Preparation and characterization of water-soluble pH-sensitive nanocarriers for drug delivery

Novel extraction, rapid assessment and bioavailability improvement of quercetin: A review

Quercetin (QUR) have got the attention of scientific society frequently due to their wide range of potential applications. QUR has been the focal point for research in various fields, especially in food development. But, the QUR is highly unstable and can be interrupted by using conventional assessment methods. Therefore, researchers are focusing on novel extraction and non-invasive tools for the non-destructive assessment of QUR. The current review elaborates the different novel extraction (ultrasound-assisted extraction, microwave-assisted extraction, supercritical fluid extraction, and enzyme-assisted extraction) and non-destructive assessment techniques (fluorescence spectroscopy, terahertz spectroscopy, near-infrared spectroscopy, hyperspectral imaging, Raman spectroscopy, and surface-enhanced Raman spectroscopy) for the extraction and identification of QUR in agricultural products. The novel extraction approaches facilitate shorter extraction time, involve less organic solvent, and are environmentally friendly. While the non-destructive techniques are non-interruptive, label-free, reliable, accurate, and environmental friendly. The non-invasive spectroscopic and imaging methods are suitable for the sensitive detection of bioactive compounds than conventional techniques. QUR has potential therapeutic properties such as anti-obesity, anti-diabetes, antiallergic, antineoplastic agent, neuroprotector, antimicrobial, and antioxidant activities. Besides, due to the low bioavailability of QUR innovative drug delivery strategies (QUR loaded gel, QUR polymeric micelle, QUR nanoparticles, glucan-QUR conjugate, and QUR loaded mucoadhesive nanoemulsions) have been proposed to improve its bioavailability and providing novel therapeutic approaches.

Multifunctional polymeric micellar nanomedicine in the diagnosis and treatment of cancer

Polymeric micelles are a prevalent topic of research for the past decade, especially concerning their fitting ability to deliver drug and diagnostic agents. This delivery system offers outstanding advantages, such as biocompatibility, high loading efficiency, water-solubility, and good stability in biological fluids, to name a few. The multifunctional polymeric micellar architect offers the added capability to adapt its surface to meet the looked-for clinical needs. This review cross-talks the recent reports, proof-of-concept studies, patents, and clinical trials that utilize polymeric micellar family architectures concerning cancer targeted delivery of anticancer drugs, gene therapeutics, and diagnostic agents. The manuscript also expounds on the underlying opportunities, allied challenges, and ways to resolve their bench-to-bedside translation for allied clinical applications.

Stimuli-Sensitive Self-Assembled Tubules Based on Lysine-Derived Surfactants for Delivery of Antimicrobial Proteins

Drug delivery vectors based on amphiphiles have important features such as versatile physicochemical properties and stimuli-responsiveness. Amino acid-based surfactants are especially promising amphiphiles due to their enhanced biocompatibility compared to conventional surfactants. They can self-organize into micelles, vesicles and complex hierarchical structures, such as fibers, twisted and coiled ribbons, and tubules. In this work, we investigated the self-assembly and drug loading properties of a family of novel anionic double-tailed lysine-derived surfactants, with variable degree of tail length mismatch, designated as mLys10 and 10Lysn, where m and n are the number of carbon atoms in the tails. These surfactants form tubular aggregates with assorted morphologies in water that undergo gelation due to dense entanglement, as evidenced by light and electron microscopy. Lysozyme (LZM), an enzyme with antimicrobial properties, was selected as model protein for loading. After the characterization of the interfacial properties and phase behavior of the amphiphiles, the LZM-loading ability of the tubules was investigated, under varying experimental conditions, to assess the efficiency of the aggregates as pH- and temperature-sensitive nanocarriers. Further, the toxicological profile of the surfactants per se and surfactant/LZM hydrogels was obtained, using human skin fibroblasts (BJ-5ta cell line). Overall, the results show that the tubule-based hydrogels exhibit very interesting properties for the transport and controlled release of molecules of therapeutic interest.

Preparation and In Vitro and In Vivo Antitumor Effects of VEGF Targeting Micelles

Background:

Doxorubicin (DOX) has antitumor effects mediated by cell viability inhibition and by inducing cellular apoptosis. However, it has limited use in clinical applications due to various factors such as hydrophobicity, dose-dependent toxicity effects on normal tissues, short cycle retention time, and low targeting ability. This study aims at enhancing hydrophilicity of DOX to restrict its toxic effects to within or around the tumor sites and also to improve its targeting ability to enhance antitumor efficiency.

