Development of pH sensitive 2-(diisopropylamino)ethyl methacrylate based nanoparticles for photodynamic therapy

Unveiling the Performance of Co-Assembled Hybrid Nanocarriers: Moving towards the Formation of a Multifunctional Lipid/Random Copolymer Nanoplatform

Despite the appealing properties of random copolymers, the use of these biomaterials in association with phospholipids is still limited, as several aspects of their performance have not been investigated. The aim of this work is the formulation of lipid/random copolymer platforms and the comprehensive study of their features by multiple advanced characterization techniques. Both biomaterials are amphiphilic, including two phospholipids (1,2-dioctadecanoyl-sn-glycero-3-phosphocholine (DSPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)) and a statistical copolymer of oligo (ethylene glycol) methyl ether methacrylate (OEGMA) and 2-(diisopropylamino) ethyl methacrylate (DIPAEMA). We examined the design parameters, including the lipid composition, the % comonomer ratio, and the lipid-to-polymer ratio that could be critical for their behavior. The structures were also probed in different conditions. To the best of the authors' knowledge, this is the first time that P(OEGMA-co-DIPAEMA)/lipid hybrid colloidal dispersions have been investigated from a membrane mechanics, biophysical, and morphological perspective. Among other parameters, the copolymer architecture and the hydrophilic to hydrophobic balance are deemed fundamental parameters for the biomaterial co-assembly, having an impact on the membrane's fluidity, morphology, and thermodynamics. Exploiting their unique characteristics, the most promising candidates were utilized for methotrexate (MTX) loading to explore their encapsulation capability and potential antitumor efficacy in vitro in various cell lines.

pH- and Photoresponsive Liquid Plasticine

Liquid marbles (LMs) can be prepared by adsorption of hydrophobic particles at the air-liquid interface of a water droplet. LMs have been studied for their application as microreaction vessels. However, their opaqueness poses challenges for internal observation. Liquid plasticines (LPs), akin to LMs, can be prepared by the adsorption of hydrophobic particles with a diameter of 50 nm or less, at the air-liquid interface of a water droplet. Unlike LMs, LPs are transparent, allowing for internal observation, thus presenting promising applications as reactors and culture vessels on a microliter scale. In this study, the surface of silica particles, approximately 20 nm in diameter, was rendered hydrophobic to prepare hydrophobic silica particles (SD0). A small amount of poly(2-(diisopropylamino)ethyl methacrylate) (PDPA) was then grafted onto the surface of SD0, yielding SD1. SD0 particles exhibited consistent hydrophobicity irrespective of the environmental pH atmosphere. Under acidic conditions, SD1 became hydrophilic due to the protonation of pendant tertiary amines in the grafted PDPA chains. However, SD1 alone was unsuitable for LP preparation due to its high surface wettability regardless of atmospheric pH, attributable to the presence of PDPA-grafted chains. Therefore, to prepare pH-responsive LP, SD1 and SD0 were mixed (SD1/SD0 = 3/7). Upon exposure to HCl gas, these LPs ruptured, with the leaked water from the LPs being absorbed by adjacent paper. Moreover, clear LPs, prepared using an aqueous solution containing a water-soluble photoacid generator (PAG), disintegrated upon exposure to light as PAG generated acid, leading to LP breakdown. In summary, pH-responsive LPs, capable of disintegration under acidic conditions and upon light irradiation, were successfully prepared in this study.

Responsive nanosystems for targeted therapy of ulcerative colitis: Current practices and future perspectives

The pharmacological approach to treating gastrointestinal diseases is suffering from various challenges. Among such gastrointestinal diseases, ulcerative colitis manifests inflammation at the colon site specifically. Patients suffering from ulcerative colitis notably exhibit thin mucus layers that offer increased permeability for the attacking pathogens. In the majority of ulcerative colitis patients, the conventional treatment options fail in controlling the symptoms of the disease leading to distressing effects on the quality of life. Such a scenario is due to the failure of conventional therapies to target the loaded moiety into specific diseased sites in the colon. Targeted carriers are needed to address this issue and enhance the drug effects. Conventional nanocarriers are mostly readily cleared and have nonspecific targeting. To accumulate the desired concentration of the therapeutic candidates at the inflamed area of the colon, smart nanomaterials with responsive nature have been explored recently that include pH responsive, reactive oxygen species responsive (ROS), enzyme responsive and thermo - responsive smart nanocarrier systems. The formulation of such responsive smart nanocarriers from nanotechnology scaffolds has resulted in the selective release of therapeutic drugs, avoiding systemic absorption and limiting the undesired delivery of targeting drugs into healthy tissues. Recent advancements in the field of responsive nanocarrier systems have resulted in the fabrication of multi-responsive systems i.e. dual responsive nanocarriers and derivitization that has increased the biological tissues and smart nanocarrier's interaction. In addition, it has also led to efficient targeting and significant cellular uptake of the therapeutic moieties. Herein, we have highlighted the latest status of the responsive nanocarrier drug delivery system, its applications for on-demand delivery of drug candidates for ulcerative colitis, and the prospects are underpinned.

