A composite hydrogel platform for the dissection of tumor cell migration at tissue interfaces

Glioblastoma multiforme (GBM), the most prevalent primary brain cancer, is characterized by diffuse infiltration of tumor cells into brain tissue, which severely complicates surgical resection and contributes to tumor recurrence. The most rapid mode of tissue infiltration occurs along blood vessels or white matter tracts, which represent topological interfaces thought to serve as "tracks" that speed cell migration. Despite this observation, the field lacks experimental paradigms that capture key features of these tissue interfaces and allow reductionist dissection of mechanisms of this interfacial motility. To address this need, we developed a culture system in which tumor cells are sandwiched between a fibronectin-coated ventral surface representing vascular basement membrane and a dorsal hyaluronic acid (HA) surface representing brain parenchyma. We find that inclusion of the dorsal HA surface induces formation of adhesive complexes and significantly slows cell migration relative to a free fibronectin-coated surface. This retardation is amplified by inclusion of integrin binding peptides in the dorsal layer and expression of CD44, suggesting that the dorsal surface slows migration through biochemically specific mechanisms rather than simple steric hindrance. Moreover, both the reduction in migration speed and assembly of dorsal adhesions depend on myosin activation and the stiffness of the ventral layer, implying that mechanochemical feedback directed by the ventral layer can influence adhesive signaling at the dorsal surface.

Protein imprinting in polyacrylamide-based gels

Protein imprinting in hydrogels is a method to produce materials capable of selective recognition and capture of a target protein. Here we report on the imprinting of fluorescently-labeled maltose binding protein (MBP) in acrylamide (AAm)/N-isopropylacrylamide (NIPAm) hydrogels. The targeting efficiency and selectivity of protein recognition is usually characterized by the imprinting factor, which in the simplest case is the ratio of protein uptake in an imprinted film divided by the uptake by the corresponding non-imprinted film. Our objective in this work is to study the dynamics of protein binding and elution in imprinted and non-imprinted films to elucidate the processes that control protein recognition. Protein elution from imprinted and non-imprinted films suggests that imprinting results in sites with a distribution of binding energies, and that only a relatively small fraction of these sites exhibit strong binding.

Accelerated cell-sheet recovery from a surface successively grafted with polyacrylamide and poly(N-isopropylacrylamide)

A double polymeric nanolayer consisting of poly(N-isopropylacrylamide) (PIPAAm) and hydrophilic polyacrylamide (PAAm) was deposited on tissue culture polystyrene (TCPS) surfaces using electron beam irradiation to form a new temperature-responsive cell culture surface in which the basal hydrophilic PAAm component in the double polymeric layer promotes the hydration of the upper PIPAAm layer and induces rapid cell detachment compared to a conventional temperature-responsive cell culture surface, PIPAAm-grafted TCPS (PIPAAm-TCPS). Take-off angle-dependent X-ray photoelectron spectroscopy spectral analysis demonstrated that the grafted PIPAAm and PAAm components were located in the upper and basal regions of the double polymeric layer, respectively, suggesting that the double polymeric layer forms an inter-penetrating-network-like structure with PAAm at the basal portion of the PIPAAm grafted chains. The wettability of the temperature-responsive cell culture surfaces with the double polymeric layer tended to be more hydrophilic, with an increase in the basal PAAm graft density at a constant PIPAAm graft density. However, when the graft densities of the upper PIPAAm and basal PAAm were optimized, the resulting temperature-responsive cell culture surface with the double polymeric layer exhibited rapid cell detachment while maintaining cell adhesive character comparable to that of PIPAAm-TCPS. The cell adhesive character was altered from cell-adhesive to cell-repellent with increasing PAAm or PIPAAm graft density. The cell adhesive character of the temperature-responsive cell culture surfaces was relatively consistent with their contact angles. These results strongly suggest that the basal PAAm surface properties affect the degree of hydration and dehydration of the subsequently grafted PIPAAm. In addition, the roles of the hydrophilic component in accelerating cell detachment are further discussed in terms of the mobility of the grafted PIPAAm chains. Applications of this insight might be useful for designing temperature-responsive cell culture surfaces for achieving efficient cell culture and quick target cell detachment.

