A disinfectant includes a source of chlorine, a buffer system, a pH adjuster, and a polar carrier. The disinfectant has a pH of 9.9 - 11 and activity against Clostridium difficile spores and Mycobacterium within a 3 minute kill time. In one embodiment, the disinfectant includes sodium hypochlorite as a source of chlorine, a carbonate or phosphate buffer system, a hydroxide pH adjuster, and a polar carrier, wherein the disinfectant has a pH of 10.0 - 10.5 and kills at least 90 % of Clostridium difficile spores and Mycobacterium within a 3 minute kill time.

A method for continuously evaluating the effectiveness of debridement of a root canal (24) of a tooth (18), the tooth (18) having an open access cavity (25) and an apex end (26), includes delivering a fluid to the open access cavity (25) of the tooth (18), evacuating the fluid near the apex end (26) of the tooth (18) such that the fluid flushes most of the root canal (24) before being evacuated, and continuously evaluating the evacuated fluid for at least one of a presence of debris (86), a concentration level of the debris (86), or a type of the debris (86). An apparatus (10) for use in debriding a root canal (24) of a tooth (18) includes a microcannula (38) or a macrocannula configured to evacuate a fluid in the root canal (24), and a sensing mechanism (14) fluidically coupled to the microcannula (38) or the macrocannula.

As a semipermeable barrier that controls the flux of biomolecules in and out the cell, the plasma membrane is critical in cell function and survival. Many proteins interact with the plasma membrane and modulate its physiology. Within this large landscape of membrane-active molecules, researchers have focused significant attention on two specific classes of peptides, antimicrobial peptides (AMPs) and cell penetrating peptides (CPPs), because of their unique properties. In this Account, we describe our efforts over the last decade to build and understand synthetic mimics of antimicrobial peptides (SMAMPs). These endeavors represent one specific example of a much larger effort to understand how synthetic molecules interact with and manipulate the plasma membrane. Using both defined molecular weight oligomers and easier to produce, but heterogeneous, polymers, we have generated scaffolds with biological potency exceeding that of the natural analogues. One of these compounds has progressed through a phase II clinical trial for pan-staph infections. Modem biophysical assays have highlighted the interplay between the synthetic scaffold and lipid composition: a negative Gaussian curvature is required both for pore formation and for the initiation of endosome creation. Although work remains to better resolve the complexity of this interplay between lipids, other bilayer components, and the scaffolds, significant new insights have been discovered. These results point to the importance of considering the various aspects of permeation and how these are related to "pore formation. More recently, our efforts have expanded toward protein transduction domains, or mimics of cell penetrating peptides. Using a combination of unique molecular scaffolds and guanidinium-rich side chains, we have produced an array of polymers with robust membrane (and delivery) activity. In this new area, researchers are just beginning to understand the fundamental interactions between these new scaffolds and the plasma membrane. Negative Gaussian curvature is also important in these systems, but the detailed relationships between molecular structure, self-assembly with lipids, and translocation will require more investigation. It has become dear that the combination of molecular design, biophysical models, and biological evaluation provides a robust approach to the generation and study of novel proteinomimetics.

Cell penetrating peptides (CPPs) and their synthetic analogs are of widespread interest. Here we report that guanidine rich small molecules can be potential membrane transporters in the presence of hydrophobic counteranion activators. To our knowledge, this is the first example of small molecules that mimic the anion-activated transport function of CPP.

Antimicrobial peptides and their synthetic analogues are well known to interact with the cell membrane, which has complex distributions of lipids. The phase behavior of DOPE/DOPG mixed lipids and the interaction between the lipids and several synthetic amphiphilic antimicrobial oligomers (AMOs) were studied by solid-state nuclear magnetic resonance (NMR). A phase diagram of the lipids over a broad window of water content was constructed. There are large areas in the phase diagram where multiple phases coexist, and the fraction of each phase at a given state is dependent on the sample's preparation and thermal history. The comparable stability of the different phases implies that even slight changes in the lipid condition could result in substantial changes to the phase structure, which may be utilized by living organisms to achieve many membrane functions. Nuclear Overhauser spectroscopy (NOESY) and several other NMR experiments indicated that the AMO primarily resides in the head group region of the lipids and that DOPE, the negative intrinsic curvature lipid, does not selectively enrich in the inverted hexagonal phase.

Synthetic mimics of antimicrobial peptides (SMAMPs) are known to disrupt cellular membranes in aqueous media. The impact of ionic strength, or the salt concentration, on membrane activity of these SMAMPs is an important issue since some AMPs are known to lose their activity at higher salt concentrations. In this report, the effect of salt concentration on membrane activity was evaluated using fluorescence dye leakage assays. Salt concentration did not affect the membrane activity of these SMAMPs significantly except for the 100% anionic vesicles (phosphatidylglycerol (PG) or phosphatidylserine (PS) only), where membrane activity decreased with increasing salt concentration. The results also indicated that the membrane activity of SMAMPs with monoamine side chains is independent on ionic strength against cardiolipin (CL) vesicles; however, SMAMPs containing bis- or tris-amines exhibited salt concentration dependent membrane activity for CL liposomes.

