Lysine Units Research Articles

Polyion complex micelle MRI contrast agents from poly(ethylene glycol)- b-poly( l-lysine) block copolymers having Gd-DOTA; preparations and their control of T1-relaxivities and blood circulation characteristics

The current study synthesized macromolecular magnetic resonance imaging (MRI) contrast agents constituted of the poly(ethylene glycol)-b-poly( l-lysine) block copolymer (PEG-P(Lys)). A chelate group, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), was attached to the primary amino group of the block copolymer in desired contents. Gd-DOTA-based macromolecular contrast agents were prepared from PEG-P(Lys) having DOTA (PEG-P(Lys-DOTA) and Gd(III) ions. All of the PEG-P(Lys) block copolymers having gadolinium ions (PEG-P(Lys-DOTA-Gd)) showed higher T 1 relaxivity (per gadolinium), r 1 = 5.6–7.3 mM − 1 s − 1 , than that of a low-molecular-weight gadolinium-chelate, diethylenetriaminepentaacetic acid-gadolinium(III) (Gd-DTPA) at 9.4 T. The study prepared the polyion complex (PIC) micelles from the amino groups of the lysine units and an oppositely charged polyanion, poly(methacrylic acid) or dextran sulfate, in an aqueous medium. In contrast, the fully DOTA-attached PEG-P(Lys-DOTA-Gd) formed a PIC with a polycation. Compared with partially DOTA-attached cationic PEG-P(Lys-DOTA-Gd), this PIC micelle yielded a forty percent decrease of r 1. This r 1 decrease was considered to result from a change in the accessibility of water molecules to gadolinium ions in the micelles' inner core. The r 1 was decreased upon formation of the PIC micelle, and this change proved that our concept worked in vitro. Blood-circulation characteristics of PIC micelles were controlled by means of changing the molecular weight of the counter anion. The PIC micelles accumulated in tumor tissues, and MRI study showed T1W image of axial slice of tumor area was significantly enhanced at 24 h after the injection.

Copolypeptide-doped polyaniline nanofibers for electrochemical detection of ultratrace trinitrotoluene

This paper demonstrates a new electrochemical method for the detection of ultratrace amount of 2,4,6-trinitrotoluene (TNT) with synthetic copolypeptide-doped polyaniline nanofibers. The copolypeptide, comprising of glutamic acid (Glu) and lysine (Lys) units, is in situ doped into polyaniline through the protonation of the imine nitrogen atoms of polyaniline by the free carboxylic groups of Glu segments, resulting in the formation of polyaniline nanofibers of emeraldine salt. The free amino groups of Lys segments at the surface of nanofibers provide the receptor sites of TNT through the formation of charge–transfer complex between the electron-rich amino groups and the electron-deficient aromatic rings. Adsorptive stripping voltammetry results demonstrate that the poly(Glu-Lys)-doped nanofibers confined onto glassy carbon electrodes exhibit a remarkable enriching effect and thus sensitive electrochemical response to TNT with a linear dynamic range of 0.5–10 μM and a detection limit down to 100 nM. Moreover, other kinds of nitro compounds show different redox behaviors from TNT at the doped nanofibers, and thus do not interfere with the electrochemical detection of TNT. This study essentially offers a new and simple method for electrochemical detection of ultratrace TNT.

First approach on transfection ability of novel amphiphilic water soluble degradable poly(ε-caprolactone)-g-poly(Llysine) copolymers

AbstractThe potential of novel amphiphilic water soluble and degradable poly(ε- caprolactone)-g-poly(L-lysine) as carriers for DNA transfection has been investigated. Two graft copolymers having the same proportion of lysine units but different structures have been synthesized following two grafting techniques. The chemical composition of these copolymers, their expected architectures and their behaviour in aqueous solutions have been studied. The benefits resulting from the use of these degradable polycationic structures as well as their ability to form polyplexes are discussed. Finally, preliminary transfection assays of MCF-7 cells by pRL-TK plasmid using poly(ε-caprolactone)-g-poly(L-lysine) copolymers as carriers are reported.

