combined as a multi-modal label-free method for pinpointing polymeric nanoparticles within the stomach, intestine, gall bladder and liver. We demonstrate for the first time that orally administered chitosan nanoparticles follow a recirculation pathway from the GI tract via enterocytes, to the liver hepatocytes and intercellular spaces and then to the gall bladder, before being re-released into the gut together with bile.

The journey of a drug-carrier in the body: an anatomo-physiological perspective

Recent advances in chemistry and material sciences have witnessed the emergence of an increasing number of novel and complex nanosized carriers for the delivery of drugs and imaging agents. Nevertheless, this raise in complexity does not necessarily offer more efficient systems. The lack of performance experienced by several colloidal drug carriers during the preclinical and clinical development processes can be explained by inadequate pharmacokinetic/biodistribution profiles and/or unacceptable toxicities. A comprehensive understanding of the body characteristics is necessary to predict and prevent these problems from the early stages of nanomaterial conception. In this manuscript, we review and discuss the anatomical and physiological elements which must be taken into account when designing new carriers for delivery or imaging purposes. This article gives a general overview of the main organs involved in the elimination of nanosized materials and briefly summarizes the knowledge acquired over more than 30 years of research and development in the field of drug targeting.

Toxicology of nanomaterials used in nanomedicine

With the development of nanotechnology, nanomaterials are being widely used in many industries as well as in medicine and pharmacology. Despite the many proposed advantages of nanomaterials, increasing concerns have been expressed on their potential adverse human health effects. In recent years, application of nanotechnology in medicine has been defined as nanomedicine. Techniques in nanomedicine make it possible to deliver therapeutic agents into targeted specific cells, cellular compartments, tissues, and organs by using nanoparticulate carriers. Because nanoparticles possess different physicochemical properties than their fine-sized analogues due to their extremely small size and large surface area, they need to be evaluated separately for toxicity and adverse health effects. In addition, in the field of nanomedicine, intravenous and subcutaneous injections of nanoparticulate carriers deliver exogenous nanoparticles directly into the human body without passing through the normal absorption process. These nanoparticulate carriers themselves may be responsible for toxicity and interaction with biological macromolecules within the human body. Second, insoluble nanoparticulate carriers may accumulate in human tissues or organs. Therefore, it is necessary to address the potential health and safety implications of nanomaterials used in nanomedicine. Toxicological studies for biosafety evaluation of these nanomaterials will be important for the continuous development of nanomedical science. This review summarizes the current knowledge on toxicology of nanomaterials, particularly on those used in nanomedicine.

Nanostructured hyaluronic acid-based materials for active delivery to cancer

IMPORTANCE OF THE FIELD

Active targeting of bioactive molecules by physicochemical association with hyaluronic acid (HA) is an attractive approach in current nanomedicine because HA is biocompatible, non-toxic and non-inflammatory.

AREAS COVERED IN THIS REVIEW

This review focuses on synthesis, physicochemical characterization and biological properties of different nanoparticulate delivery systems that include HA in their structures. Chemically based approaches to the delivery of small molecule drugs, proteins and nucleic acids in which they become chemically or physically bound to hyaluronic acid are reviewed, including the use of molecular HA conjugates and nanocarriers. The systems are considered in terms of intracellular delivery to different cultured cells that express HA-specific receptors (hyaladherines) differently. The in vivo biodistribution and therapeutic effect of these systems are discussed.

WHAT THE READER WILL GAIN

Different synthetic methodologies for preparations of HA-based nanoparticles are presented extensively. HA nanoparticulate systems of various structures can be compared with respect to their in vitro assays and in vivo biodistribution.

TAKE HOME MESSAGE

To make HA useful as an intravenous targeting carrier, strategies have to be devised to: reduce HA clearance from the blood; suppress the HA uptake by liver and spleen; and provide tumor-triggered mechanisms of release of an active drug from the HA carrier.