Methods:

Micelles composed of biodegradable poly (ethylene glycol)-poly (lactic acid) copolymers (PEG-PLA) were employed to deliver DOX via a self-assembly method and were coupled to VEGF antibodies. The morphology, size, and physical stability of PEG-PLA-DOX targeting VEGF micelles (VEGF-PEG-PLA-DOX micelles) were assessed. Then, the release ability of DOX from these micelles was monitored, and their drug loading capacity was calculated. MTT assay revealed the in vitro antitumor effect of VEGF-PEG-PLA-DOX micelles. Moreover, ROS release was measured to evaluate apoptotic effects of these nanoparticle micelles. In vivo therapeutic efficiencies of VEGF-PEG-PLA-DOX micelles on a lung cancer nude mouse model was evaluated.

Results:

DOX-loaded micelles were obtained with a drug loading capacity of 12.2% and were monodisperse with 220 nm average diameter and a controlled in vitro DOX release for extended periods. In addition, VEGF-PEG-PLA-DOX micelles displayed a larger cell viability inhibitory effect as measured via MTT assays and greater cell apoptosis induction through in vitro ROS levels compared with PEG-PLA-DOX micelles or free DOX. Furthermore, VEGF-PEG-PLA-DOX micelles could improve in vivo antitumor effects of DOX by reducing tumor volume and weight.

Conclusions:

VEGF-PEG-PLA-DOX micelles displayed a larger anti-tumor effect both in in vitro A549 cells and in an in vivo lung cancer nude mouse model compared with PEG-PLA-DOX micelles or free DOX, and hence they have potential clinical applications in human lung cancer therapy.

Nanocarriers Used Most in Drug Delivery and Drug Release: Nanohydrogel, Chitosan, Graphene, and Solid Lipid

Over the past few years, nanocarriers have become an ideal solution for safe and efficient drug delivery and release. This is mainly due to the extraordinary characteristics that nanomaterials exhibit when compared with their larger scaled forms. A variety of these carriers are more popular due to their high biocompatibility, ensuring greater efficacy especially in cancer treatments. Nanocrystal, liposomal, and micelle designs of these materials as nanocarriers for drug delivery and release have been extensively researched throughout the past 50 years. Successful applications have not only ensured a greater focus on therapeutic development but also created a new solution available in the pharmaceutical market. Herein, a brief review of research studies focused on nanocarrier materials and designs to achieve superior benefits of drugs for disease treatments is presented. Nanohydrogels, chitosan, graphene oxide, and solid lipid nanoparticle nanocarrier designs and applications are selectively given due to the great attention they have gained from being highly biocompatible and easy-to-manipulate nanocarrier options from organic and inorganic nanocarrier materials. Each summary exhibits the progress that has been achieved to date. With greater understanding of the current state in the development process of these nanomaterials, there is a rising chance to provide better treatment to patients, which is a desperate need in pharmaceutical technologies.

Phosphorus-Containing Block Copolymers from the Sequential Living Anionic Copolymerization of a Phosphaalkene with Methyl Methacrylate

Although living polymerization methods are widely applicable to organic monomers, their application to inorganic monomers is rare. For the first time, we show that the living poly(methylenephosphine) (PMP_n ^- ) anion can function as a macroinitiator for olefins. Specifically, the phosphaalkene, MesP=CPh₂ (PA), and methyl methacrylate (MMA) can be sequentially copolymerized using the BnLi-TMEDA initiator system in toluene. A series of PMP_n -b-PMMA_m copolymers with narrow dispersities are accessible (Đ=1.05-1.10). Analysis of the block copolymers provided evidence for -P-CPh₂ -CH₂ -CMe(CO₂ Me)- switching groups. Importantly, this indicates that the -P-CPh₂ ^- anion directly initiates the anionic polymerization of MMA and stands in stark contrast to the isomerization mechanism followed for the homopolymerization of PA. For the first time, the glass transition of a PMP_n homopolymer has been measured (T_g =45.1 °C, n=20). The PMP_n -b-PMMA_m copolymers do not phase separate and show a single T_g which increases with higher PMMA content.

