Jae-Won Seo

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.

Production of CNT-taxol-embedded PCL microspheres using an ammonium-based room temperature ionic liquid: as a sustained drug delivery system.

We describe a one-pot method for the mass production of polymeric microspheres containing water-soluble carbon-nanotube (w-CNT)-taxol complexes using an ammonium-based room temperature ionic liquid. Polycaprolactone (PCL), trioctylmethylammonium chloride (TOMAC; liquid state from -20 to 240°C), and taxol were used, respectively, as a model polymer, room temperature ionic liquid, and drug. Large quantities of white colored PCL powder without w-CNT-taxol complexes and gray colored PCL powders containing w-CNT-taxol (1:1 or 1:2 wt/wt) complexes were produced by phase separation between the hydrophilic TOMAC and the hydrophobic PCL. Both microsphere types had a uniform, spherical structure of average diameter 3-5μm. The amount of taxol embedded in PCL microspheres was determined by HPLC and (1)H NMR to be 8-12μg per 1.0mg of PCL (loading capacity (LC): 0.8-1.2%; entrapment efficiency (EE): 16-24%). An in vitro HPLC release assay showed sustain release of taxol without an initial burst over 60days at an average rate of 0.003-0.0073mg per day. The viability patterns of human breast cancer cells (MCF-7) for PCTx-1 and -2 showed dose-dependent inhibitory effects. In the presence of PCTx-1 and -2, the MCF-7 cells showed high viability in the concentration level of, respectably, <70 and <5μg/mL.

Ionic liquid-doped and p-NIPAAm-based copolymer (p-NIBIm): extraordinary drug-entrapping and -releasing behaviors at 38–42 °C

Ionic liquid (IL)-doping of the temperature responsive p-NIPAAm was achieved by radical copolymerization of N-isopropyl acryl amide (NIPAAm; 90 mol%) and 1-butyl-3-vinylimidazolium bromide ([BVIm]Br; 10 mol%) to give a new temperature responsive copolymer (p-NIBIm). The as-prepared p-NIBIm copolymer showed a highly increased zeta potential value and optimal LCST (lower critical solution temperatures) value, respectively, +9.8 mV at pH = 7 and 38.2 °C, compared to those (+0.3 mV at pH = 7 and 32.1 °C) of p-NIPAAm. The temperature-dependent size change of the p-NIBIm micelles was determined in the range from 25 to 45 °C by SEM under dry conditions and by a zeta sizer under wet conditions, showing a certain size contraction from 253 ± 12.1 to 90.5 ± 7.8 nm in diameter (about 95.4% of volume contraction). The thermo-sensitive behavior to entrap BSA protein at body temperature (37 °C) and to release the protein between 38–42 °C (near the LCST) were also tested by sizing of the complexes of p-NIBIm/BSA using a zeta sizer and also by a colorimetric assay (Bio-Rad DC Protein Assay), resulting in a maximum entrapment of 1.02 mg BSA for 1.0 mg of the polymer at body temperature (37 °C) and in a maximum release of 0.73 mg BSA for 1.0 mg of the polymer (about 73% release of the entrapped amount) in the temperature range of 38–42 °C. Toxicity of the p-NIBIm micelles (in the range of <0.125 mg mL−1) without drug for human embryonic kidney (HEK 293) cells was minimal in vitro. These results revealed that the IL-doped and temperature responsive co-polymeric systems have a very high applicability as a novel delivery system for charged (or polar) molecules as a natural (or synthetic) drug and DNA.

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.

Cationic effect of an ionic copolymer with a temperature-responsive charateristic on the LCST value: A broad LCST spectrum of 35 to 46 °C

A series of stimuli-responsive copolymers (p-NIBIm) of N-isopropylacrylamide (NIPAAm) and 1-butyl-3-vinyl imidazolium bromide (BVIm) with various BVIm monomer concentrations such as 5, 10, 15, and 20 mol% were synthesized by radical copolymerization. The different concentrations of the imidazolium moiety within the resulted copolymer chain were determined by 1H NMR analysis. The LCST (lower critical solution temperature) values of the copolymers that were checked by UV-Vis spectrophotometer increased with the increasing concentration of the imidazolium moiety and were ranged from 36 up to 46 °C. According to the increasing concentration of the imidazolium moiety, the p-NIBIm copolymers also showed increasing zeta potential values (from +3.4 up to +21.3 mV) at pH 7, increasing initial and final micelle sizes (from 211.5 to 69.1 and from 325.4 to 171.2 nm), respectively, at 25 and 50 °C, and increasing contraction levels of micelle volumes between 25-50 °C (from 2.69×10-18 up to 8.67×10-18 cm3). These results demonstrate that it is possible to tune the LCST value of a temperature-responsive copolymer only by changing the imidazolium unit (BVIm) concentration within the copolymer chain. Moreover, p-NIBIm10 and 15 among the prepared copolymers could demonstrate high applicability in various endeavors such as on a target drug or in a gene delivery system.

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.