A Combinational Effect of "Bulk" and "Surface" Shape-Memory Transitions on the Regulation of Cell Alignment.

A novel shape-memory cell culture platform has been designed that is capable of simultaneously tuning surface topography and dimensionality to manipulate cell alignment. By crosslinking poly(ε-caprolactone) (PCL) macromonomers of precisely designed nanoarchitectures, a shape-memory PCL with switching temperature near body temperature is successfully prepared. The temporary strain-fixed PCLs are prepared by processing through heating, stretching, and cooling about the switching temperature. Temporary nanowrinkles are also formed spontaneously during the strain-fixing process with magnitudes that are dependent on the applied strain. The surface features completely transform from wrinkled to smooth upon shape-memory activation over a narrow temperature range. Shape-memory activation also triggers dimensional deformation in an initial fixed strain-dependent manner. A dynamic cell-orienting study demonstrates that surface topographical changes play a dominant role in cell alignment for samples with lower fixed strain, while dimensional changes play a dominant role in cell alignment for samples with higher fixed strain. The proposed shape-memory cell culture platform will become a powerful tool to investigate the effects of spatiotemporally presented mechanostructural stimuli on cell fate.

The early days of PEG and PEGylation (1970s-1990s).

UNLABELLED: The idea to conjugate PEG [poly(ethylene glycol)] to a protein, i.e., to "PEGylate" a protein, was first proposed by Prof. Frank Davis (Rutgers Univ.) in the late 1960s. He wanted to make the new recombinant proteins less immunogenic in our bodies, and thereby enhance their circulation and activity lifetimes. He thought that if he could conjugate a hydrophilic polymer to the "new" protein, it might not be recognized by the immune system as a foreign molecule. This article is a contribution to the Zwitterionic Special Issue as a personal commentary tracing the story of PEGylation from its beginning with Dr. Davis through a current day post-script. STATEMENT OF SIGNIFICANCE: The author knows (or knew) personally most of the early workers in the fields of PEG, PEGylation and non-fouling surfaces, and he has also been personally active in the field since its early days.

Poly-paclitaxel/cyclodextrin-SPION nano-assembly for magnetically guided drug delivery system.

This work demonstrates the development of magnetically guided drug delivery systems and its potential on efficient anticancer therapy. The magnetically guided drug delivery system was successfully developed by utilizing superparamagnetic iron oxide nanoparticle, ß-cyclodextrin, and polymerized paclitaxel. Multivalent host-guest interactions between ß-cyclodextrin-conjugated superparamagnetic iron oxide nanoparticle and polymerized paclitaxel allowed to load the paclitaxel and the nanoparticle into the nano-assembly. Clusterized superparamagnetic iron oxide nanoparticles in the nano-assembly permitted the rapid and efficient targeted drug delivery. Compared to the control groups, the developed nano-assembly showed the enhanced anticancer effects in vivo as well as in vitro. Consequently, the strategy of the use of superparamagnetic nanoparticles and multivalent host-guest interactions has a promising potential for developing the efficient drug delivery systems.

Stimuli-responsive reagent system for enabling microfluidic immunoassays with biomarker purification and enrichment.

Immunoassays have been translated into microfluidic device formats, but significant challenges relating to upstream sample processing still limit their applications. Here, stimuli-responsive polymer-antibody conjugates are utilized in a microfluidic immunoassay to enable rapid biomarker purification and enrichment as well as sensitive detection. The conjugates were constructed by covalently grafting poly(N-isopropylacrylamide) (PNIPAAm), a thermally responsive polymer, to the lysine residues of anti-prostate specific antigen (PSA) Immunoglobulin G (IgG) using carbodiimide chemistry via the polymer end-carboxylate. The antibody-PNIPAAm (capture) conjugates and antibody-alkaline phosphatase (detection) conjugates formed sandwich immunocomplexes via PSA binding in 50% human plasma. The complexes were loaded into a recirculating poly(dimethylsiloxane) microreactor, equipped with micropumps and transverse flow features, for subsequent separation, enrichment, and quantification. The immunocomplexes were captured by heating the solution to 39 °C, mixed over the transverse features for 2 min, and washed with warm buffer. In one approach, the assay utilized immunocomplex solution that was contained in an 80 nL microreactor, which was loaded with solution at room temperature and subsequently heated to 39 °C. The assay took 25 min and resulted in 37 pM PSA limit of detection (LOD), which is comparable to a plate ELISA employing the same antibody pair. In another approach, the microreactor was preheated to 39 °C, and immunocomplex solution was flowed through the reactor, mixed, and washed. When the specimen volume was increased to 7.5 µL by repeating the capture process three times, the higher specimen volume led to immunocomplex enrichment within the microreactor. The resulting assay LOD was 0.5 pM, which is 2 orders of magnitude lower than the plate ELISA. Both approaches generate antigen specific signal over a clinically significant range. The sample processing capabilities and subsequent utility in a biomarker assay demonstrate the opportunity for stimuli-responsive polymer-protein conjugates in novel diagnostic technologies.

