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1.
J Mater Chem B ; 11(34): 8159-8169, 2023 08 30.
Article in English | MEDLINE | ID: mdl-37313622

ABSTRACT

Because of scarcity, vulnerability, and heterogeneity in the population of circulating tumor cells (CTCs), the CTC isolation system relying on immunoaffinity interaction exhibits inconsistent efficiencies for all types of cancers and even CTCs with different phenotypes in individuals. Moreover, releasing viable CTCs from an isolation system is of importance for molecular analysis and drug screening in precision medicine, which remains a challenge for current systems. In this work, a new CTC isolation microfluidic platform was developed and contains a coating of the antibody-conjugated liposome-tethered-supported lipid bilayer in a developed chaotic-mixing microfluidic system, referred to as the "LIPO-SLB" platform. The biocompatible, soft, laterally fluidic, and antifouling properties of the LIPO-SLB platform offer high CTC capture efficiency, viability, and selectivity. We successfully demonstrated the capability of the LIPO-SLB platform to recapitulate different cancer cell lines with different antigen expression levels. In addition, the captured CTCs in the LIPO-SLB platform can be detached by air foam to destabilize the physically assembled bilayer structures due to a large water/air interfacial area and strong surface tension. More importantly, the LIPO-SLB platform was constructed and used for the verification of clinical samples from 161 patients with different primary cancer types. The mean values of both single CTCs and CTC clusters correlated well with the cancer stages. Moreover, a considerable number of CTCs were isolated from patients' blood samples in the early/localized stages. The clinical validation demonstrated the enormous potential of the universal LIPO-SLB platform as a tool for prognostic and predictive purposes in precision medicine.


Subject(s)
Lipid Bilayers , Neoplastic Cells, Circulating , Humans , Lipid Bilayers/chemistry , Liposomes , Cell Separation , Neoplastic Cells, Circulating/pathology , Microfluidics
2.
Adv Mater ; 35(14): e2209956, 2023 Apr.
Article in English | MEDLINE | ID: mdl-36656747

ABSTRACT

Encryption technologies are essential for information security and product anti-counterfeiting, but they are typically restricted to planar surfaces. Encryption on complex 3D objects offers great potential to further improve security. However, it is rarely achieved owing to the lack of encoding strategies for nonplanar surfaces. Here, an approach is reported to directly encrypt on a 3D-printed object employing orthogonal photochemistry. In this system, visible light photochemistry is used for 3D printing of a hydrogel, and ultraviolet light is subsequently employed to activate its geometrically complex surface through the dissociation of ortho-nitrobenzyl ester units in a spatioselective manner for information coding. This approach offers a new way for more reliable encryption, and the underlying orthogonal photochemistry can be extended toward functional modification of 3D-printed products beyond information protection.

3.
iScience ; 25(10): 105081, 2022 Oct 21.
Article in English | MEDLINE | ID: mdl-36204272

ABSTRACT

Matching the treatment to an individual patient's tumor state can increase therapeutic efficacy and reduce tumor recurrence. Circulating tumor cells (CTCs) derived from solid tumors are promising subjects for theragnostic analysis. To analyze how CTCs represent tumor states, we established cell lines from CTCs, primary and metastatic tumors from a mouse model and provided phenotypic and multiomic analyses of these cells. CTCs and metastatic cells, but not primary tumor cells, shared stochastic mutations and similar hypomethylation levels at transcription start sites. CTCs and metastatic tumor cells shared a hybrid epithelial/mesenchymal transcriptome state with reduced adhesive and enhanced mobilization characteristics. We tested anti-cancer drugs on tumor cells from a metastatic breast cancer patient. CTC responses mirrored the impact of drugs on metastatic rather than primary tumors. Our multiomic and clinical anti-cancer drug response results reveal that CTCs resemble metastatic tumors and establish CTCs as an ex vivo tool for personalized medicine.

