Robert H. Utama

Biocompatible Glycopolymer Nanocapsules via Inverse Miniemulsion Periphery RAFT Polymerization for the Delivery of Gemcitabine

Encapsulation of hydrophilic cancer drugs in polymeric nanocapsules was achieved in a one-pot process via the inverse miniemulsion periphery RAFT polymerization (IMEPP) approach. The chosen guest molecule was gemcitabine hydrochloride, which is used as the first-line treatment of pancreatic cancer. The resulting nanocapsules were confirmed to be ∼200 nm, with excellent encapsulation (∼96%) and loading (∼12%) efficiency. Postpolymerization reaction was successfully conducted to create glyocopolymer nanocapsules without any impact on the loads as well as the nanocapsules size or morphology. The loaded nanocapsules were specifically designed to be responsive in a reductive environment. This was confirmed by the successful disintegration of the nanocapsules in the presence of glutathione. The gemcitabine-loaded nanocapsules were tested in vitro against pancreatic cancer cells (AsPC-1), with the results showing an enhancement in the cytotoxicity by two fold due to selective accumulation and release of the nanocapsules within the cells. The results demonstrated the versatility of IMEPP as a tool to synthesize functionalized, loaded-polymeric nanocapsules suitable for drug-delivery application.

SAXS Analysis of Shell Formation During Nanocapsule Synthesis via Inverse Miniemulsion Periphery RAFT Polymerization

Currently available methods for synthesis of polymeric nanocapsules only offer limited control over the shell thickness, even though it is an important parameter for various applications. Furthermore, suitable methods to critically measure this parameter in a facile way are still nonexistent. Here, lab-scale small-angle X-ray scattering (SAXS) is utilized to in situ measure the evolution of shell thickness during nanocapsule synthesis via inverse miniemulsion periphery reversible addition-fragmentation chain transfer (RAFT) polymerization (IMEPP). The measured shell thickness is consistent with estimates from the commonly used transmission electron microscopy (TEM) technique. Moreover, the individual thicknesses of two concentric shells comprising different polymeric materials (the outer shell formed via IMEPP chain extension of the inner shell) can be determined, thus further demonstrating the versatility of this approach.

Enhanced drug toxicity by conjugation of platinum drugs to polymers with guanidine containing zwitterionic functional groups that mimic cell-penetrating peptides

Inspired by the Ringsdorf model, statistical copolymers with solubility enhancers, platinum drugs and groove binders were compared. In addition, the polymer was furnished with a cell penetrating moiety using a guanidine containing polymer. A block copolymer based on poly(4-vinylbenzyl chloride) and a block carrying zwitterionic monomer prepared from arginine was obtained using RAFT polymerization. Thiol–chloride reaction was then employed to attach thioglycerol (TG) as the water-soluble functional group, 9-aminoacridine (AA) as groove binder to enhance DNA binding and reactive diamino functionality as the bidentate ligand for the conjugation of platinum drugs. The aim of this work was to create a stable bond between the polymer and the drug to answer the question if it is essential to have degradable linkers to generate high drug activity. Three platinated polymers – having only the solubility enhancer, the solubility enhancer and the groove binder and with all three moieties – were compared in regards to their ability to enter the human ovarian carcinoma A2780 cells. Unsurprisingly, the zwitterionic polymer showed the highest uptake, which also coincided with a higher toxicity of the drug. Conjugated to the zwitterionic polymer, the platinum drug showed a higher toxicity than free cisplatin. In summary, even 40 years after the concepts was first established by Ringsdorf, this design still seems to have high validity highlighting that the suitable polymer design can enhance the activity of the drug.

Modular photo-induced RAFT polymerised hydrogels via thiol–ene click chemistry for 3D cell culturing

Cell behaviour changes as a result of the local environment, particularly when transitioning from two dimensional (2D) to three dimensional (3D) environments. It has been acknowledged that there is a need for efficient, tuneable and reproducible methods for making 3D cell cultures to further understand cell behaviour in 3D environments. The development of extracellular matrix (ECM) mimics has gained popularity as a way to create highly tuneable materials that resemble the native environment around cells. The modular nature of synthetic hydrogels means that they have the potential as ECM mimics for 3D cell cultures with tuneable mechanical and chemical properties. Herein, reversible addition fragmentation chain transfer (RAFT) polymerisation was used to synthesise poly(ethylene glycol)methyl ether acrylate (PEGMEA). Hydrogels with tuneable mechanical and cell adhesive properties were synthesised. Norbornene was used as a functional unit for both crosslinking and addition of biomolecules via thiol–ene click chemistry. To obviate the need for UV light for cross-linking of the hydrogel, visible light stimulated eosin-Y was used to induce the thiol–ene reaction. Pancreatic cancer cells (KrasG12D and p53R172H) were seeded on the hydrogels to confirm that the cytotoxicity of the hydrogels was low. The attachment of CRGDS onto the hydrogel was demonstrated as a means to improve cell adhesion.

Dual Signaling DNA Electrochemistry: An Approach To Understand DNA Interfaces

Electrochemical DNA biosensors composed of a redox marker modified nucleic acid probe tethered to a solid electrode is a common experimental construct for detecting DNA and RNA targets, proteins, inorganic ions, and even small molecules. This class of biosensors generally relies on the binding-induced conformational changes in the distance of the redox marker relative to the electrode surface such that the charge transfer is altered. The conventional design is to attach the redox species to the distal end of a surface-bound nucleic acid strand. Here we show the impact of the position of the redox marker, whether on the distal or proximal end of the DNA monolayer, on the DNA interface electrochemistry. Somewhat unexpectedly, greater currents were obtained when the redox molecules were located on the distal end of the surface-bound DNA monolayer, notionally furthest away from the electrode, compared with currents when the redox species were located on the proximal end, close to the electrode. Our results suggest that a limitation in ion accessibility is the reason why smaller currents were obtained for the redox markers located at the bottom of the DNA monolayer. This understanding shows that to allow the quantification of the amount of redox labeled target DNA strand that hybridizes to probe DNA immobilized on the electrode surface, the redox species must be on the distal end of the surface-bound duplex.