Monitoring the erosion of hydrolytically-degradable nanogels via multiangle light scattering coupled to asymmetrical flow field-flow fractionation

We describe the synthesis and characterization of degradable nanogels that display bulk erosion under physiologic conditions (pH = 7.4, 37 degrees C). Erodible poly(N-isopropylmethacrylamide) nanogels were synthesized by copolymerization with N,O-(dimethacryloyl) hydroxylamine, a cross-linker previously used in the preparation of nontoxic and biodegradable bulk hydrogels. To monitor particle degradation, we employed multiangle light scattering and differential refractometry detection following asymmetrical flow field-flow fractionation. This approach allowed the detection of changes in nanogel molar mass and topology as a function of both temperature and pH. Particle erosion was evident from both an increase in nanogel swelling and a decrease in scattering intensity as a function of time. Following these analyses, the samples were recovered for subsequent characterization by direct particle tracking, which yields hydrodynamic size measurements and enables number density determination. Additionally, we confirmed the conservation of nanogel stimuli-responsivity through turbidity measurements. Thus, we have demonstrated the synthesis of degradable nanogels that erode under conditions and on time scales that are relevant for many drug delivery applications. The combined separation and light scattering detection method is demonstrated to be a versatile means to monitor erosion and should also find applicability in the characterization of other degradable particle constructs.

Intravenous transferrin, RGD peptide and dual-targeted nanoparticles enhance anti-VEGF intraceptor gene delivery to laser-induced CNV

Choroidal neovascularization (CNV) leads to loss of vision in age-related macular degeneration (AMD), the leading cause of blindness in adult population over 50 years old. In this study, we developed intravenously administered, nanoparticulate, targeted nonviral retinal gene delivery systems for the management of CNV. CNV was induced in Brown Norway rats using a 532 nm laser. We engineered transferrin, arginine-glycine-aspartic acid (RGD) peptide or dual-functionalized poly-(lactide-co-glycolide) nanoparticles to target delivery of anti-vascular endothelial growth factor (VEGF) intraceptor plasmid to CNV lesions. Anti-VEGF intraceptor is the only intracellularly acting VEGF inhibitory modality. The results of the study show that nanoparticles allow targeted delivery to the neovascular eye but not the control eye on intravenous administration. Functionalizing the nanoparticle surface with transferrin, a linear RGD peptide or both increased the retinal delivery of nanoparticles and subsequently the intraceptor gene expression in retinal vascular endothelial cells, photoreceptor outer segments and retinal pigment epithelial cells when compared to nonfunctionalized nanoparticles. Most significantly, the CNV areas were significantly smaller in rats treated with functionalized nanoparticles as compared to the ones treated with vehicle or nonfunctionalized nanoparticles. Thus, surface-functionalized nanoparticles allow targeted gene delivery to the neovascular eye on intravenous administration and inhibit the progression of laser-induced CNV in a rodent model.

Circulation and long-term fate of functionalized, biocompatible single-walled carbon nanotubes in mice probed by Raman spectroscopy

Carbon nanotubes are promising new materials for molecular delivery in biological systems. The long-term fate of nanotubes intravenously injected into animals in vivo is currently unknown, an issue critical to potential clinical applications of these materials. Here, using the intrinsic Raman spectroscopic signatures of single-walled carbon nanotubes (SWNTs), we measured the blood circulation of intravenously injected SWNTs and detect SWNTs in various organs and tissues of mice ex vivo over a period of three months. Functionalization of SWNTs by branched polyethylene-glycol (PEG) chains was developed, enabling thus far the longest SWNT blood circulation up to 1 day, relatively low uptake in the reticuloendothelial system (RES), and near-complete clearance from the main organs in approximately 2 months. Raman spectroscopy detected SWNT in the intestine, feces, kidney, and bladder of mice, suggesting excretion and clearance of SWNTs from mice via the biliary and renal pathways. No toxic side effect of SWNTs to mice was observed in necropsy, histology, and blood chemistry measurements. These findings pave the way to future biomedical applications of carbon nanotubes.

What do we (need to) know about the kinetic properties of nanoparticles in the body?

Nowadays the development and applications of nanotechnology are of major importance in both industrial and consumer areas. However, the knowledge on human exposure and possible toxicity of nanotechnology products is limited. To understand the mechanism of toxicity, thorough knowledge of the toxicokinetic properties of nanoparticles is warranted. There is a need for information on the absorption, distribution, metabolism and excretion (ADME) of nanoparticles and validated detection methods of these man-made nanoparticles. Determination of the ADME properties of nanoparticles requires specialised detection methods in different biological matrices (e.g. blood and organs). In this paper, the current knowledge on the kinetic properties of nanoparticles is reviewed. Moreover, knowledge gaps from a kinetic point of view (detection, dose, ADME processes) are identified.