Adsorption Properties of Poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) at a Hydrophobic Interface: Influence of Tribological Stress, pH, Salt Concentration, and Polymer Molecular Weight

The adsorption properties of a graft copolymer of poly(ethylene glycol) (PEG) with a polycationic backbone, namely, poly( l-lysine)- graft-poly(ethylene glycol) (PLL- g-PEG), onto nonpolar, hydrophobic PDMS surfaces from aqueous solution and the lubrication properties of the self-mated sliding contacts of PDMS surfaces modified with PLL- g-PEG have been investigated. Whereas PLL- g-PEG is spontaneously attracted to negatively charged surfaces as a result of the polycationic PLL backbone, the collective interaction of (CH 2) 4 hydrocarbon moieties on the lysine units in the PLL backbone with nonpolar, hydrophobic surfaces also enables the adsorption of PLL- g-PEG onto hydrophobic surfaces such as PDMS. The adsorption and lubrication properties of PLL- g-PEG have been investigated by varying the aqueous solution parameters, such as pH (2, 7, and 12) and KCl concentration (0, 0.01, 0.1, and 1 M) as well as the length of the PLL backbone of the copolymer (20 vs 375 kDa). In the absence of tribological stress, the adsorption of PLL- g-PEG onto PDMS surfaces was mainly governed by the KCl concentration, whereas the role of pH or the molecular weight of the copolymer was of relatively minor importance; for all pH values, the adsorbed mass decreased with increasing KCl concentration. Under tribological stress, however, a clear dependence of the lubrication properties of PLL- g-PEG on all of the studied parameters, including pH, KCl concentration, and backbone molecular weight, was observed. The adsorption strength of PLL- g-PEG on PDMS surfaces, rather than the adsorbed mass itself, appeared to be the most critical parameter in determining the lubrication properties.

Low-Molecular-Weight Gelators: Elucidating the Principles of Gelation Based on Gelator Solubility and a Cooperative Self-Assembly Model

This paper highlights the key role played by solubility in influencing gelation and demonstrates that many facets of the gelation process depend on this vital parameter. In particular, we relate thermal stability ( T gel) and minimum gelation concentration (MGC) values of small-molecule gelation in terms of the solubility and cooperative self-assembly of gelator building blocks. By employing a van't Hoff analysis of solubility data, determined from simple NMR measurements, we are able to generate T calc values that reflect the calculated temperature for complete solubilization of the networked gelator. The concentration dependence of T calc allows the previously difficult to rationalize "plateau-region" thermal stability values to be elucidated in terms of gelator molecular design. This is demonstrated for a family of four gelators with lysine units attached to each end of an aliphatic diamine, with different peripheral groups (Z or Boc) in different locations on the periphery of the molecule. By tuning the peripheral protecting groups of the gelators, the solubility of the system is modified, which in turn controls the saturation point of the system and hence controls the concentration at which network formation takes place. We report that the critical concentration ( C crit) of gelator incorporated into the solid-phase sample-spanning network within the gel is invariant of gelator structural design. However, because some systems have higher solubilities, they are less effective gelators and require the application of higher total concentrations to achieve gelation, hence shedding light on the role of the MGC parameter in gelation. Furthermore, gelator structural design also modulates the level of cooperative self-assembly through solubility effects, as determined by applying a cooperative binding model to NMR data. Finally, the effect of gelator chemical design on the spatial organization of the networked gelator was probed by small-angle neutron and X-ray scattering (SANS/SAXS) on the native gel, and a tentative self-assembly model was proposed.

Novel Amphiphilic Poly(ε-caprolactone)-g-poly(l-lysine) Degradable Copolymers

As part of the search of novel degradable polymers, amphiphilic and cationic poly(epsilon-caprolactone)-g-poly(l-lysine) (PCL-g-PlL) copolymers have been synthesized following a grafting "onto" or a grafting "from" method both applied to a macropolycarbanionic PCL derivative. The first approach led to PCL-g-PZlL containing 36% of epsilon-caprolactone and 64% of N-epsilon-Z-l-lysine units, by reaction of activated poly(N-epsilon-Z-l-lysine) on the macropolycarbanion derived from PCL. The second route was based on the anionic ring opening polymerization of N-carboxyanhydride of N-epsilon-benzyloxycarbonyl-l-lysine initiated by the macropolycarbanion derived from PCL and led to a similar copolymer containing 45% of of epsilon-caprolactone and 55% of N-epsilon-Z-l-lysine units. After deprotection of the lysine units, PCL-g-PlL copolymers were obtained. These copolymers are water-soluble and form nanometric micelle-like objects with mean diameters between 60 and 500 nm in distilled water depending on the synthesis route.

