Polymeric implants for cancer chemotherapy

Intratumoral delivery of paclitaxel-loaded poly(lactic-co-glycolic acid) microspheres for Hep-2 laryngeal squamous cell carcinoma xenografts

The introduction of induction chemotherapy provides an expectation of laryngeal function preservation without reduction in survival for patients with advanced laryngeal squamous cell carcinoma. The antitumor activity of conventional intravenous chemotherapy, however, is limited by systemic toxicity. The polymeric drug system delivered locally provides a novel modality of increasing therapeutic concentrations of drug for a prolonged period while decreasing systemic levels. In the current study, paclitaxel-loaded sustained-release microspheres were developed using poly(lactic-co-glycolic acid) as a drug carrier. Intratumoral administration of paclitaxel in the formulation of polymer showed enhanced efficacy against laryngeal squamous cell carcinoma in nude mice compared with conventional paclitaxel injection via the intratumoral or intraperitoneal route. No significant toxic reactions were observed in the experiment. Immunohistochemical findings indicated that paclitaxel exhibited antiangiogenic activity by inhibiting the expression of basic fibroblast growth factor and vascular endothelial growth factor within the tumor. Moreover, this effect could be better exploited via localized delivery of polymeric paclitaxel. In conclusion, direct administration of polymeric drug system at the tumor sites proved to be promising for the treatment of laryngeal carcinoma.

The brain tissue response to biodegradable poly(methylidene malonate 2.1.2)-based microspheres in the rat

The aim of this study was to follow the in vivo biodegradation as well as to appreciate the brain tissue response to poly(methylidene malonate 2.1.2) (PMM 2.1.2)-based microspheres implanted into the rat brain. Ninety-three adult Sprague-Dawley female rats were engaged in the study in which 54 underwent stereotactic implantation of blank gamma-sterilized PMM 2.1.2-based microspheres, prepared by an emulsion-extraction method. Twelve rats were implanted with the same 5-fluorouracil (5-FU)-loaded microspheres. Seventeen controls received the suspension medium alone (carboxymethylcellulose aqueous solution). The animals were sacrificed on post-operative days 1, 2, 8 and months 1, 2, 3, 6, 9, 12, 15 and 18. The brains were dissected, frozen, cut in a freezing microtome, and the slides were processed for immunohistological evaluation and scanning electron microscopy. During the first few days, the moderate inflammatory response to blank or loaded PMM 2.1.2 microspheres was largely a consequence of the mechanical trauma that occurs during surgery. The macrophagous-microglial reaction was similar to the one typically found following any damage in the CNS. There were also no differences in GFAP reactivity between the implanted animals and the controls. Blank microspheres began to degrade between 3 and 6 months, while 5-FU microspheres degraded between 8 days and 1 month. The polymer degradation generated in both cases a pronounced inflammatory and immunological reaction, leading to an important cell loss, a cerebral atrophy and to the death of several animals. PMM 2.1.2 was thus shown to be inadequate for intracerebral drug delivery.

Nonlinear dependence of hydraulic conductivity on tissue deformation during intratumoral infusion

Efficiency of intratumoral infusion for drug and gene delivery depends on intrinsic tissue structures as well as infusion-induced changes in these structures. To this end, we investigated effects of infusion pressure (P(inf)) and infusion-induced tissue deformation on infusion rate (Q) in three mouse tumor models (B16.F10, 4T1, and U87) and developed a poroelastic model for interpreting data and understanding mechanisms of fluid transport in tumors. The collagen concentrations in these tumors were 2.9+/-1.2, 12.2+/-0.9, and 18.1+/-3.5 microg/mg wet wt. of tissues, respectively. During the infusion, there existed a threshold infusion pressure (P(t)), below which fluid flow could not be initiated. The values of P(t) for these tumors were 7.36, 36.8, and 29.4 mmHg, respectively. Q was a bell-shaped function of P(inf) in 4T1 tumors but increased monotonically with increasing P(inf) in other tumors. These observations were consistent with results from numerical simulations based on the poroelastic model, suggesting that both the existence of P(t) and the nonlinear relationships between Q and P(inf) could be explained by infusion-induced tissue deformation that anisotropically affected the hydraulic conductivity of tissues. These results may be useful for further investigations of intratumoral infusion of drugs and genes.