Development of Hybrid DSPC:DOPC:P(OEGMA950-DIPAEMA) Nanostructures: The Random Architecture of Polymeric Guest as a Key Design Parameter

Hybrid nanoparticles have gained a lot of attention due to their advantageous properties and versatility in pharmaceutical applications. In this perspective, the formation of novel systems and the exploration of their characteristics not only from a physicochemical but also from a biophysical perspective could promote the development of new nanoplatforms with well-defined features. In the current work, lipid/copolymer bilayers were formed in different lipid to copolymer ratios and examined via differential scanning calorimetry as a preformulation study to decipher the interactions between the biomaterials, followed by nanostructure preparation by the thin-film hydration method. Physicochemical and toxicological evaluations were conducted utilizing light scattering techniques, fluorescence spectroscopy, and MTS assay. 1,2-dioctadecanoyl-sn-glycero-3-phosphocholine (DSPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) in different weight ratios were the chosen lipids, while a linear random copolymer with pH- and thermoresponsive properties comprised of oligo (ethylene glycol) methyl ether methacrylate (OEGMA) and 2-(diisopropylamino) ethyl methacrylate (DIPAEMA) in different ratios was used. According to our results, non-toxic hybrid nanosystems with stimuli-responsive properties were successfully formulated, and the main parameters influencing their overall performance were the hydrophilic/hydrophobic balance, lipid to polymer ratio, and more importantly the random copolymer topology. Hopefully, this investigation can promote a better understanding of the factors affecting the behavior of hybrid systems.

Importance of Rose Bengal Loaded with Nanoparticles for Anti-Cancer Photodynamic Therapy

Rose Bengal (RB) is a photosensitizer (PS) used in anti-cancer and anti-bacterial photodynamic therapy (PDT). The specific excitation of this PS allows the production of singlet oxygen and oxygen reactive species that kill bacteria and tumor cells. In this review, we summarize the history of the use of RB as a PS coupled by chemical or physical means to nanoparticles (NPs). The studies are divided into PDT and PDT excited by X-rays (X-PDT), and subdivided on the basis of NP type. On the basis of the papers examined, it can be noted that RB used as a PS shows remarkable cytotoxicity under the effect of light, and RB loaded onto NPs is an excellent candidate for nanomedical applications in PDT and X-PDT.

Advances in chlorin-based photodynamic therapy with nanoparticle delivery system for cancer treatment

Introduction: The treatment of tumors is one of the most difficult problems in the medical field at present. Patients often use a comprehensive therapy that combines surgery, radiotherapy, and chemotherapy. Photodynamic therapy (PDT) has prominent potential for eradicating various cancers. Chlorin-based photosensitizers (PSs), as one of the most utilized photosensitizers, have many advantages over conventional photosensitizers; however, a successful chlorin-based PDT needs multi-functional nano-carriers for selective photosensitizer delivery. The number of researches about nanoparticles designed for improved chlorin-based PSs is increasing in the current era. In this article, we give a brief review focused on the recent research progress in design of chlorin-based nanoparticles for the treatment of malignant tumors with photodynamic therapy.Areas covered: This review focuses on the current nanoparticle platforms for PDT, and describes different strategies to achieve controllable PDT by chlorin-nano-delivery systems. The challenges and prospects of PDT in clinical applications are also discussed.Expert opinions: The requirement for PDT to eradicate cancers has increased exponentially in recent years. The major clinically used photosensitizers are hydrophobic. The main obstacles in effective delivery of PSs are associated with this intrinsic nature. The design of nano-delivery systems to load PSs is pivotal for PSs' widespread use.

