Cell-penetrating peptides: a useful tool for the delivery of various cargoes into cells.

Cell-penetrating compounds are substances that enhance the cellular uptake of various molecular cargoes that do not easily cross the cellular membrane. The majority of cell-penetrating compounds described in the literature are cell-penetrating peptides (CPPs). This review summarizes the various structural types of cell-penetrating compounds, with the main focus on CPPs. The authors present a brief overview of the history of CPPs, discuss the various types of conjugation of CPPs to biologically active cargoes intended for cell internalization, examine the cell-entry mechanisms of CPPs, and report on the applications of CPPs in research and in preclinical and clinical studies.

Synthetic polymer scaffolds for soft tissue engineering.

Tissue engineering (TE) and regenerative medicine are progressively developed areas due to many novel tissue replacements and implementation strategies. Increasing knowledge involving the fabrication of biomaterials with advanced physicochemical and biological characteristics, successful isolation and preparation of stem cells, incorporation of growth and differentiation factors, and biomimetic environments gives us a unique opportunity to develop various types of scaffolds for TE. The current strategies for soft tissue reconstitution or regeneration highlight the importance of novel regenerative therapies in cases of significant soft tissue loss and in cases of congenital defects, disease, trauma and ageing. Various types of biomaterials and scaffolds have been tested for soft tissue regeneration. The synthetic types of materials have gained great attention due to high versatility, tunability and easy functionalization for better biocompatibility. This article reviews the current materials that are usually the most used for the fabrication of scaffolds for soft TE; in addition, the types of scaffolds together with examples of their applications for the regenerative purposes of soft tissue, as well as their major physicochemical characteristics regarding the increased applicability of these materials in medicine, are reviewed.

Polymer brushes based on PLLA-b-PEO colloids for the preparation of protein resistant PLA surfaces.

In this study we investigate the formation of protein-resistant polymer surfaces, such as aliphatic polyesters, through the deposition of self-assemblies of amphiphilic poly(l-lactide)-b-poly(ethylene oxide), PLLA-b-PEO, copolymers as stable nanoparticles with a kinetically frozen PLLA core on model PLLA surfaces. The length of the PEO chains in the corona was tuned to achieve polymer brushes capable of preventing protein adsorption on PLA-based biomaterials. The spectroscopic ellipsometry, IR and XPS analysis, contact angle goniometry, and AFM proved that the PEO chains adopted a brush structure and were preferably exposed on the surface. The low-fouling properties of the physisorbed PLLA-b-PEO layers approached the ones of reactive grafting methods, as shown by surface plasmon resonance spectroscopy. The anti-fouling properties of the prepared PEO brushes provided sufficient interface to prevent cell adhesion as proved in vitro. Thus, the developed surface coating with PLLA-b-PEO colloids can provide an anti-fouling background for the creation of nanopatterned biofunctionalized surfaces in biomedical applications.

Intracellular fate of polymer therapeutics investigated by fluorescence lifetime imaging and fluorescence pattern analysis.

Nanocarriers bearing anticancer drugs are promising candidates to improve the efficacy of cancer therapy and minimize side effects. The most potent cytostatics used in the treatment of various cancers are anthracyclines, e.g. doxorubicin or pirarubicin. Recently, polymer therapeutics carrying anthracyclines have been intensively studied. The precise characterization of in vitro nanocarrier biological behavior brings a better understanding of the nanocarrier characteristics and enables prediction of the behavior of the nanocarrier during in vivo application. Advanced fluorescence detection methods, e.g. fluorescence lifetime imaging microscopy (FLIM), were successfully exploited to describe the properties of various polymeric nano-systems and contributed to a complex view of anthracyclines' intracellular transport and DNA intercalation. Here, we report the application of a specific technique for processing FLIM images, called fluorescence pattern decomposition, to evaluate early events after doxorubicin or pirarubicin treatment of cells. Moreover, we characterized changes in the intracellular localization and release of the anthracyclines during the incubation of cells with polymer nanotherapeutics based on poly[N-(2-hydroxypropyl)-methacrylamide] (pHPMA).

The pH-dependent and enzymatic release of cytarabine from hydrophilic polymer conjugates.

