Purpose. To synthesize and evaluate hyperbranched polymer (HBP)-drug conjugates with high drug payload for enhanced cellular delivery. Methods. Polyol-and polyglycerol-ibuprofen conjugates with or without imaging agent fluorescein isothiocyanate (FITC) were synthesized using dicyclohexilcarbodiimide (DCC) as a coupling agent. Drug-polymer conjugates were characterized using 13 C NMR, 1 H NMR, and gel permeation chromatography (GPC). Stability of the drug-conjugates was studied using free drug release through a dialysis membrane. Cellular entry of FITC-labeled HBP conjugates was studied using fluorescence activated cell sorter (FACS), and cell supernatant was analyzed by UV-visible spectrophotometer. The intracellular localization of FITC-labeled conjugates in A549 lung epithelial cells was imaged using fluorescence microscopy. Anti-inflammatory activity of the HBP-ibuprofen conjugates was estimated in vitro by measuring the concentration of prostaglandin (PGE 2 ) using an ELISA kit. Results. The average number of ibuprofen molecules conjugated per molecule of HBP was estimated to be 50 for polyol and 53 for polyglycerol. The HBP-drug conjugates did not release the drug up to 72 h in methanol, indicating the presence of stable ester bonds. Both the polymer-drug conjugates entered the cells rapidly. The conjugates were localized in the cell cytosol as evidenced by fluorescence microscopy. Within 30 min, the HBP-drug conjugates showed rapid suppression of PGE 2 synthesis, whereas free ibuprofen did not show any activity. At later times, the conjugates showed comparable activity. Conclusions. For the first time, we report HBP conjugates with a high drug payload. HBP-drug conjugates entered the cells rapidly and produced the desired pharmacological action. This study demonstrates that hyperbranched polyol and polyglycerol are promising nanovehicles for achieving enhanced cellular delivery of drugs.

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Dendrimers and hyperbranched polymers are emerging as potentially ideal drug delivery vehicles because they provide a significant amount of tailorability and a large density of functional groups. This study explores the dynamics of cellular entry of dendrimers and hyperbranched polymers alone, and in the complexed form with ibuprofen, into A549 human lung epithelial carcinoma cells using UV/Vis spectroscopy, flow cytometry and fluorescence microscopy. Both dendrimers and hyperbranched polymers appear to enter these cells rapidly. The polyamidoamine (PAMAM) dendrimers, with NH2 and OH end functionalities appear to enter cells (in approx. 1 h) faster than the hyperbranched polyol (OH functionality) (in approx. 2 h). Cellular entry of PAMAM-NH2 was detected as early as 5 min. All branched polymers and their ibuprofen complexes entered A549 lung epithelial cells rapidly when compared to the pure drug. The drug payload was about 50% by weight in the complexes formed by PAMAM-NH2 dendrimers and was about 30% in the encapsulated form for Polyol-OH and PAMAM-OH. The complexation and encapsulation of ibuprofen with the polymers appear to facilitate rapid cellular entry of ibuprofen. The anti-inflammatory effect of the polymer-complexed drug was demonstrated by more rapid suppression of COX-2 mRNA levels than that achieved by the pure drug. This suggests that these dendritic polymers can act as efficient drug carriers, delivering high 'payloads' of drug even with complexation and encapsulation.