Infectious diseases and antibiotic resistance are now considered the most imperative global healthcare problem. In the search for new treatments, host defense, or antimicrobial, peptides have attracted considerable attention due to their various unique properties; however, attempts to develop in vivo therapies have been severely limited. Efforts to develop synthetic mimics of antimicrobial peptides (SMAMPs) have increased significantly in the last decade; and this review will focus primarily on the structural evolution of SMAMPs and their membrane activity. This review will attempt to make a bridge between the design of SMAMPs and the fundamentals of SMAMP-membrane interactions. In discussions regarding the membrane interaction of SMAMPs, close attention will be paid to the lipid composition of the bilayer. Despite many years of study, the exact conformational aspects responsible for the high selectivity of these AMPS and SMAMPs toward bacterial cells over mammalian cells are still not fully understood. The ability to design SMAMPs that are potently antimicrobial, yet nontoxic to mammalian cells has been demonstrated with a variety of molecular scaffolds. Initial animal studies show very good tissue distribution along with more than a 4-log reduction in bacterial counts. The results on SMAMPs are not only extremely promising for novel antibiotics; but also provide an optimistic picture for the greater challenge of general proteomimetics. (C) 2008 Wiley Periodicals, Inc.

It has long been recognized that cationic nanoparticles induce cell membrane permeability. Recently, it has been found that cationic nanoparticles induce the formation and/or growth of nanoscale holes in supported lipid bilayers. In this paper, we show that noncytotoxic concentrations of cationic nanoparticles induce 30-2000 pA currents in 293A (human embryonic kidney) and KB (human epidermoid carcinoma) cells, consistent with a nanoscale defect such as a single hole or group of holes in the cell membrane ranging from I to 350 nm(2) in total area. Other forms of nanoscale defects, including the nanoparticle porating agents adsorbing onto or intercalating into the lipid bilayer, are also consistent; although the size of the defect must increase to account for any reduction in ion conduction, as compared to a water channel. An individual defect forming event takes 1 - 100 ms, while membrane resealing may occur over tens of seconds. Patch-clamp data provide direct evidence for the formation of nanoscale defects in living cell membranes. The cationic polymer data are compared and contrasted with patch-clamp data obtained for an amphiphilic phenylene ethynylene antimicrobial oligomer (AMO-3), a small molecule that is proposed to make well-defined 3.4 nm holes in lipid bilayers. Here, we observe data that are consistent with AMO-3 making similar to 3 nm holes in living cell membranes.

Infectious disease is a critically important global healthcare issue. In the U.S. alone there are 2 million new cases of hospital-acquired infections annually leading to 90,000 deaths and 5 billion dollars of added healthcare costs. Couple these numbers with the appearance of new antibiotic resistant bacterial strains and the increasing occurrences of community-type outbreaks, and clearly this is an important problem. Our review attempts to bridge the research areas of natural host defense peptides (HDPs), a component of the innate immune system, and biocidal cationic polymers. Recently discovered peptidomimetics and other synthetic mimics of HDPs, that can be short oligomers as well as polymeric macromolecules, provide a unique link between these two areas. An emerging class of these mimics are the facially amphiphilic polymers that aim to emulate the physicochemical properties of HDPs but take advantage of the synthetic ease of polymers. These mimics have been designed with antimicrobial activity and, importantly, selectivity that rivals natural HDPs. In addition to providing some perspective on HDPs, selective mimics, and biocidal polymers, focus is given to the arsenal of biophysical techniques available to study their mode of action and interactions with phospholipid membranes. The issue of lipid type is highlighted and the important role of negative curvature lipids is illustrated. Finally, materials applications (for instance, in the development of permanently antibacterial surfaces) are discussed as this is an important part of controlling the spread of infectious disease. (C) 2007 Elsevier B.V. All rights reserved.

In this study, amphiphilic polyoxanorbornene with different quaternary alkyl pyridinium side chains were synthesized. The biological efficiencies of these polymers, with various alkyl substituents, were determined by bacterial growth inhibition assays and hemolytic activity (HC(50)) against human red blood cells (RBCs) to provide selectivity of these polymers for bacterial over mammalian cells. A series of polymers with different alkyl substituents (ethyl, butyl, hexyl, octyl, decyl and phenylethyl) and two different molecular weights (3 and 10 kDa) were prepared. The impact of alkyl chain length divided the biological activity into two different cases: those with an alkyl substituent containing four or fewer carbons had a minimum inhibitory concentration (MIC) of 200 mu g . mL(-1) and a HC(50) greater than 1650 mu g . mL(-1), while those with six or more carbons had lower MICs <= 12.5 mu g . mL(-1) and HC(50) < 250 mu g . mL(-1). Using MSI-78, the potent Magainin derivative which has an MIC = 12.0 mu g . mL(-1) and HC(50) = 120 mu g . mL(-1), as a comparison, the polymers with alkyl substituents <= C(4) (four carbons) were not very potent, but did show selectivity values greater than or equal to MSI-78. In contrast, those with alkyl substituents >= C6 were as potent, or more potent, than MSI-78 and in three specific cases demonstrated selectivity values similar to, or better than, MSI-78. To understand if these polymers were membrane active, polymer induced lipid membrane disruption activities were evaluated by dye leakage experiments. Lipid composition and polymer hydrophobicity were found to be important factors for dye release.