Controlled-release microchips

Efficient drug delivery remains an important challenge in medicine: continuous release of therapeutic agents over extended time periods in accordance with a predetermined temporal profile; local delivery at a constant rate to the tumour microenvironment to overcome much of the systemic toxicity and to improve antitumour efficacy; improved ease of administration, and increasing patient compliance required are some of the unmet needs of the present drug delivery technology. Microfabrication technology has enabled the development of novel controlled-release microchips with capabilities not present in the current treatment modalities. In this review, the current status and future prospects of different types of controlled-release microchips are summarised and analysed with reference to microneedle-based microchips, as well as providing an in-depth focus on microreservoir-based and nanoporous microchips.

Delivery of viral vectors to tumor cells: extracellular transport, systemic distribution, and strategies for improvement

It is a challenge to deliver therapeutic genes to tumor cells using viral vectors because (i) the size of these vectors are close to or larger than the space between fibers in extracellular matrix and (ii) viral proteins are potentially toxic in normal tissues. In general, gene delivery is hindered by various physiological barriers to virus transport from the site of injection to the nucleus of tumor cells and is limited by normal tissue tolerance of toxicity determined by local concentrations of transgene products and viral proteins. To illustrate the obstacles encountered in the delivery and yet limit the scope of discussion, this review focuses only on extracellular transport in solid tumors and distribution of viral vectors in normal organs after they are injected intravenously or intratumorally. This review also discusses current strategies for improving intratumoral transport and specificity of viral vectors.

Preparation and characterization of novel biocompatible cryogels of poly (vinyl alcohol) and egg-albumin and their water sorption study

Polyvinyl alcohol (PVA) and egg albumin are water-soluble, biocompatible and biodegradable polymers and have been widely employed in biomedical fields. In this paper, novel physically cross-linked hydrogels composed of poly (vinyl alcohol) and egg albumin were prepared by cyclic freezing/thawing processes of aqueous solutions containing PVA and egg albumin. The FTIR analysis of prepared cryogels indicated that egg albumin was successfully introduced into the formed hydrogel possibly via hydrogen bonds among hydroxyl groups, amide groups and amino groups present in PVA and egg albumin. The gels were also characterized thermally and morphologically by DSC and SEM-techniques, respectively. The prepared so called 'cryogels' were evaluated for their water uptake potential and influence of various factors such as chemical architecture of the spongy hydrogels, pH and temperature of the swelling bath were investigated on the degree of water sorption by the cryogels. The effect of salt solution and various simulated biological fluids on the swelling of cryogel was also studied. The in vitro biocompatibility of the prepared cryogel was also judged by methods such as protein (BSA) adsorption, blood clot formation and percentage hemolysis measurements.

Nanoscale polymer carriers to deliver chemotherapeutic agents to tumours

Nanoscale polymer carriers have the potential to enhance the therapeutic efficacy of antitumour drugs as they can regulate their release, improve their stability and prolong circulation time by protecting the drug from elimination by phagocytic cells or premature degradation. Moreover, nanoscale polymeric carriers are capable of accumulating in tumour cells and tissues due to enhanced permeability and retention effect or by active targeting bearing ligands designed to recognise overexpressed tumour-associated antigens. The diversity in the polymer structures being studied as drug carriers in cancer therapy allows an optimal solution for a particular drug to be provided regarding its delivery and efficacy, and thus the patient's quality of life. This review is focused on the different types of nanoscale polymer carriers used for the delivery of chemotherapeutic agents and on the factors that affect their cellular uptake and trafficking.

