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Hong, Jinkee,Kim, Byeong-Su,Char, Kookheon,Hammond, Paula T. American Chemical Society 2011 Biomacromolecules Vol.12 No.8
<P>Recent research has highlighted degradable multilayer films that enable the programmed release of different therapeutics. Multilayers constructed by the layer-by-layer (LbL) deposition that can undergo disassembly have been demonstrated to be of considerable interest, particularly for biomedical surface coatings due to their versatility and mild aqueous processing conditions, enabling the inclusion of biologic drugs with high activity. In this study, we examine the controlled release of a protein using a different mechanism for film disassembly, the gradual dissociation of film interactions under release conditions. Poly(β-amino ester)s and poly(<SMALL>l</SMALL>-lysine) (PLL) were used as the positively charged multilayer components coassembled with a model negatively charged antigen protein, ovalbumin (Ova). The release of the protein from these multilayer films is dominated by the slow shift in the charge of components under physiological pH conditions rather than by hydrolytic degradative release. The time scale of release can be varied over almost 2 orders of magnitude by varying the ratio of the two polyamines in the deposition solution. The highly versatile and tunable properties of these films form a basis for designing controlled and sequential delivery of drug coatings using a variety of polyions.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/bomaf6/2011/bomaf6.2011.12.issue-8/bm200566k/production/images/medium/bm-2011-00566k_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/bm200566k'>ACS Electronic Supporting Info</A></P>
Facilitated Ion Transport in All-Solid-State Flexible Supercapacitors
Choi, Bong Gill,Hong, Jinkee,Hong, Won Hi,Hammond, Paula T.,Park, HoSeok American Chemical Society 2011 ACS NANO Vol.5 No.9
<P>The realization of highly flexible and all-solid-state energy-storage devices strongly depends on both the electrical properties and mechanical integrity of the constitutive materials and the controlled assembly of electrode and solid electrolyte. Herein we report the preparation of all-solid-state flexible supercapacitors (SCs) through the easy assembly of functionalized reduced graphene oxide (f-RGO) thin films (as electrode) and solvent-cast Nafion electrolyte membranes (as electrolyte and separator). In particular, the f-RGO-based SCs (f-RGO-SCs) showed a 2-fold higher specific capacitance (118.5 F/g at 1 A/g) and rate capability (90% retention at 30 A/g) compared to those of all-solid-state graphene SCs (62.3 F/g at 1A/g and 48% retention at 30 A/g). As proven by the 4-fold faster relaxation of the f-RGO-SCs than that of the RGO-SCs and more capacitive behavior of the former at the low-frequency region, these results were attributed to the facilitated ionic transport at the electrical double layer by means of the interfacial engineering of RGO by Nafion. Moreover, the superiority of all-solid-state flexible f-RGO-SCs was demonstrated by the good performance durability under the 1000 cycles of charging and discharging due to the mechanical integrity as a consequence of the interconnected networking structures. Therefore, this research provides new insight into the rational design and fabrication of all-solid-state flexible energy-storage devices as well as the fundamental understanding of ion and charge transport at the interface.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2011/ancac3.2011.5.issue-9/nn202020w/production/images/medium/nn-2011-02020w_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn202020w'>ACS Electronic Supporting Info</A></P>
Multimonth controlled small molecule release from biodegradable thin films
Hsu, Bryan B.,Park, Myoung-Hwan,Hagerman, Samantha R.,Hammond, Paula T. National Academy of Sciences 2014 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.111 No.33
<P>Long-term, localized delivery of small molecules from a biodegradable thin film is challenging owing to their low molecular weight and poor charge density. Accomplishing highly extended controlled release can facilitate high therapeutic levels in specific regions of the body while significantly reducing the toxicity to vital organs typically caused by systemic administration and decreasing the need for medical intervention because of its long-lasting release. Also important is the ability to achieve high drug loadings in thin film coatings to allow incorporation of significant drug amounts on implant surfaces. Here we report a sustained release formulation for small molecules based on a soluble charged polymer–drug conjugate that is immobilized into nanoscale, conformal, layer-by-layer assembled films applicable to a variety of substrate surfaces. We measured a highly predictable sustained drug release from a polymer thin film coating of 0.5–2.7 μm that continued for more than 14 mo with physiologically relevant drug concentrations, providing an important drug delivery advance. We demonstrated this effect with a potent small molecule nonsteroidal anti-inflammatory drug, diclofenac, because this drug can be used to address chronic pain, osteoarthritis, and a range of other critical medical issues.</P>