Effects of anionic polyacrylamide products on gill histopathology in juvenile rainbow trout (Oncorhynchus mykiss)

Anionic polyacrylamide (PAM) products are commonly used to remove suspended materials from turbid waters and to help mitigate soil erosion. In the present study, juvenile rainbow trout (Oncorhynchus mykiss) were exposed to 3 mg/L to 300 mg/L of 10 commercially available PAM products (Clearflow Water Lynx Polymer Log and Clearflow Soil Lynx Granular Polymer; Clearflow Enviro Systems Group), and gill histological parameters were measured following either 7 d or 30 d of polymer exposure. A cationic polymer product (≤0.38 mg/L MagnaFloc 368; Ciba Specialty Chemical) was also tested for comparison. Mild gill lesions were observed in fish exposed to polymer products. Lamellar fusion, interlamellar hyperplasia, epithelial lifting, mucous cell metaplasia, and cell counts of epithelial swelling and necrosis/apoptosis were minimal in fish exposed to environmentally relevant concentrations of anionic polymer (≤30 mg/L). Gill morphology was largely unaffected by exposure to concentrations up to 300 mg/L of many PAM products. Several anionic polymer products noticeably affected gill tissue by increasing epithelial hypertrophy, interlamellar hyperplasia, mucous cell metaplasia, and the frequency of necrotic cells. The severity of the lesions lessened with time, suggesting that fish may have experienced a short-term irritant effect. Similar levels of gill pathology were frequently observed in fish exposed to cationic polymer MagnaFloc 368 despite the concentration being 1000-fold lower than that of the PAM products. These observations highlight the increased toxicity of cationic polymers to aquatic life compared with anionic PAMs.

Biomimetic alginate/polyacrylamide porous scaffold supports human mesenchymal stem cell proliferation and chondrogenesis

We describe the development of alginate/polyacrylamide (ALG/PAAm) porous hydrogels based on interpenetrating polymer network structure for human mesenchymal stem cell proliferation and chondrogenesis. Three ALG/PAAm hydrogels at molar ratios of 10/90, 20/80, and 30/70 were prepared and characterized with enhanced elastic and rubbery mechanical properties, which are similar to native human cartilage tissues. Their elasticity and swelling properties were also studied under different physiological pH conditions. Finally, in vitro tests demonstrated that human mesenchymal stem cells could proliferate on the as-synthesized hydrogels with improved alkaline phosphatase activities. These results suggest that ALG/PAAm hydrogels may be a promising biomaterial for cartilage tissue engineering.

Biodegradation of polyacrylamide by anaerobic digestion under mesophilic condition and its performance in actual dewatered sludge system

Polyacrylamide (PAM) used in sludge dewatering widely exists in high-solid anaerobic digestion. Degradation of polyacrylamide accompanied with accumulation of its toxic monomer is important to disposition of biogas residues. The potential of anaerobic digestion activity in microbial utilization of PAM was investigated in this study. The results indicated that the utilization rate of PAM (as nitrogen source) was influenced by accumulation of ammonia, while cumulative removal of amide group was accorded with zeroth order reaction in actual dewatered system. The adjoining amide group can combined into ether group after biodegradation. PAM can be broken down in different position of its carbon chain backbone. In actual sludge system, the hydrolytic PAM was liable to combined tyrosine-rich protein to form colloid complex, and then consumed as carbon source to form monomer when easily degradable organics were exhausted. The accumulation of acrylamide was leveled off ultimately, accompanied with the yield of methane.

Polyacrylamide application versus forest residue mulching for reducing post-fire runoff and soil erosion

For several years now, forest fires have been known to increase overland flow and soil erosion. However, mitigation of these effects has been little studied, especially outside the USA. This study aimed to quantify the effectiveness of two so-called emergency treatments to reduce post-fire runoff and soil losses at the microplot scale in a eucalyptus plantation in north-central Portugal. The treatments involved the application of chopped eucalyptus bark mulch at a rate of 10-12 Mg ha(-1), and surface application of a dry, granular, anionic polyacrylamide (PAM) at a rate of 50 kg ha(-1). During the first year after a wildfire in 2010, 1419 mm of rainfall produced, on average, 785 mm of overland flow in the untreated plots and 8.4 Mg ha(-1) of soil losses. Mulching reduced these two figures significantly, by an average 52 and 93%, respectively. In contrast, the PAM-treated plots did not differ from the control plots, despite slightly lower runoff but higher soil erosion figures. When compared to the control plots, mean key factors for runoff and soil erosion were different in the case of the mulched but not the PAM plots. Notably, the plots on the lower half of the slope registered bigger runoff and erosion figures than those on the upper half of the slope. This could be explained by differences in fire intensity and, ultimately, in pre-fire standing biomass.