4.
Macromol Rapid Commun ; 43(12): e2100614, 2022 Jun.
Article in English | MEDLINE | ID: mdl-34873776

ABSTRACT

Molecular dynamics (MD) simulations of melt films of poly(alkyl methacrylate)s (PAMAs) with methyl, ethyl, and n-butyl substituents, respectively, have been performed using an all-atom model to investigate their surface and thin film properties. The applied all-atom force fields predict the bulk densities of PAMAs in good agreement with experiments. Moreover, predictions of the surface tensions of PMMA, PEMA, and Pn-BMA melts are in reasonably good agreement with experiments. The density profiles and orientational-order parameters of chain segments show atomic-scale characteristics in the air/polymer interfacial region. In the surface region, the backbone segments of PAMAs form a well-defined layer structure with the chain vectors oriented parallel to the surface, while the ester side-chains strongly segregate to the surface region and show perpendicular orientation to the surface, with the most pronounced surface segregation noted for Pn-BMA. Such surface segregations of chain segments make it difficult to apply a simple relationship between the cohesive energy density and the surface tension of polymers, for example, and should be taken into account in relating the surface/thin film characteristics to the bulk properties of polymers in general.


Subject(s)
Methacrylates , Molecular Dynamics Simulation , Polymers/chemistry , Surface Properties , Surface Tension
5.
Molecules ; 26(24)2021 Dec 09.
Article in English | MEDLINE | ID: mdl-34946531

ABSTRACT

Understanding the impact of different bridging groups in the two-step polymerization of poly(ethylene glycol) (PEG)-incorporated polyimide (PI) materials is significant. It is known that the proton exchange membranes (PEMs) used in industry today can experience performance degradation under rising temperature conditions. Many efforts have been devoted to overcoming this problem by improving the physical and mechanical properties that extend the hygrothermal life of a PEM. This work examines the effect of oxygenated and fluorinated bridging anhydrides in the production of PI-PEG PEMs. It is shown that the dianhydride identity and the amount incorporated in the synthesis influences the properties of the segmented block copolymer (SBC) membranes, such as increased ionic liquid uptake (ILU), enhanced conductivity and higher Young's modulus favoring stiffness comparable to Nafion 115, an industrial standard. Investigations on the ionic conductivity of PI-PEG membranes were carried out to determine how thermal annealing would affect the material's performance as an ion-exchange membrane. By applying a thermal annealing process at 60 °C for one hour, the conductivities of synthesized segmented block copolymer membranes values were increased. The effect of thermal annealing on the mechanical properties was also shown for the undoped SBC via measuring the change in the Young's modulus. These higher ILU abilities and mechanical behavior changes are thought to arise from the interaction between PEG molecules and ethylammonium nitrate (EAN) ionic liquid (IL). In addition, higher interconnected routes provide a better ion-transfer environment within the membrane. It was found that the conductivity was increased by a factor of ten for undoped and a factor of two to seven for IL-doped membranes after thermal annealing.

6.
Molecules ; 26(8)2021 Apr 08.
Article in English | MEDLINE | ID: mdl-33917907

ABSTRACT

Proton exchange membranes (PEMs) suffer performance degradation under certain conditions-temperatures greater than 80 °C, relative humidity less than 50%, and water retention less than 22%. Novel materials are needed that have improved water retention, stability at higher temperatures, flexibility, conductivity, and the ability to function at low humidity. This work focuses on polyimide-poly(ethylene glycol) (PI-PEG) segmented block copolymer (SBC) membranes with high conductivity and mechanical strength. Membranes were prepared with one of two ionic liquids (ILs), either ethylammonium nitrate (EAN) or propylammonium nitrate (PAN), incorporated within the membrane structure to enhance the proton exchange capability. Ionic liquid uptake capacities were compared for two different temperatures, 25 and 60 °C. Then, conductivities were measured for a series of combinations of undoped or doped unannealed and undoped or doped annealed membranes. Stress and strain tests were performed for unannealed and thermally annealed undoped membranes. Later, these experiments were repeated for doped unannealed and thermally annealed. Mechanical and conductivity data were interpreted in the context of prior small angle X-ray scattering (SAXS) studies on similar materials. We have shown that varying the compositions of polyimide-poly(ethylene glycol) (PI-PEG) SBCs allowed the morphology in the system to be tuned. Since polyimides (PI) are made from the condensation of dianhydrides and diamines, this was accomplished using components having different functional groups. Dianhydrides having either fluorinated or oxygenated functional groups and diamines having either fluorinated or oxygenated diamines were used as well as mixtures of these species. Changing the morphology by creating macrophase separation elevated the IL uptake capacities, and in turn, increased their conductivities by a factor of three or more compared to Nafion 115. The stiffness of the membranes synthesized in this work was comparable to Nafion 115 and, thus, sufficient for practical applications.