Hydrazone linkages in pH responsive drug delivery systems

Stimuli-responsive polymeric drug delivery systems using various triggers to release the drug at the sites have become a major focus area. Among various stimuli-responsive materials, pH-responsiveness has been studied extensively. The materials used for fabricating pH-responsive drug delivery systems include a specific chemical functionality in their structure that can respond to changes in the pH of the surrounding environment. Various chemical functionalities, for example, acetal, amine, ortho ester, amine and hydrazone, have been used to design materials that are capable of releasing their payload at the acidic pH conditions of the tumor or infection sites. Hydrazone linkages are significant synthons for numerous transformations and have gained importance in pharmaceutical sciences due to their various biological and clinical applications. These linkages have been employed in various drug delivery vehicles, such as linear polymers, star shaped polymers, dendrimers, micelles, liposomes and inorganic nanoparticles, for pH-responsive drug delivery. This review paper focuses on the synthesis and characterization methods of hydrazone bond containing materials and their applications in pH-responsive drug delivery systems. It provides detailed suggestions as guidelines to materials and formulation scientists for designing biocompatible pH-responsive materials with hydrazone linkages and identifying future studies.

Tumor-targeted docetaxel-loaded hyaluronic acid-quercetin polymeric micelles with p-gp inhibitory property for hepatic cancer therapy

Herein, a novel targeted drug delivery nanosystem based on hyaluronic acid (HA) and quercetin (QU) was designed to improve the in vivo therapeutic efficacy of DTX on HC through HA-CD44 mediated targeting and QU-based p-gp efflux inhibition.

Coaxial nanotubes of stimuli responsive polymers with tunable release kinetics

Stimuli responsive polymeric (SRP) nanotubes have great potential as nanocarriers of macromolecules due to their large surface areas and release mechanisms that can be activated externally. In this work, we demonstrate vapor phase synthesis of coaxial nanotubes with layers of different SRP polymers for improved release kinetics. Temperature responsive poly(N-isopropylacrylamide) (pNIPAAm), pH responsive poly(methacrylic acid) (pMAA) and poly(hydroxyethyl methacrylate) (pHEMA) are used to fabricate the responsive coaxial nanotubes and the phloroglucinol dye is used as the model molecule to study the release kinetics. Fastest release is observed with single layer pNIPAAm nanotubes with rates of 0.134 min(-1), whereas introducing pHEMA or pMAA as inner layers slows down the release, enabling tuning of the response. Furthermore, repeating the release studies multiple times shows that the release rates remain similar after each run, confirming the stability of the nanotubes.

Enhancing oral bioavailability of quercetin using novel soluplus polymeric micelles

To improve its poor aqueous solubility and stability, the potential chemotherapeutic drug quercetin was encapsulated in soluplus polymeric micelles by a modified film dispersion method. With the encapsulation efficiency over 90%, the quercetin-loaded polymeric micelles (Qu-PMs) with drug loading of 6.7% had a narrow size distribution around mean size of 79.00 ± 2.24 nm, suggesting the complete dispersibility of quercetin in water. X-ray diffraction (XRD) patterns illustrated that quercetin was in amorphous or molecular form within PMs. Fourier transform infrared spectroscopy (FTIR) indicated that quercetin formed intermolecular hydrogen bonding with carriers. An in vitro dialysis test showed the Qu-PMs possessed significant sustained-release property, and the formulation was stable for at least 6 months under accelerated conditions. The pharmacokinetic study in beagle dogs showed that absorption of quercetin after oral administration of Qu-PMs was improved significantly, with a half-life 2.19-fold longer and a relative oral bioavailability of 286% as compared to free quercetin. Therefore, these novel soluplus polymeric micelles can be applied to encapsulate various poorly water-soluble drugs towards a development of more applicable therapeutic formulations.

Stimuli-responsive hydrogels in drug delivery and tissue engineering

Hydrogels are the three-dimensional network structures obtained from a class of synthetic or natural polymers which can absorb and retain a significant amount of water. Hydrogels are one of the most studied classes of polymer-based controlled drug release. These have attracted considerable attention in biochemical and biomedical fields because of their characteristics, such as swelling in aqueous medium, biocompatibility, pH and temperature sensitivity or sensitivity towards other stimuli, which can be utilized for their controlled zero-order release. The hydrogels are expected to explore new generation of self-regulated delivery system having a wide array of desirable properties. This review highlights the exciting opportunities and challenges in the area of hydrogels. Here, we review different literatures on stimuli-sensitive hydrogels, such as role of temperature, electric potential, pH and ionic strength to control the release of drug from hydrogels.

