LIPSS-based functional surfaces produced by multi-beam nanostructuring with 2601 beams and real-time thermal processes measurement.

A unique combination of the ultrashort high-energy pulsed laser system with exceptional beam quality and a novel Diffractive Optical Element (DOE) enables simultaneous production of 2601 spots organized in the square-shaped 1 × 1 mm matrix in less than 0.01 ms. By adjusting the laser and processing parameters each spot can contain Laser Induced Periodic Surface Structures (LIPSS, ripples), including high-spatial frequency LIPSS (HFSL) and low-spatial frequency LIPSS (LSFL). DOE placed before galvanometric scanner allows easy integration and stitching of the pattern over larger areas. In addition, the LIPSS formation was monitored for the first time using fast infrared radiometry for verification of real-time quality control possibilities. During the LIPSS fabrication, solidification plateaus were observed after each laser pulse, which enables process control by monitoring heat accumulation or plateau length using a new signal derivation approach. Analysis of solidification plateaus after each laser pulse enabled dynamic calibration of the measurement. Heat accumulation temperatures from 200 to 1000 °C were observed from measurement and compared to the theoretical model. The temperature measurements revealed interesting changes in the physics of the laser ablation process. Moreover, the highest throughput on the area of 40 × 40 mm reached 1910 cm2/min, which is the highest demonstrated throughput of LIPSS nanostructuring, to the best of our knowledge. Thus, showing great potential for the efficient production of LIPSS-based functional surfaces which can be used to improve surface mechanical, biological or optical properties.

Enhanced antitumor activity of combinations of free and HPMA copolymer-bound drugs.

The synergism in anticancer effect toward human renal carcinoma A498 cells by binary combinations of free and N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-bound anticancer drugs, SOS thiophene (SOS), doxorubicin (DOX), and mesochlorin e6 monoethylenediamine (Mce6), was evaluated. The combination index (CI) analysis was used to quantify the synergism, antagonism, and additive effects. Both free drugs and HPMA copolymer conjugates, when used as single agents or in combination, exhibited cytotoxic activities against A498 cells, as determined using a modified MTT assay. As single agents, SOS and P-GFLG-SOS (HPMA copolymer conjugates containing SOS bound via glycylphenylalanylleucylglycine [GFLG] spacer) were significantly more effective than the other agents evaluated. The synergistic effects ranked in the order SOS+DOX>P-GFLG-DOX+P-GFLG-Mce6 approximately DOX+Mce6>P-GFLG-SOS+P-GFLG-DOX approximately SOS+Mce6>P-GFLG-SOS+P-GFLG-Mce6. The combination of SOS+DOX proved to be synergistic over all cell growth inhibition levels. All other combinations exhibited synergism in a wide range of drug effect levels. The SOS+Mce6 and P-GFLG-SOS+P-GFLG-Mce6 combinations displayed synergism up to drug affected fraction (fa) values of about 0.8 and reached slight antagonism and nearly additivity at fa=0.95, respectively. However, all other combinations were synergistic up to fa<0.9 and were additive at higher fa values. The observations that most combinations produced synergistic effects will be important for clinical translation.

Low temperature a/b nanotwins in Ni50Mn25+xGa25-x Heusler alloys.

We have found low temperature a/b nanotwins having (110) twinning plane in a five-layered modulated martensite phase of Ni50Mn25+xGa25-x (at. %) Heusler alloys and identified the particular region in phase diagram where the nanotwinning occurs. Evolution of the structure with decreasing temperature was studied by X-ray diffraction using single crystals exhibiting magnetic shape memory effect. The merging of (400) and (040) lines upon cooling for 2.6 < x < 3.5 indicated a/b nanotwinning originating from the refinement of initially coarse a/b twins. Refinement of the twins with decreasing temperature was observed directly using scanning electron microscopy. The prerequisite for nanotwinning is an extremely low twin boundary energy, which we estimated using first-principles calculations to be 0.16 meV/Å2. As the nanotwinning distorts the relation between the crystal lattice and the X-ray diffraction pattern, it should be taken into consideration in structural studies of Ni-Mn-Ga Heusler alloys.