Host defense peptides (HDPs), part of the innate immune system, selectively target the membranes of bacterial cells over that of host cells. As a result, their antimicrobial properties have been under intense study. Their selectivity strongly depends on the chemical and mostly structural properties of the lipids that make up different cell membranes. The ability to synthesize HDP mimics has recently been demonstrated. To better understand how these HDP mimics interact with bilayer membranes, three homologous antimicrobial oligomers (AMOs) 1-3 with an m-phenylene ethynylene backbone and alkyl amine side chains were studied. Among them, AMO 1 is nonactive, AMO 2 is specifically active, and AMO 3 is nonspecifically active against bacteria over human red blood cells, a standard model for mammalian cells. The interactions of these three AMOs with liposomes having different lipid compositions are characterized in detail using a fluorescent dye leakage assay. AMO 2 and AMO 3 caused more leakage than AMO 1 from bacteria membrane mimic liposomes composed of PE/PG lipids. The use of E. coli lipid vesicles gave the same results. Further changes of the lipid compositions revealed that AMO 2 has selectively higher affinity toward PE/PG and E. coli lipids than PC, PC/PG or PC/PS lipids, the major components of mammalian cell membranes. In contrast, AMO 3 is devoid of this lipid selectivity and interacts with all liposomes with equal ease; AMO 1 remains inactive. These observations suggest that lipid type and structure are more important in determining membrane selectivity than lipid headgroup charges for this series of HDP mimics.

Host defense peptides (HDPs), part of the innate immune system, selectively target the membranes of bacterial cells over that of host cells. As a result, their antimicrobial properties have been under intense study. Their selectivity strongly depends on the chemical and mostly structural properties of the lipids that make up different cell membranes. The ability to synthesize HDP mimics has recently been demonstrated. To better understand how these HDP mimics interact with bilayer membranes, three homologous antimicrobial oligomers (AMOs) 1-3 with an m-phenylene ethynylene backbone and alkyl amine side chains were studied. Among them, AMO 1 is nonactive, AMO 2 is specifically active, and AMO 3 is nonspecifically active against bacteria over human red blood cells, a standard model for mammalian cells. The interactions of these three AMOs with liposomes having different lipid compositions are characterized in detail using a fluorescent dye leakage assay. AMO 2 and AMO 3 caused more leakage than AMO 1 from bacteria membrane mimic liposomes composed of PE/PG lipids. The use of E. coli lipid vesicles gave the same results. Further changes of the lipid compositions revealed that AMO 2 has selectively higher affinity toward PE/PG and E. coli lipids than PC, PC/PG or PC/PS lipids, the major components of mammalian cell membranes. In contrast, AMO 3 is devoid of this lipid selectivity and interacts with all liposomes with equal ease; AMO 1 remains inactive. These observations suggest that lipid type and structure are more important in determining membrane selectivity than lipid headgroup charges for this series of HDP mimics.

We have investigated how doubly selective synthetic mimics of antimicrobial peptides (SMAMPs), which can differentiate not only between bacteria and mammalian cells, but also between Gram-negative and Gram-positive bacteria, make the latter distinction. By dye-leakage experiments on model vesicles and complementary experiments oil bacteria, we were able to relate the Grain selectivi-ty to structural differences of these bacteria types. We showed that the double membrane of E. coli rather than the difference in lipid composition between E. coli and S. aureus was rasponsible for Gram selectivity. The molecular-weight-dependent antimicrobial activity of the SMAMPs was shown to be a sieving effect: while the 3000 g mol(-1) SMAMP was able to penetrate the peptidoglycan layer of the Gram-positive S. aureus bacteria, the 5000 gmol-(1) SMAMP got stuck and consequently did not have antimicrobial activity.

We report that decreasing beta-sheet length in homologous multifunctional rigid-rod beta-barrels with internal histidines increases ion channel stability by three orders of magnitude, reduces binding activity by four orders of magnitude, and reduces esterase activity up to 22-times. These results are further used to evaluate methods employed to characterize suprastructure and activity of synthetic multifunctional pores formed by p-octiphenyl beta-barrels with emphasis on applicability of the Hille model to determine internal diameters and the Woodhull equation to locate internal active sites.