research on developing nanoparticles with high drug loading (> 10 wt%) from the perspective of synthesis strategies, including post-loading, co-loading, and pre-loading. Based on these three different strategies, various nanoparticle systems with different materials and drugs are summarized and discussed in terms of their synthesis methods, drug loadings, encapsulation efficiencies, release profiles, stabilities, and their applications in drug delivery. The advantages and disadvantages of these strategies are presented with an objective of providing useful design rules for future development of high-drug-loading nanoparticles.

No abstract

In this paper, we report a high-yield procedure for the synthesis of isolated W6S8(4-tert-butylpyridine)6 clusters from isolated tungsten chloride clusters. We also show that the 4-tert-butylpyridine ligand can be exchanged with triethylphosphine and piperidine.

A series of functionalized poly(ε-caprolactone) copolymers, poly(ε-caprolactone-co-vinylphosphonic acid) and poly(ε-caprolactone-co-dimethyl vinylphosphonate), were synthesized by the free-radical copolymerization of 2-methylene-1,3-dioxepane with two vinyl monomers, vinylphosphonic acid and dimethyl vinylphosphonate. The copolymers have ester groups in the backbone as well as pendant functional groups. The structure of each copolymer was established by 1H and 13C NMR as well as IR spectroscopy. Differential scanning calorimetry indicated that the copolymer had a random structure. NMR study showed hydrogen transfer during the copolymerization. The copolymers have different solubility behavior due to the presence of different pendant functional groups.

Eleven organic Lewis bases were investigated as potential ligands (L) on W(6)S(8)L'(6) clusters by exploring ligand exchange reactions to form W(6)S(8)L(6) clusters. Six new homoleptic W(6)S(8)L(6) cluster complexes were prepared and characterized with L = tri-n-butylphosphine (P(n)Bu(3)), triphenylphosphine (PPh(3)), tert-butylisocyanide ((t)BuNC), morpholine, methylamine (MeNH(2)), and tert-butylamine ((t)BuNH(2)). While partial replacement of ligands occurred with diethylamine (Et(2)NH) and dibutylamine (Bu(2)NH), homoleptic clusters could not be prepared by these exchange reactions. When aniline, tribenzylamine, and tri-tert-butylphosphine were the potential ligands, no exchange was observed. From ligand exchange studies of these ligands and others previously studied, a thermodynamic series of binding free energies for ligands on W(6)S(8)L(6) clusters was established as the following: non-Lewis base solvents, aniline, P(t)()Bu(3), etc. << Et(2)NH, Bu(2)NH < (t)BuNH(2) < morpholine, piperidine < or = (n)BuNH(2), MeNH(2) < or = 4-tert-butylpyridine, pyridine < (t)BuNC < tricyclohexylphosphine (PCy(3)) < PPh(3), P(n)Bu(3) < or = triethylphosphine (PEt(3)). Structures of the new cluster complexes were determined by X-ray crystallography. The new compounds were also characterized by NMR spectroscopy and thermogravimetric analyses (TGA). The W-L bond orders and TGA data qualitatively agree with the thermodynamic series above.