Polymerizable Fab' antibody fragments for targeting of anticancer drugs.

We have designed a new pathway for the synthesis of targeted polymeric drug delivery systems, using polymerizable antibody Fab' fragments (MA-Fab'). The targeted systems can be directly prepared by copolymerization of the MA-Fab', N-(2-hydroxypropyl)methacrylamide (HPMA) and drug-containing monomers. Both MA-Fab' and the Fab'-targeted copolymers can effectively bind to target cells. An MA-Fab' (from OV-TL 16 Ab) targeted HPMA copolymer containing mesochlorin e6 (Mce6) was synthesized by copolymerization of MA-Fab', HPMA, and MA-GFLG-Mce6. The targeted copolymer exhibited a higher cytotoxicity toward OVCAR-3 human ovarian carcinoma cells than the nontargeted Mce6-containing copolymer or free Mce6. The targeted copolymer was internalized more efficiently by OVCAR-3 cells than the nontargeted copolymer.

Combination chemotherapy and photodynamic therapy with N-(2-hydroxypropyl) methacrylamide copolymer-bound anticancer drugs inhibit human ovarian carcinoma heterotransplanted in nude mice.

This study characterizes the efficacy and toxicity of: (a) free Adriamycin and N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer-Adriamycin conjugate (P-A); (b) free and HPMA copolymer-meso-chlorin e6 monoethylene diamine disodium salt (Mce6) conjugate (P-C) and light-induced photodynamic therapy; and (c) combinations of the HPMA copolymer conjugates (P-A and P-C) in the destruction of human epithelial ovarian carcinoma heterotransplanted in the nude mouse (OVCAR-3). Eight-week-old female nu/nu mice were injected in both flanks with 0.04-0.05 cm3 OVCAR-3 solid tumor dispersed in media. When bilateral tumors reached a minimum volume of 0.18 cm3 (one axis, 2.0-mm minimum) and demonstrated consistent growth, the experiments were initiated. Drugs were given i.v. unless otherwise noted. Tumor-bearing mice were allocated to the following protocols: (a) Adriamycin at 1 mg/kg, P-A at 30 mg/kg (2.2 mg/kg Adriamycin equivalent), and controls (n = 6 each); (b) Mce6 and light (2 h after administration: 650 nm light for 15 min to deliver 220 J/cm2) at 1.25, 2.5, 5, and 10 mg/kg (n = 6 each), 2.5 mg/kg i.p. (n = 4), and controls (n = 6); (c) P-C at 12.5, 25, and 75 mg/kg (1.5, 2.9, and 8.7 mg/kg Mce6 equivalent, respectively with light (18 h after administration; 650 nm light for 15 min to deliver 220 J/cm2), P-C at 25 mg/kg (2.9 mg/kg Mce6 equivalent) with no light administration, and controls (n = 7 each); and (d) a combination of P-A (30 mg/kg, 2.2 mg/kg adriamycin equivalent) and P-C (12.5 and 75 mg/kg, 1.5 mg/kg and 8.7 mg/kg Mce6 equivalent, respectively) with and without light (n = 7 each; 18 h after administration; 650 nm light for 15 min to deliver 220 J/cm2) and controls (n = 12). Tumor volumes and animals weights were assessed for significant differences from the treated and controls groups by Student's t test. Adriamycin (1 mg/kg) and P-A (30 mg/kg. 2.2 mg/kg Adriamycin equivalent) caused less than a 10% weight loss, and treated tumor volumes (day 10-32) were significantly less than those of controls (all P < 0.045). Mce6 (2.5-10 mg/kg i.v.), caused tumor regression in 80% of tumors and a shock syndrome in 17-83%. i.p. dosing (2.5 mg/kg) was uniformly fatal. Mce6 at 1.25 mg/kg did not show reproducible efficacy. P-C with light (25 and 75 mg/kg, 2.9 and 8.7 mg/kg Mce6 equivalent, respectively) demonstrated significant tumor destruction (P < 0.003) but not complete ablation. The combinations of P-A (30 mg/kg, 2.2 mg/kg Adriamycin equivalent) plus P-C (12.5 and 75 mg/kg; 1.5 mg/kg and 8.7 mg/kg of Mce6 equivalent, respectively) with light resulted in tumor volumes that were significantly less than control tumor volumes and the tumor volumes of mice receiving either P-A (30 mg/kg, 2.2 mg/kg Adriamycin equivalent) or P-C with light (12.5 or 75 mg/kg. 1.5 or 8.7 mg/kg Mce6 equivalent, respectively) alone (all P < 0.02). P-C (75 mg/kg, 8.7 mg/kg Mce6 equivalent) added to P-A (30 mg/kg, 2.2 mg/kg Adriamycin equivalent) resulted in complete tumor ablation. Free Mce6 demonstrates a narrow margin of safety, which is extended by incorporation into HPMA copolymers. P-A demonstrates safety and efficacy in vivo. The combined chemotherapy and photodynamic therapy of P-A (30 mg/kg, 2.2 mg/kg Adriamycin equivalent) with P-C and light (12.5 and 75 mg/kg 1.5 and 8.7 mg/kg Mce6 equivalent, respectively) was nontoxic and allowed us to attain a significant improvement in tumor cures than those obtained by P-A or P-C with light alone.