7.
Angew Chem Int Ed Engl ; 60(14): 7971-7979, 2021 Mar 29.
Article in English | MEDLINE | ID: mdl-33403788

ABSTRACT

Monodispersed metal and semiconductor nanocrystals have attracted great attention in fundamental and applied research due to their tunable size, morphology, and well-defined chemical composition. Utilizing these nanocrystals in a controllable way is highly desirable especially when using them as building blocks for the preparation of nanostructured materials. Their deposition onto oxide materials provide them with wide applicability in many areas, including catalysis. However, so far deposition methods are limited and do not provide control to achieve high particle loadings. This study demonstrates a general approach for the deposition of hydrophobic ligand-stabilized nanocrystals on hydrophilic oxide supports without ligand-exchange. Surface functionalization of the supports with primary amine groups either using an organosilane ((3-aminopropyl)trimethoxysilane) or bonding with aminoalcohols (3-amino-1,2-propanediol) were found to significantly improve the interaction between nanocrystals and supports achieving high loadings (>10 wt. %). The bonding method with aminoalcohols guarantees the opportunity to remove the binding molecules thus allowing clean metal/oxide materials to be obtained, which is of great importance in the preparation of supported nanocrystals for heterogeneous catalysis.

8.
J Am Chem Soc ; 142(34): 14481-14494, 2020 08 26.
Article in English | MEDLINE | ID: mdl-32786792

ABSTRACT

Supported metal nanoparticles are essential components of high-performing catalysts, and their structures are intensely researched. In comparison, nanoparticle spatial distribution in powder catalysts is conventionally not quantified, and the influence of this collective property on catalyst performance remains poorly investigated. Here, we demonstrate a general colloidal self-assembly method to control uniformity of nanoparticle spatial distribution on common industrial powder supports. We quantify distributions on the nanoscale using image statistics and show that the type of nanospatial distribution determines not only the stability, but also the activity of heterogeneous catalysts. Widely investigated systems (Au-TiO2 for CO oxidation thermocatalysis and Pd-TiO2 for H2 evolution photocatalysis) were used to showcase the universal importance of nanoparticle spatial organization. Spatially and temporally resolved microkinetic modeling revealed that nonuniformly distributed Au nanoparticles suffer from local depletion of surface oxygen, and therefore lower CO oxidation activity, as compared to uniformly distributed nanoparticles. Nanoparticle spatial distribution also determines the stability of Pd-TiO2 photocatalysts, because nonuniformly distributed nanoparticles sinter while uniformly distributed nanoparticles do not. This work introduces new tools to evaluate and understand catalyst collective (ensemble) properties in powder catalysts, which thereby pave the way to more active and stable heterogeneous catalysts.


Subject(s)
Carbon Monoxide/chemistry , Gold/chemistry , Hydrogen/chemistry , Nanoparticles/chemistry , Palladium/chemistry , Titanium/chemistry , Catalysis , Oxidation-Reduction , Particle Size , Photochemical Processes , Powders , Surface Properties
9.
Polymers (Basel) ; 12(5)2020 May 06.
Article in English | MEDLINE | ID: mdl-32384644

ABSTRACT

Molecular dynamics simulations of free-standing thin films of neat melts of polyethylene (PE) chains up to C150H302 and their binary mixtures with n-C13H28 are performed employing a united atom model. We estimate the surface tension values of PE melts from the atomic virial tensor over a range of temperatures, which are in good agreement with experimental results. Compared with short n-alkane systems, there is an enhanced surface segregation of methyl chain ends in longer PE chains. Moreover, the methyl groups become more segregated in the surface region with decreasing temperature, leading to the conclusion that the surface-segregation of methyl chain ends mainly arises from the enthalpic origin attributed to the lower cohesive energy density of terminal methyl groups. In the mixtures of two different chain lengths, the shorter chains are more likely to be found in the surface region, and this molecular segregation in moderately asymmetric mixtures in the chain length (C13H28 + C44H90) is dominated by the enthalpic effect of methyl chain ends. Such molecular segregation is further enhanced and dominated by the entropic effect of conformational constraints in the surface for the highly asymmetric mixtures containing long polymer chains (C13H28 + C150H3020). The estimated surface tension values of the mixtures are consistent with the observed molecular segregation characteristics. Despite this molecular segregation, the normalized density of methyl chain ends of the longer chain is more strongly enhanced, as compared with the all-segment density of the longer chain itself, in the surface region of melt mixtures. In addition, the molecular segregation results in higher order parameter of the shorter-chain segments at the surface and deeper persistence of surface-induced segmental order into the film for the longer chains, as compared with those in neat melt films.