Insights on the polypyrrole based nanoformulations for photodynamic therapy

This review is written to endow updated information on polypyrrole based photosensitizers for the treatment of deadly diseases such as cancer and microbial infection. Tetrapyrrolic macromolecules such as porphyrins and phthalocyanines hold unique photophysical properties which make them very useful compounds for various biomedical applications. Besides their properties, they also have some limitations such as low water solubility, bioavailability, biocompatibility and lack of specificity, etc. Researchers are trying to overcome these limitations by incorporating photosensitizers into the different types of nanoparticles and improve the quality of photodynamic therapy. We have contributed to this field by synthesizing and developing polypyrrolic photosensitizer based nanoparticles for potential applications in antimicrobial and anticancer photodynamic activity. Throughout this review, newly synthesized and existing PSs conjugated/encapsulated/doped/incorporated with nanoparticles are emphasized, which are essential for current and future research themes. Also in this review, we briefly summarized the research work carried over the past few years by considering the porphyrin based photosensitizers as alternative therapeutic entities for the treatment of microbial infections, cancers, and many other diseases.

Vesicular drug delivery for the treatment of topical disorders: current and future perspectives

OBJECTIVES

Vesicular drug delivery has become a useful approach for therapeutic administration of pharmaceutical compounds. Lipid vesicles have found application in membrane biology, immunology, genetic engineering and theragnostics. This review summarizes topical delivery, specifically dermal/transdermal, ocular and transungual, via these vesicles, including future formulation perspectives.

KEY FINDINGS

Liposomes and their subsequent derivatives, viz. niosomes, transferosomes, pharmacososmes and ethosomes, form a significant part of vesicular systems that have been successfully utilized in treating an array of topical disorders. These vesicles are thought to be a safe and effective mode of improving the delivery of lipophilic and hydrophilic drugs.

SUMMARY

Several drug molecules are available for topical disorders. However, physicochemical properties and undesirable toxicity have limited their efficacy. Vesicular delivery systems have the potential to overcome these shortcomings due to properties such as high biocompatibility, simplicity of surface modification and suitability as controlled delivery vehicles. However, incorporating these systems into environmentally responsive dispersants such as hydrogels, ionic liquids and deep eutectic solvents may further enhance therapeutic prowess of these delivery systems. Consequently, improved vesicular drug delivery can be achieved by considering combining some of these formulation approaches.

Bioresponsive Functional Phenylboronic Acid-Based Delivery System as an Emerging Platform for Diabetic Therapy

The glucose-sensitive self-adjusting drug delivery system simulates the physiological model of the human pancreas-secreting insulin and then precisely regulates the release of hypoglycemic drugs and controls the blood sugar. Thus, it has good application prospects in the treatment of diabetes. Presently, there are three glucose-sensitive drug systems: phenylboronic acid (PBA) and its derivatives, concanavalin A (Con A), and glucose oxidase (GOD). Among these, the glucose-sensitive polymer carrier based on PBA has the advantages of better stability, long-term storage, and reversible glucose response, and the loading of insulin in it can achieve the controlled release of drugs in the human environment. Therefore, it has become a research hotspot in recent years and has been developed very rapidly. In order to further carry out a follow-up study, we focused on the development process, performance, and application of PBA and its derivatives-based glucose-sensitive polymer drug carriers, and the prospects for the development of this field.

Residence Time-Extended Nanoparticles by Magnetic Field Improve the Eradication Efficiency of Helicobacter pylori

Helicobacter pylori infection is one of the leading causes of several gastroduodenal diseases, such as gastritis, peptic ulcer, and gastric cancer. In fact, H. pylori eradication provides a preventive effect against the incidence of gastric cancer. Amoxicillin is a commonly used antibiotic for H. pylori eradication. However, due to its easy degradation by gastric acid, it is necessary to administer it in a large dosage and to combine it with other antibiotics. This complexity and the strong side effects of H. pylori eradication therapy often lead to treatment failure. In this study, the chitosan/poly (acrylic acid) particles co-loaded with superparamagnetic iron oxide nanoparticles and amoxicillin (SPIO/AMO@PAA/CHI) are used as drug nano-carriers for H. pylori eradication therapy. In vitro and in vivo results show that the designed SPIO/AMO@PAA/CHI nanoparticles are biocompatible and could retain the biofilm inhibition and the bactericidal effect of amoxicillin against H. pylori. Moreover, the mucoadhesive property of chitosan allows SPIO/AMO@PAA/CHI nanoparticles to adhere to the gastric mucus layer and rapidly pass through the mucus layer after exposure to a magnetic field. When PAA is added, it competes with amoxicillin for chitosan, so that amoxicillin is quickly and continuously released between the mucus layer and the gastric epithelium and directly acts on H. pylori. Consequently, the use of this nano-carrier can extend the drug residence time in the stomach, reducing the drug dose and treatment period of H. pylori eradication therapy.