Grain-resolved analysis of localized deformation in nickel-titanium wire under tensile load.

The stress-induced martensitic transformation in tensioned nickel-titanium shape-memory alloys proceeds by propagation of macroscopic fronts of localized deformation. We used three-dimensional synchrotron x-ray diffraction to image at micrometer-scale resolution the grain-resolved elastic strains and stresses in austenite around one such front in a prestrained nickel-titanium wire. We found that the local stresses in austenite grains are modified ahead of the nose cone-shaped buried interface where the martensitic transformation begins. Elevated shear stresses at the cone interface explain why the martensitic transformation proceeds in a localized manner. We established the crossover from stresses in individual grains to a continuum macroscopic internal stress field in the wire and rationalized the experimentally observed internal stress field and the topology of the macroscopic front by means of finite element simulations of the localized deformation.

Nanofaceting as a stamp for periodic graphene charge carrier modulations.

The exceptional electronic properties of monatomic thin graphene sheets triggered numerous original transport concepts, pushing quantum physics into the realm of device technology for electronics, optoelectronics and thermoelectrics. At the conceptual pivot point is the particular two-dimensional massless Dirac fermion character of graphene charge carriers and its volitional modification by intrinsic or extrinsic means. Here, interfaces between different electronic and structural graphene modifications promise exciting physics and functionality, in particular when fabricated with atomic precision. In this study we show that quasiperiodic modulations of doping levels can be imprinted down to the nanoscale in monolayer graphene sheets. Vicinal copper surfaces allow to alternate graphene carrier densities by several 10(13) carriers per cm(2) along a specific copper high-symmetry direction. The process is triggered by a self-assembled copper faceting process during high-temperature graphene chemical vapor deposition, which defines interfaces between different graphene doping levels at the atomic level.

Evaluation of protein-N-(2-hydroxypropyl)methacrylamide copolymer conjugates as targetable drug carriers. 1. Binding, pinocytic uptake and intracellular distribution of transferrin and anti-transferrin receptor antibody conjugates.