10.
Langmuir ; 35(13): 4460-4470, 2019 Apr 02.
Article in English | MEDLINE | ID: mdl-30836748

ABSTRACT

Depositing a morphologically uniform monolayer film of graphene oxide (GO) single-layer sheets is an important step in the processing of many composites and devices. Conventional Langmuir-Blodgett (LB) deposition is often considered to give the highest degree of morphology control, but film microstructures still vary widely between GO samples. The main challenge is in the sensitive self-assembly of GO samples with different sheet sizes and degrees of oxidation. To overcome this drawback, here, we identify a general method that relies on robust assembly between GO and a cationic surfactant (cationic surfactant-assisted LB). We systematically compared conventional LB and cationic surfactant-assisted LB for three common GO samples of widely different sheet sizes and degrees of oxidation. Although conventional LB may occasionally provide satisfactory film morphology, cationic surfactant-assisted LB is general and allows deposition of films with tunable and uniform morphologies-ranging from close-packed to overlapping single layers-from all three types of GO samples investigated. Because cationic surfactant-assisted LB is robust and general, we expect this method to broaden and facilitate the use of GO in many applications where precise control over film morphology is crucial.

11.
Biomaterials ; 182: 299-311, 2018 11.
Article in English | MEDLINE | ID: mdl-30149262

ABSTRACT

Generation of human organoids from induced pluripotent stem cells (iPSCs) offers exciting possibilities for developmental biology, disease modelling and cell therapy. Significant advances towards those goals have been hampered by dependence on animal derived matrices (e.g. Matrigel), immortalized cell lines and resultant structures that are difficult to control or scale. To address these challenges, we aimed to develop a fully defined liver organoid platform using inverted colloid crystal (ICC) whose 3-dimensional mechanical properties could be engineered to recapitulate the extracellular niche sensed by hepatic progenitors during human development. iPSC derived hepatic progenitors (IH) formed organoids most optimally in ICC scaffolds constructed with 140 µm diameter pores coated with type I collagen in a two-step process mimicking liver bud formation. The resultant organoids were closer to adult tissue, compared to 2D and 3D controls, with respect to morphology, gene expression, protein secretion, drug metabolism and viral infection and could integrate, vascularise and function following implantation into livers of immune-deficient mice. Preliminary interrogation of the underpinning mechanisms highlighted the importance of TGFß and hedgehog signalling pathways. The combination of functional relevance with tuneable mechanical properties leads us to propose this bioengineered platform to be ideally suited for a range of future mechanistic and clinical organoid related applications.


Subject(s)
Induced Pluripotent Stem Cells/cytology , Liver/cytology , Organoids/cytology , Polyethylene Glycols/chemistry , Tissue Engineering/methods , Tissue Scaffolds/chemistry , Biocompatible Materials/chemistry , Cells, Cultured , Crystallization , Humans , Induced Pluripotent Stem Cells/metabolism
12.
Langmuir ; 34(33): 9683-9691, 2018 08 21.
Article in English | MEDLINE | ID: mdl-30025460

ABSTRACT

Langmuir-Blodgett deposition is a popular route to produce thin films of graphene oxide for applications such as transparent conductors and biosensors. Unfortunately, film morphologies vary from sample to sample, often with undesirable characteristics such as folded sheets and patchwise depositions. In conventional Langmuir-Blodgett deposition of graphene oxide, alcohol (typically methanol) is used to spread the graphene oxide sheets onto an air-water interface before deposition onto substrates. Here we show that methanol gives rise to Marangoni flow, which fundamentally limits control over Langmuir-Blodgett depositions of graphene oxide. We directly identified the presence of Marangoni flow by using photography, and we evaluated depositions with atomic force microscopy and scanning electron microscopy. The disruptive effect of Marangoni flow was demonstrated by comparing conventional Langmuir-Blodgett depositions to depositions where Marangoni flow was suppressed by a surfactant. Because methanol is the standard spreading solvent for conventional Langmuir-Blodgett deposition of graphene oxide, Marangoni flow is a general problem and may partly explain the wide variety of undesirable film morphologies reported in the literature.

