Copolymer Micelles: A Focus on Recent Advances for Stimulus-Responsive Delivery of Proteins and Peptides

Historically used for the delivery of hydrophobic drugs through core encapsulation, amphiphilic copolymer micelles have also more recently appeared as potent nano-systems to deliver protein and peptide therapeutics. In addition to ease and reproducibility of preparation, micelles are chemically versatile as hydrophobic/hydrophilic segments can be tuned to afford protein immobilization through different approaches, including non-covalent interactions (e.g., electrostatic, hydrophobic) and covalent conjugation, while generally maintaining protein biological activity. Similar to many other drugs, protein/peptide delivery is increasingly focused on stimuli-responsive nano-systems able to afford triggered and controlled release in time and space, thereby improving therapeutic efficacy and limiting side effects. This short review discusses advances in the design of such micelles over the past decade, with an emphasis on stimuli-responsive properties for optimized protein/peptide delivery.

Dual stimuli-responsive mesoporous silica nanoparticles for efficient loading and smart delivery of doxorubicin to cancer with RGD-integrin targeting

The recent progress in nanoparticle applications, such as tumor-targeting, has enabled specific delivery of chemotherapeutics to malignant tissues with enhanced local efficacy while limiting side effects. However, existing delivery systems leave much room for improvement in terms of achieving enhanced colloidal stability in fluid medium, efficient targeting of intended sites, and effective release of therapeutic drugs into diseased cells. Here, an efficient stimuli-responsive nanocarrier for mammalian cells, termed RGD-NAMs, was developed, which enabled temperature- and pH-sensitive release of drug loads. The RGD-NAMs comprise two parts: a stimuli-responsive copolymer shell (NIBIm-AA-RGD) and drug-container core (MSNs). The RGD-NAMs have a stable drug-loading capacity with a marked difference in the release rate depending on the temperature and pH conditions. The RGD-NAMs also exhibit high colloidal stability in SBF (Stimulated body fluid) solutions and minimal toxicity in skeletal myoblasts (C2C12) and bovine arterial endothelial cells (BAEC). The doxorubicin-loaded RGD-NAMs induced a cytotoxic effect in a dose-dependent manner, which was furthered by an increase in temperature from 37 to 40 °C. Moreover, significant control of the release rate and the amount were achieved through pH change. This novel, smart drug-delivery system with high responsiveness to temperature and pH changes has wide application prospects in biomedical fields, including the theragnosis of tumors and vascular diseases.

Nanomaterials based on thermosensitive polymer in biomedical field

The progress of nanotechnology enables us to make use of the special properties of materials on the nanoscale and open up many new fields of biomedical research. Among them, thermosensitive nanomaterials stand out in many biomedical fields because of their “intelligent” behavior in response to temperature changes. However, this article mainly reviews the research progress of thermosensitive nanomaterials, which are popular in biomedical applications in recent years. Here, we simply classify the thermally responsive nanomaterials according to the types of polymers, focusing on the mechanisms of action and their advantages and potential. Finally, we deeply investigate the applications of thermosensitive nanomaterials in drug delivery, tissue engineering, sensing analysis, cell culture, 3D printing, and other fields and probe the current challenges and future development prospects of thermosensitive nanomaterials.

Electrical and thermal stimulus-responsive nanocarbon-based 3D hydrogel sponge for switchable drug delivery

Smart hydrogels that are responsive to various external (e.g. electrical and/or thermal) stimulation have become increasingly popular in recent years for simple, rapid, and precise drug delivery that can be controlled and turned on or off with external stimuli. For such a switchable drug delivery material, highly homogeneous dispersion and distribution of the hydrophobic, electrically conductive nanomaterials throughout a hydrophilic three-dimensional (3D) hydrogel network remains a challenge and is essential for achieving well-connected electrical and thermal conducting paths. Herein we developed electrical and thermal stimulus-responsive 3D hydrogels based on (i) carbon nanotubes (CNTs) as the core unit and an electrical/thermal conductor, (ii) chitosan (Chit) as the shell unit and a hydrophilic dispersant, and (iii) poly(NIPAAm-co-BBVIm) (pNIBBIm) as the drug carrier and a temperature-responsive copolymer. By formulating the CNT-core and Chit-shell units and constructing a CNT sponge framework, uniform distribution and 3D connectivity of the CNTs were improved. The 3D hydrogel based on the CNT sponge, namely the 3D frame CNT-Chit/pNIBBIm hydrogel, delivered approximately 37% of a drug, ketoprofen used for the treatment of musculoskeletal pain, during about 30% shrinkage after electrical and thermal switches on/off and exhibited the best potential for future use in a smart transdermal drug delivery system. The physicochemical, mechanical, electrical, thermal, and biocompatible characteristics of this nanocarbon-based 3D frame hydrogel led to remarkable electrical and thermal stimulus-responsive properties capable of developing an excellent controllable and switchable drug delivery platform for biomedical engineering and medicine applications.

