Using synthetic genome readers/regulators to interrogate chromatin processes: A brief review

Aberrant gene expression underlies numerous human ailments. Hence, developing small molecules to target and remedy dysfunctional gene regulation has been a long-standing goal at the interface of chemistry and medicine. A major challenge for designing small molecule therapeutics aimed at targeting desired genomic loci is the minimization of widescale disruption of genomic functions. To address this challenge, we rationally design polyamide-based multi-functional molecules, i.e., Synthetic Genome Readers/Regulators (SynGRs), which, by design, target distinct sequences in the genome. Herein, we briefly review how SynGRs access chromatin-bound and chromatin-free genomic sites, then highlight the methods for the study of chromatin processes using SynGRs on positioned nucleosomes in vitro or disease-causing repressive genomic loci in vivo.

Changes in carbohydrate metabolism and soil microorganisms under the stress of polyamide and polyethylene nanoplastics during rice (Oryza sativa L.) growth

Nanoplastics (NPs) presence in agricultural soils can affect plant growth and impact the quality of agricultural products. To investigate the effect of polyamide (PA) NPs and polyethylene (PE) NPs on carbohydrate metabolism and soil microorganisms during rice growth, rice seedlings were exposed to soil containing 2 g/kg of 100 nm PA or 100 nm PE powder for 33 d. The results revealed that 100 nm PE reduced shoot length and dry weight of rice by 4.14 % and 15.68 %, respectively. Analyzing the expression of hexokinase-2 (HXK), phosphofructokinase-1 (PFK), pyruvate kinase (PK) and isocitrate dehydrogenase (IDH), which are four genes related to carbohydrate metabolism, 100 nm PA decreased the expression of PFK and increased the expression of PK and IDH. 100 nm PE increased the expression of HXK, PFK, PK, and IDH. The results of soil microorganisms showed that 100 nm PA significantly effects on 3 bacterial phyla (Bacteroidota, Deinococcota, and Desulfobacterota), whereas 100 nm PE significantly effects on phylum Rozellomycota, class Umbelopsidomycetes, and an unclassified Firmicutes. Our study provides direct evidence of the negative effects of PA and PE on rice, which may be important for assessing the risk of NPs on agroecosystems.

Development of multifunctional pyrrole-imidazole polyamides that increase hepatocyte growth factor and suppress transforming growth factor-β1

PURPOSE

The DNA recognition peptide compounds pyrrole-imidazole (PI) polyamides bind to the minor groove and can block the binding of transcription factors to target sequences. To develop more PI polyamides as potential treatments for fibrotic diseases, including chronic renal failure, we developed multifunctional PI polyamides that increase hepatocyte growth factor (HGF) and decrease transforming growth factor (TGF)-β1.

METHODS

We designed seven PI polyamides (HGF-1 to HGF-7) that bind to the chicken ovalbumin upstream promoter transcription factor-1 (COUP-TF1) binding site of the HGF promoter sequence. We selected PI polyamides that increase HGF and suppress TGF-β1 in human dermal fibroblasts (HDFs).

FINDINGS

Gel shift assays showed that HGF-2 and HGF-4 bound the appropriate dsDNAs. HGF-2 and HGF-4 significantly inhibited the TGF-β1 mRNA expression in HDFs stimulated by phorbol 12-myristate 13-acetate. HGF-2 and HGF-4 significantly inhibited the TGF-β1 protein expression in HDFs with siRNA targeting HGF, indicating that HGF-2 and HGF-4 directly inhibited the expression of TGF-β1.

CONCLUSION

The designed and synthetic HGF PI polyamides targeting the HGF promoter, which increased the expression of HGF and suppressed the expression of TGF-β, will be a potential practical medicine for fibrotic diseases, including progressive renal diseases.

Effect of florfenicol on Piscirickettsia salmonis biofilm formed in materials used in salmonid nets, nylon and high-density polyethylene

Piscirickettsiosis is the most prevalent bacterial disease affecting seawater salmon in Chilean salmon industry. Antibiotic therapy is the first alternative to counteract infections caused by Piscirickettsia salmonis. The presence of bacterial biofilms on materials commonly used in salmon farming may be critical for understanding the bacterial persistence in the environment. In the present study, the CDC Biofilm Reactor® was used to investigate the effect of sub- and over-MIC of florfenicol on both the pre-formed biofilm and the biofilm formation by P. salmonis under the antibiotic stimuli on Nylon and high-density polyethylene (HDPE) surfaces. This study demonstrated that FLO, at sub- and over-MIC doses, decreases biofilm-embedded live bacteria in the P. salmonis isolates evaluated. However, it was shown that in the P. salmonis Ps007 strain the presence of sub-MIC of FLO reduced its biofilm formation on HDPE surfaces; however, biofilm persists on Nylon surfaces. These results demonstrated that P. salmonis isolates behave differently against FLO and also, depending on the surface materials. Therefore, it remains a challenge to find an effective strategy to control the biofilm formation of P. salmonis, and certainly other marine pathogens that affect the sustainability of the Chilean salmon industry.

A cyclic pyrrole-imidazole polyamide reduces pathogenic RNA in CAG/CTG triplet repeat neurological disease models

Expansion of CAG and CTG (CWG) triplet repeats causes several inherited neurological diseases. The CWG repeat diseases are thought to involve complex pathogenic mechanisms through expanded CWG repeat-derived RNAs in a noncoding region and polypeptides in a coding region, respectively. However, an effective therapeutic approach has not been established for the CWG repeat diseases. Here, we show that a CWG repeat DNA-targeting compound, cyclic pyrrole-imidazole polyamide (CWG-cPIP), suppressed the pathogenesis of coding and noncoding CWG repeat diseases. CWG-cPIP bound to the hairpin form of mismatched CWG DNA, interfering with transcription elongation by RNA polymerase through a preferential activity toward repeat-expanded DNA. We found that CWG-cPIP selectively inhibited pathogenic mRNA transcripts from expanded CWG repeats, reducing CUG RNA foci and polyglutamine accumulation in cells from patients with myotonic dystrophy type 1 (DM1) and Huntington's disease (HD). Treatment with CWG-cPIP ameliorated behavioral deficits in adeno-associated virus-mediated CWG repeat-expressing mice and in a genetic mouse model of HD, without cytotoxicity or off-target effects. Together, we present a candidate compound that targets expanded CWG repeat DNA independently of its genomic location and reduces both pathogenic RNA and protein levels. CWG-cPIP may be used for the treatment of CWG repeat diseases and improvement of clinical outcomes.

Anticancer Activities of DNA-Alkylating Pyrrole-Imidazole Polyamide Analogs Targeting RUNX Transcription Factors against p53-Mutated Pancreatic Cancer PANC-1 Cells

The runt-related transcription factor (RUNX) family is known to play important roles in the progression of cancer. Conjugate 1, which covalently binds to the RUNX-binding sequences, was reported to inhibit the binding of RUNX proteins to their target sites and suppress cancer growth. Here, we evaluated the anticancer effects of 1 and its analogs 2-4 against p53-mutated PANC-1 pancreatic cancer cells. We found that they possessed different DNA-alkylating properties in vitro. And conjugates 1-3 were shown to have anticancer effects by inducing apoptosis in PANC-1 cells. Furthermore, conjugates 2 and 3 suppressed cancer growth in PANC-1 xenograft mice, with activity equivalent to a 50-fold dose of gemcitabine. Especially, 3 showed the highest alkylation efficiency, specificity, and better anticancer effects against pancreatic cancer than 1 in vivo without significant body weight loss. Our results revealed the potential of our compounds as new candidates for cancer therapy.

Toxic effects of sub-acute microplastic (polyamide) exposure on the accumulation, hematological, and antioxidant responses in crucian carp, Carassius carassius

The purpose of this study is to investigate the impact of microplastics (MPs) on fish and to confirm the toxic effects of MPs on fish, as well as to clarify the standard indicators. MPs are present in a large amount in the aquatic environment and can have various adverse effects on aquatic animals. Crucian carp, Carassius carassius (mean weight, 23.7 ± 1.6 g; mean length, 13.9 ± 1.4 cm), were exposed to PA (Polyamide) concentrations of 0, 4, 8, 16, 32 and 64 mg/L for 2 weeks. The PA accumulation profile in C. carassius decreased from the intestine to the gill to the liver. Hematological parameters such as red blood cell (RBC) counts, hemoglobin (Hb), and hematocrit (Ht) notably decreased at high levels of PA exposure. Plasma components such as calcium, magnesium, glucose, cholesterol, total protein, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) were significantly altered by PA exposure. The activities of superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST) and glutathione (GSH) of liver, gill and intestine significantly increased following PA exposure. The results of this study suggest that MP exposure affects the hematological physiology and antioxidant responses in C. carassius as well as accumulation in specific tissues.