Biodegradable cationic nanogels with tunable size, swelling and pKa for drug delivery

Cationic polymers have garnered significant interest for their utility in intracellular drug delivery and gene therapy. However, due to their associated toxicities, novel synthesis approaches must be explored to develop materials that are biocompatible. The novel library of nanoparticles synthesized in this study exhibit tunable hydrodynamic diameters, composition and pH-responsive properties as a function of synthesis parameters. In addition, differences in the responsiveness of these nanoparticles under different pH conditions affords greater control over intracellular drug release.

Stimuli-Responsive Polymeric Nanosystem for Colon Specific Drug Delivery

An ideal colon specific drug delivery system needs to perform multiple functions like greater bio availability, less toxicity and higher therapeutic efficacy, all of which require high degree of smartness. This article focuses on the overview of the stimuli-responsive polymers and various nanodrug delivery systems which have found applications in colon specific delivery of drugs as this system provide a link between therapeutic need and drug delivery. These polymers exhibit a non-linear response to a small stimulus leading to a macroscopic alteration in their structure/properties. Stimuli responsive polymers display a significant physio chemical change in response to small changes in their environment (temperature, pH, light etc.). Colonic drug delivery has gained increased importance in treating diseases like Crohn's disease, ulcerative colitis, colon cancer etc. The expansion in the development of polymers based system with greater flexibility, versatility and unexplored potential enables new opportunities for them in uplifting bio medicine. Applying the concepts of smartness in the context of clinically relevant therapeutic and diagnostic systems, it can prelude in a new era of 'smart' therapeutics that can improve the health care fields. In particular, due to its high sensitivity to the stimuli, this system has been identified as a sensible platform for releasing drug at suitable site and at appropriate time.

Current state of the nanoscale delivery systems for temoporfin-based photodynamic therapy: Advanced delivery strategies

Enthusiasm for photodynamic therapy (PDT) as a promising technique to eradicate various cancers has increased exponentially in recent decades. The majority of clinically approved photosensitizers are hydrophobic in nature, thus, the effective delivery of photosensitizers at the targeted site is the main hurdle associated with PDT. Temoporfin (mTHPC, medicinal product name: Foscan®), is one of the most potent clinically approved photosensitizers, is not an exception. Successful temoporfin-PDT requires nanoscale delivery systems for selective delivery of photosensitizer. Over the last 25 years, the number of papers on nanoplatforms developed for mTHPC delivery such as conjugates, host-guest inclusion complexes, lipid-and polymer-based nanoparticles and carbon nanotubes is burgeoning. However, none of them appeared to be "ultimate". The present review offers the description of different challenges and achievements in nanoparticle-based mTHPC delivery focusing on the synergetic combination of various nano-platforms to improve temoporfin delivery at all stages of biodistribution. Furthermore, the association of different nanoparticles in one nanoplatform might be considered as an advanced strategy allowing the combination of several treatment modalities.

Promising immunotherapy: Highlighting cytokine-induced killer cells

For many years, cancer therapy has appeared to be a challenging issue for researchers and physicians. By the introduction of novel methods in immunotherapy, the prospect of cancer therapy even more explained than before. Cytokine-induced killer (CIK) cell-based immunotherapy demonstrated to have potentiality in improving clinical outcomes and relieving major side effects of standard treatment options. In addition, given the distinctive features such as high safety, low toxicity effects on healthy cells, numerous clinical trials conducted on CIK cells. Due to the shortcomings that observed in CIK cell immunotherapy alone, arising a tendency to make modifications (combined modality therapy or combination therapy) including the addition of various types of cytokines, genetic engineering, combination with immune checkpoints, and so on. In this review, we have tried to bring forth the latest immunotherapy methods and their overview. We have discussed the combination therapies with CIK cells and the conducted clinical trials. This helps the future studies to use integrated therapies with CIK cells as a promising treatment of many types of cancers.

Functional Polymer Nanocarriers for Photodynamic Therapy

Photodynamic therapy (PDT) is an appealing therapeutic modality in management of some solid tumors and other diseases for its minimal invasion and non-systemic toxicity. However, the hydrophobicity and non-selectivity of the photosensitizers, inherent serious hypoxia of tumor tissues and limited penetration depth of light restrict PDT further applications in clinic. Functional polymer nanoparticles can be used as a nanocarrier for accurate PDT. Here, we elucidate the mechanism and application of PDT in cancer treatments, and then review some strategies to administer the biodistribution and activation of photosensitizers (PSs) to ameliorate or utilize the tumor hypoxic microenvironment to enhance the photodynamic therapy effect.