PEG-based block catiomers possessing DNA anchoring and endosomal escaping functions to form polyplex micelles with improved stability and high transfection efficacy

For the development of polyplex systems showing a high transfection efficacy without a large excess of polycations, a lysine (Lys) unit as a DNA anchoring moiety was introduced into the amino acid sequence in poly(ethylene glycol)- b-cationic poly( N-substituted asparagine) with a flanking N-(2-aminoethyl)-2-aminoethyl group (PEG- b-Asp(DET)) resulting in PEG- b-P[Lys/Asp(DET)], in which the Asp(DET) unit acts as a buffering moiety inducing endosomal escape with minimal cytotoxicity. PEG- b-P[Lys/Asp(DET)]/DNA polyplexes exhibited a narrow size distribution of ∼ 90 nm without secondary aggregates at the stoichiometric N/P 1, suggesting the formation of PEG-shielded polyplex micelles. The introduction of Lys units into the catiomer sequence facilitated cellular uptake and a 100-fold higher level of gene expression with PEG- b-P[Lys/Asp(DET)]/DNA polyplex micelles prepared even at a lowered N/P 2, possibly due to the enhanced association power of the anchoring Lys units.

Leucyl/phenylalanyl(L/F)‐tRNA‐protein transferase‐mediated aminoacyl transfer of a nonnatural amino acid to the N‐terminus of peptides and proteins and subsequent functionalization by bioorthogonal reactions

We report here a new strategy for derivatizing peptides and proteins at the N-terminus. To achieve this, a nonnatural amino acid was charged onto a tRNA and then enzymatically transferred to a lysine (Lys) unit at the N-terminus of a peptide or a protein by using L/F-tRNA-protein transferase. By using the chemoenzymatic technique, beta-(2-quinolyl)-L-alanine, p-azido-L-phenylalanine, and p-acetyl-L-phenylalanine were introduced to the N-terminus. The latter two nonnatural amino acids possess bioorthogonal functional groups to which artificial tags can be introduced. Actually, a biotin tag was coupled to the bioorthogonal ketone group of acetylphenylalanine at the N-terminus of a peptide. N-terminal-specific biotinylation and fluorescence derivatization of the bioorthogonal azido-containing protein or peptide was also carried out based on a [3 + 2] cycloaddition. The enzymatic transfer of a nonnatural amino acid to the N-terminus of target peptides or proteins was also successfully achieved in the presence of other peptides or crude protein mixtures.

Evanescent wave infrared chemical sensor possessing a sulfonated sensing phase for the selective detection of arginine in biological fluids

This paper describes a new infrared (IR) sensing scheme for the determination of arginine (Arg). In this method, the surface of an IR evanescent wave sensing element was modified with sulfonic acid groups to selectively interact with Arg through specific interactions with its guanidine moiety. The sulfonated sensing phase was prepared using a two-layer modification approach. To demonstrate that this assembly could be used for selective infrared sensing, a large number of amino acids were subjected to analysis. Although the sulfonate groups on the surface of the sensing element did interact selectively with the guanidine groups of Arg species, lysine and histidine units caused some interference; this problem could be minimized because of the unique IR absorption bands of the guanidine moiety of Arg. To optimize the detection conditions, we studied the effects of both the pH and the composition of the polymer. The most intense signal was obtained at pH 9. We observed different adsorption rates for the detection of Arg at different values of pH, which we attribute to changes in the accessibility of the analytes to the pore structures of the sensing phase. The composition of the base polymer was also optimized; 60% PVBC (w/w) provided a water-stable, sensitive phase for the detection of Arg in aqueous solution. Under the optimized conditions, we obtained a linear range of detection up to 0.1 mM with a detection limit of ca. 5 μM.

Interaction of Poly(L-Lysine)- g-Poly(Ethylene Glycol) with Supported Phospholipid Bilayers

Interactions between the graft copolymer poly(L-lysine)- g-poly(ethylene glycol), PLL- g-PEG, and two kinds of surface-supported lipidic systems (supported phospholipid bilayers and supported vesicular layers) were investigated by a combination of microscopic and spectroscopic techniques. It was found that the application of the copolymer to zwitterionic or negatively charged supported bilayers in a buffer of low ionic strength led to their decomposition, with the resulting formation of free copolymer–lipid complexes. The same copolymer had no destructive effect on a supported vesicular layer made up of vesicles of identical composition. A comparison between poly(L-lysine), which did not induce decomposition of supported bilayers, and PLL- g-PEG copolymers with various amounts of PEG side chains per backbone lysine unit, suggested that steric repulsion between the PEG chains that developed upon adsorption of the polymer to the nearly planar surface of a supported phospholipid bilayer (SPB) was one of the factors responsible for the destruction of the SPBs by the copolymer. Other factors included the ionic strength of the buffer used and the quality of the bilayers, pointing toward the important role defects present in the SPBs play in the decomposition process.