The transferrin receptor of human skin fibroblasts was studied as an in vitro model target antigen receptor for interaction with protein-polymer conjugates having potential for targeted drug delivery. Pinocytic uptake of 125I-labelled N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer conjugated to monoclonal antibody B3/25 (specific for the transferrin receptor) or transferrin was up to 9-fold greater than uptake of the parent HPMA copolymer. The ability of these conjugates to bind specifically was confirmed by Scatchard analysis. Pinocytic internalisation was dependent on the molecular mass of the conjugate. Intracellular routing following internalisation was evaluated using density-gradient centrifugation. Unmodified HPMA copolymer was transferred via the endosomal compartment into secondary lysosomes, where, being resistant to degradation, it accumulated. Although the majority of endocytosed transferrin is recycled via the endosome, it was shown that any transferrin reaching the lysosomes was rapidly degraded and low-molecular-weight degradation products were released. Monoclonal antibody B3/25 showed a subcellular distribution consistent with prolongation on the cell surface, followed by internalisation and subcellular trafficking, via endosomes, into the lysosomal compartment, with subsequent degradation. Conjugation of protein to HPMA copolymer increased lysosomal accumulation of polymer up to 9-fold, with no detectable degradation of conjugate. The data presented here have implications regarding clinical potential of protein-HPMA copolymer conjugates designed for lysosomotropic drug delivery.

Targeting of N-(2-hydroxypropyl)methacrylamide copolymers to liver by incorporation of galactose residues.

Soluble synthetic polymers have potential as targetable carriers of pharmacological agents. Here we report that incorporation into poly[N-(2-hydroxypropyl)methacrylamide)] of an oligopeptide side-chain terminating in galactose enhanced the polymer's pinocytic uptake from the rat bloodstream by the liver. Within the liver lysosomes enzymic digestion led to the intracellular release of a drug analogue also bound to oligopeptide side-chains of the polymer.

Pinocytic uptake and intracellular degradation of N-(2-hydroxypropyl)methacrylamide copolymers. A potential drug delivery system.

Synthetic 125I-labelled N-(2-hydroxypropyl)methacrylamide copolymers containing four different, potentially degradable peptidyl side chains were incubated with rat visceral yolk sacs cultured in vitro. All copolymers were captured by fluid-phase pinocytosis and three of the side chains were susceptible to lysosomal hydrolysis, resulting in release of [125I]iodotyrosine back into the culture medium. Uptake and degradation was completely inhibited by 2,4-dinitrophenol. The thiol-proteinase inhibitor leupeptin did not affect the rate of pinocytosis, but caused different degrees of inhibition of hydrolysis depending on side chain composition.

Tyrosinamide residues enhance pinocytic capture of N-(2-hydroxypropyl)methacrylamide copolymers.

N-(2-Hydroxypropyl)methacrylamide ( HPMA ) copolymers have been proposed as a potential lysosomotropic drug delivery system. HPMA copolymers bearing tyrosinamide residues, bound either directly to the polymer backbone or via a glycylglycine spacer, were radiolabelled with [125I]iodide and the effect of tyrosinamide content on their rate of pinocytic uptake by rat visceral yolk sacs cultured in vitro was measured. Incorporation of tyrosinamide enhanced uptake of the copolymer, most markedly at substitutions above 10 mol%. 2,4-Dinitrophenol, an inhibitor of pinocytosis, was used to confirm that tissue association of 125I-radiolabelled copolymer was due to pinocytic uptake. The side-chain -Gly-Gly-Tyr-NH2 was degraded following the internalization of copolymers containing this spacer and degradation was partially sensitive to the lysosomal thiol-proteinase inhibitor leupeptin. It is postulated that the effect of tyrosinamide residues is to increase the hydrophobicity of poly( HPMA ) and thus to increase its capacity for nonspecific adsorptive pinocytosis.

Fate of N-(2-hydroxypropyl)methacrylamide copolymers with pendent galactosamine residues after intravenous administration to rats.