Dual-triggered drug-release vehicles for synergistic cancer therapy

Cancer is a complex and tenacious disease. Drug-delivery systems in combination with multimodal therapy strategies are very promising candidates for cancer theranostic applications. In this study, a new drug-delivery vehicle that combine human serum albumin (HSA)- and poly(sodium 4-styrenesulfonate) (PSS)-coated gold nanorod nanoparticles(GNR/PSS/HSA NPs) was developed for synergistic cancer therapy. Doxorubicin (DOX) was loaded onto GNR/PSS/HSA NPs, by electrostatic and hydrophobic forces, to create multimodal DOX@GNR/PSS/HSA NPs. DOX@GNR/PSS/HSA NPs were found to be highly biocompatible and stable in physiological solutions. Furthermore, GNR/PSS/HSA NPs with or without DOX were designed to exhibit strong absorbance in the near-infrared region and high photothermal conversion efficiency. Therefore, bimodal DOX release from DOX@GNR/PSS/HSA NPs could be triggered by an acidic pH and by near-infrared irradiation after NPs preferentially accumulated at tumor sites, leading to a significant chemotherapeutic effect. Moreover, DOX@GNR/PSS/HSA NPs were designed to be applied during chemo- and photo-thermal combination therapy and exhibited a synergistic anticancer effect that was superior to the effect of monotherapy, from both in vitro and in vivo results. These results suggest that DOX@GNR/PSS/HSA NPs are a strong candidate for a nanoplatform for future antitumor therapeutic strategies.

pH-responsive Drug Delivery Systems

Acidic microenvironments exist in selected organs, tissues, and subcellular compartments, as well as in many dysregulated pathological states. A continuous effort has been made to harness the unique acidic properties of biological tissues for site-specific delivery of drugs. Various pH-responsive drug delivery systems have been designed and developed with improved spatio-temporal control of payload delivery with enhanced efficacy. This chapter will focus on the recent advances in the development of pH-sensitive materials, mechanisms of payload release, and pH-triggered drug targeting in various biomedical applications.

pH-Responsive Nanophotosensitizer for an Enhanced Photodynamic Therapy of Colorectal Cancer Overexpressing EGFR

Photodynamic therapy (PDT) has been shown to kill cancer cells and improve survival and quality of life in cancer patients, and numerous new approaches have been considered for maximizing the efficacy of PDT. In this study, a new multifunctional nanophotosensitizer Ce6/GE11-^(pH)micelle was developed to target epidermal growth factor receptor (EGFR) overexpressing colorectal cancer (CRC) cells. This nanophotosensitizer was synthesized using a micelle comprising pH-responsive copolymers (PEGMA-PDPA), biodegradable copolymers (mPEG-PCL), and maleimide-modified biodegradable copolymers (Mal-PEG-PCL) to entrap the potential hydrophobic photosensitizer chlorin e6 (Ce6) and to present EGFR-targeting peptides (GE11) on its surface. In the presence of Ce6/GE11-^(pH)micelles, Ce6 uptake by EGFR-overexpressing CRC cells significantly increased due to GE11 specificity. Moreover, Ce6 was released from Ce6/GE11-^(pH)micelles in tumor environments, leading to improved elimination of cancer cells in PDT. These results indicate enhanced efficacy of PDT using Ce6/GE11-^(pH)micelle, which is a powerful nanophotosensitizer with high potential for application to future PDT for CRC.

Panitumumab-Conjugated Pt-Drug Nanomedicine for Enhanced Efficacy of Combination Targeted Chemotherapy against Colorectal Cancer

Targeted combination chemotherapy (TCT) has recently been used to increase the induction of tumor cell death. In particular, the combination of Panitumumab and the platinum (Pt)-derived chemotherapeutic drug Oxaliplatin is clinically effective against KRAS and BRAF wild-type colorectal cancer (CRC) cells that overexpress epidermal growth factor receptors, and significantly greater efficacy is observed than with either drug alone. However, low accumulation of Pt drug in tumor sites prevents achievement of ideal efficacy. To develop an alternative drug therapy that achieves the ideal efficacy of TCT, the novel nanomedicine NANO_Pt-Pan using self-assembled dichloro(1,2-diaminocyclohexane)Pt(II)-modified Panitumumab is generated. Treatments with NANO_Pt-Pan lead to significant accumulation of Pt drug and Panitumumab in tumors, reflecting enhanced permeability and retention effect, active targeting, and sustained circulation of the Pt drug in the blood. In addition, NANO_Pt-Pan has excellent in vivo anti-CRC efficacy. These data indicate that NANO_Pt-Pan has high potential as a candidate nanomedicine for CRC.