Doxorubicin-conjugated PLA-PEG-Folate based polymeric micelle for tumor-targeted delivery: synthesis and in vitro evaluation

BACKGROUND

Selective delivery of anticancer agents to target areas in the body is desirable to minimize the side effects while maximizing the therapeutic efficacy. Anthracycline antibiotics such as doxorubicin (DOX) are widely used for treatment of a wide variety of solid tumors.This study evaluated the potential of a polymeric micellar formulation of doxorubicin as a nanocarrier system for targeted therapy of a folate-receptor positive human ovarian cancer cell in line.

RESULTS

DOX-conjugated targeting and non-targeting micelles prepared by the dialysis method were about 188 and 182 nm in diameter, respectively and their critical micelle concentration was 9.55 μg/ml. The DOX-conjugated micelles exhibited a potent cytotoxicity against SKOV3 human ovarian cancer cells. Moreover, the targeting micelles showed higher cytotoxicity than that of non-targeting ones (IC₅₀= 4.65 μg/ml vs 13.51 μg/ml).

CONCLUSION

The prepared micelle is expected to increase the efficacy of DOX against cancer cells and reduce its side effects.

Temperature- and pH-sensitive Polymeric Micelles for Drug Encapsulation, Release and Targeting

More than 50% of the drugs in the market and 70% of the new candidates are poorly water soluble according to the Biopharmaceutic Classification System (BCS(. Poor aqueous solubility and physico-chemical stability of drugs in biological fluids remain key limitations in oral, parenteral and transdermal administration and contribute to an increase the drug attrition rate. Motivated by the outbreak of nanotechnology, different nanocarriers made of lipids and polymers have been designed and developed to address these limitations. Moreover, robust platforms were exploited to achieve the temporal and spatial release of drugs, thus constraining the systemic exposure to toxic agents and the appearance of severe adverse effects and improving the safety ratio. Owing to unique features such as (i( great chemical flexibility, (ii( capacity to host, solubilize and physico-chemically stabilize poorly water soluble drugs, (iii( ability to accumulate selectively in highly vascularized solid tumors and (iv( ability of single amphiphile molecules (unimers( to inhibit the activity of different pumps of the ATP-binding cassette superfamily (ABCs(, polymeric micelles have emerged as one of the most versatile nanotechnologies. Despite their diverse applications to improve the therapeutic outcomes, polymeric micelles remain clinically uncapitalized. The present chapter overviews the most recent applications of temperature- and pH-responsive polymeric micelles for the encapsulation, release and targeting of drugs and discusses the perspectives for these unique nanocarriers in the near future.

Investigation of coumarin functionality on the formation of polymeric nanoparticles

The effect of coumarin molecules on the formation of polymeric nanoparticles is examined using a model polymer, poly(methyl methacrylate) (PMMA), functionalized with varying amounts of coumarin pendant groups (PCM). PCM nanoparticles are prepared in a continuous manner by Flash NanoPrecipitation (FNP). PCM forms spherical nanoparticles in water, while the PMMA without coumarin functionality fails to form nanoparticles. As the amount of coumarin functionality increases, the nanoparticle size and size polydispersity are decreased and the nanoparticle stability in water is enhanced. In particular, well-isolated spherical nanoparticles are generated from PCM with 20 mol% coumarin side chain functionality. These results can be explained by an observed increase in the negative surface charge with increasing coumarin content in the polymer.

Immunomicelles for advancing personalized therapy

Personalized medicine, which ultimately seeks to afford tailored therapeutic regimens for individual patients, is quickly emerging as a new paradigm in the diagnosis and treatment of diseases. The idea of casting aside generic treatments in favor of patient-centric therapies has become feasible owing to advances in nanotechnology and drug delivery coupled with an enhanced knowledge of genomics and an understanding of disease at the molecular level. This review highlights polymeric immunomicelles as a class of nanocarriers that have the potential to combine diagnosis, targeted drug therapy, as well as imaging and monitoring of therapeutic response, to render a personalized approach to the management of disease. Smart multi-functional immunomicelles, as the next generation of nanocarriers, are poised for facilitating personalized cancer treatment. This review provides an assessment of immunomicelles as tools for advancing personalized therapy of diseases, with cancer being the major focus.