Cytarabine is one of the most efficient drugs in the treatment of hematological malignancies. In this work, we describe the synthesis and characterization of two different polymer conjugates of cytarabine that were designed for the controlled release of cytarabine within the leukemia cells. Reactive copolymers of N-(2-hydroxypropyl)methacrylamide (HPMA) and 3-(3-methacrylamidopropa-noyl)thiazolidine-2-thione) or 3-(Nmethacryloylglycyl-phenylalanylleucylglycyl)thiazolidine-2-thione were used in the study as reactive polymer precursors for reaction with cytarabine. The enzymatic release of cytarabine from the conjugate containing a GFLG spacer utilizing cathepsin B was verified. In addition to enzymolysis, the pH-dependent hydrolysis of cytarabine from both copolymers was also confirmed. Approximately 40 % and 20 % of the drug was released by spontaneous hydrolysis at pH 7.4 within 72 h from the polymer conjugates with the GFLG and beta-Ala spacers, respectively. At pH 6.0, the spontaneous hydrolysis slowed down, and less than 10 % of the drug was liberated within 72 h. The results of the cytotoxicity evaluation of the polymer conjugates in vitro against various cell lines showed that the cytotoxicity of the polymer conjugates is approximately three times lower in comparison to free cytarabine.

Micelle-forming HPMA copolymer conjugates of ritonavir bound via a pH-sensitive spacer with improved cellular uptake designed for enhanced tumor accumulation.

We describe design, synthesis, physico-chemical characterization and preliminary biological evaluation of micelle-forming polymer drug conjugates with controlled drug release intended for tumor treatment. The structure of the conjugates was designed to enable tumor tissue- and cell-specific drug release and micelle disassembly to avoid side effects accompanying classic chemotherapy and guarantee safe elimination of the drug-free carrier from the organisms. The amphiphilic polymer conjugates consisted of a hydrophobic hexaleucine block and a hydrophilic block based on the N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer with an antiviral and cytostatic drug, ritonavir, bound through a pH-sensitive spacer. Diblock copolymers with low dispersity (D∼ 1.1) were prepared via reversible addition-fragmentation chain transfer (RAFT) copolymerization using a hexaleucine derivative as a chain transfer agent. The associative properties of the copolymers depend on the hydrophilic polymer block length and the hydrophobic ritonavir content. The micelles dissociated under mild acidic conditions mimicking the environment inside tumor tissue/cells, because of the decrease in polymer hydrophobicity after the rapid release of the hydrophobic drug from the polymer carrier. Unexpectedly, the polymer-ritonavir conjugates internalized into HeLa cells significantly more than the polymers without ritonavir. The enhanced cell penetration and pH-triggered micelle disassembly predetermine the polymer-ritonavir conjugates to become promising tumor-targeted drug carriers.

Silica-modified monodisperse hexagonal lanthanide nanocrystals: synthesis and biological properties.

Oleic acid-stabilized hexagonal NaYF4:Yb(3+)/Er(3+) nanocrystals, emitting green and red luminescence, were prepared by the high-temperature co-precipitation of lanthanide chlorides. By varying the reaction time and the Ln(3+)/Na(+) ratio, the nanocrystal size can be controlled within the range 16-270 nm. The maximum upconversion quantum yield is achieved under 970 nm excitation. The reverse microemulsion technique using hydrolysis and condensation of tetraethoxysilane is a suitable method to coat the nanocrystal surface with a silica shell to make the particles dispersible and colloidally stable in aqueous media. During the subsequent functionalization, (3-aminopropyl)trimethoxysilane introduced amino groups onto the silica to enable future bioconjugation with the target molecules. All specimens were characterized by TEM microscopy, electron and X-ray diffraction, ATR FT-IR spectroscopy, and upconversion luminescence. Finally, in vitro cytotoxicity and intracellular nanoparticle uptake (using confocal microscopy) were determined with human cervical carcinoma HeLa and mRoGFP HeLa cells, respectively. From the investigated particles, amino-functionalized NaYF4:Yb(3+)/Er(3+) nanocrystals internalized into the cells most efficiently. The nanoparticles proved to be nontoxic at moderate concentrations, which is important when considering their prospective application in biolabeling and luminescence imaging of various cell types.