Photoinduced effects of m-tetrahydroxyphenylchlorin loaded lipid nanoemulsions on multicellular tumor spheroids

BACKGROUND

Photosensitizers are used in photodynamic therapy (PDT) to destruct tumor cells, however, their limited solubility and specificity hampers routine use, which may be overcome by encapsulation. Several promising novel nanoparticulate drug carriers including liposomes, polymeric nanoparticles, metallic nanoparticles and lipid nanocomposites have been developed. However, many of them contain components that would not meet safety standards of regulatory bodies and due to difficulties of the manufacturing processes, reproducibility and scale up procedures these drugs may eventually not reach the clinics. Recently, we have designed a novel lipid nanostructured carrier, namely Lipidots, consisting of nontoxic and FDA approved ingredients as promising vehicle for the approved photosensitizer m-tetrahydroxyphenylchlorin (mTHPC).

RESULTS

In this study we tested Lipidots of two different sizes (50 and 120 nm) and assessed their photodynamic potential in 3-dimensional multicellular cancer spheroids. Microscopically, the intracellular accumulation kinetics of mTHPC were retarded after encapsulation. However, after activation mTHPC entrapped into 50 nm particles destroyed cancer spheroids as efficiently as the free drug. Cell death and gene expression studies provide evidence that encapsulation may lead to different cell killing modes in PDT.

CONCLUSIONS

Since ATP viability assays showed that the carriers were nontoxic and that encapsulation reduced dark toxicity of mTHPC we conclude that our 50 nm photosensitizer carriers may be beneficial for clinical PDT applications.

Synthesis of well-defined alkyne terminated poly(N-vinyl caprolactam) with stringent control over the LCST by RAFT

The reversible addition-fragmentation chain transfer (RAFT) of N-vinyl caprolactam (NVCL) using two new xanthates with alkyne functionalities is reported. The kinetic data obtained for polymerization of this non-activated monomer using a protected alkyne-terminated RAFT agent (PAT-X1) revealed a linear increase of the polymer molecular weight with the monomer conversion as well as low dispersity (Đ) during the entire course of the polymerization. The system reported here allowed us to enhance the final conversion, diminish Đ and reduce the polymerization temperature compared to the typical values reported in the scarce literature available for the RAFT polymerization of NVCL. The resulting PNVCL was fully characterized using 1H nuclear magnetic resonance (1H NMR), matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), Fourier-transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) techniques. The temperature-responsive features of PNVCL in aqueous solutions were fully investigated under different conditions using turbidimetry. The presented strategy allows the synthesis of well-defined PNVCL with sharp and reversible phase transition temperatures around 37 °C. By manipulating the polymer molecular weight, or the solution properties, it is possible to tune the PNVCL phase transition. As a proof-of concept, the alkyne functionalized PNVCL was used to afford new linear block copolymers, by reacting with an azide-terminated poly(ethylene glycol) (N3-PEG) through the copper catalyzed azide-alkyne [3+2] dipolar cycloaddition (CuAAC) reaction. The results presented establish a robust system to afford the synthesis of PNCVL with fine tuned characteristics that will enable more efficient exploration of the remarkable potential of this polymer in biomedical applications.

Enhanced efficacy of chemotherapeutic drugs against colorectal cancer using ligand-decorated self-breakable agents

Targeting self-breakable micelles could facilitate Caco2 cancer cells in acidic tumor microenvironment to take up SN38 which the micelle loaded with and trigger drug release in cancer cells, resulting in enhanced drug efficacy.

Endocytic capsule sensors for probing cellular internalization

A new class of polymer capsules with an in-built endocytic pH-coupled fluorescence switch is reported. These capsules display reversible "on/off" fluorescence in response to cellular pH variations. Using this system, the high-throughput quantification between surface-bound and internalized capsules is demonstrated. This system allows a fundamental study of the interaction between nanoengineered materials and biological systems at a cellular level.

Smart polymers for the controlled delivery of drugs - a concise overview

Smart polymers have enormous potential in various applications. In particular, smart polymeric drug delivery systems have been explored as “intelligent” delivery systems able to release, at the appropriate time and site of action, entrapped drugs in response to specific physiological triggers. These polymers exhibit a non-linear response to a small stimulus leading to a macroscopic alteration in their structure/properties. The responses vary widely from swelling/contraction to disintegration. Synthesis of new polymers and crosslinkers with greater biocompatibility and better biodegradability would increase and enhance current applications. The most fascinating features of the smart polymers arise from their versatility and tunable sensitivity. The most significant weakness of all these external stimuli-sensitive polymers is slow response time. The versatility of polymer sources and their combinatorial synthesis make it possible to tune polymer sensitivity to a given stimulus within a narrow range. Development of smart polymer systems may lead to more accurate and programmable drug delivery. In this review, we discuss various mechanisms by which polymer systems are assembled in situ to form implanted devices for sustained release of therapeutic macromolecules, and we highlight various applications in the field of advanced drug delivery.