Substitution to hydrophobic linker and formation of host-guest complex enhanced the effect of synthetic transcription factor made of pyrrole-imidazole polyamide

GAA repeat expansion in the first intron of the frataxin (FXN) gene represses the transcription of FXN, and that induces Friedreich's ataxia (FRDA). Pyrrole-imidazole polyamides (PIPs) are the class of oligopeptide that targets double-stranded DNA with sequence selectivity. Previously, bromodomain inhibitors such as JQ1 conjugated with PIPs were reported to selectively increase transcription. Here, we report the synthesis of a compound that increases the transcription of FXN in cells derived from an FRDA patient. The compound was effective in lower (one tenth) concentration than the compound that previously reported. High concentration of the compound is toxic, but toxicity was reduced with a host-guest complex.

Size-dependent effects of microplastics on antibiotic resistance genes fate in wastewater treatment systems: The role of changed surface property and microbial assemblages in a continuous exposure mode

Microplastics (MPs) were continuously transported to wastewater treatment systems and accumulated in sludge constantly, potentially affecting systems function and co-occurrent contaminants fate. However, previous studies were based on acute exposure of MPs, which could not reflect the dynamics of MPs accumulation. Herein, this study firstly raised a more realistic method to evaluate the practical impacts of MPs on systems purification efficiency and antibiotic resistance genes (ARGs) fate. Continuous exposure of MPs did not pose negative effects on nutrients removal, but significantly changed the occurrence patterns of ARGs. ARGs abundances increased by 42.8 % and 54.3 % when exposed to millimeter-size MPs (mm-MPs) polyamide and polyethylene terephthalate, but increased by 31.3 % and 39.4 % to micron-size MPs (μm-MPs), respectively. Thus, mm-MPs posed severer effects on ARGs than μm-MPs. Further, mm-MPs surface properties were obviously altered after long-term exposure (higher specific surface area and O-containing species), which benefited microbes attachment. More importantly, more taxa linkages and changed topological properties (higher average degree and average weight) of co-occurrent network were observed in sludge with mm-MPs than with μm-MPs, as well as totally different potential host bacteria of ARGs. Rough surface of MPs and closer relations between ARGs and bacteria taxa contributed to the propagation of ARGs, which accounted for the observed higher ARGs abundances of mm-MPs. This study demonstrated that long-term accumulation of MPs in wastewater treatment systems affected ARGs fate, and mm-MPs caused severer risk due to their enrichment of ARGs. The results would promote the understanding of MPs real environmental behavior and influences.

Permanent, Antimicrobial Coating to Rapidly Kill and Prevent Transmission of Bacteria, Fungi, Influenza, and SARS-CoV-2

Microbial adhesion and contamination on shared surfaces can lead to life-threatening infections with serious impacts on public health, economy, and clinical practices. The traditional use of chemical disinfectants for sanitization of surfaces, however, comes with its share of health risks, such as hazardous effects on the eyes, skin, and respiratory tract, carcinogenicity, as well as environmental toxicity. To address this, we have developed a nonleaching quaternary small molecule (QSM)-based sprayable coating which can be fabricated on a wide range of surfaces such as nylon, polyethylene, surgical mask, paper, acrylate, and rubber in a one-step, photocuring technique. This contact-active coating killed pathogenic bacteria and fungi including drug-resistant strains of Staphylococcus aureus and Candida albicans within 15-30 min of contact. QSM coatings withstood multiple washes, highlighting their durability. Interestingly, the coated surfaces exhibited rapid killing of pathogens, leading to the prevention of their transmission upon contact. The coating showed membrane disruption of bacterial cells in fluorescence and electron microscopic investigations. Along with bacteria and fungi, QSM-coated surfaces also showed the complete killing of high loads of influenza (H1N1) and SARS-CoV-2 viruses within 30 min of exposure. To our knowledge, this is the first report of a coating for multipurpose materials applied in high-touch public places, hospital equipment, and clinical consumables, rapidly killing drug-resistant bacteria, fungi, influenza virus, and SARS-CoV-2.

Feeding of Marine Zooplankton on Microplastic Fibers

The goal of our study was to examine the effects of low abundances of nylon fibers on feeding rates of calanoid copepods (Crustacea, Copepoda) and doliolids (Tunicata, Thaliacea) in the presence of diatoms at near environmental concentration levels. In addition, we examined microscopically the fecal pellets produced by copepods and doliolids in the presence of fibers. Adult females of the calanoid Eucalanus pileatus and early gonozooids of Dolioletta gegenbauri (both of similar dry weight) cleared the diatom Rhizosolenia alata at similar rates. Nylon fibers were cleared at higher rates by Dolioletta gegenbauri compared to Eucalanus pileatus. Examination of fecal pellets revealed that copepods and doliolids could ingest the about 300 µm long fibers. The latter also ingested the occasionally occurring fibers of > 1 mm length. It appears that in seawater fiber abundances of about seven fibers ml^-1 did not have a negative effect on feeding of either E. pileatus or D. gegenbauri. As doliolids and copepods remove plastic fibers from seawater by packing them into their pellets, they might play a role in the reduction of microplastic pollution and the microplastic transfer from the water column to the seafloor. Calanoid copepods may limit ingesting fibers by not perceiving them, as compared to doliolids which do not seem to be able to avoid ingesting them.

Silencing of HMGA2 by siRNA Loaded Methotrexate Functionalized Polyamidoamine Dendrimer for Human Breast Cancer Cell Therapy

The transcription factor high mobility group protein A2 (HMGA2) plays an important role in the pathogenesis of some cancers including breast cancer. Polyamidoamine dendrimer generation 4 is a kind of highly branched polymeric nanoparticle with surface charge and highest density peripheral groups that allow ligands or therapeutic agents to attach it, thereby facilitating target delivery. Here, methotrexate (MTX)- modified polyamidoamine dendrimer generation 4 (G4) (G4/MTX) was generated to deliver specific small interface RNA (siRNA) for suppressing HMGA2 expression and the consequent effects on folate receptor (FR) expressing human breast cancer cell lines (MCF-7, MDA-MB-231). We observed that HMGA2 siRNA was electrostatically adsorbed on the surface of the G4/MTX nanocarrier for constructing a G4/MTX-siRNA nano-complex which was verified by changing the final particle size and zeta potential. The release of MTX and siRNA from synthesized nanocomplexes was found in a time- and pH-dependent manner. We know that MTX targets FR. Interestingly, G4/MTX-siRNA demonstrates significant cellular internalization and gene silencing efficacy when compared to the control. Besides, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay demonstrated selective cell cytotoxicity depending on the folate receptor expressing in a dose-dependent manner. The gene silencing and protein downregulation of HMGA2 by G4/MTX-siRNA was observed and could significantly induce cell apoptosis in MCF-7 and MDA-MB-231 cancer cells compared to the control group. Based on the findings, we suggest that the newly developed G4/MTX-siRNA nano-complex may be a promising strategy to increase apoptosis induction through HMGA2 suppression as a therapeutic target in human breast cancer.

Zinc-Embedded Polyamide Fabrics Inactivate SARS-CoV-2 and Influenza A Virus

Influenza A viruses (IAV) and SARS-CoV-2 can spread via liquid droplets and aerosols. Face masks and other personal protective equipment (PPE) can act as barriers that prevent the spread of these viruses. However, IAV and SARS-CoV-2 are stable for hours on various materials, which makes frequent and correct disposal of these PPE important. Metal ions embedded into PPE may inactivate respiratory viruses, but confounding factors such as adsorption of viruses make measuring and optimizing the inactivation characteristics difficult. Here, we used polyamide 6.6 (PA66) fibers containing embedded zinc ions and systematically investigated if these fibers can adsorb and inactivate SARS-CoV-2 and IAV H1N1 when woven into a fabric. We found that our PA66-based fabric decreased the IAV H1N1 and SARS-CoV-2 titer by approximately 100-fold. Moreover, we found that the zinc content and the virus inactivating property of the fabric remained stable over 50 standardized washes. Overall, these results provide insights into the development of reusable PPE that offer protection against RNA virus spread.