13.
JCI Insight ; 2(11)2017 Jun 02.
Article in English | MEDLINE | ID: mdl-28570275

ABSTRACT

A major challenge for studying authentic liver cell function and cell replacement therapies is that primary human hepatocytes rapidly lose their advanced function in conventional, 2-dimensional culture platforms. Here, we describe the fabrication of 3-dimensional hexagonally arrayed lobular human liver tissues inspired by the liver's natural architecture. The engineered liver tissues exhibit key features of advanced differentiation, such as human-specific cytochrome P450-mediated drug metabolism and the ability to support efficient infection with patient-derived inoculums of hepatitis C virus. The tissues permit the assessment of antiviral agents and maintain their advanced functions for over 5 months in culture. This extended functionality enabled the prediction of a fatal human-specific hepatotoxicity caused by fialuridine (FIAU), which had escaped detection by preclinical models and short-term clinical studies. The results obtained with the engineered human liver tissue in this study provide proof-of-concept determination of human-specific drug metabolism, demonstrate the ability to support infection with human hepatitis virus derived from an infected patient and subsequent antiviral drug testing against said infection, and facilitate detection of human-specific drug hepatotoxicity associated with late-onset liver failure. Looking forward, the scalability and biocompatibility of the scaffold are also ideal for future cell replacement therapeutic strategies.

14.
J Chem Phys ; 146(20): 203314, 2017 May 28.
Article in English | MEDLINE | ID: mdl-28571360

ABSTRACT

United-atom molecular-dynamics computer simulations of atactic polystyrene (PS) were performed for the bulk and free-standing films of 2 nm-20 nm thickness, for both linear and cyclic polymers comprised of 80 monomers. Simulated volumetric glass-transition temperatures (Tg) show a strong dependence on the film thickness below 10 nm. The glass-transition temperature of linear PS is 13% lower than that of the bulk for 2.5 nm-thick films, as compared to less than 1% lower for 20 nm films. Our studies reveal that the fraction of the chain-end groups is larger in the interfacial layer with its outermost region approximately 1 nm below the surface than it is in the bulk. The enhanced population of the end groups is expected to result in a more mobile interfacial layer and the consequent dependence of Tg on the film thickness. In addition, the simulations show an enrichment of backbone aliphatic carbons and concomitant deficit of phenyl aromatic carbons in the interfacial film layer. This deficit would weaken the strong phenyl-phenyl aromatic (π-π) interactions and, hence, lead to a lower film-averaged Tg in thin films, as compared to the bulk sample. To investigate the relative importance of the two possible mechanisms (increased chain ends at the surface or weakened π-π interactions in the interfacial region), the data for linear PS are compared with those for cyclic PS. For the cyclic PS, the reduction of the glass-transition temperature is also significant in thin films, albeit not as much as for linear PS. Moreover, the deficit of phenyl carbons in the film interface is comparable to that observed for linear PS. Therefore, chain-end effects alone cannot explain the observed pronounced Tg dependence on the thickness of thin PS films; the weakened phenyl-phenyl interactions in the interfacial region seems to be an important cause as well.

15.
Nat Commun ; 6: 7417, 2015 Jul 15.
Article in English | MEDLINE | ID: mdl-26174864

ABSTRACT

Dynamic covalent materials are stable materials that possess reversible behaviour triggered by stimuli such as light, redox conditions or temperature; whereas supramolecular crosslinks depend on the equilibrium constant and relative concentrations of crosslinks as a function of temperature. The combination of these two reversible chemistries can allow access to materials with unique properties. Here, we show that this combination of dynamic covalent and supramolecular chemistry can be used to prepare organogels comprising distinct networks. Two materials containing hemiaminal crosslink junctions were synthesized; one material is comprised of dynamic covalent junctions and the other contains hydrogen-bonding bis-hemiaminal moieties. Under specific network synthesis conditions, these materials exhibited self-healing behaviour. This work reports on both the molecular-level detail of hemiaminal crosslink junction formation as well as the macroscopic behaviour of hemiaminal dynamic covalent network (HDCN) elastomeric organogels. These materials have potential applications as elastomeric components in printable materials, cargo carriers and adhesives.

