Polypropylene and all industrially produced polyolefins are linear molecules containing chain ends. Employing a tungsten catalyst, Veige and co-workers polymerize propyne to give cyclic polypropyne followed by hydrogenation to produce atactic polypropylene. Evidence for a cyclic topology comes from dynamic and static light-scattering techniques and rheology. Compared with linear polypropylene, the atactic cyclic polypropylene exhibits a >20 C increase in its glass transition temperature (T g ).

Circular bivalent aptamers (cb-apt) comprise an emerging class of chemically engineered aptamers with substantially improved stability and molecular recognition ability. Its therapeutic application, however, is challenged by the lack of functional modules to control the interactions of cb-apt with therapeutics. We present the design of a β-cyclodextrin-modified cb-apt (cb-apt-βCD) and its supramolecular interaction with molecular therapeutics via host-guest chemistry for targeted intracellular delivery. The supramolecular ensemble exhibits high serum stability and enhanced intracellular delivery efficiency compared to a monomeric aptamer. The cb-apt-βCD ensemble delivers green fluorescent protein into targeted cells with efficiency as high as 80%, or cytotoxic saporin to efficiently inhibit tumor cell growth. The strategy of conjugating βCD to cb-apt, and subsequently modulating the supramolecular chemistry of cb-apt-βCD, provides a general platform to expand and diversify the function of aptamers, enabling new biological and therapeutic applications.

This report describes the synthesis and characterization of novel N-heterocyclic carbene (NHC) gold(I) complexes and their bioconjugation to the CCRF-CEM leukemia specific aptamer sgc8c. Confirmation of successful bioconjugation was achieved by using fluorescent tags on both the NHC-Au(I) complex and the aptamer. Cell viability assays indicate the NHC-Au(I)-aptamer conjugate is more cytotoxic than the NHC-gold complex alone. A combination of flow cytometry, confocal microscopy, and cell viability assays provide clear evidence that the NHC-Au(I)-aptamer conjugate is selective for targeted CCRF-CEM leukemia cells.

Cyclic polymers possess properties that are significantly different from their linear analogs, such as higher densities, smaller hydrodynamic volumes, and higher glass transition temperatures. Poly­(4-methyl-1-pentene) (PMP), a linear polyolefin, is a commercial transparent thermoplastic and has applications in packaging materials and release membranes. Polymerizing 4-methyl-1-pentyne with a tungsten alkylidyne catalyst and subsequent hydrogenation (>99%) provided cyclic poly­(4-methyl-1-pentene) ( c-PMP). Evidence of a cyclic topology comes from rheology/viscosity studies, light scattering measurements, and size-exclusion chromatography. Importantly, atactic c-PMP exhibits a T g (39 °C) 10 °C higher than the linear analog. A 15 g-scale cyclic polymerization was also achieved with 1-pentyne. Subsequent hydrogenation yielded 10 g of cyclic poly­(1-pentene). Measurements of initial rates during the polymerization of 1-pentyne reveal a catalyst activity of 180,000,000 g/molcat/h.