Detection and cellular localisation of the synthetic soluble macromolecular drug carrier pHPMA

Abstract

Synthetic macromolecules such as copolymers of N-(2-hydroxypropyl)methacrylamide (pHPMA) are potential carriers for the delivery of drugs owing to their ability to passively accumulate in solid tumours [enhanced permeation and retention (EPR) effect]. To gain further knowledge about the biodistribution and the cellular localisation, poly(HPMA) was prepared for labelling by introducing biotin molecules. Biotinylated pHPMA (5 mol%) was intravenously injected into tumour-bearing rats and the accumulation of biotin-pHPMA was visualised using a streptavidin-alkaline phosphatase technique at day 7 post injection. In spite of the high solubility of pHPMA copolymers and the lack of attachment to cell structures, the biotinylated polymer could be easily detected in tissues fixed in 10% paraformaldehyde-phosphate buffer at 4 degrees C for 48 h. While biotin-pHPMA could be detected intracytoplasmically in liver and spleen, a predominantly interstitial localisation was observed within the anaplastic prostate carcinoma (Dunning R3327-AT1). How biotin as a label influences the biodistribution of poly(HPMA) was assessed by scintigraphy, autoradiography and histology comparing homopolymer poly(HPMA) with biotin-pHPMA. The organ distribution patterns of the two polymers correlated well, except with respect to kidney. It is assumed that the accumulation of biotin-pHPMA in the distal tubuli is due to a biotin transporter in the brush border membrane. The technique presented is useful for a more comprehensive understanding of the biodistribution of soluble macromolecules.

Novel Amphiphilic Degradable Poly(ε‐caprolactone)‐graft‐poly(4‐vinyl pyridine), Poly(ε‐caprolactone)‐graft‐poly(dimethylaminoethyl methacrylate) and Water‐Soluble Derivatives

“…Interestingly, it is accepted that short chains of methacrylic or methacrylamide-type polymers (M n < 30 kDa) can be cleared from the body by renal excretion. [30,31] PCL-g-P4VP can thus be considered as fully bioresorbable since the PCL backbone is biodegradable and P4VP chains are short enough to be excreted.…”

Drug Solubilization with Organic Solvents, or Using Micellar Solutions or Other Colloidal Dispersed Systems

“…If it is found necessary to investigate the more complex systems such as (4) and (5) above, the anticipated route of administration must be considered as most of these chemical modifi cations or formulation types can be degraded to some extent in the gastrointestinal tract. They are primarily intended for parenteral delivery.…”

Long‐Circulating and Passively Tumor‐Targeted Polymer‐Drug Conjugates Improve the Efficacy and Reduce the Toxicity of Radiochemotherapy

“…The TyrNH 2 groups incorporated into the copolymers were radiolabeled using the Iodogen method. [12] After 10 min of incubation, the mixture of iodine-131, Iodogen, and the copolymer was applied to a Biogel-P6 column and it was eluted with 30 mL of PBS. The eluate was recovered in 1 mL fractions and the radioactivity of each of these fractions was determined by means of a scintillation counter.…”

“…And second, again in line with effective EPR-mediated drug targeting to tumors, Figure 3D nicely exemplifies that the tumor concentrations of HPMA copolymers correlate well with their average molecular weights: for 23, 31, and 65 kDa poly-(HPMA), for instance, levels in tumors were 0.2, 0.4, and 1.3% of the injected dose per gram tumor, respectively. [8,12] Using fluorescence microscopy and HPLC, it was finally also demonstrated that by means of their beneficial biodistribution, HPMA copolymers are able to improve the tumordirected delivery of doxorubicin, increasing its target site accumulation at 24 h p.i. by more than a three-fold ( Fig.…”

“…(F) HPLC analysis of the amount of doxorubicin in tumors at 24 p.i., exemplifying the beneficial effect of drug targeting. Adapted, with permission, from ref [7,8,12]. .…”