Release of a macromolecular drug from alginate-impregnated microspheres

Macroporous microspheres were impregnated with calcium alginate to encapsulate fluorescein isothiocyanate-labeled dextran (FITC-dextran) and control its release. The detailed study of the impregnation process lead to its optimization: the quantity of alginate in the impregnated microspheres and the FITC-dextran encapsulation efficiency were increased. FITC-dextran diffused out of the impregnated microspheres in a slow rate in deionised water, while in presence of sodium ions, its release rate was increased as a consequence of the progressive swelling and erosion of calcium alginate. Release studies from different formulations of impregnated microspheres were performed in a continuous flow apparatus. The release profiles were composed of a slow release phase explained by the progressive erosion of calcium alginate and a faster release phase related to eroded impregnated microspheres. Therefore, the delayed release by microspheres induced by impregnation would permit the delivery of their payload at the vascular occlusion site, limit the amount of drug lost in the systemic circulation and improve the therapy.

Hybrid films from blends of chitosan and egg phosphatidylcholine for localized delivery of paclitaxel

Chitosan and egg phosphatidylcholine (ePC) were used as a unique combination to prepare composite films for localized drug delivery. In comparison to other phospholipids analyzed, ePC was found to produce chitosan-based films with minimal swelling and a high degree of stability. The properties of the chitosan-ePC films were characterized and found to be dependent on the ratio of chitosan:ePC present. FTIR analysis of chitosan-ePC films revealed that their high stability may be attributed to interactions present between these two biomaterials. In vitro evaluation of the cytotoxicity and protein adsorption properties of the films were used to provide a preliminary indication of their biocompatibility. The chitosan-ePC film was also evaluated as a matrix for the localized delivery of the anti-cancer agent, paclitaxel. Nanoparticles containing paclitaxel were dispersed throughout the chitosan-ePC film to result in a drug:material ratio of 1:8 (wt/wt). The film was found to provide a sustained release of paclitaxel over a 4-month period in biologically relevant media. The biological activity of paclitaxel loaded in the chitosan-ePC film was confirmed in SKOV-3 human ovarian cancer cells.

Quantitative determination of the antitumor alkyl ether phospholipid edelfosine by reversed-phase liquid chromatography–electrospray mass spectrometry: application to cell uptake studies and characterization of drug delivery systems

Edelfosine is a synthetic alkyl ether phospholipid that represents a promising class of antitumor agents. However, analytical methods to measure these type compounds are scarce. The lack of a reliable methodology to quantify edelfosine is a major problem in ongoing and scheduled preclinical and clinical trials with this drug. We evaluated the applicability of high-performance liquid chromatography-mass spectrometry to determine edelfosine in biological samples and polymeric delivery systems. Sample pre-treatment involved polymer precipitation or cell lysis with methanol. HPLC separation was performed on an Alltima RPC(18) narrow-bore column and edelfosine quantification was done by electrospray ionization mass spectrometry (ESI-MS) using positive ion mode and selected ion monitoring. Assays were linear in the tested range of 0.3-10 microg/ml. The limit of quantification was 0.3 ng/sample in both matrices, namely biological samples and polymeric delivery systems. The interassay precision ranging from 0.79 to 1.49%, with relative errors of -6.7 and 12.8%. Mean extraction recovery was 95.6%. HPLC-ESI-MS is a reliable system for edelfosine analysis and quantification in samples from different sources, combining advantages of full automation (rapidity, ease of use, no need of extensive extraction procedures) with high analytical performance and throughput.

The characterization of novel polymeric paste formulations for intratumoral delivery

The objective of this work was to characterize a polymeric paste formulation of the anticancer drug paclitaxel that was injectable through a narrow gauge needle at room temperature and set to a solid implant in vivo for the intratumoral treatment of localized cancer. Pastes were manufactured from a triblock copolymer composed of poly(D,L-lactide-co-caprolactone)-block-polyethylene glycol-block-poly(D,L-lactide-co-caprolactone) (PLC-PEG-PLC) or triblock blended with a low molecular weight polymer methoxypolyethylene glycol (MePEG). Characterization of pastes was performed using differential scanning calorimetry (DSC), gel permeation chromatography (GPC) and drug release studies. Paste integrity in water was measured by determining the degree of fragmentation under initial agitation. MePEG was found to be miscible with the triblock polymer and paclitaxel dissolved in various blends of these polymers up to 15% drug loading. Pastes composed of 40:60 triblock:MePEG blends and 10% paclitaxel were found to inject through a 23-gauge needle and set to a solid pellet in phosphate-buffered saline at 37 degrees C. Such pellets released paclitaxel in a controlled manner over 7 weeks. Pastes composed of 40:60 triblock:MePEG blends containing 10% paclitaxel are proposed as suitable injectable formulations of the drug for intratumoral therapy.