Polymeric and Ceramic Nanoparticles in Biomedical Applications

Materials in the nanometer size range may possess unique and beneficial properties, which are very useful for different medical applications including stomatology, pharmacy, and implantology tissue engineering. The application of nanotechnology to medicine, known as nanomedicine, concerns the use of precisely engineered materials at this length scale to develop novel therapeutic and diagnostic modalities. Nanomaterials have unique physicochemical properties, such as small size, large surface area to mass ratio, and high reactivity, which are different from bulk materials of the same composition. Polymeric and ceramic nanoparticles have been extensively studied as particulate carriers in the pharmaceutical and medical fields, because they show promise as drug delivery systems as a result of their controlled- and sustained-release properties, subcellular size, and biocompatibility with tissue and cells. These properties can be used to overcome some of the limitations found in traditional therapeutic and diagnostic agents. Nanotechnology is showing promising developments in many areas and may benefit our health and welfare. However, a wide range of ethical issues has been raised by this innovative science. Many authorities believe that these advancements could lead to irreversible disasters if not limited by ethical guidelines.

"Nanoantibiotics": a new paradigm for treating infectious diseases using nanomaterials in the antibiotics resistant era

Despite the fact that we live in an era of advanced and innovative technologies for elucidating underlying mechanisms of diseases and molecularly designing new drugs, infectious diseases continue to be one of the greatest health challenges worldwide. The main drawbacks for conventional antimicrobial agents are the development of multiple drug resistance and adverse side effects. Drug resistance enforces high dose administration of antibiotics, often generating intolerable toxicity, development of new antibiotics, and requests for significant economic, labor, and time investments. Recently, nontraditional antibiotic agents have been of tremendous interest in overcoming resistance that is developed by several pathogenic microorganisms against most of the commonly used antibiotics. Especially, several classes of antimicrobial nanoparticles (NPs) and nanosized carriers for antibiotics delivery have proven their effectiveness for treating infectious diseases, including antibiotics resistant ones, in vitro as well as in animal models. This review summarizes emerging efforts in combating against infectious diseases, particularly using antimicrobial NPs and antibiotics delivery systems as new tools to tackle the current challenges in treating infectious diseases.

pH-sensitive amphiphilic biodegradable graft co-polymer aggregates based on polyaspartamide for intracellular delivery

A biodegradable, pH-sensitive amphiphilic co-polymer, o-(2-aminoethyl)-o'-methylpolyethylene glycol/1-(3-aminopropyl)imidazole/lactic acid oligomers-g-polyaspartamide (MPEG/API/LAs-g-PASPAM), was synthesized. The hydrophobic biodegradable poly (lactic acid) (PLA), the hydrophilic MPEG and the pH-sensitive API were successfully introduced into the biodegradable polysuccinimide (PSI) backbone by grafting. In its synthesis, the feed ratio of MPE to PLA was varied to provide different amphiphilic balances. FT-IR and (1)H-NMR spectroscopy were used to identify the chemical structure of the MPEG/API/LAs-g-PASPAM co-polymers synthesized. Tens to a few hundreds of nanometer-scaled aggregates, appropriate for intracellular drug-carrier applications, were developed in the simulated buffer solution, and their self-assembling behavior was significantly affected by the environmental pH. The size and morphology of self-aggregates were investigated using dynamic light scattering and transmission electron microscopy. The buffering effect was observed in the endosomal pH range. The drug loading and release experiments were conducted for a series of co-polymer aggregate systems, and it was noted that the release behavior was mostly governed by diffusion. The biodegradable kinetics was also studied to ascertain the drug-release mechanism.

Bioresponsive matrices in drug delivery

For years, the field of drug delivery has focused on (1) controlling the release of a therapeutic and (2) targeting the therapeutic to a specific cell type. These research endeavors have concentrated mainly on the development of new degradable polymers and molecule-labeled drug delivery vehicles. Recent interest in biomaterials that respond to their environment have opened new methods to trigger the release of drugs and localize the therapeutic within a particular site. These novel biomaterials, usually termed "smart" or "intelligent", are able to deliver a therapeutic agent based on either environmental cues or a remote stimulus. Stimuli-responsive materials could potentially elicit a therapeutically effective dose without adverse side effects. Polymers responding to different stimuli, such as pH, light, temperature, ultrasound, magnetism, or biomolecules have been investigated as potential drug delivery vehicles. This review describes the most recent advances in "smart" drug delivery systems that respond to one or multiple stimuli.