Chemical characterization (LC-MS-ESI), cytotoxic activity and intracellular localization of PAMAM G4 in leukemia cells

Generation 4 of polyamidoamine dendrimer (G4-PAMAM) has several biological effects due to its tridimensional globular structure, repetitive branched amides, tertiary amines, and amino-terminal subunit groups liked to a common core. G4-PAMAM is cytotoxic due to its positive charges. However, its cytotoxicity could increase in cancer cells due to the excessive intracellular negative charges in these cells. Furthermore, this work reports G4-PAMAM chemical structural characterization using UHPLC-QTOF-MS/MS (LC-MS) by electrospray ionization to measure its population according to its positive charges. Additionally, the antiproliferative effects and intracellular localization were explored in the HMC-1 and K-562 cell lines by confocal microscopy. The LC-MS results show that G4-PAMAM generated multivalent mass spectrum values, and its protonated terminal amino groups produced numerous positive charges, which allowed us to determine its exact mass despite having a high molecular weight. Additionally, G4-PAMAM showed antiproliferative activity in the HMC-1 tumor cell line after 24 h (IC50 = 16.97 µM), 48 h (IC50 = 7.02 µM) and 72 h (IC50 = 5.98 µM) and in the K-562 cell line after 24 h (IC50 = 15.14 µM), 48 h (IC50 = 14.18 µM) and 72 h (IC50 = 9.91 µM). Finally, our results showed that the G4-PAMAM dendrimers were located in the cytoplasm and nucleus in both tumor cell lines studied.

Bacterial Biofilms on Polyamide Nanofibers: Factors Influencing Biofilm Formation and Evaluation

Electrospun polyamide (PA) nanofibers have great potential for medical applications (in dermatology as antimicrobial compound carriers or surgical sutures). However, little is known about microbial colonization on these materials. Suitable methods need to be chosen and optimized for the analysis of biofilms formed on nanofibers and the influence of their morphology on biofilm formation. We analyzed 11 PA nanomaterials, both nonfunctionalized and functionalized with AgNO₃, and tested the formation of a biofilm by clinically relevant bacteria (Escherichia coli CCM 4517, Staphylococcus aureus CCM 3953, and Staphylococcus epidermidis CCM 4418). By four different methods, it was confirmed that all of these bacteria attached to the PAs and formed biofilms; however, it was found that the selected method can influence the outcomes. For studying biofilms formed by the selected bacteria, scanning electron microscopy, resazurin staining, and colony-forming unit enumeration provided appropriate and comparable results. The values obtained by crystal violet (CV) staining were misleading due to the binding of the CV dye to the PA structure. In addition, the effect of nanofiber morphology parameters (fiber diameter and air permeability) and AgNO₃ functionalization significantly influenced biofilm maturation. Furthermore, the correlations between air permeability and surface density and fiber diameter were revealed. Based on the statistical analysis, fiber diameter was confirmed as a crucial factor influencing biofilm formation (p ≤ 0.01). The functionalization of PAs with AgNO₃ (from 0.1 wt %) effectively suppressed biofilm formation. The PA functionalized with a concentration of 0.1 wt % AgNO₃ influenced the biofilm equally as nonfunctionalized PA 8% 2 g/m². Therefore, biofilm formation could be affected by the above-mentioned morphology parameters, and ultimately, the risk of infections from contaminated medical devices could be reduced.

Experimental and mathematical characterization of coronary polyamide-12 balloon catheter membranes

The experimental quantification and modeling of the multiaxial mechanical response of polymer membranes of coronary balloon catheters have not yet been carried out. Due to the lack of insights, it is not shown whether isotropic material models can describe the material response of balloon catheter membranes expanded with nominal or higher, supra-nominal pressures. Therefore, for the first time, specimens of commercial polyamide-12 balloon catheters membranes were investigated during uniaxial and biaxial loading scenarios. Furthermore, the influence of kinematic effects on the material response was observed by comparing results from quasi-static and dynamic biaxial extension tests. Novel clamping techniques are described, which allow to test even tiny specimens taken from the balloon membranes. The results of this study reveal the semi-compliant, nonlinear, and viscoelastic character of polyamide-12 balloon catheter membranes. Above nominal pressure, the membranes show a pronounced anisotropic mechanical behavior with a stiffer response in the circumferential direction. The anisotropic feature intensifies with an increasing strain-rate. A modified polynomial model was applied to represent the realistic mechanical response of the balloon catheter membranes during dynamic biaxial extension tests. This study also includes a compact set of constitutive model parameters for the use of the proposed model in future finite element analyses to perform more accurate simulations of expanding balloon catheters.

Phosphonium Modification Leads to Ultrapermeable Antibacterial Polyamide Composite Membranes with Unreduced Thickness

Water transport rate in network membranes is inversely correlated to thickness, thus superior permeance is achievable with ultrathin membranes prepared by complicated methods circumventing nanofilm weakness and defects. Conferring ultrahigh permeance to easily prepared thicker membranes remains challenging. Here, a tetrakis(hydroxymethyl) phosphonium chloride (THPC) monomer is discovered that enables straightforward modification of polyamide composite membranes. Water permeance of the modified membrane is ≈6 times improved, give rising to permeability (permeance × thickness) one magnitude higher than state-of-the-art polymer nanofiltration membranes. Meanwhile, the membrane exhibits good rejection (R_Na2SO4 = 98%) and antibacterial properties under crossflow conditions. THPC modification not only improves membrane hydrophilicity, but also creates additional angstrom-scale channels in polyamide membranes for unimpeded transport of water. This unique mechanism provides a paradigm shift in facile preparation of ultrapermeable membranes with unreduced thickness for clean water and desalination.

Prolonged inhibitory effects against planktonic growth, adherence, and biofilm formation of pathogens causing ventilator-associated pneumonia using a novel polyamide/silver nanoparticle composite-coated endotracheal tube

Microbial cells can rapidly form biofilm on endotracheal tubes (ETT) causing ventilator-associated pneumonia, a serious complication in patients receiving mechanical ventilation. A novel polyamide with a good balance of hydrophilic/hydrophobic moieties was used for the embedment of green-reduction silver nanoparticles (AgNPs) for the composite-coated ETT. The films were conformal with a thickness of ∼ 17 ± 3 µm accommodating high loading of 60 ± 35 nm spherical-shaped AgNPs. The coated ETT resulted in a significant difference in reducing both planktonic growth and microbial adhesion of single and mixed-species cultures, compared with uncoated ETT (p < 0.05). A time-kill assay demonstrated rapid bactericidal effects of the coating on bacterial growth and cell adhesion to ETT surface. Biofilm formation by Pseudomonas aeruginosa and Staphylococcus aureus, commonly encountered pathogens, was inhibited by > 96% after incubation for 72 h. Polyamide/AgNP composite-coated ETT provided a broad-spectrum activity against both Gram-positive and Gram-negative bacteria as well as Candida albicans and prolonged antimicrobial activity.

Contribution of TGF-β1 and Effects of Gene Silencer Pyrrole-Imidazole Polyamides Targeting TGF-β1 in Diabetic Nephropathy

TGF-β1 has been known to induce diabetic nephropathy with renal fibrosis and glomerulosclerosis. DNA-recognized peptide compound pyrrole-imidazole (PI) polyamides as novel biomedicines can strongly bind promoter lesions of target genes to inhibit its transcription. We have developed PI polyamide targeting TGF-β1 for progressive renal diseases. In the present study, we evaluated the contribution of TGF-β1 in the pathogenesis of diabetic nephropathy, and examined the effects of PI polyamide targeting TGF-β1 on the progression of diabetic nephropathy in rats. For in vitro experiments, rat renal mesangial cells were incubated with a high (25 mM) glucose concentration. Diabetic nephropathy was established in vivo in eight-week-old Wistar rats by intravenously administering 60 mg/kg streptozotocin (STZ). We examined the effects of PI polyamide targeting TGF-β1 on phenotype and the growth of mesangial cells, in vitro, and the pathogenesis of diabetic nephropathy in vivo. High glucose significantly increased expression of TGF-β1 mRNA, changed the phenotype to synthetic, and increased growth of mesangial cells. STZ diabetic rats showed increases in urinary excretions of protein and albumin, glomerular and interstitial degenerations, and podocyte injury. Treatment with PI polyamide targeting TGF-β1 twice weekly for three months improved the glomerular and interstitial degenerations by histological evaluation. Treatment with PI polyamide improved podocyte injury by electron microscopy evaluation. These findings suggest that TGF-β1 may be a pivotal factor in the progression of diabetic nephropathy, and PI polyamide targeting TGF-β1 as a practical medicine may improve nephropathy.