N-(2-Hydroxypropyl)methacrylamide (HPMA) copolymers bearing galactosamine residues accumulate in the liver after intravenous administration to rats (Duncan, R., Kopecek, J., Rejmanová, P. and Lloyd, J.B. (1983) Biochim. Biophys. Acta 755, 518-521). In this study HPMA copolymers bearing pendent galactosamine residues (1.0-11.6 mol%) were injected intravenously into rats and their rates of blood clearance and liver accumulation were measured. A level of substitution of 4 mol% was found to be sufficient to cause substantial deposition in the liver 30 min after administration. The most highly substituted polymer (11.6 mol%) was directed rapidly to the liver, 80-90% being recovered there less than 10 min after administration. Separation of liver into hepatocytes and non-parenchymal cells indicated that polymer was largely associated with the hepatocytes, and density-gradient subcellular fractionation of liver at various times after administration confirmed that polymer was internalized by liver cells and transported, with time, into the secondary lysosomes. Experiments using isolated rat hepatocytes indicated that HPMA copolymers with high galactosamine content have higher affinity for the hepatocyte plasma membrane. HPMA copolymers containing galactosamine and in addition glycylglycyltyrosinamide side-chains were used to demonstrate release of a drug analogue across the lysosomal membrane. These polymers were radioiodinated and, following intravenous administration to rats, the liver lysosomes were isolated and incubated at 37 degrees C in 0.25 M sucrose. Radioactivity was released from the lysosomes faster than the lysosomal enzyme arylsulphatase, an observation that indicates intralysosomal hydrolysis of the copolymer side-chain with subsequent passage of low molecular weight degradation product across the lysosomal membrane.

Antitumor activity of N-(2-hydroxypropyl) methacrylamide copolymer-Mesochlorine e6 and adriamycin conjugates in combination treatments.

This study demonstrates the selective tumor targeting and the antitumor efficacy of the N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-bound mesochlorin e6 monoethylenediamine (Mce6) and HPMA copolymer-bound Adriamycin (ADR) in combination photodynamic therapy (PDT) and chemotherapy against human ovarian OVCAR-3 carcinoma xenografted in female athynmic mice. The concentrations of Mce6 and ADR in blood and tissues, in free or HPMA copolymer-bound form, were determined by fluorescence and high-performance liquid chromatography fluorescence assays, respectively. Xenograft responses to single and combination therapies were recorded. The peak concentration of HPMA copolymer-Mce6 conjugate in tumor was achieved 18 h after administration. For HPMA copolymer-bound drugs, the concentration ratios of liver and spleen versus muscle were significantly higher than those of free drugs. The HPMA copolymer-bound drugs demonstrated selective targeting and accumulation in the tumor, probably attributed to the enhanced permeability and retention effect. In vivo studies revealed that all tumors in the treatment groups showed significant responses after receiving any of the various types of therapy as compared with controls (P < 0.001). PDT with HPMA copolymer-Mce6 conjugate (PDTMC) at a dose of 13.4 mg/kg (1.5 mg/kg of Mce6 equivalent) and light doses of 110 J/cm2 at 12 and 18 h, respectively, resulted in significant suppression of the growth of OVCAR-3 tumors. Three courses of chemotherapy using 35 mg/kg (2.2 mg/kg of ADR equivalent) of HPMA copolymer-ADR conjugate (CHEMO) were effective in suppressing the growth of tumors. Single PDTMC plus multiple CHEMO exhibited significantly greater therapeutic efficacy than multiple CHEMO. In the group of mice receiving multiple PDTMC, tumor recurrence became obvious after day 20. However, 10 of 12 tumors exhibited complete responses in the group of mice receiving multiple PDTMC plus multiple CHEMO. The least to most effective treatments were ranked as follows: multiple CHEMO < single PDTMC plus multiple CHEMO < multiple PDTMC < multiple PDTMC plus multiple CHEMO. The results clearly demonstrate that: (a) HPMA copolymer-bound drugs exhibited selective tumor accumulation contrary to free drugs; (b) PDT using HPMA copolymer-Mce6 conjugate with multiple light irradiations was a better therapy than that with single light irradiation; and (c) combination chemotherapy and photodynamic therapy with HPMA copolymer-ADR and HPMA copolymer-Mce6 conjugates was the most effective regimen.