Poly-cyclodextrin and poly-paclitaxel nano-assembly for anticancer therapy.

Effective anticancer therapy can be achieved by designing a targeted drug-delivery system with high stability during circulation and efficient uptake by the target tumour cancer cells. We report here a novel nano-assembled drug-delivery system, formed by multivalent host-guest interactions between a polymer-cyclodextrin conjugate and a polymer-paclitaxel conjugate. The multivalent inclusion complexes confer high stability to the nano-assembly, which efficiently delivers paclitaxel into the targeted cancer cells via both passive and active targeting mechanisms. The ester linkages between paclitaxel and the polymer backbone permit efficient release of paclitaxel within the cell by degradation. This novel targeted nano-assembly exhibits significant antitumour activity in a mouse tumour model. The strategy established in this study also provides knowledge for the development of advanced anticancer drug delivery.

Design of smart nanogels that respond to physiologically relevant pH values and temperatures.

Herein, we report the synthesis and characterization of monodisperse 'smart' nanogels that exhibit a sharp volume phase transition at physiologically relevant temperatures and pH values. The nanogels were prepared by precipitation copolymerization of N-isopropylacrylamide (NIPAAm) and propylacrylic acid (PAA). Briefly, the reaction was performed using a PAA feed of between 0 and 10 mol% in the presence of a crosslinker at 70 degrees C. The size of the nanogel particles was determined as a function of pH and temperature using dynamic light scattering (DLS). At room temperature, the NIPAAm-PAA nanogels were discrete, spherical structures with diameters ranging from 200 to 250 nm. The hydrodynamic diameter of the nanogels decreased to ca. 100-150 nm when the solution temperature was increased to 37 degrees C. At 37 degrees C, when the pKa was below that of the NIPAAm-PAA (ca. 6.0), the gels collapsed and aggregated. However, at 37 degrees C and a physiological pH of 7.4, the nanogels did not fully collapse due to the charge-charge repulsion derived from the ionized carboxyl groups of the PAA. Similar phase transition behavior was observed with the corresponding linear copolymers. Thus, such nanogel particles could be useful for releasing drugs in regions of local acidosis, including sites of infection, tumors, ischemia, and intracellular endosomes.

A nanopatterned cell-seeded cardiac patch prevents electro-uncoupling and improves the therapeutic efficacy of cardiac repair.

The heart is an extremely sophisticated organ with nanoscale anisotropic structure, contractility and electro-conductivity; however, few studies have addressed the influence of cardiac anisotropy on cell transplantation for myocardial repair. Here, we hypothesized that a graft's anisotropy of myofiber orientation determines the mechano-electrical characteristics and the therapeutic efficacy. We developed aligned- and random-orientated nanofibrous electrospun patches (aEP and rEP, respectively) with or without seeding of cardiomyocytes (CMs) and endothelial cells (ECs) to test this hypothesis. Atomic force microscopy showed a better beating frequency and amplitude of CMs when cultured on aEP than that from cells cultured on rEP. For the in vivo test, a total of 66 rats were divided into six groups: sham, myocardial infarction (MI), MI + aEP, MI + rEP, MI + CM-EC/aEP and MI + CM-EC/rEP (n ≥ 10 for each group). Implantation of aEP or rEP provided mechanical support and thus retarded functional aggravation at 56 days after MI. Importantly, CM-EC/aEP implantation further improved therapeutic outcomes, while cardiac deterioration occurred on the CM-EC/rEP group. Similar results were shown by hemodynamic and infarct size examination. Another independent in vivo study was performed and electrocardiography and optical mapping demonstrated that there were more ectopic activities and defective electro-coupling after CM-EC/rEP implantation, which worsened cardiac functions. Together these results provide comprehensive functional characterizations and demonstrate the therapeutic efficacy of a nanopatterned anisotropic cardiac patch. Importantly, the study confirms the significance of cardiac anisotropy recapitulation in myocardial tissue engineering, which is valuable for the future development of translational nanomedicine.