Novel dendritic cores based on thiacalix[4]arene derivatives

Thiacalix[4]arenes possessing carboxylic groups were used for the design of potential dendritic cores with amino surface groups. The known tetraacetic acid in the 1,3-alternate conformation gave the desired product in very low yield because of steric hindrance on thiacalix[4]arene moiety. Therefore, synthetic strategy based on withdrawing of the carboxyl groups via benzylic spacer from the thiacalix[4]arene moiety was successfully applied for the realization of novel thiacalix[4]arenes bearing two or four protected lysine units.

Towards an understanding of (bio)silicification: the role of amino acids and lysine oligomers in silicification

In order to understand the role that proteins play in the generation of well regulated biosilica structures we need to understand the contribution of the components, singly and in combination. To this end we have performed a systematic study of the effect of amino acids and small peptide oligomers on silica formation from aqueous solution. Silicas produced from a potassium silicon catecholate salt at ca. pH 7 in the presence of the amino acids (Gly, Arg, Asn, Gln, Glx, Ser, Thr, Tyr, Pro, Ala, Lys) at a 2 Si : 1 amino acid molar ratio have shown that these amino acids affect the kinetics of small oligomer formation, the growth of aggregate structures and the morphology and surface properties of the silicas produced. The effects seen during the early stages of oligomer formation carry through to the properties of the particles and aggregates produced after extended periods of reaction. The behaviour of the amino acids relates to the pI and hydrophobicity of the individual amino acids. The presence of the nitrogen containing amino acids generates larger particles and the presence of amino acids containing hydroxyl and hydrophobic groups generates silicas with smaller particles than are produced for silicas produced in the absence of amino acids. An extensive study of the effect of the number of lysine and glycine units per peptide was also performed (for lysine, 1–5 and ca. 150 and for glycine, 1,4,5). Increasing the number of glycine units per additive molecule had little effect on the kinetics, aggregation, sample morphology, surface area and porosity of the silicas produced. A distinct relationship between the number of lysine units per additive molecule and an increased rate of oligomer formation, aggregate growth and a reduction in silica surface area and broadening of pore sizes was observed. A distinct change over in behaviour, particularly in regard to the porosity characteristics of the silica produced was noted for between (lys) 3 and (lys) 4 as well as this being the smallest size of peptide that was incorporated into the siliceous material formed. Aggregation was observed to accelerate exponentially over the full range of lysine oligomers used. Consecutive sequences of the same amino acid residues were shown to produce effects much larger than the sum of the effects of the individual residues, and at extremes mediate macroscopic morphological changes. The consequences of these findings for biosilicification are discussed. It is clear that all amino acid functional groups in proteins that are accessible to silica during the stages of formation from orthosilicic acid through to the final material have a role to play in determining the physical nature and structure of the material that forms.

Polyion complex micelles from plasmid DNA and poly(ethylene glycol)–poly( l-lysine) block copolymer as serum-tolerable polyplex system: physicochemical properties of micelles relevant to gene transfection efficiency

Polyion complex (PIC) micelles composed of the poly(ethylene glycol)–poly( l-lysine) (PEG–PLL) block copolymer and plasmid DNA (pDNA) were investigated in this study from a physicochemical viewpoint to get insight into the structural feature of the PIC micellar vector system to show practical gene transfection efficacy particularly under serum-containing medium. The residual ratio ( r) of the lysine units in PEG–PLL to the phosphate units of pDNA in the system significantly affects the size of the PIC micelles evaluated from dynamic light scattering, being decreased from approximately 120 to 80 nm with an increase in the r value for the region with r⩾1.0. The zeta potential of the complexes slightly increased with r in the same region, yet maintained a very small absolute value and leveled off to a few mV at r≈2.0. These results suggest that the micelles are most likely to take the core-shell structure with dense PEG palisades surrounding the PIC core to compartmentalize the condensed pDNA. Furthermore, an increasing r value in the region of r⩾1 induces a rearrangement of the stoichiometric complex formed at r=1.0 to the non-stoichiometric complex composed of the excess block copolymer. The association number of pDNA and the block copolymer in the micelle was estimated from the apparent micellar molecular weight determined by static light scattering measurements, indicating that a single pDNA molecule was incorporated in each of the micelles prepared from the PEG ( M w=12,000 g/mol)–PLL (polymerization degree of PLL segment: 48) (12-48) block copolymer at r=2.0. These 12-48/pDNA micelles showed a gene expression comparable to the lipofection toward cultured 293 cells, though 100 μ m chloroquine was required in the transfection medium. Notably, even in the presence of serum, the PIC micelles achieved appreciable cellular association to attain a high gene expression, which is in sharp contrast with the drastic decrease in the gene expression for lipoplex system in the presence of serum. A virus-comparable size (∼100 nm) with a serum-tolerable property of the PIC micelles indeed suggests their promising feasibility as non-viral gene-vector systems used for clinical gene therapy.