KR‑12‑a6 promotes the osteogenic differentiation of human bone marrow mesenchymal stem cells via BMP/SMAD signaling

Considering the increased resistance to antibiotics in the clinic and the ideal antibacterial properties of KR‑12, the effects of KR‑12‑a6, an important analogue of KR‑12, on the osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) were investigated. Osteogenic differentiation‑associated experiments were conducted in hBMSCs, and KR‑12‑a6 was used as an additional stimulating factor during osteogenic induction. Quantitative analysis of alkaline phosphatase (ALP) and alizarin red staining, and reverse transcription‑quantitative PCR analysis of the expression of osteogenesis‑associated genes were performed to determine the effects of KR‑12‑a6 on the osteogenic differentiation of hBMSCs. LDN‑212854 was selected to selectively suppress BMP/SMAD signaling. Western blotting was performed to investigate the underlying mechanisms. The intensity of ALP and alizarin red staining gradually increased with increasing KR‑12‑a6 concentrations. KR‑12‑a6 induced the strongest staining at 40 µg/ml, whereas 60 µg/ml and 80 µg/ml concentrations did not further increase the intensity of staining. The mRNA expression levels of RUNX2 and ALP increased in a dose‑dependent manner as early as 3 days post‑KR‑12‑a6 treatment. The mRNA expression of COL1A1, BSP and BMP2 exhibited significant upregulation from day 7 post‑KR‑12‑a6 treatment. In contrast, the mRNA levels of OSX, OCN and OPN were enhanced dramatically at day 14 following KR‑12‑a6 stimulation. Additionally, KR‑12‑a6 significantly promoted the phosphorylation of Smad1/5. Furthermore, LDN‑212854 suppressed the activation of Smad1/5 and inhibited the upregulation of several osteogenic differentiation‑associated genes in KR‑12‑a6‑treated hBMSCs. KR‑12‑a6 promoted the osteogenic differentiation of hBMSCs via BMP/SMAD signaling.

An investigation of targeted inhibition of transcription factor activity with pyrrole imidazole polyamide (PA) in chronic myeloid leukemia (CML) blast crisis cells

Tyrosine kinase inhibitor (TKI) therapy is the standard treatment for chronic phase (CP)-chronic myeloid leukemia (CML), yet patients in blast crisis (BC) phase of CML are unlikely to respond to TKI therapy. The transcription factor E2F1 is a down-stream target of the tyrosine kinase BCR-ABL1 and is up-regulated in TKI-resistant leukemia stem cells (LSC). Pyrrole imidazole polyamides (PA) are minor groove binders which can be programmed to target DNA sequences in a gene-selective manner. This manuscript describes such an approach with a PA designed to down-regulate E2F1 controlled gene expression by targeting a DNA sequence within 100 base pairs (bp) upstream of the E2F1 consensus sequence. Human BC-CML KCL22 cells were assessed after treatment with PA, TKI or their combination. Our PA inhibited BC-CML cell expansion based on cell density analysis compared to an untreated control after a 48-hour time-course of PA treatment. However, no evidence of cell cycle arrest was observed among BC-CML cells treated with PA, with respect to their no drug control counterparts. Thus, this work demonstrates that PAs are effective in inhibiting E2F1 TF activity which results in a temporal reduction in BC-CML cell number. We envisage that PAs could be used in the future to map genes under E2F1 control in CML LSCs.

Preclinical Study of DNA-Recognized Peptide Compound Pyrrole-Imidazole Polyamide Targeting Human TGF-β1 Promoter for Progressive Renal Diseases in the Common Marmoset

Pyrrole-imidazole (PI) polyamides are novel gene silencers that strongly bind the promoter region of target genes in a sequence-specific manner to inhibit gene transcription. We created a PI polyamide targeting human TGF-β1 (hTGF-β1). To develop this PI polyamide targeting hTGF-β1 (Polyamide) as a practical medicine for treating progressive renal diseases, we examined the effects of Polyamide in two common marmoset models of nephropathy. We performed lead optimization of PI polyamides that targeted hTGF-β1 by inhibiting in a dose-dependent manner the expression of TGF-β1 mRNA stimulated by PMA in marmoset fibroblasts. Marmosets were housed and fed with a 0.05% NaCl and magnesium diet and treated with cyclosporine A (CsA; 37.5 mg/kg/day, eight weeks) to establish chronic nephropathy. We treated the marmosets with nephropathy with Polyamide (1 mg/kg/week, four weeks). We also established a unilateral urethral obstruction (UUO) model to examine the effects of Polyamide (1 mg/kg/week, four times) in marmosets. Histologically, the renal medulla from CsA-treated marmosets showed cast formation and interstitial fibrosis in the renal medulla. Immunohistochemistry showed strong staining of Polyamide in the renal medulla from CsA-treated marmosets. Polyamide treatment (1 mg/kg/week, four times) reduced hTGF-β1 staining and urinary protein excretion in CsA-treated marmosets. In UUO kidneys from marmosets, Polyamide reduced the glomerular injury score and tubulointerstitial injury score. Polyamide significantly suppressed hTGF-β1 and snail mRNA expression in UUO kidneys from the marmosets. Polyamide effectively improved CsA- and UUO-associated nephropathy, indicating its potential application in the prevention of renal fibrosis in progressive renal diseases.

Quasi-3D morphology and modulation of focal adhesions of human adult stem cells through combinatorial concave elastomeric surfaces with varied stiffness

In vivo cell niches are complex architectures that provide a wide range of biochemical and mechanical stimuli to control cell behavior and fate. With the aim to provide in vitro microenvironments mimicking physiological niches, microstructured substrates have been exploited to support cell adhesion and to control cell shape as well as three dimensional morphology. At variance with previous methods, we propose a simple and rapid protein subtractive soft lithographic method to obtain microstructured polydimethylsiloxane substrates for studying stem cell adhesion and growth. The shape of adult renal stem cells and nuclei is found to depend predominantly on micropatterning of elastomeric surfaces and only weakly on the substrate mechanical properties. Differently, focal adhesions in their shape and density but not in their alignment mainly depend on the elastomer stiffness almost regardless of microscale topography. Local surface topography with concave microgeometry enhancing adhesion drives stem cells in a quasi-three dimensional configuration where stiffness might significantly steer mechanosensing as highlighted by focal adhesion properties.

Cancer Cells Invade Confined Microchannels via a Self-Directed Mesenchymal-to-Amoeboid Transition

Cancer cell invasion through physical barriers in the extracellular matrix (ECM) requires a complex synergy of traction force against the ECM, mechanosensitive feedback, and subsequent cytoskeletal rearrangement. PDMS microchannels were used to investigate the transition from mesenchymal to amoeboid invasion in cancer cells. Migration was faster in narrow 3 μm-wide channels than in wider 10 μm channels, even in the absence of cell-binding ECM proteins. Cells permeating narrow channels exhibited blebbing and had smooth leading edge profiles, suggesting an ECM-induced transition from mesenchymal invasion to amoeboid invasion. Live cell labeling revealed a mechanosensing period in which the cell attempts mesenchymal-based migration, reorganizes its cytoskeleton, and proceeds using an amoeboid phenotype. Rho/ROCK (amoeboid) and Rac (mesenchymal) pathway inhibition revealed that amoeboid invasion through confined environments relies on both pathways in a time- and ECM-dependent manner. This demonstrates that cancer cells can dynamically modify their invasion programming to navigate physically confining matrix conditions.

The influence of the nylon balloon stiffness on the efficiency of the intra-aortic balloon occlusion

In interventional procedures, the balloon inflation is used to occlude the artery and thus reduce bleeding. There is no practically accepted measure of the procedure efficiency. A finite element method model with state-of-the-art modelling techniques was built in order to predict the occlusion levels under the influence of different balloon inflation and its material stiffness. The geometries of a healthy human thoracic aorta and an occlusion balloon were idealized. The non-linear constitutive material of Gasser-Ogden-Holzapfel model was employed for the thoracic aorta; the balloon was model as the hyperelastic model. The realistic physiological blood pressure and the balloon inflation pressures were applied to simulate the different occlusion levels. The final outcome shows an important influence of the material stiffness on the balloon deformation and thus the occlusion efficiency.

Antibiofilm Activity of Polyamide 11 Modified with Thermally Stable Polymeric Biocide Polyhexamethylene Guanidine 2-Naphtalenesulfonate

The choice of efficient antimicrobial additives for polyamide resins is very difficult because of their high processing temperatures of up to 300 °C. In this study, a new, thermally stable polymeric biocide, polyhexamethylene guanidine 2-naphtalenesulfonate (PHMG-NS), was synthesised. According to thermogravimetric analysis, PHMG-NS has a thermal degradation point of 357 °C, confirming its potential use in joint melt processing with polyamide resins. Polyamide 11 (PA-11) films containing 5, 7 and 10 wt% of PHMG-NS were prepared by compression molding and subsequently characterised by FTIR spectroscopy. The surface properties were evaluated both by contact angle, and contactless induction. The incorporation of 10 wt% of PHMG-NS into PA-11 films was found to increase the positive surface charge density by almost two orders of magnitude. PA-11/PHMG-NS composites were found to have a thermal decomposition point at about 400 °C. Mechanical testing showed no change of the tensile strength of polyamide films containing PHMG-NS up to 7 wt%. Antibiofilm activity against the opportunistic bacteria Staphylococcus aureus and Escherichia coli was demonstrated for films containing 7 or 10 wt% of PHMG-NS, through a local biocide effect possibly based on an influence on the bacterial eDNA. The biocide hardly leached from the PA-11 matrix into water, at a rate of less than 1% from its total content for 21 days.