Macrophages of athymic nude mice: Fc receptors, C receptors, phagocytic and pinocytic activities.

Expression of Fc receptors (FcR) for IgG1, IgG2A, IgG2B, IgM, IgA and IgE, binding of C3 and C5 complement components and phagocytic and pinocytic activities were determined in peritoneal and omental macrophages of nu/nu, nu/+ and +/+ Balb/c mice. nu/nu mice showed a higher proportion of FcR and complement receptor-bearing peritoneal macrophages along with a significantly higher phagocytic activity of peritoneal macrophages both in vitro and in vivo. Tests of pinocytic activity in these cells and phagocytic activity in omental phagocytes yielded similar results. We conclude that athymic mice compensate their immune defects by a higher phagocytic activity of their professional phagocytes and a higher expression of receptors mediating this process.

Design of a multivalent galactoside ligand for selective targeting of HPMA copolymer-doxorubicin conjugates to human colon cancer cells.

N-(2-hydroxypropyl)methacrylamide (HPMA)-based copolymers have been shown to be efficient carriers for anticancer drugs because of their versatile chemistry and good biocompatibility. As demonstrated with hepatocytes, targeting efficacy of anticancer drugs could be further improved when the drug (doxorubicin) was conjugated to HPMA copolymers with biorecognisable groups, such as simple carbohydrates. The present study was devised to learn whether the cluster (multivalent) construction of carbohydrate residues could improve the targeting capability of HPMA copolymer-doxorubicin (DOX) conjugates towards human colon adenocarcinoma cells. DOX was linked via a lysosomally degradable tetrapeptide sequence to HPMA copolymers bearing galactosamine (GalN), lactose (Lac), or multivalent galactose residues (TriGal) to produce targetable polymeric drug carriers. The effect of the type of sugar moiety and its three-dimensional cluster arrangement on biorecognition by three human colon-adenocarcinoma cell lines was studied. The role of galectin-3 in the biorecognition of HPMA copolymer conjugates was explored. Biorecognition of the targetable (glycoside-bearing) conjugates decreased their IC(50) doses in comparison to the non-targetable (non-glycosylated) conjugates. The biorecognition of the TriGal-containing HPMA copolymer-doxorubicin conjugate by the cells was superior with concomitant decrease of its IC(50) doses. It is suggested that the increased cytotoxicity of the glycosylated HPMA-copolymer-DOX conjugates toward human colon-adenocarcinoma cells was caused by their biorecognition and effective internalisation via receptor-mediated endocytosis. All three human colon adenocarcinoma cell lines tested, Colo-205, SW-480 and SW-620, expressed the galectin-3 protein and the galectin-3-specific RNA. However, contrary to expectation, Colo-205 cells did not express a detectable amount of galectin-3 on the cell surface. This suggests that the binding of the glycoside-bearing HPMA copolymer-DOX conjugates to the cells was mediated not only by galectin-3. We conclude that targeting of the anticancer agent, doxorubicin, using HPMA copolymer conjugates bearing multivalent galactoside residues can improve their cytotoxicity.

Biodistribution and antitumour efficacy of long-circulating N-(2-hydroxypropyl)methacrylamide copolymer-doxorubicin conjugates in nude mice.

