Date of Degree

2-2018

Document Type

Dissertation

Degree Name

Ph.D.

Program

Chemistry

Advisor(s)

Michal Kruk

Shuiqin Zhou

Committee Members

Shi Jin

Teresa Bandosz

Subject Categories

Chemistry

Keywords

Mesoporous Silicas, Microgels, Nanogels, Drug Delivery

Abstract

The research work in this dissertation describes the study of the applications of polymers in several important areas. Two synthesis methods for bicontinuous cubic KIT6 silicas with block copolymer Pluronic P123 as templates were developed, expanding the range of available pore size and enchancing mesopore volume. In addition, two types of drug delivery systems were developed based on polymer nanoparticles.

In Chapter 2, it was shown that the addition of a suitable swelling agent at temperatures somewhat lower than those typically used in the syntheses of silicas with cubic Ia3d structure (19−25 °C vs 30−35 °C) allows one to induce the formation of highly ordered cubic Ia3d phase in the presence of SDS. The swelling agents 1,3,5-triisopropylbenzene (TIPB), 1,3,5-triethylbenzene, and 1,4-diisopropylbenzene were found to be suitable. Our swelling-agent-based synthesis of phase-pure highly ordered KIT-6 is capable of providing exceptionally high mesopore volumes (above 1.5 cm3/g) and high surface areas (850−1050 m2/g). Moreover, the swelling-agent-enhanced synthesis of the cubic Ia3d silica works in a rather wide condition.

In Chapter 3, in the presence of butanol, the use of Pluronic P123 as a micelle template allowed us to synthesize the silica with well-defined bicontinuous cubic Ia3d structure with large or even unprecedented pore size at or below room temperature. The sequence of addition of reagents to the surfactant solution was tetraethyl orthosilicate (TEOS), TIPB and then butanol. The synthesis method was proved to be reproducible, even though a slight adjustment of the amount of TIPB may be needed when different batches of surfactant Pluronic P123 were used. Similar to the SDS-assisted (SDS: Sodium dodecyl sulfate) synthesis method for bicontinuous cubic KIT-6 described in Chapter 2, the lowering of the initial synthesis temperature accompanied with the gradual increase of TIPB and BuOH is a feasible way to enlarge the pore size in this butanol-assisted synthesis method. In the hydrothermal treatment temperature range of 100 – 130 oC, it was found that bicontinuous cubic KIT-6 samples were obtained and higher hydrothermal treatment temperature leads to a larger pore diameter and pore volume. It also should be noted that, compared to the previous reported synthesis methods for bicontinuous cubic KIT-6 silicas which afforded samples with a pore diameter up to around 12 nm, the present butanol-assisted synthesis method achieved much a larger pore size up to ~ 15 nm.

In Chapter 4, a type of multifunctional hybrid microgels was successfully prepared using the simple one-pot free radical dispersion polymerization of the rationally designed hydrogen-bonding complexes. The reversible glucose-sensitive volume phase transition of the poly(4-vinylphenylboronic acid-co-acrylamide) (poly(VPBA-AAm)) microgel network can modify the physicochemical environment of the embedded carbon dots (CDs) and thus manipulate the near infrared (NIR) upconversion fluorescence intensity of the hybrid microgels, which can sense the glucose concentration change in a clinically relevant range at physiological pH. The porous poly(VPBA-AAm)-CDs hybrid microgels provide a high loading capacity for insulin molecules. Furthermore, the insulin release rate from the hybrid microgels can be triggered by the glucose concentration in the dispersion medium. The increase in glucose concentration speed up the insulin release. The hybrid microgels exhibit no cytotoxicity to both healthy (HEK293T) and tumor (4T1 and B16F10) cells in the concentration range of 12.5−100 μg/mL.

In Chapter 5, a core-shell structured hybrid nanogels composed of a hydrophobic CDs-poly(4-allylanisole) hybrid nanogel as core and temperature-/pH-dual responsive CDs-polyethylene glycol-chitosan nanogel as shell can be synthesized in aqueous phase based on the precipitation polymerization of nonlinear polyethylene glycol (PEG) monomers complexed with CDs and chitosan. The hybrid nanogels exhibit dual-responsive volume phase transitions with the most distinct volume change occurring from temperature of 30° to 36° and pH of 5.0 to 6.5. The resultant CDs-poly(4-allylanisole)@CDs-PEG-chitosan hybrid nanogels was able to enter into cells and light up the interior of cells benefited from the bright fluorescence of CDs embedded in the nanogel. The core-shell hybrid nanogels with poly(4-allylanisole) network core display very high drug loading capacities for the extremely hydrophobic curcumin because of the rationally designed p-p stacking and hydrophobic association between curcumin molecules and the anisole units, which can be also extended to load other hydrophobic drug such as doxorubicin (DOX) at high capacities. The core-shell hybrid nanogels are nontoxic to cells, but can carry high dose of drug into cancer cells and release them in a sustained manner to kill cancer cell effectively. Compared to the same dose of free drugs, the drugs encapsulated in the core-shell nanogels provide a much high therapeutic efficacy against cancer cells.

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