Toxicities and therapeutic effect of 5-fluorouracil controlled release implant on tumor-bearing rats

AIM: To investigate the toxicities, biodistribution and anticancer effect of 5-fluorouracil controlled release implant (5-FUCI) on Walker 256 carcinosarcoma cells in Wistar rats.

METHODS: Experiment 1: Wistar rats were randomly divided into three groups (27 rats per group). Blank implant was implanted in left lobe of the liver, and rats were treated with saline solution (in group A) or 5-fluorouracil (subcutaneous injection, group B). 5-FUCI was inserted in left lobe of the liver (group C). The gastrointestinal and hematological toxicities were observed and contents of element F in group C were assayed. Experiment 2: on day 6 after Walker-256 carcinosarcoma transplantation in left lobe of the liver, 5-FUCI was implanted in right lobe of the liver (group E) or left lobe (group F), and rats in control group (group D) were inserted blank implant. Tumor inhibition rate and survival time were investigated.

RESULTS: 5-FUCI showed no obvious toxic effect, extraction of Evan’s blue from gastrointestinal tissue was normal, the peripheral white blood cells and bone marrow nucleated cells were not reduced, compared with control group (P > 0.05). Histological examination revealed that there were no visible changes in small intestinal mucosa, The concentration of 5-fluorouracil in left lobe of the liver was 9.84, 28, 34 times as much as those of right lobe of the liver, heart and kidney respectively after the implantation in group C. They kept a high level of fluorouracil in left lobe of the liver, ranging from (4.414% ± 0.482%) to (7.800% ± 0.804%), for eight weeks. Survival days were 28.0 ± 2.2, 30.0 ± 3.2 and 38.7 ± 6.7 d in group D, E and F, respectively.

CONCLUSION: 5-FUCI shows no obvious toxicities to gastrointestinal tract and myelotoxicity. After implantation, it kept a high level of 5- fluorouracil in surrounding tissues of the implant for eight weeks. Its antitumor effect on Walker-256 carcinosarcoma is demonstrated.

Integrin-mediated targeting of drug delivery to irradiated tumor blood vessels

The objective of this study was to target drug delivery to radiation-induced neoantigens, which include activated receptors within the tumor vasculature. These responses include posttranslational changes in pre-existing proteins, which can be discovered by phage-displayed peptide libraries administered to mice bearing irradiated tumors. Phage-displayed peptides recovered from irradiated tumors included the amino acid sequence RGDGSSV. This peptide binds to integrins within the tumor microvasculature. Immunohistochemical staining of irradiated tumors showed accumulation of fibrinogen receptor alpha(2b)beta(3) integrin. We studied tumor targeting efficiency of ligands to radiation-induced alpha(2b)beta(3). Radiopharmaceuticals were localized to irradiated tumors by use of alpha(2b)beta(3) ligands conjugated to nanoparticles and liposomes. Fibrinogen-conjugated nanoparticles bind to the radiation-activated receptor, obliterate tumor blood flow, and significantly increase regression and growth delay in irradiated tumors. Radiation-guided drug delivery to tumor blood vessels is a novel paradigm for targeted drug delivery.