Self-assembled Polyion Complex Micelles based on PVP-b-PAMPS and PVP-b-PDMAEMA for Drug Delivery

The double hydrophilic block copolymer, poly(N-vinylpyrrolidone)-block-poly(2-acrylamido-2-methyl-1-propanesulfonic acid), was synthesized by reversible addition-fragmentation chain transfer RAFT polymerization. Gel permeation chromatography, 1H-NMR, and FTIR were used to determine the structure and composition. In aqueous media, this block copolymer spontaneously forms polyion complex (PIC) micelles with an oppositely charged block copolymer, poly(N-vinylpyrrolidone)-block-poly(N, N-dimethylaminoethyl methacrylate). Dynamic light scattering and transmission electron micrograph showed that the micelles were <200 nm in diameter and had a narrow single distribution. The release profiles of folic acid, incorporated into the micelles, showed remarkable pH responsive behavior. The PIC micelles exhibited good biocompatibility based on MTT assay with human embryonic kidney (HEK293) cells. These PIC micelles have the potential as pH-sensitive carriers for drug delivery.

Polymeric micelles: polyethylene glycol-phosphatidylethanolamine (PEG-PE)-based micelles as an example

One of the renowned nanosized pharmaceutical carriers for delivery of poorly soluble drugs, especially, in cancer, is micelles, which are self-assembled colloidal particles with a hydrophobic core and hydrophilic shell. Among the micelle-forming compounds, micelles made of polyethylene glycol-phosphatidylethanolamine (PEG-PE) have gained more attention due to some attractive properties such as good stability, longevity, and ability to accumulate in the areas with an abnormal vasculature via the enhanced permeability and retention effect (into the areas with leaky vasculature, such as tumors). Additionally these micelles can be made "targeted" by attaching specific targeting ligand molecules to the micelle surface or can be comprised of stimuli-responsive amphiphilic block copolymers. Addition of second component such as surfactant or another hydrophobic material to the main micelle forming material further improves the solubilizing capacity of micelles without compromising their stability. Micelles carrying various contrast agents may become the imaging agents of choice in different imaging modalities. Here, we have discussed various protocols for preparation and evaluation of PEG-PE-based micelles.

Emerging trends of nanomedicine--an overview

Nanotechnology is an emerging branch of science for designing tools and devices of size 1 to 100 nm with unique function at the cellular, atomic and molecular levels. The concept of using nanotechnology in medical research and clinical practice is known as nanomedicine. Nanoparticles possess some novel properties not seen with the macro molecules and they can be manipulated by attaching therapeutic components to help in diagnosis and treatment. They can also be used to probe cellular movements and molecular changes associated with pathological states. Nanodevices like carbon nanotubes to locate and deliver anticancer drugs at the specific tumour site are under research. Nanotechnology promises construction of artificial cells, enzymes and genes. This will help in the replacement therapy of many disorders which are due to deficiency of enzymes, mutation of genes or any repair in the synthesis of proteins. Currently nanodevices like respirocytes, microbivores and probes encapsulated by biologically localized embedding have a greater application in treatment of anaemia and infections. Thus in the present scenario, nanotechnology is spreading its wings to address the key problems in the field of medicine. Hence this review discusses in detail the applications of nanotechnology in medicine with more emphasis on drug delivery and therapy.

UV resonance Raman determination of molecular mechanism of poly(N-isopropylacrylamide) volume phase transition

Poly(N-isopropylacrylamide) (PNIPAM) is the premier example of a macromolecule that undergoes a hydrophobic collapse when heated above its lower critical solution temperature (LCST). Here we utilize dynamic light scattering, H-NMR, and steady-state and time-resolved UVRR measurements to determine the molecular mechanism of PNIPAM's hydrophobic collapse. Our steady-state results indicate that in the collapsed state the amide bonds of PNIPAM do not engage in interamide hydrogen bonding, but are hydrogen bonded to water molecules. At low temperatures, the amide bonds of PNIPAM are predominantly fully water hydrogen bonded, whereas, in the collapsed state one of the two normal CO hydrogen bonds is lost. The NH-water hydrogen bonding, however, remains unperturbed by the PNIPAM collapse. Our kinetic results indicate a monoexponential collapse with tau approximately 360 (+/-85) ns. The collapse rate indicates a persistence length of n approximately 10. At lengths shorter than the persistence length the polymer acts as an elastic rod, whereas at lengths longer than the persistence length the polymer backbone conformation forms a random coil. On the basis of these results, we propose the following mechanism for the PNIPAM volume phase transition. At low temperatures PNIPAM adopts an extended, water-exposed conformation that is stabilized by favorable NIPAM-water solvation shell interactions which stabilize large clusters of water molecules. As the temperature increases an increasing entropic penalty occurs for the water molecules situated at the surface of the hydrophobic isopropyl groups. A cooperative transition occurs where hydrophobic collapse minimizes the exposed hydrophobic surface area. The polymer structural change forces the amide carbonyl and N-H to invaginate and the water clusters cease to be stabilized and are expelled. In this compact state, PNIPAM forms small hydrophobic nanopockets where the (i, i + 3) isopropyl groups make hydrophobic contacts. A persistent length of n approximately 10 suggests a cooperative collapse where hydrophobic interactions between adjacent hydrophobic pockets stabilize the collapsed PNIPAM.