An in Situ Infrared Spectroscopic Investigation of Lysine Peptide and Polylysine Adsorption to TiO2 from Aqueous Solutions

An in situ infrared spectroscopic study of the adsorption of lysine peptides with n = 2–5 lysine units and polylysine (n = 169) on hydrous TiO2 particle films is reported. Using attenuated total reflection infrared spectroscopy, it was found that dilysine adsorption to negatively charged TiO2 from aqueous solutions pH 7.4 arose from electrostatic interactions. Increasing the number of lysine units to n = 3–5 resulted in infrared spectra which were changed, compared to solution species, upon adsorption to TiO2. This indicated that the carboxylate group was involved in the peptide/TiO2 interaction. Binding constants (K) for lysine peptide adsorption to TiO2 were calculated by applying the Langmuir isotherm model. The K values obtained supported the onset of a stronger peptide–TiO2 interaction going from dilysine to trilysine. Polylysine also adsorbed to TiO2 from aqueous pH 7.4 solutions. Prolonged exposure of polylysine to TiO2 (16.5 h) resulted in changed infrared spectra, implying that the secondary structure of polylysine was affected by adsorption. In contrast, the lysine peptides and polylysine did not adsorb to the hydrophobic ZnSe surface or positively charged chromium(III) oxide–hydroxide films, under the same experimental conditions. This indicates that electrostatic interactions of the lysine peptides with the adsorbent are of main importance to adsorption.

Covalent immobilization of proteins onto (Maleic anhydride-alt-methyl vinyl ether) copolymers: enhanced immobilization of recombinant proteins.

Two genetically modified HIV-1 capsid p24 proteins, RH24 and RH24K, were covalently bound to maleic anhydride-alt-methyl vinyl ether (MAMVE) copolymer, under aqueous conditions. We demonstrated that the addition of a six lysine unit tag at the COOH-terminus of RH24K greatly improved the grafting reaction which could take place under many different experimental conditions. The course of the reaction was controlled by electrostatic attractive forces between the protein and the negatively charged polymer, as the chemical binding was more efficient at low ionic strength. The maximum loading capacity of the polymer depended on whether the protein bore the lysine tag (RH24K) or not (RH24). Twenty-four molecules of RH24 could be immobilized per polymer chain and 49 for RH24K. Such a difference could be explained by a difference of orientation of the protein on the polymer, side-on for RH24 and end-on for RH24K to account for the observed high packing density.

Distamycin‐NA: A DNA analog with an aromatic heterocyclic polyamide backbone. Part 2. Solid‐phase synthesis of distamycin‐NAs containing the nucleobase uracil: Unexpected solvent participation in the coupling step

AbstractThe synthesis of the Fmoc‐protected amino acid 2 is presented. First attempts of amide‐bond formation to the homodimer 4 in solution showed only poor coupling yields indicative for the low reactivity of the amino and carboxy groups in the building blocks 1 and 2, respectively (Scheme 1). Best coupling yields were found using dicyclohexylcarbodiimide (DCC) without any additive. The oligomerization of building block 2 adopting the Fmoc ((9H‐fluoren‐9‐ylmethoxy)carbonyl) solid‐phase synthesis yielded a mixture of N‐terminal‐modified distamycin‐NA derivatives. By combined HPLC and MALDI‐TOF‐MS analysis, the N‐terminal functional groups could be identified as acetamide and N,N‐dimethylformamidine functions, arising from coupling of the N‐terminus of the growing chain with residual AcOH or DCC‐activated solvent DMF. An improved preparation of building block 2 and coupling protocol led to the prevention of the N‐terminal acetylation. However, ‘amidination’ could not be circumvented. A thus isolated tetramer of 2, containing a lysine unit at the C‐terminus and a N,N‐dimethylformamidine‐modified N‐terminus, not unexpectedly, showed no complementary base pairing to DNA and RNA, as determined by standard UV‐melting‐curve analysis.