The role of internal and external stimuli in the rational design of skin-specific drug delivery systems

The concept of skin-specific drug delivery with a spatio-temporal control has just recently received concerns in dermatology. Inspired by the progress in smart materials and their perspective application in medicine science, development of stimuli responsive drug delivery systems with skin-specificity has become possible, which has led to a new era in the localized treatment of skin diseases. This review highlights both the internal and external stimuli that have been employed in this field, with a focus on their implication on the rational design of pharmaceutical formulations, especially those nanoscale drug carriers that are able to provide release of payloads with a precise spatio-temporal control in response to specific stimuli. Also, the strategy of dual stimuli responsive drug delivery systems will be discussed for further improvement of the efficacy of skin drug delivery. The prominent examples of the established approaches are described as comprehensive and current as possible. The review is expected to provide some inspiration for utilizing different stimuli for realizing the site-specific and on-demand drug delivery to the skin.

Small intestine- and colon-specific smart oral drug delivery system with controlled release characteristic

In recent years, there has been a significant increase in strategies for the development of small intestine (and colon)-specific oral drug-delivery systems to maximize the efficiency of therapeutic agents and reduce side effects. However, only a few strategies are capable of working in the complicated environment of the human intestinal tract. In this study, the preparation of a basic pH/temperature-responsive co-polymer (p-NIVIm) and its in-vitro-drug delivery function in the pH range of 1-8 and temperature range of 25-42 °C are reported. The basic copolymer was prepared by radical copolymerization of N-isopropyl acryl amide (NIPAAm) and N-vinylimidazole (VIm). The lower critical solution temperature (LCST) of p-NIVIm was higher in stomach pH (~1.0) conditions (36.5-42 °C) and lower in small intestine and/or colon pH (~8.0) conditions (35.8-38.2 °C). The ability to uptake a model protein (BSA) at body temperature and to release it in conditions of 37 °C and pH 1-8 was determined. The drug loading capacity (0.231 mg per 1.0 mg copolymer) and efficiency (92.4%) were high at 37 °C/pH 7. The drug carrier showed a slow release pattern at pH 1 (~0.084 mg; ~35%) and then a sudden release pattern (~0.177 mg; ~73%) at pH 8. The cytotoxicity of p-NIVIm to MCF-7 cells in vitro was minimal at concentrations <168.9 μg/mL after 72 h. The prepared copolymer with its pH-/temperature-responsive protein-entrapping and -releasing behavior at body temperature may potentially be applied as a novel small intestine (and colon)-specific oral drug delivery system.

Biological Activity of Ionic Liquids and Their Application in Pharmaceutics and Medicine

Ionic liquids are remarkable chemical compounds, which find applications in many areas of modern science. Because of their highly tunable nature and exceptional properties, ionic liquids have become essential players in the fields of synthesis and catalysis, extraction, electrochemistry, analytics, biotechnology, etc. Apart from physical and chemical features of ionic liquids, their high biological activity has been attracting significant attention from biochemists, ecologists, and medical scientists. This Review is dedicated to biological activities of ionic liquids, with a special emphasis on their potential employment in pharmaceutics and medicine. The accumulated data on the biological activity of ionic liquids, including their antimicrobial and cytotoxic properties, are discussed in view of possible applications in drug synthesis and drug delivery systems. Dedicated attention is given to a novel active pharmaceutical ingredient-ionic liquid (API-IL) concept, which suggests using traditional drugs in the form of ionic liquid species. The main aim of this Review is to attract a broad audience of chemical, biological, and medical scientists to study advantages of ionic liquid pharmaceutics. Overall, the discussed data highlight the importance of the research direction defined as "Ioliomics", studies of ions in liquids in modern chemistry, biology, and medicine.