The application of poly(N-isopropylacrylamide)-co-polystyrene nanofibers as an additive agent to facilitate the cellular uptake of an anticancer drug

In this paper, we have fabricated poly(N-isopropylacrylamide)-co-polystyrene (PNIPAM-co-PS) nanofibers by electrospinning and explored the possibility to utilize the PNIPAM-co-PS nanofibers to enhance the permeation and uptake of the anticancer drug daunorubicin in drug-sensitive and drug-resistant leukemia K562 cells. Our MTT assay and electrochemical studies demonstrate that PNIPAM-co-PS nanofibers could play an important role in facilitating the cell track and drug delivery to the cancer cells. Meanwhile, the observations of atomic force microscopy (AFM) and confocal fluorescence microscopy indicate that the relevant interaction of the PNIPAM-co-PS nanofibers with bioactive molecules on the membrane of leukemia cell lines could affect the intracellular drug uptake positively and lead to the efficient accumulation of daunorubicin in drug-sensitive and drug-resistant cancer cells.

Pluronic and tetronic copolymers with polyglycolyzed oils as self-emulsifying drug delivery systems

The potential of poly(ethylene oxide)-poly(propylene oxide) block copolymers Pluronic F127 (PF127) and Tetronic 304 (T304), 904 (T904) and 1307 (T1307) as components of solid self-(micro)emulsifying dosage forms, S(M)EDDS, was evaluated. The dependence of the self-associative properties of Tetronics on pH explained the low ability of the micelles to solubilize griseofulvin at acid pH (sevenfold increase) compared to at alkaline pH (12-fold). Blends of polyglycolyzed glycerides (Labrasol, Labrafac CC, and Labrafil M 1944CS) with each copolymer at two different weight ratios (80:20 and 60:40) were prepared, diluted in water, and characterized in terms of globule size, appearance and griseofulvin solubility. The blends with Labrasol led to microemulsions that are able to increase drug solubility up to 30-fold. SMEDD hard gelatine capsules filled with griseofulvin and Labrasol or Labrasol/copolymer 80:20 showed a remarkable increase in drug solubility and dissolution rate, particularly when T904, T1307 or PF127 was present in the blend. This effect was more remarkable when the volume of the dissolution medium was 200 ml (compared to 900 ml), which can be related to a higher stability of the microemulsion when there is a greater concentration of the copolymer and glyceride in the medium.

Blends of TiO2 nanoparticles and poly (N-isopropylacrylamide)-co-polystyrene nanofibers as a means to promote the biorecognition of an anticancer drug

The poly (N-isopropylacrylamide)-co-polystyrene (PNIPAM-co-PS) nanofibers have been fabricated by electrospinning, and the blends of PNIPAM-co-PS nanofibers with titanium dioxide (TiO(2)) nanoparticles have been characterized and utilized as the new nanocomposites to enhance the relevant detection sensitivity of biomolecular recognition of an anticancer drug daunorubicin. Our observations demonstrate that upon application of the nanoTiO(2)-PNIPAM-co-PS polymer nanocomposites, the drug molecules could be readily deposited on the surface of the relevant blends so that the remarkable enhancement effect of the new nanocomposites on the respective biorecognition of daunorubicin could be observed, suggesting the potential valuable application of the blending of the nanoTiO(2) and PNIPAM-co-PS polymer nanocomposites in high sensitive bioanalysis.

A review of stimuli-responsive nanocarriers for drug and gene delivery

Nanotechnology has shown tremendous promise in target-specific delivery of drugs and genes in the body. Although passive and active targeted-drug delivery has addressed a number of important issues, additional properties that can be included in nanocarrier systems to enhance the bioavailability of drugs at the disease site, and especially upon cellular internalization, are very important. A nanocarrier system incorporated with stimuli-responsive property (e.g., pH, temperature, or redox potential), for instance, would be amenable to address some of the systemic and intracellular delivery barriers. In this review, we discuss the role of stimuli-responsive nanocarrier systems for drug and gene delivery. The advancement in material science has led to design of a variety of materials, which are used for development of nanocarrier systems that can respond to biological stimuli. Temperature, pH, and hypoxia are examples of "triggers" at the diseased site that could be exploited with stimuli-responsive nanocarriers. With greater understanding of the difference between normal and pathological tissues and cells and parallel developments in material design, there is a highly promising role of stimuli-responsive nanocarriers for drug and gene delivery in the future.