Arginine-based poly(ester amide) nanoparticle platform: From structure-property relationship to nucleic acid delivery

Many different types of polycations have been vigorously studied for nucleic acid delivery, but a systematical investigation of the structure-property relationships of polycations for nucleic acid delivery is still lacking. In this study, a new library of biodegradable and biocompatible arginine-based poly(ester amide) (Arg-PEA) biomaterials was designed and synthesized with a tunable structure for such a comprehensive structure-property research. Nanoparticle (NP) complexes were formed through the electrostatic interactions between the polycationic Arg-PEAs and anionic nucleic acids. The following structure effects of the Arg-PEAs on the transfection efficiency of nucleic acids were investigated: 1) the linker/spacer length (length effect and odd-even effect); 2) salt type of arginine; 3) the side chain; 4) chain stiffness; 5) molecular weight (MW). The data obtained revealed that a slight change in the Arg-PEA structure could finely tune its physicochemical property such as hydrophobicity, and this could subsequently affect the nanoparticle size and zeta potential, which, in turn, regulate the transfection efficiency and silencing outcomes. A further study of the Arg-PEA/CpG oligodeoxynucleotide NP complexes indicated that the polymer structure could precisily regulate the immune response of CpG, thus providing a new potential nano-immunotherapy strategy. The in vitro data have further confirmed that the Arg-PEA NPs showed a satisfactory delivery performance for a variety of nucleic acids. Therefore, the data from the current study provide comprehensive information about the Arg-PEA structure-transfection property relationship; the tunable property of the library of Arg-PEA biomaterials can be one of the promising candidates for nucleic acid delivery and other biomedical applications.

STATEMENT OF SIGNIFICANCE

Polycations have being intensive utilized for nucleic acid delivery. However, there has not been elucidated about the relationship between polycation's structure and the physicochemical properties/biological function. In this timely report, an arginine based poly(ester amide) (Arg-PEA) library was prepared with finely tunable structure to systematically investigate the structure-property relationships of polycations for nucleic acid delivery. The results revealed that slight change of Arg-PEA structure could finely tune the physicochemical property (such as hydrophobicity), which subsequently affect the size and zeta potential of Arg-PEA/nucleic acid nanoparticles(NPs), and finally regulate the resulting transfection or silencing outcomes. Further study of Arg-PEA/CpG NPs indicated that the polymer structure could precisely regulate immuno response of CpG, providing new potential nano-immunotherapy strategy. In vitro evaluations confirmed that the NPs showed satisfied delivery performance for a variety types of nucleic acids. Therefore, these studies provide comprehensive information of Arg-PEA structure-property relationship, and the tunable properties of Arg-PEAs make them promising candidates for nucleic acid delivery and other biomedical applications. Overall, we have shown enough significance and novelty in terms of nucleic acid delivery, biomaterials, pharmaceutical science and nanomedicine.

Impact of surface topography on biofilm formation by Candida albicans

Candida albicans is a fungal pathogen that causes serious biofilm-based infections. Here we have asked whether surface topography may affect C. albicans biofilm formation. We tested biofilm growth of the prototypical wild-type strain SC5314 on a series of polydimethylsiloxane (PDMS) solids. The surfaces were prepared with monolayer coatings of monodisperse spherical silica particles that were fused together into a film using silica menisci. The surface topography was varied by varying the diameter of the silica particles that were used to form the film. Biofilm formation was observed to be a strong function of particle size. In the particle size range 4.0-8.0 μm, there was much more biofilm than in the size range 0.5-2.0 μm. The behavior of a clinical isolate from a clade separate from SC5314, strain p76067, showed results similar to that of SC5314. Our results suggest that topographic coatings may be a promising approach to reduce C. albicans biofilm infections.

Interference with DNA repair after ionizing radiation by a pyrrole-imidazole polyamide

Pyrrole-imidazole (Py–Im) polyamides are synthetic non-genotoxic minor groove-binding small molecules. We hypothesized that Py–Im polyamides can modulate the cellular response to ionizing radiation. Pre-treatment of cells with a Py-Im polyamide prior to exposure to ionizing radiation resulted in a delay in resolution of phosphorylated γ-H2AX foci, increase in XRCC1 foci, and reduced cellular replication potential. RNA-sequencing of cell lines exposed to the polyamide showed induction of genes related to the ultraviolet radiation response. We observed that the polyamide is almost 10-fold more toxic to a cell line deficient in DNA ligase 3 as compared to the parental cell line. Alkaline single cell gel electrophoresis reveals that the polyamide induces genomic fragmentation in the ligase 3 deficient cell line but not the corresponding parental line. The polyamide interferes directly with DNA ligation in vitro. We conclude that Py-Im polyamides may be further explored as sensitizers to genotoxic therapies.

A Polyamide Inhibits Replication of Vesicular Stomatitis Virus by Targeting RNA in the Nucleocapsid

Polyamides have been shown to bind double-stranded DNA by complementing the curvature of the minor groove and forming various hydrogen bonds with DNA. Several polyamide molecules have been found to have potent antiviral activities against papillomavirus, a double-stranded DNA virus. By analogy, we reason that polyamides may also interact with the structured RNA bound in the nucleocapsid of a negative-strand RNA virus. Vesicular stomatitis virus (VSV) was selected as a prototype virus to test this possibility since its genomic RNA encapsidated in the nucleocapsid forms a structure resembling one strand of an A-form RNA duplex. One polyamide molecule, UMSL1011, was found to inhibit infection of VSV. To confirm that the polyamide targeted the nucleocapsid, a nucleocapsid-like particle (NLP) was incubated with UMSL1011. The encapsidated RNA in the polyamide-treated NLP was protected from thermo-release and digestion by RNase A. UMSL1011 also inhibits viral RNA synthesis in the intracellular activity assay for the viral RNA-dependent RNA polymerase. The crystal structure revealed that UMSL1011 binds the structured RNA in the nucleocapsid. The conclusion of our studies is that the RNA in the nucleocapsid is a viable antiviral target of polyamides. Since the RNA structure in the nucleocapsid is similar in all negative-strand RNA viruses, polyamides may be optimized to target the specific RNA genome of a negative-strand RNA virus, such as respiratory syncytial virus and Ebola virus.IMPORTANCE Negative-strand RNA viruses (NSVs) include several life-threatening pathogens, such as rabies virus, respiratory syncytial virus, and Ebola virus. There are no effective antiviral drugs against these viruses. Polyamides offer an exceptional opportunity because they may be optimized to target each NSV. Our studies on vesicular stomatitis virus, an NSV, demonstrated that a polyamide molecule could specifically target the viral RNA in the nucleocapsid and inhibit viral growth. The target specificity of the polyamide molecule was proved by its inhibition of thermo-release and RNA nuclease digestion of the RNA bound in a model nucleocapsid, and a crystal structure of the polyamide inside the nucleocapsid. This encouraging observation provided the proof-of-concept rationale for designing polyamides as antiviral drugs against NSVs.

Polythiacalix[4]amides as a Novel Category of Macromolecules; Synthesis, Antibacterial Evaluation and Investigation on their Spectral and Thermophysical Characteristics

Polythiacalix[4]amides as a novel category of polyamides, with high sorption capability towards some environmentally hazardous metal cations, especially Hg2+, have been synthesized via direct polycondensation protocol using a thiacalix[4] arene dicarboxylic acid and commercial diamines. The polyamides were obtained in high yields and possess inherent viscosities in the range of 0.55-0.75 dl/g. The photophysical characteristic was studied by looking for the maximum absorption wavelength of each polymer using UV absorption spectroscopy. Thermogravimetric analysis displayed high thermal stability for these polyamides in range of 337 to 346 °C at the point of 10% weight loss, and their char yields were about 32.9-58.5% at 600 °C. Also, glass transition temperatures were between 157 and 178 °C. To survey on possible sorption capability of these polythiacalixamides, solid-liquid extraction of some toxic transition metal cations, such as Cu2+, Co2+, Cd2+, Pb2+ and Hg2+ from wastewater was performed. Antibacterial evaluation was conducted using Gram positive and Gram negative bacteria strains and some reliable results have been obtained. The results showed some promising features of their ability for being employed as possible ingredients of industrial antibacterial membranes.