The aim of this study was to evaluate the influence of the molecular weight (mol. wt) of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-doxorubicin (DOX) conjugates (P-DOX) on biodistribution and therapeutic efficacy in nu/nu mice bearing human ovarian carcinoma OVCAR-3 xenografts. Copolymerisation of HPMA, a polymerisable derivative of DOX (N-methacryloylglycylphenylalanylleucylglycyl doxorubicin) and a newly designed crosslinking agent, N(2),N(5)-bis(N-methacryloylglycylphenylalanyl-leucylglycyl)ornithine methyl ester monomers resulted in novel, high mol. wt, branched, water-soluble P-DOX containing lysosomally degradable oligopeptide sequences as crosslinks and side-chains terminated in DOX. Four conjugates with mol. wt of 22, 160, 895 and 1230 kDa were prepared. The results indicated that the half-life in blood and the elimination rate from the tumour were up to 28 times longer and 25 times slower, respectively, for P-DOX (mol. wt=1230 kDa) than for free DOX. Treatment with P-DOX (mol. wt > or = 160 kDa) inhibited tumour growth more efficiently than that of 22 kDa P-DOX or free DOX (P<0.02) at a 2.2 mg/kg DOX equivalent dose. In conclusion, the administration of long circulating P-DOX resulted in enhanced tumour accumulation with a concomitant increase in therapeutic efficacy.

An advantageous method for detection of Fc-receptors and for studying Fc-receptor-mediated phagocytosis.

A method employing fluorescent 2-hydroxyethyl methacrylate copolymer particles with dinitrophenyl haptenic group and anti-haptenic murine monoclonal antibodies of different isotypes is described for tracing Fc-receptors and for studies of phagocytosis via these cell surface structures. The possibility of quenching the fluorescence of non-phagocytosed particles enables us to distinguish clearly and reliably between internalized and cell surface-bound particles.

Phagocytosis of human blood leukocytes: a simple micromethod.

A simple micromethod for testing human blood leukocyte phagocytosis employing synthetic hydrophilic particles based on 2-hydroxyethylmethacrylate is described. The normal level of phagocytosing leukocytes in healthy children was 20.1 +/- 2.7%, and in healthy adult donors 34.3 +/- 6.1%. The method was found suitable for routine testing in both clinical and laboratory practice.

Intracellularly biorecognizable derivatives of 5-fluorouracil. Implications for site-specific delivery in the human condition.

The release of 5-fluorouracil from polymer-based conjugates can be influenced by the type of linkages used to bind the drug to the polymer carrier. The use of specific oligopeptide sequences designed to be biorecognizable by intracellular enzymes is a promising approach for increasing the site-specific release of 5-fluorouracil from polymer-based conjugates. In this study, we investigated the biorecognizability of specific oligopeptide sequences linking 5-fluorouracil to a water-soluble copolymer carrier based on N-(2-hydroxypropyl) methacrylamide by human cathepsin B (EC 3.4.22.1), cathepsin H(EC 3.4.22.6), and a homogenate of the human colon adenocarcinoma cell line SW 480. The cathepsins were chosen based on the hypothesis that they were two principal lysosomal enzymes responsible for the release of 5-fluorouracil from these conjugates. Our results support this hypothesis; however, these two enzymes may not be the only lysosomal enzymes responsible for the release kinetics observed. While the results for cathepsin B corresponded well to our hypothesis, the cleavage via cathepsin H was lower than predicted, suggesting the presence of additional lysosomal enzymes with catalytic activity toward these 5-fluorouracil derivatives.

The pharmacokinetics of polymer-bound adriamycin.

Adriamycin (ADR) covalently bound to N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers via biodegradable (Gly-Phe-Leu-Gly) oligopeptide sequences shows antitumour activity against model tumours in vivo. In this study we have examined the distribution of ADR bound to such HPMA copolymers following intravenous administration to mice (ADR concentration 5 mg/kg). An established fluorimetric HPLC method was used to measure levels of free ADR in plasma and tissue samples, and a new technique was developed to quantitate levels of polymer-bound anthracycline. The high initial levels of free ADR in plasma observed following administration of free drug were absent in the case of polymer-bound ADR, and the subsequently high levels of free ADR seen in other tissues were also abolished. In contrast, the circulating half-life of HPMA copolymer-ADR was approximately 15 times longer than that of the free drug. The initial peak level of free ADR in the heart was reduced 100-fold following administration of drug-conjugate. These alterations in pharmacokinetics may account for the decreased toxicity and improved efficacy reported previously.