Biological and biochemical studies on the ‘basic’ isoenzyme of endo-polygalacturonase secreted by Monilinia fructigena

Monilinia fructigena secretes one molecular form of endo-polygalacturonase (PG) in apple fruits infected by it. This PG, purified from culture filtrate to homogeneity, had an M r of ca 33 000 (SDS electrophoresis) and a pI value of ca 9.75. It had little or no effect on the structural integrity of potato tuber tissues, nor on the viability of apple callus cells in suspension. Modification of the lysine units of the purified enzyme by pyridoxal phosphate resulted in ca 50% decrease in PG activity. PG thus modified appeared to bind to an apple fibre preparation less than did PG not treated with pyridoxal phosphate. Lysine residues may thus be involved in subsites binding this PG to carboxyl groups in the polygalacturonate.

NMR-titrations with complexes between ds-DNA and indole derivatives including tryptophane containing peptides

It is shown that NMR titrations can be used on a quantitative basis to derive binding constants and binding modes of ds-DNA ligand complexes from several signals. The results are partially at variance with literature conclusions; they can be interpreted by additive and independent contributions of electrostatic interactions between DNA phosphate and ammonium centers in the side chain of the ligands, and of very weak stacking contributions of the indole rings. While gramine and tryptamine are found to intercalate, tryptophane-containing peptides do so only, if the tryptophane is flanked by at least two lysine units.

Effects of extrusion on the dye-binding, fluorodinitrobenzene-reactive and total lysine content of soyabean meal and peas

Commercial soyabean meal (hexane extracted and toasted) and peas were processed with a single- and twin-screw extruder, respectively, to test the effects of initial moisture level and die product temperature on the reactive lysine contents. For soyabean meal, extrusion temperatures ranged from 90 to 140°C with moisture levels of 25–40%. Extrusion of peas was carried out at temperatures ranging from 105 to 140°C at moisture levels of 15–30%. Extruded and non-extruded samples were analysed for total lysine, and for reactive lysine, determined by the fluorodinitrobenzene (FDNB) method and the dye-binding lysine (DBL) method. Extrusion of soyabean meal at moderate temperatures (140°C) and high moisture levels (27–40%) resulted in a reduction in FDNB-reactive lysine ranging from 10 to 14%. Increased moisture levels in the soyabean meal resulted in slightly lower FDNB-reactive lysine values; the major decrease was caused by the processing temperature. Extrusion of peas gave a 16% reduction in FDNB-reactive lysine only when the temperature was 140°C and the moisture level was low (15%). Although ther was a marked reduction in reactive lysine units, caused by the heat treatment, this was not detected by total lysine analysis, while DBL analysis gave a significant correlation ( r = 0.97; P < 0.001) with the FDNB-reactive lysine procedure for the extruded soyabean meal but not for the extruded peas. For unextruded samples there was close agreement between the total and FDNB-reactive lysine content. Overall, and based on the present findings, it is concluded that the FDNB method is useful for measuring the reduction in nutritional value after extrusion of soyabean meal and peas whereas the rapid DBL procedure gives inconsistent results. The extrusion of soyabean meal and peas at moderate temperatures can lead to loss of reactive lysine units.

Tissue-targeting ability of saccharide-poly(L-lysine) conjugates.

To evaluate the effect of introducing a saccharide moiety to poly(amino acids) on tissue distribution, several glycoconjugates of epsilon-(2-methoxyethoxyacetyl)-poly(L-lysine) of three molecular weights were synthesized using an octylene spacer between the sugar and polymer chain. Methoxyethoxyacetylation of the epsilon-amino group of the lysine unit in poly(L-lysine) was useful for avoiding nonspecific distribution to many tissues as the result of cationic charges. The tissue-targeting ability of each saccharide moiety was considered as the actual amount changed in each tissue caused by saccharide modification. Galactose terminated saccharides such as galactose, lactose and N-acetylgalactosamine accumulated exclusively in the liver, probably by the hepatic receptor. These conjugates could therefore be good carriers for a drug delivery system to the liver. On the other hand, the mannosyl and fucosyl conjugates were preferentially delivered to the reticuloendothelial systems such as those in the liver, spleen and bone marrow. In particular, fucosyl conjugates accumulated more in the bone marrow than in the spleen. Xylosyl conjugates accumulated mostly in the liver and lung. Generally, the accumulated amount in the target tissue increased with increasing molecular weight and an increased number of saccharides on one molecule of polymer.