A synthetic DNA-binding inhibitor of SOX2 guides human induced pluripotent stem cells to differentiate into mesoderm

Targeted differentiation of human induced pluripotent stem cells (hiPSCs) using only chemicals would have value-added clinical potential in the regeneration of complex cell types including cardiomyocytes. Despite the availability of several chemical inhibitors targeting proteins involved in signaling pathways, no bioactive synthetic DNA-binding inhibitors, targeting key cell fate-controlling genes such as SOX2, are yet available. Here, we demonstrate a novel DNA-based chemical approach to guide the differentiation of hiPSCs using pyrrole-imidazole polyamides (PIPs), which are sequence-selective DNA-binding synthetic molecules. Harnessing knowledge about key transcriptional changes during the induction of cardiomyocyte, we developed a DNA-binding inhibitor termed PIP-S2, targeting the 5'-CTTTGTT-3' and demonstrated that inhibition of SOX2-DNA interaction by PIP-S2 triggers the mesoderm induction in hiPSCs. Genome-wide gene expression analyses revealed that PIP-S2 induced mesoderm by targeted alterations in SOX2-associated gene regulatory networks. Also, employment of PIP-S2 along with a Wnt/β-catenin inhibitor successfully generated spontaneously contracting cardiomyocytes, validating our concept that DNA-binding inhibitors could drive the directed differentiation of hiPSCs. Because PIPs can be fine-tuned to target specific DNA sequences, our DNA-based approach could be expanded to target and regulate key transcription factors specifically associated with desired cell types.

Evaluation of the Antimicrobial Activity of Cationic Polymers against Mycobacteria: Toward Antitubercular Macromolecules

Antimicrobial resistance is a global healthcare problem with a dwindling arsenal of usable drugs. Tuberculosis, caused by Mycobacterium tuberculosis, requires long-term combination therapy and multi- and totally drug resistant strains have emerged. This study reports the antibacterial activity of cationic polymers against mycobacteria, which are distinguished from other Gram-positive bacteria by their unique cell wall comprising a covalently linked mycolic acid-arabinogalactan-peptidoglycan complex (mAGP), interspersed with additional complex lipids which helps them persist in their host. The present study finds that poly(dimethylaminoethyl methacrylate) has particularly potent antimycobacterial activity and high selectivity over two Gram-negative strains. Removal of the backbone methyl group (poly(dimethylaminoethyl acrylate)) decreased antimycobacterial activity, and poly(aminoethyl methacrylate) also had no activity against mycobacteria. Hemolysis assays revealed poly(dimethylaminoethyl methacrylate) did not disrupt red blood cell membranes. Interestingly, poly(dimethylaminoethyl methacrylate) was not found to permeabilize mycobacterial membranes, as judged by dye exclusion assays, suggesting the mode of action is not simple membrane disruption, supported by electron microscopy analysis. These results demonstrate that synthetic polycations, with the correctly tuned structure are useful tools against mycobacterial infections, for which new drugs are urgently required.

Modulation of topoisomerase IIα expression and chemosensitivity through targeted inhibition of NF-Y:DNA binding by a diamino p-anisyl-benzimidazole (Hx) polyamide

BACKGROUND

Sequence specific polyamide HxIP 1, targeted to the inverted CCAAT Box 2 (ICB2) on the topoisomerase IIα (topo IIα) promoter can inhibit NF-Y binding, re-induce gene expression and increase sensitivity to etoposide. To enhance biological activity, diamino-containing derivatives (HxI*P 2 and HxIP* 3) were synthesised incorporating an alkyl amino group at the N1-heterocyclic position of the imidazole/pyrrole.

METHODS

DNase I footprinting was used to evaluate DNA binding of the diamino Hx-polyamides, and their ability to disrupt the NF-Y:ICB2 interaction assessed using EMSAs. Topo IIα mRNA (RT-PCR) and protein (Immunoblotting) levels were measured following 18h polyamide treatment of confluent A549 cells. γH2AX was used as a marker for etoposide-induced DNA damage after pre-treatment with HxIP* 3 and cell viability was measured using Cell-Titer Glo®.

RESULTS

Introduction of the N1-alkyl amino group reduced selectivity for the target sequence 5'-TACGAT-3' on the topo IIα promoter, but increased DNA binding affinity. Confocal microscopy revealed both fluorescent diamino polyamides localised in the nucleus, yet HxI*P 2 was unable to disrupt the NF-Y:ICB2 interaction and showed no effect against the downregulation of topo IIα. In contrast, inhibition of NF-Y binding by HxIP* 3 stimulated dose-dependent (0.1-2μM) re-induction of topo IIα and potentiated cytotoxicity of topo II poisons by enhancing DNA damage.

CONCLUSIONS

Polyamide functionalisation at the N1-position offers a design strategy to improve drug-like properties. Dicationic HxIP* 3 increased topo IIα expression and chemosensitivity to topo II-targeting agents.

GENERAL SIGNIFICANCE

Pharmacological modulation of topo IIα expression has the potential to enhance cellular sensitivity to clinically-used anticancer therapeutics. This article is part of a Special Issue entitled: Nuclear Factor Y in Development and Disease, edited by Prof. Roberto Mantovani.

Self-interrupted synthesis of sterically hindered aliphatic polyamide dendrimers

2,2-Bis(azidomethyl)propionic acid was prepared in four steps and 85% yield from the commercially available 2,2-bis(hydroxymethyl)propionic acid and used as the starting building block for the divergent, convergent, and double-stage convergent-divergent iterative methods for the synthesis of dendrimers and dendrons containing ethylenediamine (EDA), piperazine (PPZ), and methyl 2,2-bis(aminomethyl)propionate (COOMe) cores. These cores have the same multiplicity but different conformations. A diversity of synthetic methods were used for the synthesis of dendrimers and dendrons. Regardless of the method used, a self-interruption of the synthesis was observed at generation 4 for the dendrimer with an EDA core and at generation 5 for the one with a PPZ core, whereas for the COOMe core, self-interruption was observed at generation 6 dendron, which is equivalent to generation 5 dendrimer. Molecular modeling and molecular-dynamics simulations demonstrated that the observed self-interruption is determined by the backfolding of the azide groups at the periphery of the dendrimer. The latter conformation inhibits completely the heterogeneous hydrogenation of the azide groups catalyzed by 10% Pd/carbon as well as homogeneous hydrogenation by the Staudinger method. These self-terminated polyamide dendrimers are enzymatically and hydrolytically stable and also exhibit antimicrobial activity. Thus, these nanoscale constructs open avenues for biomedical applications.

Antialgal activity of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes against the marine alga Ulva

Marine biofouling has detrimental effects on the environment and economy, and current antifouling coatings research is aimed at environmentally benign, non-toxic materials. The possibility of using contact-active coatings is explored, by considering the antialgal activity of cationic poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes. The antialgal activity was investigated via zoospore settlement and sporeling growth assays of the marine algae Ulva linza and U. lactuca. The assay results for PDMAEMA brushes were compared to those for anionic and neutral surfaces. It was found that only PDMAEMA could disrupt zoospores that come into contact with it, and that it also inhibits the subsequent growth of normally settled spores. Based on the spore membrane properties, and characterization of the PDMAEMA brushes over a wide pH range, it is hypothesized that the algicidal mechanisms are similar to the bactericidal mechanisms of cationic polymers, and that further development could lead to successful contact-active antialgal coatings.

In vitro and in vivo biocompatibility and osteogenesis of graphene-reinforced nanohydroxyapatite polyamide66 ternary biocomposite as orthopedic implant material

Graphene and its derivatives have been receiving increasing attention regarding their application in bone tissue engineering because of their excellent characteristics, such as a vast specific surface area and excellent mechanical properties. In this study, graphene-reinforced nanohydroxyapatite/polyamide66 (nHA/PA66) bone screws were prepared. The results of scanning electron microscopy observation and X-ray diffraction data showed that both graphene and nHA had good dispersion in the PA66 matrix. In addition, the tensile strength and elastic modulus of the composites were significantly improved by 49.14% and 21.2%, respectively. The murine bone marrow mesenchymal stem cell line C3H10T1/2 exhibited better adhesion and proliferation in graphene reinforced nHA/PA66 composite material compared to the nHA/PA66 composites. The cells developed more pseudopods, with greater cell density and a more distinguishable cytoskeletal structure. These results were confirmed by fluorescent staining and cell viability assays. After C3H10T1/2 cells were cultured in osteogenic differentiation medium for 7 and 14 days, the bone differentiation-related gene expression, alkaline phosphatase, and osteocalcin were significantly increased in the cells cocultured with graphene reinforced nHA/PA66. This result demonstrated the bone-inducing characteristics of this composite material, a finding that was further supported by alizarin red staining results. In addition, graphene reinforced nHA/PA66 bone screws were implanted in canine femoral condyles, and postoperative histology revealed no obvious damage to the liver, spleen, kidneys, brain, or other major organs. The bone tissue around the implant grew well and was directly connected to the implant. The soft tissues showed no obvious inflammatory reaction, which demonstrated the good biocompatibility of the screws. These observations indicate that graphene-reinforced nHA/PA66 composites have great potential for application in bone tissue engineering.