Nanotherapeutics with anthracyclines: methods of determination and quantification of anthracyclines in biological samples.

Anthracyclines, e.g. doxorubicin, pirarubicin, are widely used as cytostatic agents in the polymer nanotherapeutics designed for the highly effective antitumor therapy with reduced side effects. However, their precise dosage scheme needs to be optimized, which requires an accurate method for their quantification on the cellular level in vitro during nanocarrier development and in body fluids and tissues during testing in vivo. Various methods detecting the anthracycline content in biological samples have already been designed. Most of them are highly demanding and they differ in exactness and reproducibility. The cellular uptake and localization is predominantly observed and determined by microscopy techniques, the anthracycline content is usually quantified by chromatographic analysis using fluorescence detection. We reviewed and compared published methods concerning the detection of anthracycline nanocarriers.

[Gene therapy of the graft versus host reaction]. / Genová terapie reakce stepu proti hostiteli.

Graft-versus-host-disease (GVHD) is a frequent and dangerous complication of allogenic transplantations of bone marrow. Gene therapy offers a way to deal with the problem. It is based on the introduction of suicide genes (SG) into the donor's T lymphocytes, which are responsible for the development of GVHD. If it develops, the presence of SG in the effector cells gives an opportunity to get rid of them, because their products are capable of changing otherwise innocuous substances into highly cytotoxic metabolites. For the transduction of SG retrovirus-based vectors are used. The authors tried to employ for this purpose recombinant adeno-associated viruses (rAAV). The attempt was unsuccessful. When using rAAV as vectors, the efficacy of transduction was very low. Further experiments indicated that this failure was due to the absence of receptor for AAV in T lymphocytes. It seems clear that until the surface of rAAV is modified to facilitate their penetration into T cells, they cannot replace retroviruses for transfer of SG into this cell type.

Combined suicide gene and immunostimulatory gene therapy using AAV-mediated gene transfer to HPV-16 transformed mouse cell: decrease of oncogenicity and induction of protection.

To test the effects of combined transduction of a suicide gene and genes coding for various immunostimulatory factors on the oncogenicity and immunogenicity of TC-1 cells (HPV-16 transformed C57BL/6 mouse cells), several bicistronic recombinant adeno-associated viruses (rAAV) were constructed. Each of these constructs carried, and in infected cells expressed, the herpes simplex type 1 thymidine-kinase gene (HSV-TK) and the gene of one of the following immunostimulatory factors: human monocyte chemoattractant protein 1 (MCP-1), mouse B7.1 costimulatory molecule (B7.1), or mouse granulocyte-macrophage colony-stimulating factor (GM-CSF). For control purposes, an rAAV carrying the HSV-TK gene and neomycin resistance gene (neo) and an rAAV containing the lacZ gene were used. All of these constructs proved functional both in mouse TC-1 and human 293T cells. For experiments in mice, TC-1 cells were infected in vitro with the AAV recombinants at an input multiplicity of 50 particles/cell; these cells were then administered to 5-week-old mice. As from day 5, half of the animals were given ganciclovir (GCV) (2.5 mg/day) for 10 days. With a single exception, none of the mice inoculated with cells treated with rAAV expressing HSV-TK + B7.1 or HSV-TK + MCP-1 developed tumour irrespective of GCV treatment. The tumour suppressive effect was less marked in animals inoculated with TC-1 cells infected with rAAV expressing HSV-TK + GM-CSF, and among these it was somewhat more pronounced in GCV-untreated animals. A clear antitumour effect of GCV treatment was only observed in mice inoculated with TC-1 cells transduced with rAAV expressing HSV-TK but no immunostimulatory factor. Mice that remained tumour-free on day 54 were challenged with untreated TC-1 cells. The tumour resistance rates found were related not only to the immunostimulatory gene used for the transduction, but also to GCV treatment. The best protection was recorded in mice pre-inoculated with TC-1 cells transduced with either B7.1 or MCP-1-expressing rAAV and not given GCV.