No abstract

We have grown an antimicrobial polymer directly on the surfaces of glass and paper using atom transfer radical polymerization (ATRP). The method described here results in potentially permanent nonleaching antibacterial surfaces without the need to chemically graft the antimicrobial material to the substratum. The tertiary amine 2-(dimethylamino)ethyl methacrylate was polymerized directly onto Whatman #1 filter paper or glass slides via atom transfer radical polymerization. Following the polymerization, the tertiary amino groups were quaternized using an alkyl halide to produce a large concentration of quaternary ammonium groups on the polymer-modified surfaces. Incubating the modified materials with either Escherichia coli or Bacillus subtilis demonstrated that the modified surfaces had substantial antimicrobial capacity. The permanence of the antimicrobial activity was demonstrated through repeated use of a modified glass without significant loss of activity. Quaternary amines are believed to cause cell death by disrupting cell membranes allowing release of the intracellular contents. Atomic force microscopic imaging of cells on modified glass surfaces supports this hypothesis.

Polypropylene (PP) coated by a non-leachable biocide was prepared by chemically attaching poly(quaternary ammonium) (PQA) to the surface of PP. The well-defined poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA), a precursor of PQA, was grown from the surface of PP via atom transfer radical polymerization (ATRP). The tertiary ammine groups in PDMAEMA were consequently converted to QA in the presence of ethyl bromide. Successful surface modification was confirmed by ATR-FTIR, contact angle measurement, and an antibacterial activity test against Escherichia coli (E. coli). The biocidal activity of the resultant surfaces depends on the amount of the grafted polymers (the number of available quaternary ammonium units). With the same grafting density, the surface grafted with relatively high MW polymers (M(n) > 10,000 g/mol) showed almost 100% killing efficiency (killing all of the input E. coli (2.9 x 10(5)) in the shaking test), whereas a low biocidal activity (85%) was observed for the surface grafted with shorter PQA chains (M(n) = 1,500 g/mol).

Antimicrobial surfaces were prepared using the "grafting onto" technique. Well-defined block copolymers containing poly(2-(dimethylamino)ethyl methacrylate) and poly(3-(trimethoxysilyl)propyl methacrylate) segments (PDMAEMA/PTMSPMA) and corresponding random copolymers were prepared via atom transfer radical polymerization (ATRP), followed by covalent attachment to a glass surface through reaction of the trimethoxysilyl groups with surface silanol groups. The density of quaternary ammonium (QA) groups available to bind small molecules in solution increased with polymer solution concentration and immobilization time. For the PDMAEMA 97- b-PTMSPMA xdiblock copolymers with a fixed length of PDMAEMA segment (degree of polymerization (DP) = 97) and varied lengths of PTMSPMA segments, maximal available surface charge was observed when the ratio of DP PDMAEMA to DP PTMSPMA was 5:1. The tertiary amino groups in immobilized PDMAEMA segments were reacted with ethyl bromide to form QA groups. Alternatively, block copolymers with prequaternized PDMAEMA segments were attached to surfaces. Biocidal activity of the surfaces with grafted polymers versus Escherichia coli ( E. coli) increased with the density of available QA units on the surface. The number of bacteria killed by the surface increased from 0.06 x 10(5) units/cm2 to 0.6 x 10(5) units/cm2, when the density of surface QA increased from 1.0 x 10(14) unit/cm2 to 6.0 x 10(14) unit/cm2. The killing efficiency of QA on all surfaces was similar with approximately 1 x 10(10) units of QA needed to kill one bacterium. The AFM analysis indicated that grafting onto the surface resulted in small patches of highly concentrated polymer. These patches appear to increase the killing efficiency as compared to surfaces prepared by grafting onto with the same average polymer density but with a uniform distribution.

This novel screening system supersedes current in vitro fibroplasia models, as a fast, quantitative and non-destructive technique. This method distinguishes a reduction in collagen I deposition, excluding collagen cross-linking, and allows full evaluation of inhibitors of C-proteinase/BMP-1 and other matrix metalloproteinases.

Highly efficient recyclable antibacterial magnetite nanoparticles consisting of a magnetic Fe(3)O(4) core with an antibacterial poly(quaternary ammonium) (PQA) coating were prepared in an efficient four-step process. The synthetic pathway included: (1) preparation of Fe(3)O(4) nanoparticles via coprecipitation of Fe(2+)/Fe(3+) in the presence of an alkaline solution; (2) attachment of an ATRP initiating functionality to the surface of the nanoparticles; (3) surface-initiated atom transfer radical polymerization (ATRP) of 2-(dimethylamino)ethyl methacrylate (DMAEMA); and (4) transformation of PDMAEMA brushes to PQA via quaternization with ethyl bromide. The success of the surface functionalization was confirmed by FT-IR, thermal gravimetric analysis (TGA), elemental analysis, and transmission electron microscopy (TEM). The PQA-modified magnetite nanoparticles were dispersed in water and exhibited a response to an external magnetic field, making the nanoparticles easy to remove from water after antibacterial tests. The PQA-modified magnetite nanoparticles retained 100% biocidal efficiency against E. coli (10(5) to 10(6)E. coli/mg nanoparticles) during eight exposure/collect/recycle procedures without washing with any solvents or water.

The attachment of inert polymers, such as polyethylene glycol, to proteins has driven the emergence of a multibillion dollar biotechnology industry. In all cases, proteins have been stabilized or altered by covalently coupling the pre-existing polymer to the surface of the protein. This approach is inherently limited by a lack of exquisite control of polymer architecture, site and density of attachment. Using a novel water-soluble atom transfer radical polymerization initiator, we have grown temperature- and pH-responsive polymers from the surface of a model protein, the enzyme chymotrypsin. Poly(2-(dimethylamino)ethyl methacrylate) changes in conformation with altered temperature and pH. Growing the polymer from the surface of chymotrypsin we were able to demonstrate that changes in temperature or pH can change predictably the conformation of the polymer surrounding the enzyme, which in turn enabled the rational tailoring of enzyme activity and stability. Using what we now term "Polymer-Based Protein Engineering", we have increased the activity and stability of chymotrypsin by an order of magnitude at pHs where the enzyme is usually inactive or unstable.

In this study, we report on multimodal temperature-responsive chymotrypsin-poly(sulfobetaine methacrylamide)-block-poly(N-isopropylacrylamide) (CT-pSBAm-block-pNIPAm) protein-polymer conjugates. Using polymer-based protein engineering (PBPE) with aqueous atom transfer radical polymerization (ATRP), we synthesized three different molecular weight CT-pSBAm-block-pNIPAm bioconjugates that responded structurally to both low and high temperature. In the block copolymer grown from the surface of the enzyme, upper critical solution temperature (UCST) phase transition was dependent on the chain length of the polymers in the conjugates, whereas lower critical solution temperature (LCST) phase transition was independent of molecular weight. Each CT-pSBAm-block-pNIPAm conjugate showed temperature dependent changes in substrate affinity and productivity when assayed from 0 to 40 °C. In addition, these conjugates showed higher stability to harsh conditions, including temperature, low pH, and protease degradation. Indeed, the PBPE-modified enzyme was active for over 8 h in the presence of a stomach protease at pH 1.0. Using PBPE, we created a dual zone shell surrounding each molecule of enzyme. The thickness of each zone of the shell was engineered to be separately responsive to temperature.