Comprehensive characterizations of nanoparticle biodistribution following systemic injection in mice.

Various nanoparticle (NP) properties such as shape and surface charge have been studied in an attempt to enhance the efficacy of NPs in biomedical applications. When trying to undermine the precise biodistribution of NPs within the target organs, the analytical method becomes the determining factor in measuring the precise quantity of distributed NPs. High performance liquid chromatography (HPLC) represents a more powerful tool in quantifying NP biodistribution compared to conventional analytical methods such as an in vivo imaging system (IVIS). This, in part, is due to better curve linearity offered by HPLC than IVIS. Furthermore, HPLC enables us to fully analyze each gram of NPs present in the organs without compromising the signals and the depth-related sensitivity as is the case in IVIS measurements. In addition, we found that changing physiological conditions improved large NP (200-500 nm) distribution in brain tissue. These results reveal the importance of selecting analytic tools and physiological environment when characterizing NP biodistribution for future nanoscale toxicology, therapeutics and diagnostics.

A photoinduced nanoparticle separation in microchannels via pH-sensitive surface traps.

A microfluidic surface trap was developed for capturing pH-sensitive nanoparticles via a photoinitiated proton-releasing reaction of o-nitrobenzaldehyde (o-NBA) that reduces the solution pH in microchannels. The surface trap and nanoparticles were both modified with a pH-responsive polymer-poly(N-isorpopylacylamide-co-propylacrylic acid), P(NIPAAm-co-PAA). The o-NBA-coated microchannel walls demonstrated rapid proton release upon UV light irradiation, allowing the buffered solution pH in the microchannel to decrease from 7.4 to 4.5 in 60 s. The low solution pH switched the polymer-modified surfaces to be more hydrophobic, which enabled the capture of the pH-sensitive nanobeads onto the trap. When a photomask was utilized to limit the UV irradiation to a specific channel region, we were able to restrict the particle separation to only the exposed region. Via control of the UV irradiation, this technique enables not only prompt pH changes within the channel but also the capture of target molecules at specific channel locations.

Stimuli-responsive polymers: biomedical applications and challenges for clinical translation.

Over the past 25 years many interesting biomedical uses have been proposed for stimuli-responsive polymers, including uses in diagnostics, drug delivery, tissue engineering (regenerative medicine), and cell culture. This article briefly overviews the field of stimuli-responsive polymers and describes some of the most successful biomedical applications to date of such "smart" polymers. Other interesting potential applications are also discussed. The major barriers to future clinical translation of smart polymers are also critically discussed.

Multiplexed enrichment and detection of malarial biomarkers using a stimuli-responsive iron oxide and gold nanoparticle reagent system.

There is a need for simple yet robust biomarker and antigen purification and enrichment strategies that are compatible with current rapid diagnostic modalities. Here, a stimuli-responsive nanoparticle system is presented for multiplexed magneto-enrichment and non-instrumented lateral flow strip detection of model antigens from spiked pooled plasma. The integrated reagent system allows purification and enrichment of the gold-labeled biomarker half-sandwich that can be applied directly to lateral flow test strips. A linear diblock copolymer with a thermally responsive poly(N-isopropylacrylamide) (pNIPAm) segment and a gold-binding block composed of NIPAm-co-N,N-dimethylaminoethylacrylamide was prepared by reversible addition-fragmentation chain transfer polymerization. The diblock copolymer was used to functionalize gold nanoparticles (AuNPs), with subsequent bioconjugation to yield thermally responsive pNIPAm-AuNPs that were co-decorated with streptavidin. These AuNPs efficiently complexed biotinylated capture antibody reagents that were bound to picomolar quantities of pan-aldolase and Plasmodium falciparum histidine-rich protein 2 (PfHRP2) in spiked pooled plasma samples. The gold-labeled biomarker half-sandwich was then purified and enriched using 10 nm thermally responsive magnetic nanoparticles that were similarly decorated with pNIPAm. When a thermal stimulus was applied in conjunction with a magnetic field, coaggregation of the AuNP half-sandwiches with the pNIPAm-coated iron oxide nanoparticles created large aggregates that were efficiently magnetophoresed and separated from bulk serum. The purified biomarkers from a spiked pooled plasma sample could be concentrated 50-fold into a small volume and applied directly to a commercial multiplexed lateral flow strip to dramatically improve the signal-to-noise ratio and test sensitivity.