Controllable Heparin-Based Comb Copolymers and Their Self-assembled Nanoparticles for Gene Delivery

Polysaccharide-based copolymers have attracted much attention due to their effective performances. Heparin, as a kind of polysaccharide with high negative charge densities, has attracted much attention in biomedical fields. In this work, we report a flexible way to adjust the solubility of heparin from water to oil via the introduction of tetrabutylammonium groups for further functionalization. A range of heparin-based comb copolymers with poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMEMA), poly(dimethylaminoethyl methacrylate) (PDMAEMA), or PPEGMEMA-b-PDMAEMA side chains were readily synthesized in a MeOH/dimethylsulfoxide mixture via atom-transfer radical polymerization. The heparin-based polymer nanoparticles involving cationic PDMAEMA were produced due to the electrostatic interaction between the negatively charged heparin backbone and PDMAEMA grafts. Then the pDNA condensation ability, cytotoxicity, and gene transfection efficiency of the nanoparticles were characterized in comparison with the reported gene vectors. The nanoparticles were proved to be effective gene vectors with low cytotoxicity and high transfection efficiency. This study demonstrates that by adjusting the solubility of heparin, polymer graft functionalization of heparin can be readily realized for wider applications.

Antifouling and Antibacterial Multifunctional Polyzwitterion/Enzyme Coating on Silicone Catheter Material Prepared by Electrostatic Layer-by-Layer Assembly

The formation of bacterial biofilms on indwelling medical devices generally causes high risks for adverse complications such as catheter-associated urinary tract infections. In this work, a strategy for synthesizing innovative coatings of poly(dimethylsiloxane) (PDMS) catheter material, using layer-by-layer assembly with three novel functional polymeric building blocks, is reported, i.e., an antifouling copolymer with zwitterionic and quaternary ammonium side groups, a contact biocidal derivative of that polymer with octyl groups, and the antibacterial hydrogen peroxide (H2O2) producing enzyme cellobiose dehydrogenase (CDH). CDH oxidizes oligosaccharides by transferring electrons to oxygen, resulting in the production of H2O2. The design and synthesis of random copolymers which combine segments that have antifouling properties by zwitterionic groups and can be used for electrostatically driven layer-by-layer (LbL) assembly at the same time were based on the atom-transfer radical polymerization of dimethylaminoethyl methacrylate and subsequent partial sulfobetainization with 1,3-propane sultone followed by quaternization with methyl iodide only or octyl bromide and thereafter methyl iodide. The alternating multilayer systems were formed by consecutive adsorption of the novel polycations with up to 50% zwitterionic groups and of poly(styrenesulfonate) as the polyanion. Due to its negative charge, enzyme CDH was also firmly embedded as a polyanionic layer in the multilayer system. This LbL coating procedure was first performed on prefunctionalized silicon wafers and studied in detail with ellipsometry as well as contact angle (CA) and zetapotential (ZP) measurements before it was transferred to prefunctionalized PDMS and analyzed by CA and ZP measurements as well as atomic force microscopy. The coatings comprising six layers were stable and yielded a more neutral and hydrophilic surface than did PDMS, the polycation with 50% zwitterionic groups having the largest effect. Enzyme activity was found to be dependent on the depth of embedment in the multilayer coating. Depending on the used polymeric building block, up to a 60% reduction in the amount of adhering bacteria and clear evidence for killed bacteria due to the antimicrobial functionality of the coating could be confirmed. Overall, this work demonstrates the feasibility of an easy to perform and shape-independent method for preparing an antifouling and antimicrobial coating for the significant reduction of biofilm formation and thus reducing the risk of acquiring infections by using urinary catheters.

Chewing efficiency and occlusal forces in PMMA, acetal and polyamide removable partial denture wearers

PURPOSE

Thermoplastic materials, such as acetal (AC) and polyamide (PA), constitute an alternative to polymethyl methacrylate (PMMA) based resins as the materials for removable partial dentures. However, none of the previous studies compared chewing efficiency and occlusal forces in the wearers of dentures made of various materials. Therefore, the aim of this study was to determine and compare the chewing efficiency and occlusal forces in PMMA, PA and AC RPDs' wearers. The hypothesis was that the type of denture base material shows a significant effect on chewing efficiency (expressed as a degree of food fragmentation) and occlusal force.

METHODS

The experiment included the group of 30 patients using removable partial dentures. The dentures made of PMMA, acetal and polyamide were tested in each patient. Each denture was worn for 90 days, with a random sequence of the denture manufacturing and insertion. After 7, 30 and 90 days of each denture wear, chewing efficiency coefficient was determined with the aid of a sieving method, and occlusal force was measured with a dynamometer.

RESULTS

The use of dentures made of PMMA or acetal was reflected by a marked increase in chewing efficiency and occlusal force. None of these parameters changed significantly with the time of denture wear. Moreover, no significant correlation was found between chewing efficiency and occlusal forces.

CONCLUSIONS

Denture base material exerts significant effects on the degree of food fragmentation and the level of occlusal forces. The use of dentures and clasps made of materials with lower modulus of elasticity is associated with lower chewing efficiency and lower occlusal forces.

Simple surface engineering of polydimethylsiloxane with polydopamine for stabilized mesenchymal stem cell adhesion and multipotency

Polydimethylsiloxane (PDMS) has been extensively exploited to study stem cell physiology in the field of mechanobiology and microfluidic chips due to their transparency, low cost and ease of fabrication. However, its intrinsic high hydrophobicity renders a surface incompatible for prolonged cell adhesion and proliferation. Plasma-treated or protein-coated PDMS shows some improvement but these strategies are often short-lived with either cell aggregates formation or cell sheet dissociation. Recently, chemical functionalization of PDMS surfaces has proved to be able to stabilize long-term culture but the chemicals and procedures involved are not user- and eco-friendly. Herein, we aim to tailor greener and biocompatible PDMS surfaces by developing a one-step bio-inspired polydopamine coating strategy to stabilize long-term bone marrow stromal cell culture on PDMS substrates. Characterization of the polydopamine-coated PDMS surfaces has revealed changes in surface wettability and presence of hydroxyl and secondary amines as compared to uncoated surfaces. These changes in PDMS surface profile contribute to the stability in BMSCs adhesion, proliferation and multipotency. This simple methodology can significantly enhance the biocompatibility of PDMS-based microfluidic devices for long-term cell analysis or mechanobiological studies.

Correlating antimicrobial activity and model membrane leakage induced by nylon-3 polymers and detergents

Most antimicrobial peptides act upon target microorganisms by permeabilizing their membranes. The mode of action is often assessed by vesicle leakage experiments that use model membranes, with the assumption that biological activity correlates with the permeabilization of the lipid bilayer. The current work aims to extend the interpretation of vesicle leakage results and examine the correlation between vesicle leakage and antimicrobial activity. To this end, we used a lifetime-based leakage assay with calcein-loaded vesicles to study the membrane permeabilizing properties of a novel antifungal polymer poly-NM, two of its analogs, and a series of detergents. In conjunction, the biological activities of these compounds against Candida albicans were assessed and correlated with data from vesicle leakage. Poly-NM induces all-or-none leakage in polar yeast lipid vesicles at the polymer's MIC, 3 μg mL(-1). At this and higher concentrations, complete leakage after an initial lag time was observed. Concerted activity tests imply that this polymer acts independently of the detergent octyl glucoside (OG) for both vesicle leakage and activity against C. albicans spheroplasts. In addition, poly-NM was found to have negligible activity against zwitterionic vesicles and red blood cells. Our results provide a consistent, detailed picture of the mode of action of poly-NM: this polymer induces membrane leakage by electrostatic lipid clustering. In contrast, poly-MM:CO, a nylon-3 polymer comprised of both cationic and hydrophobic segments, seems to act by a different mechanism that involves membrane asymmetry stress. Vesicle leakage for this polymer is transient (limited to <100%) and graded, non-specific among zwitterionic and polar yeast lipid vesicles, additive with detergent action, and correlates poorly with biological activity. Based on these results, we conclude that comprehensive leakage experiments can provide a detailed description of the mode of action of membrane permeabilizing compounds. Without this thorough approach, it would have been logical to assume that the two nylon-3 polymers we examined act via similar mechanisms; it is surprising that their mechanisms are so distinct. Some, but not all mechanisms of vesicle permeabilization allow for antimicrobial activity.