Environmentally benign tetramethylguanidinium cation based ionic liquids

Ionic liquids (ILs) are being considered as greener alternatives to conventional organic solvents.

Thermo conductive carbon nanotube-framed membranes for skin heat signal-responsive transdermal drug delivery

Smart carbon nanotube (CNT)-framed (SCNF) membranes were prepared by self-assembly of highly thermo conductive CNT molecules hybridized with chitosan (Chit) in a core–shell structure and then by chemical integration of a temperature-responsive copolymer, poly(NIPAAm-co-BVIm) (or pNIBIm), as an additional outer shell.

Triple Hit with Drug Carriers: pH- and Temperature-Responsive Theranostics for Multimodal Chemo- and Photothermal Therapy and Diagnostic Applications

Currently there is a strong need for new drug delivery systems, which enable targeted and controlled function in delivering drugs while satisfying highly sensitive imaging modality for early detection of the disease symptoms and damaged sites. To meet these criteria we develop a system that integrates therapeutic and diagnostic capabilities (theranostics). Importantly, therapeutic efficacy of the system is enhanced by exploiting synergies between nanoparticles, drug, and hyperthermia. At the core of our innovation is near-infrared (NIR) responsive gold nanorods (Au) coated with drug reservoirs--mesoporous silica shell (mSi)--that is capped with thermoresponsive polymer. Such design of theranostics allows the detection of the system using computed tomography (CT), while finely controlled release of the drug is achieved by external trigger, NIR light irradiation--ON/OFF switch. Doxorubicin (DOX) was loaded into mSi formed on the gold core (Au@mSi-DOX). Pores were then capped with the temperature-sensitive poly(N-isopropylacrylamide)-based N-butyl imidazolium copolymer (poly(NIPAAm-co-BVIm)) resulting in a hybrid system-Au@mSi-DOX@P. A 5 min exposure to NIR induces polymer transition, which triggers the drug release (pores opening), increases local temperature above 43 °C (hyperthermia), and upregulates particle uptake (polymer becomes hydrophilic). The DOX release is also triggered by drop in pH enabling localized drug release when particles are taken up by cancer cells. Importantly, the synergies between chemo- and photothermal therapy for DOX-loaded theranostics were confirmed. Furthermore, higher X-ray attenuation value of the theranostics was confirmed via X-ray CT test indicating that the nanoparticles act as contrast agent and can be detected by CT.

Ionic and thermo-switchable polymer-masked mesoporous silica drug-nanocarrier: High drug loading capacity at 10°C and fast drug release completion at 40°C

The preparation of the ideal smart drug-delivery systems were successfully achieved by the in situ co-polymerization of a vinyl group-functionalized mesoporous silica nanoparticle (f-MSN) with 1-butyl-3-vinyl imidazolium bromide (BVIm) and N-isopropylacrylamide (NIPAAm) monomers. The thickness of the capping copolymer layer, poly(NIPAAm-co-BVIm) (p-NIBIm), was controlled at between 2.5nm and 5nm, depending on the monomers/f-MSN ratio in the reaction solution. The finally obtained smart drug-delivery systems are named as p-MSN2.5 and p-MSN5.0 (MSNs integrated by 2.5nm and 5nm p-NIBIm layer in thickness). The key roles of the mesoporous-silica-nanoparticle (MSN) core and the p-NIBIm shell are drug-carrying (or containing) and pore-capping, respectively, and the latter has an on/off function that operates in accordance with temperature changes. According to the swelling- or shrinking-responses of the smart capping copolymer to temperature changes between 10°C and 40°C, the loading and releasing patterns of the model drug cytochrome c were studied in vitro. The developed system showed interesting performances such as a cytochrome-c-loading profile (loading capacity for 3h=26.3% and 19.8% for p-MSN2.5 and p-MSN5.0, respectively) at 10°C and a cytochrome-c-releasing profile (releasing efficiency=>95% within 3 days and 4 days for p-MSN2.5 and p-MSN5.0, respectively) at 40°C. The cytotoxicity of the drug delivery systems, p-MSN2.5 and p-MSN5.0 (in the concentration range of <0.125mg/mL without drug), for human embryonic kidney (HEK 293) cells were minimal in vitro compared with that of a blank MSN. These results may be reasonably applied in the field of specified drug delivery.