Drug delivery systems - an overview

This is an overview of drug delivery systems (DDS), starting with various routes of drug administration. Various drug formulations, as well as devices used for drug delivery and targeted drug delivery, are then described. Delivery of proteins and peptides presents special challenges. Nanoparticles are considered to be important in refining drug delivery; they can be pharmaceuticals as well as diagnostics. Refinements in drug delivery will facilitate the development of personalized medicine, which includes pharmacogenomics, pharmacogenetics, and pharmacoproteomics. The ideal DDS, commercial aspects, current achievements, challenges, and future prospects are also discussed.

Rapidly Reversible Hydrophobization: An Approach to High First-Pass Drug Extraction

We have investigated a rapidly reversible hydrophobization of therapeutic agents for improving first-pass uptake in locoregional drug therapy. This approach involves the attachment of a hydrophobic moiety to the drug by highly labile chemical linkages that rapidly hydrolyze upon injection. Hydrophobization drastically enhances cell-membrane association of the prodrug and, consequently, drug uptake, while the rapid lability protects nontargeted tissues from exposure to the highly active agent. Using the membrane-impermeable DNA intercalator propidium iodide, and melphalan, we report results from in vitro cellular internalization and toxicity studies. Additionally, we report in vivo results after a single liver arterial bolus injection, demonstrating both tumor targeting and increased survival in a mouse tumor model.

Triggered destabilisation of polymeric micelles and vesicles by changing polymers polarity: an attractive tool for drug delivery

Polymeric micelles and vesicles have emerged as versatile drug carriers during the past decades. Furthermore, stimuli-responsive systems are developed whose properties change after applying certain external triggers. Therefore, a triggered release of drugs from stimuli-sensitive micelles and vesicles has become an interesting challenge in the pharmaceutical field. Polymeric micelles or vesicles are mainly composed of amphiphilic block copolymers that are held together in water due to strong hydrophobic interactions between the insoluble hydrophobic blocks, thus forming a core-shell or bilayer morphology. Consequently, destabilisation of these assemblies is induced by increasing the polarity of the hydrophobic blocks. Preferably, this process should be the consequence of an external trigger, or take place in a certain time frame or at a specific location. A variety of mechanisms has recently been described to accomplish this transition, which will be reviewed in this paper. These mechanisms include the destabilisation of polymeric micelles and vesicles by temperature, pH, chemical or enzymatic hydrolysis of side chains, oxidation/reduction processes, and light.

Phase transition behavior of novel pH-sensitive polyaspartamide derivatives grafted with 1-(3-aminopropyl)imidazole

New pH-sensitive polyaspartamide derivatives were synthesized by grafting 1-(3-aminopropyl)imidazole and/or O-(2-aminoethyl)-O'-methylpoly(ethylene glycol) 5000 on polysuccinimide for application in intracellular drug delivery systems. The DS of 1-(3-aminopropyl)imidazole was adjusted by the feed molar ratio, and the structure of the prepared polymer was confirmed using FT-IR and 1H NMR spectroscopy. Their pH-sensitive properties were characterized by light transmittance measurements, and the particle size and its distribution were investigated by dynamic light scattering measurements at varying pH values. The pH-sensitive phase transition was clearly observed in polymer solutions with a high substitution of 1-(3-aminopropyl)imidazole. The prepared polymers showed a high buffering capacity between pH 5 and 7, and this increased with the DS of 1-(3-aminopropyl)imidazole. The pH dependence of the aggregation and de-aggregation behavior was examined using a fluorescence spectrometer. For MPEG/imidazole-g-polyaspartamides with a DS of 1-(3-aminopropyl)imidazole over 82%, self aggregates associated with the hydrophobic interactions of the unprotonated imidazole groups were observed at pH values above 7, and their mean size was over 200 nm, while the aggregates of polymers were dissociated at pH values below 7 by the protonation of imidazole groups. These pH-sensitive polyaspartamide derivatives are potential basic candidates for intracellular drug delivery carriers triggered by small pH changes.