In vitro study of the specific interaction between poly(2-dimethylamino ethylmethacrylate) based polymers with platelets and red blood cells

Poly(2-dimethylamino)ethyl methacrylate (PDMAEMA) is an attractive polycation frequently proposed as a non-viral vector for gene therapy. As expected for other cationic carriers, intravenous administration of PDMAEMA can result in its ionic complexation with various negatively charged domains found within the blood. To gain more insight into this polycation hemoreactivity, we followed the binding kinetics of a free form (FF) of fluorescein labelled PDMAEMA (Mn below 15 kDa) in normal human blood using flow cytometry. This in vitro study highlighted that platelets display higher affinity for this polycation compared to red blood cells (RBCs), with an adsorption isotherm characteristics of a specific saturable binding site. PDMAEMA (1-20 μg/mL) exerted a concentration dependent proaggregant effect with a biphasic aggregation of washed platelets. Activation of platelets was also noticed in whole blood with the expression of P-selectin and fibrinogen on platelet surface. Although additional studies would be needed in order to elucidate the mechanism of PDMAEMA mediated activation of platelets, our manuscript provides important information on the hemoreactivity of FF PDMAEMA.

Nuclear Localization and Gene Expression Modulation by a Fluorescent Sequence-Selective p-Anisyl-benzimidazolecarboxamido Imidazole-Pyrrole Polyamide

Synthetic pyrrole (P)-imidazole (I) containing polyamides can target predetermined DNA sequences and modulate gene expression by interfering with transcription factor binding. We have previously shown that rationally designed polyamides targeting the inverted CCAAT box 2 (ICB2) of the topoisomerase IIα (topo IIα) promoter can inhibit binding of transcription factor NF-Y, re-inducing expression of the enzyme in confluent cells. Here, the A/T recognizing fluorophore, p-anisylbenzimidazolecarboxamido (Hx) was incorporated into the hybrid polyamide HxIP, which fluoresces upon binding to DNA, providing an intrinsic probe to monitor cellular uptake. HxIP targets the 5'-TACGAT-3' sequence of the 5' flank of ICB2 with high affinity and sequence specificity, eliciting an ICB2-selective inhibition/displacement of NF-Y. HxIP is readily taken up by NIH3T3 and A549 cells, and detected in the nucleus within minutes. Exposure to the polyamide at confluence resulted in a dose-dependent upregulation of topo IIα expression and enhanced formation of etoposide-induced DNA strand breaks.

Synergistic Effect of PEI and PDMAEMA on Transgene Expression in Vitro

Polyethylenimine (PEI) and poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) have both been used for DNA delivery. PDMAEMA has been shown to exhibit better gene transfection efficiency but lower expression ability than PEI. We mixed the two polymers at different ratios to investigate whether the resulting "dual" polyplex (PEI/PDMAEMA/DNA) could enhance both gene transfection efficiency and DNA expression ability. Experimental results showed a significant increase in DNA internalization and DNA expression for the PDMAEMA/PEI/DNA polyplexes at a ratio of 1:3 or 1:9 (PDMAEMA: PEI), depending on cell type, in comparison with PEI/DNA, PDMAEMA/DNA, and PDMAEMA/PEI/DNA at other ratios. PDMAEMA/PEI/DNA polyplexes did not reduce cell viability. In contrast to with the conventional approach using covalently modified PEI, the proposed "combination" approach provided a more convenient and effective way to improve transgene expression efficiency.

Polymer-Ag nanocomposites with enhanced antimicrobial activity against bacterial infection

Herein, a nontoxic nanocomposite is synthesized by reduction of silver nitrate in the presence of a cationic polymer displaying strong antimicrobial activity against bacterial infection. These nanocomposites with a large concentration of positive charge promote their adsorption to bacterial membranes through electrostatic interaction. Moreover, the synthesized nanocomposites with polyvalent and synergistic antimicrobial effects can effectively kill both Gram-positive and Gram-negative bacteria without the emergence of bacterial resistance. Morphological changes obtained by transmission electron microscope observation show that these nanocomposites can cause leakage and chaos of intracellular contents. Analysis of the antimicrobial mechanism confirms that the lethal action of nanocomposites against the bacteria started with disruption of the bacterial membrane, subsequent cellular internalization of the nanoparticles, and inhibition of intracellular enzymatic activity. This novel antimicrobial material with good cytocompatibility promotes healing of infected wounds in diabetic rats, and has a promising future in the treatment of other infectious diseases.

Medium effects on minimum inhibitory concentrations of nylon-3 polymers against E. coli

Minimum inhibitory concentrations (MICs) against E. coli were measured for three nylon-3 polymers using Luria-Bertani broth (LB), brain-heart infusion broth (BHI), and a chemically defined complete medium (EZRDM). The polymers differ in the ratio of hydrophobic to cationic subunits. The cationic homopolymer is inert against E. coli in BHI and LB, but becomes highly potent in EZRDM. A mixed hydrophobic/cationic polymer with a hydrophobic t-butylbenzoyl group at its N-terminus is effective in BHI, but becomes more effective in EZRDM. Supplementation of EZRDM with the tryptic digest of casein (often found in LB) recapitulates the LB and BHI behavior. Additional evidence suggests that polyanionic peptides present in LB and BHI may form electrostatic complexes with cationic polymers, decreasing activity by diminishing binding to the anionic lipopolysaccharide layer of E. coli. In contrast, two natural antimicrobial peptides show no medium effects. Thus, the use of a chemically defined medium helps to reveal factors that influence antimicrobial potency of cationic polymers and functional differences between these polymers and evolved antimicrobial peptides.

Tertiary-amine functionalized polyplexes enhanced cellular uptake and prolonged gene expression

Ultrasound (US) has been found to facilitate the transport of DNA across cell membranes. However, the transfection efficiency is generally low, and the expression duration of the transfected gene is brief. In this study, a tertiary polycation, Poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA), was used as a carrier for US-mediated gene transfection. Its in-vitro and in-vivo effects on the transfection efficiency and the expression duration were evaluated. A mixture of pCI-neo-luc and PDMAEMA was transfected to cultured cells or mouse muscle by exposure to 1-MHz pulse US. A strong expression of luciferase was found 10 days after the transfection in vitro regardless of US exposure. However, effective transfection only occurred in the US groups in vivo. The transfection ability depended on the weight ratio of PDMAEMA to DNA, and was different for the in-vitro and in-vivo conditions. Lower weight ratios, e.g., 0.25, exhibited better in-vivo expression for at least 45 days.

Tuning the biological activity profile of antibacterial polymers via subunit substitution pattern

Binary nylon-3 copolymers containing cationic and hydrophobic subunits can mimic the biological properties of host-defense peptides, but relationships between composition and activity are not yet well understood for these materials. Hydrophobic subunits in previously studied examples have been limited mostly to cycloalkane-derived structures, with cyclohexyl proving to be particularly promising. The present study evaluates alternative hydrophobic subunits that are isomeric or nearly isomeric with the cyclohexyl example; each has four sp(3) carbons in the side chains. The results show that varying the substitution pattern of the hydrophobic subunit leads to relatively small changes in antibacterial activity but causes significant changes in hemolytic activity. We hypothesize that these differences in biological activity profile arise, at least in part, from variations among the conformational propensities of the hydrophobic subunits. The α,α,β,β-tetramethyl unit is optimal among the subunits we have examined, providing copolymers with potent antibacterial activity and excellent prokaryote vs eukaryote selectivity. Bacteria do not readily develop resistance to the new antibacterial nylon-3 copolymers. These findings suggest that variation in subunit conformational properties could be generally valuable in the development of synthetic polymers for biological applications.

Structure-activity relationships among antifungal nylon-3 polymers: identification of materials active against drug-resistant strains of Candida albicans

Fungal infections are a major challenge to human health that is heightened by pathogen resistance to current therapeutic agents. Previously, we were inspired by host-defense peptides to develop nylon-3 polymers (poly-β-peptides) that are toxic toward the fungal pathogen Candida albicans but exert little effect on mammalian cells. Based on subsequent analysis of structure-activity relationships among antifungal nylon-3 polymers, we have now identified readily prepared cationic homopolymers active against strains of C. albicans that are resistant to the antifungal drugs fluconazole and amphotericin B. These nylon-3 polymers are nonhemolytic. In addition, we have identified cationic-hydrophobic copolymers that are highly active against a second fungal pathogen, Cryptococcus neoformans, and moderately active against a third pathogen, Aspergillus fumigatus.