Micropatterning hydroxy-PAAm hydrogels and Sylgard 184 silicone elastomers with tunable elastic moduli

This protocol describes a simple method to deposit protein micropatterns over a wide range of culture substrate stiffness (three orders of magnitude) by using two complementary polymeric substrates. In the first part, we introduce a novel polyacrylamide hydrogel, called hydroxy-polyacrylamide (PAAm), that permits to surmount the intrinsically nonadhesive properties of polyacrylamide with minimal requirements in cost or expertize. We present a protocol for tuning easily the rigidity of "soft" hydroxy-PAAm hydrogels between ~0.5 and 50 kPa and a micropatterning method to locally deposit protein micropatterns on these hydrogels. In a second part, we describe a protocol for tuning the rigidity of "stiff" silicone elastomers between ~100 and 1000 kPa and printing efficiently proteins from the extracellular matrix. Finally, we investigate the effect of the matrix rigidity on the nucleus of primary endothelial cells by tuning the rigidity of both polymeric substrates. We envision that the complementarity of these two polymeric substrates, combined with an efficient microprinting technique, can be further developed in the future as a powerful mechanobiology platform to investigate in vitro the effect of mechanotransduction cues on cellular functions, gene expression, and stem cell differentiation.

One-dimensional SDS-polyacrylamide gel electrophoresis (1D SDS-PAGE)

This protocol describes a denaturing polyacrylamide gel system utilizing sodium dodecyl sulfate (SDS) to separate protein molecules based on size as first described by Laemmli (1970). SDS-PAGE can be used to monitor protein purifications, check the purity of samples, and to estimate molecular weights for unknown proteins.

In situ formation of silver nanoparticles in linear and branched polyelectrolyte matrices using various reducing agents

Silver nanoparticles were synthesized in linear and branched polyelectrolyte matrices using different reductants and distinct synthesis conditions. The effect of the host hydrolyzed linear polyacrylamide and star-like copolymers dextran-graft-polyacrylamide of various compactness, the nature of the reductant, and temperature were studied on in situ synthesis of silver sols. The related nanosystems were analyzed by high-resolution transmission electron microscopy and UV-vis absorption spectrophotometry. It was established that the internal structure of the polymer matrix as well as the nature of the reductant determines the process of the silver nanoparticle formation. Specifically, the branched polymer matrices were much more efficient than the linear ones for stable nanosystem preparation.

Performance of a novel sieving matrix of poly(vinyl alcohol)/acrylamide copolymer in electrophoretic separations of high molecular weight proteins from red cell membrane

The analysis of high molecular weight (HMW) proteins from complex mixtures is still a challenge in proteomics. This work introduces a novel hydrogel obtained by the copolymerization of an allyl-PVA derivative with acrylamide and bisacrylamide and applies this matrix to the electrophoretic separation of HMW proteins. By inducing gelation of polyacrylamide in the presence of variable amounts of allyl-PVA, it is possible to control and vary the average gel porosity. This gel is easy to produce and handle and offers the advantage of being highly mechanically resistant and macroporous. The new matrix was tested in mono-dimensional separations of complex protein mixtures extracted from red cell membranes with different detergents. The improved performance of this macroporous matrix allowed to identify new proteins by MS and immunoblot analysis using specific antibodies. In particular, the resolution of proteins ranging in size between 97 and 279 kDa was greatly improved here compared to standard polyacrylamide gels, suggesting that this matrix can be a useful tool in routine analysis of HMW proteins in cell biology.

Check dam and polyacrylamide performance under simulated stormwater runoff

High levels of turbidity and fine suspended sediments are often found in stormwater discharges from construction sites even when best management practices (BMPs) for sediment control are in place. This study evaluated turbidity reduction by three check dam types: 1) rock check dam representing a standard BMP, 2) excelsior wattle representing a fiber check dam (FCD), and 3) rock check dam wrapped with excelsior erosion control blanket (rock + excelsior ECB) representing an alternative FCD. Three check dams (all same type) were installed in a lined, 24-m ditch on a 5-7% slope and three consecutive simulated stormwater flows were run in the ditch. Additional tests were performed by adding granular polyacrylamide (PAM) on the check dams in the same manner using two sediment sources differing in clay content. Without PAM treatment, significantly higher effluent turbidity (>900 nephelometric turbidity units (NTU)) exited the ditch with rock check dams than with excelsior wattles or rock + excelsior ECBs (<440 NTU). The extent of sediment deposition between the check dam types was in the order of excelsior wattle > rock + excelsior ECB > rock check dam, indicating better water pooling behind the wattle. The PAM treatment reduced turbidity substantially (>75% relative to no PAM treatment) for all check dam types and it was very effective in excelsior wattles (<57 NTU) and rock + excelsior ECBs (<90 NTU) even during the third storm event. This study demonstrates that the passive treatment of runoff with PAM on FCDs (or rock + excelsior ECB) in construction site ditches can be very effective for sediment retention and turbidity reduction.

