Carboxyfluorescein-dPEG®₂₄-amido-dPEG®₂₄-DSPE

Carboxyfluorescein-dPEG®24-amido-dPEG®24-DSPE, product number 11385 (PN11385), consists of the lipid 1,2-Distearoyl-SN-glycero-3-phosphoethanolamine modified by a single molecular weight, discrete polyethylene glycol (dPEG®) spacer that has been functionalized with 5(6)-carboxyfluorescein. The product is designed for use in liposomes and micelles where a fluorescent dye label is needed. The carboxyfluorescein dye has an absorbance maximum (λex) of 497 nm and an emission maximum (λem) of 524 nm, with an extinction coefficient of 63303 M-1 cm-1 at 497 nm, and an A280 correction factor of 0.18.

Liposomes and Micelles
Liposomes and micelles have revolutionized drug delivery. Formed into nanoparticles between 30 and 200 nm diameter, liposomes and micelles possess several desirable features as drug carriers of both hydrophilic and hydrophobic cytotoxic agents. These features include reasonable stability in vitro and in vivo; extended circulation time in the bloodstream; increased accumulation in tumors due to the enhanced permeation and retention (EPR) effect; and reduced systemic toxicity, because cytotoxic agents remain sequestered in the liposome or micelle until membrane fusion with a cell occurs, releasing the cargo. To date, several liposome and micelle formulations have been approved for clinical use.

In vivo, liposomes and micelles are subject to clearance from the bloodstream by the reticuloendothelial system (RES), also known as the macrophage phagocytic system (MPS). This system works through opsonization. In opsonization, proteins known as opsonins bind to a target molecule to mark the target for destruction. The marked molecule is then engulfed by phagocytes and destroyed. To protect liposomes and micelles from opsonization, various molecules are used to modify the head groups of the lipids from which the liposomes or micelles are composed. Polyethylene glycol (PEG) is the most commonly used surface coating of liposomes and micelles. A sufficiently dense coating of PEG creates a hydrophilic, flexible, steric barrier around the PEGylated liposomes and micelles, thus preventing opsonization and removal by the RES. Consequently, liposomes and micelles circulate longer in the bloodstream, which results in lower dosing requirements.

PEGylation of Liposomes and Micelles
Traditional PEG is a disperse polymer (Đ > 1). Polymeric PEG consists of a complex mixture of different chain lengths and molecular weights. In contrast, our dPEG® products are single molecular weight compounds. Each dPEG® product contains a single, discrete PEG chain (Đ = 1). This results in a uniform product that is easier to analyze and use.

Liposomes and micelles are often coated with traditional, polymeric PEG2000 (a polymer PEG having an average molecular weight of 2,000 Daltons) at a density of about 5 – 8 mole%. PN11385, carboxyfluorescein-dPEG®24-amido-dPEG®24-DSPE is equivalent to a comparably functionalized PEG2000. Unlike a traditional PEG2000, however, PN11385 is a single product. That is, the product consists of a single, discrete-length PEG chain conjugated to DSPE, giving a product with a single molecular weight rather than an averaged molecular weight.

PN11385, carboxyfluorescein-dPEG®24-amido-dPEG®24-DSPE provides a convenient dye label for liposomes and micelles. This allows labeled liposomes and micelles to be tracked over time. In addition, the product can be mixed with other DSPE products from Quanta BioDesign with different reactive, protective, or functional groups. Examples of other functions include methoxy-terminated dPEG® to provide a non-reactive surface coating and active esters (N-hydroxysuccinimidyl ester or tetrafluorophenyl ester) that can be used to add, for example, targeting ligands to the liposomal or micellar surface.

The product sizes for PN11385, carboxyfluorescein-dPEG®24-amido-dPEG®24-DSPE, are 5 mg and 10 mg; however, Quanta BioDesign has the capacity to scale this product to any size you need. If you need large quantities of this product, please contact us for a quote.

Application References:

Hermanson, G. T. Chapter 18, PEGylation and Synthetic Polymer Modification. Bioconjugate Techniques, 3rd edition. Academic Press: New York, 2013, 787-838.
Hermanson, G. T. Chapter 21, Liposome Conjugates and Derivatives. Bioconjugate Techniques, 3rd edition. Academic Press: New York, 2013, 921-949.
Thau, L.; Mahajan, K. Physiology, Opsonization. In StatPearls; StatPearls Publishing: Treasure Island (FL), 2018. https://www.ncbi.nlm.nih.gov/books/NBK534215/
Stefanick, J. F.; Ashley, J. D.; Kiziltepe, T.; Bilgicer, B. A Systematic Analysis of Peptide Linker Length and Liposomal Polyethylene Glycol Coating on Cellular Uptake of Peptide-Targeted Liposomes. ACS Nano 2013, 7(4), 2935–2947. https://doi.org/10.1021/nn305663e.
Stefanick, J. F.; Ashley, J. D.; Bilgicer, B. Enhanced Cellular Uptake of Peptide-Targeted Nanoparticles through Increased Peptide Hydrophilicity and Optimized Ethylene Glycol Peptide-Linker Length. ACS Nano 2013, 7(9), 8115–8127. https://doi.org/10.1021/nn4033954.
Noble, G. T.; Stefanick, J. F.; Ashley, J. D.; Kiziltepe, T.; Bilgicer, B. Ligand-Targeted Liposome Design: Challenges and Fundamental Considerations. Trends in Biotechnology 2014, 32(1), 32–45. https://doi.org/10.1016/j.tibtech.2013.09.007.
Saw, P. E.; Park, J.; Lee, E.; Ahn, S.; Lee, J.; Kim, H.; Kim, J.; Choi, M.; Farokhzad, O. C.; Jon, S. Effect of PEG Pairing on the Efficiency of Cancer-Targeting Liposomes. Theranostics 2015, 5(7), 746–754. https://doi.org/10.7150/thno.10732.
Bulbake, U.; Doppalapudi, S.; Kommineni, N.; Khan, W. Liposomal Formulations in Clinical Use: An Updated Review. Pharmaceutics 2017, 9(2), 12. https://doi.org/10.3390/pharmaceutics9020012.

Please contact us at for specific academic pricing.