Nanostructured materials for applications in drug delivery and tissue engineering

Research in the areas of drug delivery and tissue engineering has witnessed tremendous progress in recent years due to their unlimited potential to improve human health. Meanwhile, the development of nanotechnology provides opportunities to characterize, manipulate and organize matter systematically at the nanometer scale. Biomaterials with nano-scale organizations have been used as controlled release reservoirs for drug delivery and artificial matrices for tissue engineering. Drug-delivery systems can be synthesized with controlled composition, shape, size and morphology. Their surface properties can be manipulated to increase solubility, immunocompatibility and cellular uptake. The limitations of current drug delivery systems include suboptimal bioavailability, limited effective targeting and potential cytotoxicity. Promising and versatile nano-scale drug-delivery systems include nanoparticles, nanocapsules, nanotubes, nanogels and dendrimers. They can be used to deliver both small-molecule drugs and various classes of biomacromolecules, such as peptides, proteins, plasmid DNA and synthetic oligodeoxynucleotides. Whereas traditional tissue-engineering scaffolds were based on hydrolytically degradable macroporous materials, current approaches emphasize the control over cell behaviors and tissue formation by nano-scale topography that closely mimics the natural extracellular matrix (ECM). The understanding that the natural ECM is a multifunctional nanocomposite motivated researchers to develop nanofibrous scaffolds through electrospinning or self-assembly. Nanocomposites containing nanocrystals have been shown to elicit active bone growth. Drug delivery and tissue engineering are closely related fields. In fact, tissue engineering can be viewed as a special case of drug delivery where the goal is to accomplish controlled delivery of mammalian cells. Controlled release of therapeutic factors in turn will enhance the efficacy of tissue engineering. From a materials point of view, both the drug-delivery vehicles and tissue-engineering scaffolds need to be biocompatible and biodegradable. The biological functions of encapsulated drugs and cells can be dramatically enhanced by designing biomaterials with controlled organizations at the nanometer scale. This review summarizes the most recent development in utilizing nanostructured materials for applications in drug delivery and tissue engineering.

Pluronic block copolymers as novel polymer therapeutics for drug and gene delivery

Pluronic block copolymers are found to be an efficient drug delivery system with multiple effects. The incorporation of drugs into the core of the micelles formed by Pluronic results in increased solubility, metabolic stability and circulation time for the drug. The interactions of the Pluronic unimers with multidrug-resistant cancer cells result in sensitization of these cells with respect to various anticancer agents. Furthermore, the single molecular chains of copolymer, unimers, inhibit drug efflux transporters in both the blood-brain barrier and in the small intestine, which provides for the enhanced transport of select drugs to the brain and increases oral bioavailability. These and other applications of Pluronic block copolymers in various drug delivery and gene delivery systems are considered.

Efficacy of lactosaminated and intact N-succinylchitosan-mitomycin C conjugates against M5076 liver metastatic cancer

In this study,lactosaminated N-succinyl-chitosan (Lac-Suc) was investigated for its liver targeting ability in the early metastatic stage of liver cancer, and subsequently Lac-Suc-mitomycin C conjugate (Lac-Suc-MMC) and highly-succinylated N-succinyl-chitosan (Suc(II))-MMC conjugate (Suc(II)-MMC) were examined for efficacy against the liver metastasis. Mice into which M5076 cells were inoculated intravenously were used as liver metastatic models. Fluorescently labelled Lac-Suc (Lac-Suc-FTC) was intravenously administered at a daily dose of 0.2 mg/mouse for 4 days or at a single dose of 0.8 mg/mouse at 3 days post-inoculation. At a dose of 0.2 mg/mouse for 4 days, liver accumulation of Lac-Suc-FTC was increased after all except the fourth injection, indicating that the capacity of accumulation might be limited to around 110 microg per mouse with repeated daily administration at 0.2 mg/mouse. As to the efficacy of intravenous administration at 7 days post-inoculation, Lac-Suc-MMC was less effective at a dose of 1 mg kg(-1) for 4 days than a single dose of 4 mg kg(-1). This result was not in accordance with that expected from the biodistribution study. On the other hand, with intravenous administration at 3 days post-inoculation, Suc(II)-MMC was more effective on repeated administration, and it showed higher efficacy than Lac-Suc-MMC at both 1 mg kg(-1) for 4 days and 4 mg kg(-1) as a single dose. Further, with intravenous administration at 3 days post-inoculation, Suc(II)-MMC exhibited a much higher survival effect at a dose of 4 mg kg(-1) for 4 days.

