Phenylboronic Acid-polymers for Biomedical Applications

Background: Phenylboronic acid-polymers (PBA-polymers) have attracted tremendous attention as potential stimuli-responsive materials with applications in drug-delivery depots, scaffolds for tissue engineering, HIV barriers, and biomolecule-detecting/sensing platforms. The unique aspect of PBA-polymers is their interactions with diols, which result in reversible, covalent bond formation. This very nature of reversible bonding between boronic acids and diols has been fundamental to their applications in the biomedical area. Methods: We have searched peer-reviewed articles including reviews from Scopus, PubMed, and Google Scholar with a focus on the 1) chemistry of PBA, 2) synthesis of PBA-polymers, and 3) their biomedical applications. Results: We have summarized approximately 179 papers in this review. Most of the applications described in this review are focused on the unique ability of PBA molecules to interact with diol molecules and the dynamic nature of the resulting boronate esters. The strong sensitivity of boronate ester groups towards the surrounding pH also makes these molecules stimuli-responsive. In addition, we also discuss how the re-arrangement of the dynamic boronate ester bonds renders PBA-based materials with other unique features such as self-healing and shear thinning. Conclusion: The presence of PBA in the polymer chain can render it with diverse functions/ relativities without changing their intrinsic properties. In this review, we discuss the development of PBA polymers with diverse functions and their biomedical applications with a specific focus on the dynamic nature of boronate ester groups.

Photo-reversible bonding and cleavage of block copolymers

We introduce a synthetic avenue for the completely photoreversible formation of block copolymers based on anthracene chemistry.

Fabrication of UV-Curing Polyurethane Methacrylate (PUMA) Microchannel and Fluidics Interconnect for Microfluidics Applications

Microfluidics platform offers a great advantage in bio-sensing and clinical diagnostics miniaturization. The requirement of inexpensive and rapid-prototyping materials are essential in microfluidics device commercialization. This paper presents rapid prototyping of UV-curing Polyurethane Methacrylate (PUMA) microchannel from the Polydimethlsiloxane (PDMS) mold. Two techniques in PUMA microchannel UV-curing rapid prototyping have successfully demonstrated in this work. The first technique utilized thin film transparency sheet as PUMA resin top surface cover in facilitating PUMA UV-curing. The second method exploited confined nitrogen gas environment in Pyrex dish chamber in expediting PUMA curing under UV light exposure. In this work, two different approaches of fluidic interconnect tubings for PUMA microchannel inlet and outlet are also presented. Reversible bonding techniques using corona discharge treatment are utilized for bonding of PUMA microchannel and fluidic interconnect with PUMA, silicon, glass and PDMS substrate. Accomplishment of preliminary fluid flow testing using PUMA microchannel proved its capability for microfluidics applications.

Design, Simulation and Fabrication of Polydimethylsiloxane (PDMS) Microchannel for Lab-on-Chip (LoC) Applications

Microchannel of micron-to milimeter in dimension has been immensely used for fluid handling in transporting, mixing and separating biological cells in Lab-on-Chip (LoC) applications. In this paper, design, simulation and fabrication of Polydimethylsiloxane (PDMS) microfluidic channel are presented. The microchannel is designed with one inlet and outlet. A reservoir or chamber is proposed as an extra component in the microchannel design for ease of separating the intended biological cells as used in LoC magnetic separator and micro-incubator. Finite Element Analysis (FEA) shows laminar flow characteristic is maintained in the proposed microchannel design operating at volumetric flow rate between 0.5 to 1000 μL/min. In addition, pressure drop data across the microchannel are also been obtained from the FEA in determining the safe operation limit of the microchannel. The PDMS microchannels of two different chamber geometries have been successfully fabricated using replica molding technique from SU-8 negative photoresist mold. The fabricated SU-8 mold and the PDMS microchannel structure dimension are characterized using Scanning Electron Microscopy (SEM). Reversible bonding of PDMS microchannel layer and PDMS tubing layer has successfully accomplished by activating the PDMS surfaces using corona discharge. The preliminary testing of the microchannel confirmed its function for LoC continuous flow applications.