In order to probe the nanoparticle shape/size effect on cellular uptake, a spherical and two cylindrical nanoparticles, whose lengths were distinctively varied, were constructed by the selective crosslinking of amphiphilic block copolymer micelles. Herein, we demonstrate that, when the nanoparticles were functionalized with the protein transduction domain of human immunodeficiency virus type 1 Tat protein (HIV Tat PTD), the smaller, spherical nanoparticles had a higher rate of cell entry into Chinese Hamster Ovary (CHO) cells than did the larger, cylindrical nanoparticles. It was also found that nanoparticles were released after internalization, and that the rate of cell exit was dependent on both the nanoparticle shape and the amount of surface-bound PTD.

The unusual structural forms of telomere DNA, which protect the ends of chromosomes during replication, may render it vulnerable to unprecedented photodamage, possibly involving nonadjacent bases that are made proximate by folding. The G-quadruplex for the human telomere sequence consisting of a repeating d(T-TAGGG) is one unusual form. Tel22, d[AGGG(TTAGGG)3], forms a basket structure in the presence of Na ؉ and may form multiple equilibrating structures in the presence of K ؉ with hybrid-type structures predominating. UVB irradiation of d[AGGG(TTAGGG)3] in the presence of Na ؉ results in a cis,syn thymine dimer between two adjacent Ts in a TTA loop and a mixture of nonadjacent anti thymine dimers between various loops. Irradiation in the presence of K ؉ , however, produces, in addition to these same products, a large amount of specific anti thymine dimers formed between either T in loop 1 and the central T in loop 3. These latter species were not observed in the presence of Na ؉ . Interloop-specific anti thymine dimers are incompatible with hybrid-type structures, but could arise from a chair or basket-type structure or from triplex intermediates involved in interconverting these structures. If these unique nonadjacent anti thymine dimer photoproducts also form in vivo, they would constitute a previously unrecognized type of DNA photodamage that may interfere with telomere replication and present a unique challenge to DNA repair. Furthermore, these unusual anti photoproducts may be used to establish the presence of G-quadruplex or quadruplex-like structures in vivo.mass spectrometry ͉ photochemistry ͉ nonadjacent dimer ͉ DNA ͉ UV T elomeres are repetitive sequences at the ends of chromosomes that function in concert with telomerase and a number of other proteins to protect the ends of chromosomes from shortening during successive rounds of replication (1-3). The human telomere sequence consists of repeating d(TTAGGG) that may fold into various repeating G-quadruplex structures. Short fragments of the human telomere sequence can exist in a myriad of structures that depend on their sequence and on the cations present (4-7). To date, basket (8, 9), parallel (10), and (3 ϩ 1) structures including hybrid-1 and hybrid-2 (11-14) type G-quadruplex forms have been determined by NMR and crystallography. The oligodeoxynucleotide, d[AGGG(TTAGGG) 3 ] (Tel22), adopts a basket structure in solutions containing Na ϩ (8), whereas in the presence of K ϩ , the predominant intracellular cation, the hybrid-type structures are favored over the basket (11, 13) and/or chair (15) structures (Fig. 1).Recently, we discovered that a highly unusual interstrand-type nonadjacent, anti thymine photodimer (Fig. 2B), previously only found in dried or ethanolic solutions of UVC irradiated DNA (16), can form in aqueous solution. Irradiation of d(GTATCAT-GAGGTGC) with UVB light produced a high yield of cis,anti thymine photodimer between T2 and T7 under slightly acidic conditions (17). This anti photodimer must originate from some folded structur...

No abstract

Polymer vesicles with diameters of ca. 100-600 nm and bearing benzaldehyde functionalities within the vesicular walls were constructed through self assembly of an amphiphilic block copolymer PEO 45 -b-PVBA 26 in water. The reactivity of the benzaldehyde functionalities was verified by crosslinking the polymersomes, and also by a one-pot crosslinking and functionalization approach to further render the vesicles fluorescent, each via reductive amination. In vitro studies found these labelled nanostructures to undergo cell association. Keywords amphiphilic block copolymers; vesicular nanostructures; reactive polymersPolymer vesicles, also known as "polymersomes", 1-6 are supramolecular assemblies of amphiphilic block copolymers 7-14 or complementary random copolymers 15 with sizes ranging from tens of nanometers to several hundreds of microns ("giant vesicles"). Similar to liposomes, polymersomes are composed of closed bilayer membranes with hollow cavities and, therefore, have tremendous potential for encapsulation and controlled delivery. [16][17][18][19][20] Moreover, their structures can be manipulated on both polymeric and supramolecular levels to afford tunability of their properties, including size control over nanoscale to microscale dimensions, 21-24 external stimulus responses, 25-32 mechanical properties, 33-35 membrane permeability, 36-39 and in vivo fate. 40, 41 Starting from the middle of the 1990s, a variety of polymer vesicles have been developed and studied as efficient and promising candidates for the delivery of both hydrophilic (encapsulated inside the hollow cavity) and hydrophobic (loaded within the bilayer membrane wall) molecules. However, most of them consisted of amphiphilic block copolymers with limited functionalities for chemical transformations after vesicle construction. While polymersome surface functionalizations have been reported through reactions with the functionalities installed at the chain ends of the hydrophilic segments, 42, 43 there are limited literature reports associated with modifications of wall domains of polymersomes. Up to date, only radical polymerization, 33, 44 photo-induced [2+2] cyclo-addition, 15, 45-47 base-catalyzed self condensation of siloxanes, 28, 48 and ring-opening of epoxides 49 have been employed to crosslink the walls of polymer vesicles. With the increasing interests in potential biomedical applications that utilize the membrane of polymersomes as a functional unit, 18, 41, 50-53 introduction of highly reactive functionalities into polymer vesicles is being explored to expand the scope of chemistries that can be incorporated within such nanostructures. Herein, we report our approach for constructing sizetunable polymersomes with benzaldehyde functionalities (a diverse electrophile that undergoes reaction under mild conditions), as well as their crosslinking and fluorophore-functionalization via reductive amination (Scheme 1). Results and Discussion Synthesis of Amphiphilic Block Copolymer PrecursorPoly(ethylene oxide)-b-poly(4-vinyl ben...

Peptide nucleic acids have a number of features that make them an ideal platform for the development of in vitro biological probes and tools. Unfortunately, their inability to pass through membranes has limited their in vivo application as diagnostic and therapeutic agents. Herein, we describe the development of cationic shell-crosslinked knedel-like (cSCK) nanoparticles as highly efficient vehicles for the delivery of PNAs into cells, either through electrostatic complexation with a PNA•ODN hybrid, or through a bioreductively cleavable disulfide linkage to a PNA. These delivery systems are better than the standard lipofectamine/ODN-mediated method and much better than the Arg9-mediated method for PNA delivery in HeLa cells, showing lower toxicity and higher bioactivity. The cSCKs were also found to facilitate both endocytosis and endosomal release of the PNAs, while themselves remaining trapped in the endosomes.