In situ supramolecular assembly and modular modification of hyaluronic acid hydrogels for 3D cellular engineering.

A facile in situ supramolecular assembly and modular modification of biocompatible hydrogels were demonstrated using cucurbit[6]uril-conjugated hyaluronic acid (CB[6]-HA), diaminohexane-conjugated HA (DAH-HA), and tags-CB[6] for cellular engineering applications. The strong and selective host-guest interaction between CB[6] and DAH made possible the supramolecular assembly of CB[6]/DAH-HA hydrogels in the presence of cells. Then, the 3D environment of CB[6]/DAH-HA hydrogels was modularly modified by the simple treatment with various multifunctional tags-CB[6]. Furthermore, we could confirm in situ formation of CB[6]/DAH-HA hydrogels under the skin of nude mice by sequential subcutaneous injections of CB[6]-HA and DAH-HA solutions. The fluorescence of modularly modified fluorescein isothiocyanate (FITC)-CB[6] in the hydrogels was maintained for up to 11 days, reflecting the feasibility to deliver the proper cues for cellular proliferation and differentiation in the body. Taken together, CB[6]/DAH-HA hydrogels might be successfully exploited as a 3D artificial extracellular matrix for various tissue engineering applications.

Biosafety of non-surface modified carbon nanocapsules as a potential alternative to carbon nanotubes for drug delivery purposes.

BACKGROUND: Carbon nanotubes (CNTs) have found wide success in circuitry, photovoltaics, and other applications. In contrast, several hurdles exist in using CNTs towards applications in drug delivery. Raw, non-modified CNTs are widely known for their toxicity. As such, many have attempted to reduce CNT toxicity for intravenous drug delivery purposes by post-process surface modification. Alternatively, a novel sphere-like carbon nanocapsule (CNC) developed by the arc-discharge method holds similar electric and thermal conductivities, as well as high strength. This study investigated the systemic toxicity and biocompatibility of different non-surface modified carbon nanomaterials in mice, including multi-walled carbon nanotubes (MWCNTs), single-walled carbon nanotubes (SWCNTs), carbon nanocapsules (CNCs), and C 60 fullerene (C 60). The retention of the nanomaterials and systemic effects after intravenous injections were studied. METHODOLOGY AND PRINCIPAL FINDINGS: MWCNTs, SWCNTs, CNCs, and C 60 were injected intravenously into FVB mice and then sacrificed for tissue section examination. Inflammatory cytokine levels were evaluated with ELISA. Mice receiving injection of MWCNTs or SWCNTs at 50 µg/g b.w. died while C 60 injected group survived at a 50% rate. Surprisingly, mortality rate of mice injected with CNCs was only at 10%. Tissue sections revealed that most carbon nanomaterials retained in the lung. Furthermore, serum and lung-tissue cytokine levels did not reveal any inflammatory response compared to those in mice receiving normal saline injection. CONCLUSION: Carbon nanocapsules are more biocompatible than other carbon nanomaterials and are more suitable for intravenous drug delivery. These results indicate potential biomedical use of non-surface modified carbon allotrope. Additionally, functionalization of the carbon nanocapsules could further enhance dispersion and biocompatibility for intravenous injection.

Facilitated intracellular delivery of peptide-guided nanoparticles in tumor tissues.

Macromolecular nanoparticles can extravasate and accumulate within tumor tissues via the passive targeting system, reflecting enhanced permeability and the retention effect. However, the unsatisfactory tumor therapeutic efficacy of the passive-targeting system, attributable to the retention of extravasated nanoparticles in the vicinity of tumor vessels, argues that a new system that facilitates intracellular delivery of nanoparticles within tumors is needed. Here, we developed hydrophobically modified glycol chitosan (HGC) nanoparticles conjugated with interleukin-4 receptor (IL-4R) binding peptides, termed I4R, and tested them in mice bearing IL-4R-positive tumors. These HGC-I4R nanoparticles exhibited enhanced IL-4R-dependent cellular uptake in tumors compared to nonconjugated nanoparticles, leading to better therapeutic and imaging efficacy. We conclude that I4R facilitates and enhances cellular uptake of nanoparticles in tumor tissues. This study suggests that the intracelluar uptake of nanoparticles in tumors is an essential factor to consider in designing nanoparticles for tumor-targeted drug delivery and imaging.