16.
ChemSusChem ; 8(8): 1472-83, 2015 Apr 24.
Article in English | MEDLINE | ID: mdl-25820199

ABSTRACT

There is a delicate balance between ion exchange capacity (IEC), conductivity, and dimensional stability in anion exchange membranes as higher charge content can lead to increased water uptake, causing excessive swelling and charge dilution. Using highly-charged benzyltrimethylammonium polysulfone (IEC=2.99 mEq g(-1) ) as a benchmark (which ruptured in water even at room temperature), we report the ability to dramatically decrease water uptake using a semi-interpenetrating network wherein we reinforced the linear polyelectrolyte with a crosslinked poly(styrene-co-divinylbenzene) network. These membranes show enhanced dimensional stability as a result of lower water uptake (75 % vs. 301 % at 25 °C) while maintaining excellent hydroxide conductivity (up to 50 mS cm(-1) at 25 °C). These improvements produced an enhanced alkaline fuel cell capable of generating 236 mW cm(-2) peak power density at 80 °C. This method is easily adaptable and can be a viable strategy for stabilizing existing systems.


Subject(s)
Electric Power Supplies , Membranes, Artificial , Electric Conductivity , Electrodes , Hydrogen-Ion Concentration , Hydroxides/chemistry , Ion Exchange , Kinetics , Mechanical Phenomena , Polymers/chemistry , Polystyrenes/chemistry , Sulfones/chemistry , Temperature , Water/chemistry
17.
J Biomed Mater Res A ; 103(10): 3157-65, 2015 Oct.
Article in English | MEDLINE | ID: mdl-25778285

ABSTRACT

We evaluated the biocompatibility of a poly(ethylene glycol) and poly(acrylic acid) (PEG/PAA) interpenetrating network hydrogel designed for artificial cornea in a rabbit model. PEG/PAA hydrogel measuring 6 mm in diameter was implanted in the corneal stroma of twelve rabbits. Stromal flaps were created with a microkeratome. Randomly, six rabbits were assigned to bear the implant for 2 months, two rabbits for 6 months, two rabbits for 9 months, one rabbit for 12 months, and one rabbit for 16 months. Rabbits were evaluated monthly. After the assigned period, eyes were enucleated, and corneas were processed for histology and immunohistochemistry. There were clear corneas in three of six rabbits that had implantation of hydrogel for 2 months. In the six rabbits with implant for 6 months or longer, the corneas remained clear in four. There was a high rate of epithelial defect and corneal thinning in these six rabbits. One planned 9-month rabbit developed extrusion of implant at 4 months. The cornea remained clear in the 16-month rabbit but histology revealed epithelial in-growth. Intrastromal implantation of PEG/PAA resulted in a high rate of long-term complications.


Subject(s)
Acrylic Resins/chemistry , Cornea , Hydrogels/chemistry , Implants, Experimental , Materials Testing , Polyethylene Glycols/chemistry , Animals , Rabbits
18.
J Mater Sci Mater Med ; 26(2): 107, 2015 Feb.
Article in English | MEDLINE | ID: mdl-25665845

ABSTRACT

Three-dimensional scaffolds based on inverted colloidal crystals (ICCs) were fabricated from sequentially polymerized interpenetrating polymer network (IPN) hydrogels of poly(ethyleneglycol) and poly(acrylic acid). This high-strength, high-water-content IPN hydrogel may be suitable for use in an artificial cornea application. Development of a highly porous, biointegrable region at the periphery of the artificial cornea device is critical to long-term retention of the implant. The ICC fabrication technique produced scaffolds with well-controlled, tunable pore and channel dimensions. When surface functionalized with extracellular matrix proteins, corneal fibroblasts were successfully cultured on IPN hydrogel scaffolds, demonstrating the feasibility of these gels as materials for the artificial cornea porous periphery. Porous hydrogels with and without cells were visualized non-invasively in the hydrated state using variable-pressure scanning electron microscopy.