Synthesis of well-defined functionalized poly(2-(diisopropylamino)ethyl methacrylate) using ATRP with sodium dithionite as a SARA agent

2-(Diisopropylamino)ethyl methacrylate was polymerized by Atom Transfer Radical Polymerization using sodium dithionite as a reducing agent and supplemental activator with a Cu(ii)Br₂/Me₆TREN catalytic system.

pH-sensitive drug-delivery systems for tumor targeting

Drug-delivery system responses to stimuli have been well investigated recently. As pH decrease is observed in most solid tumors, drug-delivery systems responsive to the slightly acidic extracellular pH environment of solid tumors have been developed as a general strategy for tumor targeting. Drug vehicles that are sensitive to acidic endosome/lysosome pH have been constructed for efficient drug release in tumor cells. This review explains the mechanisms of acidic pH in the tumor microenvironment and endocytic-related organelles, endosomes and lysosomes. Nanoparticle responses to acidic extracellular pH are discussed, along with approaches for improving tumor-specific therapy. Endosome/lysosome pH-triggered vehicles are reviewed, which achieve rapid drug release in tumor cells and overcome multidrug resistance.

Remote and local control of stimuli responsive materials for therapeutic applications

Materials offering the ability to change their characteristics in response to presented stimuli have demonstrated application in the biomedical arena, allowing control over drug delivery, protein adsorption and cell attachment to materials. Many of these smart systems are reversible, giving rise to finer control over material properties and biological interaction, useful for various therapeutic treatment strategies. Many smart materials intended for biological interaction are based around pH or thermo-responsive materials, although the use of magnetic materials, particularly in neural regeneration, has increased over the past decade. This review draws together a background of literature describing the design principles and mechanisms of smart materials. Discussion centres on recent literature regarding pH-, thermo-, magnetic and dual responsive materials, and their current applications for the treatment of neural tissue.

High resolution fluorescence imaging of cancers using lanthanide ion-doped upconverting nanocrystals

During the last decade inorganic luminescent nanoparticles that emit visible light under near infrared (NIR) excitation (in the biological window) have played a relevant role for high resolution imaging of cancer. Indeed, semiconductor quantum dots (QDs) and metal nanoparticles, mostly gold nanorods (GNRs), are already commercially available for this purpose. In this work we review the role which is being played by a relatively new class of nanoparticles, based on lanthanide ion doped nanocrystals, to target and image cancer cells using upconversion fluorescence microscopy. These nanoparticles are insulating nanocrystals that are usually doped with small percentages of two different rare earth (lanthanide) ions: The excited donor ions (usually Yb3+ ion) that absorb the NIR excitation and the acceptor ions (usually Er3+, Ho3+ or Tm3+), that are responsible for the emitted visible (or also near infrared) radiation. The higher conversion efficiency of these nanoparticles in respect to those based on QDs and GNRs, as well as the almost independent excitation/emission properties from the particle size, make them particularly promising for fluorescence imaging. The different approaches of these novel nanoparticles devoted to "in vitro" and "in vivo" cancer imaging, selective targeting and treatment are examined in this review.

Nanoparticles-mediated drug delivery approaches for cancer targeting: a review

Cancer has become the leading cause of death among different populations of the world. The treatment is limited to chemotherapy, radiation, and surgery. Selective targeting to the tumor cells is possible by nanoparticles-based drug delivery system. It maximizes the drug concentration at the desired target and protects the surrounding healthy tissues at the same time. To improve the targeting potential of the anticancer drugs, nanoparticles were optimized for the size and surface characteristics to enhance their circulation time and targeting efficiency. Passive targeting involves surface modification with polyethylene glycol to avoid its elimination by natural body defense mechanism. Active targeting involves chemical interaction with certain antigen, receptors, and genes which are over expressed during progression of disease. In addition, the article highlights recent developments in "smart"-stimulus-responsive-drug carriers designed to enhance the localization and efficacy of therapeutic payloads as compared with free drug. Enhanced targeting potential, imaging, and controlled release of drugs or therapeutic molecules could be possible through multi-functional nanocarrier. Such multi-faceted, versatile nanocarriers and drug delivery systems promise a substantial increase in the efficacy of diagnostic and therapeutic applications in pharmaceutical sciences.