Role of integrated cancer nanomedicine in overcoming drug resistance

Cancer remains a major killer of mankind. Failure of conventional chemotherapy has resulted in recurrence and development of virulent multi drug resistant (MDR) phenotypes adding to the complexity and diversity of this deadly disease. Apart from displaying classical physiological abnormalities and aberrant blood flow behavior, MDR cancers exhibit several distinctive features such as higher apoptotic threshold, aerobic glycolysis, regions of hypoxia, and elevated activity of drug-efflux transporters. MDR transporters play a pivotal role in protecting the cancer stem cells (CSCs) from chemotherapy. It is speculated that CSCs are instrumental in reviving tumors after the chemo and radiotherapy. In this regard, multifunctional nanoparticles that can integrate various key components such as drugs, genes, imaging agents and targeting ligands using unique delivery platforms would be more efficient in treating MDR cancers. This review presents some of the important principles involved in development of MDR and novel methods of treating cancers using multifunctional-targeted nanoparticles. Illustrative examples of nanoparticles engineered for drug/gene combination delivery and stimuli responsive nanoparticle systems for cancer therapy are also discussed.

Commercial versus synthesized polymers for soil erosion control and growth of Chinese cabbage

Soil erosion leads to environmental degradation and reduces soil productivity. The use of anionic polyacrylamide (PAM) and synthesized biopolymer (BP) using lignin, corn starch, acrylamide, and acrylic acid were tested to evaluate soil erosion, water quality, and growth of Chinese cabbage (Brassica campestris L.). Each treatment of PAM and BP was applied at 200 kg ha^-1 to loamy sand soil and subjected to a slope of 36% with a 20 mm h^-1 simulated rainfall. Application of BP decreased soil pH compared to the untreated check (CK); however, the soil pH was not altered with PAM. The decrease in pH might most likely be due to availability of anionic sites to be protonated on soils having pH >6 and soil buffering capacity. Both PAM and BP applications may not induce eutrophication with stable levels of total contents of N and P. With PAM and BP, the average values of suspended soil (SS) and turbidity were reduced by up to 96.0 and 99.9%, respectively, compared to CK. Reduction of SS can be attributed to increasing soil stability and shear strength by clay flocculation. There was no toxicity effects resulting from germination tests and the dry weight was increased by 17.7% (vs. CK) when PAM and BP were applied. These results are attributed to increases in water retention and plant-available water. The use of polymeric soil amendments is an environmentally friendly way to mitigate soil erosion and nonpoint source pollution.

Controllable immobilization of polyacrylamide onto glass slide: synthesis and characterization

A novel route was introduced to synthesize dense polyacrylamide (PAM) onto the glass slide surface. To investigate the surface chemistry of the PAM on the glass slides, X-ray photoelectron spectroscopy (XPS) was utilized to obtain detailed chemical state information on the PAM layer constituents. The XPS peak data were consistent with the presented model of the PAM on the glass slide surface. Scanning electron microscopy and atomic force microscope data indicated the presence of PAM on the glass slides, which consist of nodules. The results showed that PAM was successfully immobilized onto glass slides with a two-tier structure under aqueous condition and a monolayer structure under anhydrous condition. Compared with those under aqueous condition, the controllability of the molecular layer on glass slides and the reproducibility under anhydrous condition were much better, which makes anhydrous condition an advisable condition for the study of the reaction mechanisms of glass slides modified by PAM.

Isolation and study of the properties of an interferon-like inhibitor of viruses from normal human blood serum

A protein with a molecular weight of 17,400 daltons and an isoelectric point at pH 4.9 has been isolated from the blood serum of healthy donors by successive ion-exchange chromatography of QAE-Sephadex A-50, affinity chromatography on DNA-cellulose, and polyacrylamide gel electrophoresis, in the presence of sodium dodecyl sulfate. The protein isolated, like interferon, suppresses the development of the cytopathogenic action of the viruses of vesicular stomatitis and murine ecephalomyocarditis in cultures of human cells of the L-41 and M-19 lines. The amino acid composition of the protein isolated differs from those of various fractions of human interferons.