Subject(s)
Acrylic Resins/chemistry , Bioprosthesis , Corneal Transplantation/instrumentation , Hydrogels/chemical synthesis , Polyethylene Glycols/chemistry , Tissue Scaffolds , Bioartificial Organs , Guided Tissue Regeneration/instrumentation , Hardness , Materials Testing , Porosity , Viscosity
19.
PLoS One ; 10(2): e0117738, 2015.
Article in English | MEDLINE | ID: mdl-25689864

ABSTRACT

Microdroplets are an effective platform for segregating individual cells and amplifying DNA. However, a key challenge is to recover the contents of individual droplets for downstream analysis. This paper offers a method for embedding cells in alginate microspheres and performing multiple serial operations on the isolated cells. Rhodobacter sphaeroides cells were diluted in alginate polymer and sprayed into microdroplets using a fingertip aerosol sprayer. The encapsulated cells were lysed and subjected either to conventional PCR, or whole genome amplification using either multiple displacement amplification (MDA) or a two-step PCR protocol. Microscopic examination after PCR showed that the lumen of the occupied microspheres contained fluorescently stained DNA product, but multiple displacement amplification with phi29 produced only a small number of polymerase colonies. The 2-step WGA protocol was successful in generating fluorescent material, and quantitative PCR from DNA extracted from aliquots of microspheres suggested that the copy number inside the microspheres was amplified up to 3 orders of magnitude. Microspheres containing fluorescent material were sorted by a dilution series and screened with a fluorescent plate reader to identify single microspheres. The DNA was extracted from individual isolates, re-amplified with full-length sequencing adapters, and then a single isolate was sequenced using the Illumina MiSeq platform. After filtering the reads, the only sequences that collectively matched a genome in the NCBI nucleotide database belonged to R. sphaeroides. This demonstrated that sequencing-ready DNA could be generated from the contents of a single microsphere without culturing. However, the 2-step WGA strategy showed limitations in terms of low genome coverage and an uneven frequency distribution of reads across the genome. This paper offers a simple method for embedding cells in alginate microspheres and performing PCR on isolated cells in common bulk reactions, although further work must be done to improve the amplification coverage of single genomes.


Subject(s)
Alginates/chemistry , Cell Separation/methods , Genome, Bacterial/genetics , Microspheres , Polymerase Chain Reaction/methods , Rhodobacter sphaeroides/cytology , Rhodobacter sphaeroides/genetics , Capsules , Feasibility Studies , Glucuronic Acid/chemistry , Hexuronic Acids/chemistry , Sequence Analysis, DNA
20.
J Mater Chem B ; 3(34): 6953-6963, 2015 Sep 14.
Article in English | MEDLINE | ID: mdl-32262545

ABSTRACT

Micellar composite hydrogel systems represent a promising class of materials for biomolecule and drug delivery applications. In this work a system combining micellar drug delivery with supramolecular hydrogel assemblies is developed, representing an elegant marriage of aqueous hydrophobic drug delivery and next-generation injectable viscoelastic materials. Novel shear thinning and injectable micellar composite hydrogels were prepared using an amphiphilic ABA-type triblock copolymer consisting of a hydrophilic middle block and cholesterol-functionalized polycarbonates as terminal hydrophobic blocks. Varying the concentration and relative hydrophobic-hydrophilic content of the amphiphilic species conferred the ability to tune the storage moduli of these gels from 200 Pa to 3500 Pa. This tunable system was used to encapsulate drug-loaded polymeric micelles, demonstrating a straightforward and modular approach to developing micellar viscoelastic materials for a variety of applications such as delivery of hydrophobic drugs. These hydrogels were also mixed with cholesterol-containing cationic polycarbonates to render antimicrobial activity and capability for anionic drug delivery. Additionally, small-angle X-ray scattering (SAXS) and electron microscopy (EM) results probed the mesoscale structure of these micellar composite materials, lending molecular level insight into the self-assembly properties of these gels. The antimicrobial composite hydrogels demonstrated strong microbicidal activity against Gram-negative and Gram-positive bacteria, and C. albicans fungus. Amphotericin B (AmB, an antifungal drug)-loaded micelles embedded within the hydrogel demonstrated sustained drug release over 4 days and effective eradication of fungi. Our findings demonstrate that materials of different nature (i.e. small molecule drugs or charged macromolecules) can be physically combined with ABA-type triblock copolymer gelators to form hydrogels for potential pharmaceutical applications.

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