Hong, Jinkee,Alvarez, Luis M,Shah, Nisarg J,Griffith, Linda G,Kim, Byeong-Su,Char, Kookheon,Hammond, Paula T Springer US 2012 Drug delivery and translational research Vol.2 No.5
<P>The promise of cellular therapy lies in healing damaged tissues and organs in vivo as well as generating tissue constructs in vitro for subsequent transplantation. Adult stem cells are ideally suited for cellular therapies due to their pulripotency and the ease with which they can be cultured on novel functionalized substrates. Creating environments to control and successively driving their differentiation toward a lineage of choice is one of the most important challenges of current cell-based engineering strategies. In recent years, a variety of biomedical platforms have been prepared for stem cell cultures, primarily to provide efficient delivery of growth or survival factors to cells and a conducive microenvironment for their growth. Here, we demonstrate that repeating tetralayer structures composed of biocompatible poly(methacrylic acid) (PMAA)/poly(acryl amide) (PAAm)/poly(methacrylic acid) (PMAA)/poly(ethylene oxide)-block-poly(ε-caprolactone) (PEO-b-PCL) micelles arrayed in layer-by-layer (LbL) films can serve as a payload region for dexamethasone (dex) delivery to human mesenchymal stem cells (MSCs). This architecture can induce MSC differentiation into osteoblasts in a dose-dependent manner. The amount of dex loaded in the films is controlled by varying the deposition conditions and the film thickness. Furthermore, release of dex is also controlled by changing the amount of covalent crosslinking of multilayers via thermal treatments. The multilayer architecture including payload and cell-adhesion region introduced here are well suited for extended cell culture thus affording the important and protective effect of both dex release and immobilization. These films may find applications in the local delivery of immobilized therapeutics for biomedical applications, as they can be deposited on a wide range of substrates with different shapes, sizes, and composition.</P>
Choi, Bong Gill,Hong, Jinkee,Park, Young Chul,Jung, Doo Hwan,Hong, Won Hi,Hammond, Paula T.,Park, HoSeok American Chemical Society 2011 ACS NANO Vol.5 No.6
<P>The chemistry and structure of ion channels within the polymer electrolytes are of prime importance for studying the transport properties of electrolytes as well as for developing high-performance electrochemical devices. Despite intensive efforts on the synthesis of polymer electrolytes, few studies have demonstrated enhanced target ion conduction while suppressing unfavorable ion or mass transport because the undesirable transport occurs through an identical pathway. Herein, we report an innovative, chemical strategy for the synthesis of polymer electrolytes whose ion-conducting channels are physically and chemically modulated by the ionic (not electronic) conductive, functionalized graphenes and for a fundamental understanding of ion and mass transport occurring in nanoscale ionic clusters. The functionalized graphenes controlled the state of water by means of nanoscale manipulation of the physical geometry and chemical functionality of ionic channels. Furthermore, the confinement of bound water within the reorganized nanochannels of composite membranes was confirmed by the enhanced proton conductivity at high temperature and the low activation energy for ionic conduction through a Grotthus-type mechanism. The selectively facilitated transport behavior of composite membranes such as high proton conductivity and low methanol crossover was attributed to the confined bound water, resulting in high-performance fuel cells.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2011/ancac3.2011.5.issue-6/nn2013113/production/images/medium/nn-2011-013113_0003.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn2013113'>ACS Electronic Supporting Info</A></P>
Roh, Young Hoon,Deng, Jason Z.,Dreaden, Erik C.,Park, Jae Hyon,Yun, Dong Soo,Shopsowitz, Kevin E.,Hammond, Paula T. John Wiley and Sons Inc. 2016 Angewandte Chemie. international edition Vol.55 No.10
<P><B>Abstract</B></P><P>Packaging multiple small interfering RNA (siRNA) molecules into nanostructures at precisely defined ratios is a powerful delivery strategy for effective RNA interference (RNAi) therapy. We present a novel RNA nanotechnology based approach to produce multiple components of polymerized siRNA molecules that are simultaneously self‐assembled and densely packaged into composite sponge‐like porous microstructures (Multi‐RNAi‐MSs) by rolling circle transcription. The Multi‐RNAi‐MSs were designed to contain a combination of multiple polymeric siRNA molecules with precisely controlled stoichiometry within a singular microstructure by manipulating the types and ratios of the circular DNA templates. The Multi‐RNAi‐MSs were converted into nanosized complexes by polyelectrolyte condensation to manipulate their physicochemical properties (size, shape, and surface charge) for favorable delivery, while maintaining the multifunctional properties of the siRNAs for combined therapeutic effects. These Multi‐RNAi‐MS systems have great potential in RNAi‐mediated biomedical applications, for example, for the treatment of cancer, genetic disorders, and viral infections.</P>