Temoporfin (Foscan®, 5,10,15,20-tetra(m-hydroxyphenyl)chlorin)--a second-generation photosensitizer

This review traces the development and study of the second-generation photosensitizer 5,10,15,20-tetra(m-hydroxyphenyl)chlorin through to its acceptance and clinical use in modern photodynamic (cancer) therapy. The literature has been covered up to early 2011.

Polymersome-loaded capsules for controlled release of DNA

The formation of a novel drug-delivery carrier for the controlled release of plasmid DNA that comprises layer-by-layer polymer capsules subcompartmentalized with pH-sensitive nanometer-sized polymersomes is reported. The amphiphilic diblock copolymer poly(oligoethylene glycol methacrylate)-block-poly(2-(diisopropylamino)ethyl methacrylate) forms polymersomes at physiological pH, but transitions to unimeric polymer chains upon acidification to cellular endocytic pH. These polymersomes can thus release an encapsulated payload in response to a change in pH from physiological to endocytic conditions. Multicomponent layer-by-layer capsules are formed by exploiting the ability of tannic acid to act as an efficient hydrogen-bond donor for both the polymersomes and poly(N-vinyl pyrrolidone) at physiological pH. These capsules show release of a plasmid DNA payload encapsulated within the polymersome subcompartments in response to changes in pH between physiological and endocytic conditions.

Development of thermosensitive poly(n-isopropylacrylamide-co-((2-dimethylamino) ethyl methacrylate))-based nanoparticles for controlled drug release

Thermosensitive nanoparticles based on poly(N-isopropylacrylamide-co-((2-dimethylamino)ethylmethacrylate)) (poly(NIPA-co-DMAEMA)) copolymers were successfully fabricated by free radical polymerization. The lower critical solution temperature (LCST) of the synthesized nanoparticles was 41 °C and a temperature above which would cause the nanoparticles to undergo a volume phase transition from 140 to 100 nm, which could result in the expulsion of encapsulated drugs. Therefore, we used the poly(NIPA-co-DMAEMA) nanoparticles as a carrier for the controlled release of a hydrophobic anticancer agent, 7-ethyl-10-hydroxy-camptothecin (SN-38). The encapsulation efficiency and loading content of SN-38-loaded nanoparticles at an SN-38/poly(NIPA-co-DMAEMA) ratio of 1/10 (D/P = 1/10) were about 80% and 6.293%, respectively. Moreover, the release profile of SN-38-loaded nanoparticles revealed that the release rate at 42 °C (above LCST) was higher than that at 37 °C (below LCST), which demonstrated that the release of SN-38 could be controlled by increasing the temperature. The cytotoxicity of the SN-38-loaded poly(NIPA-co-DMAEMA) nanoparticles was investigated in human colon cancer cells (HT-29) to compare with the treatment of an anticancer drug, Irinotecan(®) (CPT-11). The antitumor efficacy evaluated in a C26 murine colon tumor model showed that the SN-38-loaded nanoparticles in combination with hyperthermia therapy efficiently suppressed tumor growth. The results indicate that these thermo-responsive nanoparticles are potential carriers for controlled drug delivery.

Tumor ablation and nanotechnology

Next to surgical resection, tumor ablation is a commonly used intervention in the treatment of solid tumors. Tumor ablation methods include thermal therapies, photodynamic therapy, and reactive oxygen species (ROS) producing agents. Thermal therapies induce tumor cell death via thermal energy and include radiofrequency, microwave, high intensity focused ultrasound, and cryoablation. Photodynamic therapy and ROS producing agents cause increased oxidative stress in tumor cells leading to apoptosis. While these therapies are safe and viable alternatives when resection of malignancies is not feasible, they do have associated limitations that prevent their widespread use in clinical applications. To improve the efficacy of these treatments, nanoparticles are being studied in combination with nonsurgical ablation regimens. In addition to better thermal effect on tumor ablation, nanoparticles can deliver anticancer therapeutics that show a synergistic antitumor effect in the presence of heat and can also be imaged to achieve precision in therapy. Understanding the molecular mechanism of nanoparticle-mediated tumor ablation could further help engineer nanoparticles of appropriate composition and properties to synergize the ablation effect. This review aims to explore the various types of nonsurgical tumor ablation methods currently used in cancer treatment and potential improvements by nanotechnology applications.