Nanosized cationic hydrogels for drug delivery: preparation, properties and interactions with cells

A new family of nanoscale materials on the basis of dispersed networks of cross-linked ionic and nonionic hydrophilic polymers is being developed. One example is the nanosized cationic network of cross-linked poly(ethylene oxide) (PEO) and polyethyleneimine (PEI), PEO-cl-PEI nanogel. Interaction of anionic amphiphilic molecules or oligonucleotides with PEO-cl-PEI results in formation of nanocomposite materials in which the hydrophobic regions from polyion-complexes are joined by the hydrophilic PEO chains. Formation of polyion-complexes leads to the collapse of the dispersed gel particles. However, the complexes form stable aqueous dispersions due to the stabilizing effect of the PEO chain. These systems allow for immobilization of negatively charged biologically active compounds such as retinoic acid, indomethacin and oligonucleotides (bound to polycation chains) or hydrophobic molecules (incorporated into nonpolar regions of polyion-surfactant complexes). The nanogel particles carrying biological active compounds have been modified with polypeptide ligands to enhance receptor-mediated delivery. Efficient cellular uptake and intracellular release of oligonucleotides immobilized in PEO-cl-PEI nanogel have been demonstrated. Antisense activity of an oligonucleotide in a cell model was elevated as a result of formulation of oligonucleotide with the nanogel. This delivery system has a potential of enhancing oral and brain bioavailability of oligonucleotides as demonstrated using polarized epithelial and brain microvessel endothelial cell monolayers.

Passage of intratracheally instilled ultrafine particles from the lung into the systemic circulation in hamster

The mechanisms of particulate pollution-related cardiovascular morbidity and mortality are not well understood. We studied the passage of radioactively labeled ultrafine particles after their intratracheal instillation. Hamsters received a single intratracheal instillation of 100 microg albumin nanocolloid particles (nominal diameter < or = 80 nm) labeled with 100 microCi technetium-99m and were killed after 5, 15, 30, and 60 min. In blood, radioactivity, expressed as percentage of total body radioactivity per gram blood, amounted to 2.88 +/- 0.80%, 1.30 +/- 0.17%, 1.52 +/- 0.46%, and 0.21 +/- 0.06% at 5, 15, 30, and 60 min, respectively. Thin-layer chromatography showed only one peak of radioactivity corresponding to unaltered (99m)Tc-albumin nanocolloid. In the liver, radioactivity, expressed as percentage of total radioactivity per organ, amounted to 0.10 +/- 0.07%, 0.23 +/- 0.06%, 1.24 +/- 0.27%, and 0.06 +/- 0.02% at 5, 15, 30, and 60 min, respectively. Lower values were observed in the heart, spleen, kidneys, and brain. Dose dependence was assessed at 30 min following instillation of 10 microg and 1 microg (99m)Tc-albumin per animal (n = 3 at each dose), and values of the same relative magnitudes as after instillation of 100 microg were obtained. We conclude that a significant fraction of (99m)Tc-albumin, taken as a model of ultrafine particles, rapidly diffuses from the lungs into the systemic circulation.

Biliary excretion of polystyrene microspheres depends on the type of receptor-mediated uptake in rat liver

Hepatic uptake and biliary excretion of fluorescein isothiocyanate-labeled polystyrene microspheres with a particle size of 50 nm (MS-50) were studied in rats. Liver perfusion studies revealed that not only apo-E-mediated but also asialoglycoprotein receptor-mediated uptake is involved in the mechanism of the serum protein-dependent uptake of MS-50 in the liver. The uptake of MS-50 mediated by apo-E contributes more to the total uptake of MS-50 by the hepatocytes than that via asialoglycoprotein receptor in the presence of serum in the perfusate. Furthermore, it was found that MS-50 is substantially excreted into the bile by transcytosis. The extent of exocytosis of MS-50 taken up by the hepatocytes was much higher after MS-50 was endocytosed via asialoglycoprotein receptor than after taken up via the process mediated by apo-E. On the basis of these results, a possible regulation of the intracellular sorting of ligands, depending on the receptor-mediated uptake mechanism, was inferred.