Membrane-encased polymer millirods for sustained release of 5-fluorouracil

This article describes the design and development of a novel membrane-encased polymer millirod for the sustained release of an anticancer drug, 5-fluorouracil (5-FU). The millirod consists of two functional compartments: (1) an inner 5-FU-loaded monolithic millirod as the drug depot, and (2) an outer NaCl-impregnated polymer membrane to control the release rate of 5-FU. The inner millirod is fabricated by a compression-heat molding procedure to permit the entrapment of 5-FU particles in the poly(D,L-lactide-co-glycolide) (PLGA) matrix. The drug loading density is controlled at 30 w/w% to achieve a burst release of 5-FU (>90% of the drug are released within 48 h) from the monolithic millirod. The NaCl-impregnated PLGA membrane is generated by solvent casting and is then wrapped over the monolithic millirod to produce the membrane-encased millirod. Scanning electron microscopy shows that dissolution of NaCl particles produces a semipermeable polymer membrane to provide a sustained release of 5-FU. The membrane thickness and the density of NaCl particles inside the membrane are useful parameters to control the release kinetics of 5-FU. Under the experimental conditions in this study, sustained release of 5-FU [rates between 0.1 and 0.4 mg/(day. cm of millirod)] is achieved for 2 to 5 weeks in phosphate-buffered saline (pH 7.4) at 37 degrees C. Results from this study demonstrate that membrane-encased polymer millirods provide controllable sustained release kinetics for applications in intratumoral drug delivery.

Localized delivery of paclitaxel in solid tumors from biodegradable chitin microparticle formulations

Paclitaxel (Taxol)-containing chitin and chitin-Pluronic F-108 microparticles were formulated as biodegradable systems for localized administration in solid tumors. The microparticles were characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and swelling studies in phosphate-buffered saline (PBS, pH 7.4). Lysozyme-induced degradation and in vitro release of paclitaxel was examined in PBS at 37 degrees C. The percent change in tumor volume was used to assess efficacy of the Formulations after local administration in murine Lewis lung carcinoma model. FT-IR confirmed higher degree of acetylation in chitin microparticles from the starting chitosan sample and the SEM showed that the chitin-Pluronic F-108 microparticles were significantly more porous than chitin microparticles. Due to higher porosity, chitin-Pluronic microparticles were able to imbibe higher swelling medium and degraded much faster in the presence of lysozyme than chitin microparticles. After 48 h. 51% of incorporated paclitaxel was released from chitin-Pluronic microparticles as compared to 28% from chitin microparticles. In vivo studies in Lewis lung carcinoma-bearing mice showed that the tumor volumes after 6 days using paclitaxel-loaded chitin and chitin-Pluronic F-108 microparticles was 458 and 307 mm3, respectively. In contrast, the tumor volume was 997 mm3 for the untreated control. The results of this study show that chitin and chitin-Pluronic F-108 microparticles are biodegradable drug delivery systems that can be useful for localized delivery of paclitaxel in solid tumors.

Intratumoral administration of paclitaxel in an in situ gelling poloxamer 407 formulation

In order to examine the efficacy of paclitaxel (Taxol, Bristol-Myers Squibb) after administration locally at the tumor site, we have developed a thermo-reversible gelling formulation in poloxamer 407 (Pluronic F-127) solution. Paclitaxel was incorporated in poloxamer 407 [20% (w/w)] at 0.5- and 1.0-mg/mL concentrations. The in vitro release studies were carried out in phosphate-buffered saline (pH 7.4) at 37 degrees C. Control and paclitaxel-poloxamer 407 formulations were administered intratumorally at a dose of 20 mg/kg in B16F1 melanoma-bearing mice. The change in tumor volume as a function of time and the survival of treated animals were used as measures of efficacy. Poloxamer 407 solution undergoes a reversible sol-gel transition when the temperature is raised to above 21 degrees C. In vitro paclitaxel release from poloxamer 407 gels was very slow (only 6.1% after 6 hr) probably due to the poor aqueous solubility of the drug. Significant enhancement in the anti-tumor efficacy was noted following intratumoral administration of paclitaxel-poloxamer 407 formulation. The initial tumor growth rate was delayed by 67% and the tumor volume doubling time was increased by 72% relative to saline control. In addition, more than 91% of the tumor-bearing animals that received paclitaxel in poloxamer 407 gel survived on day 15 post-administration as compared to 58% in the control group. The results of this study show significant benefit of paclitaxel for solid tumor when administered locally in an in situ gelling poloxamer 407 formulation.

Relation between dissolution profiles and toxicity of cisplatin-loaded microspheres

The aim of this study is to evaluate and compare the dissolution profiles of cisplatin-loaded microspheres (CDDP-MS) in vitro and in vivo, and to determine the relationship between the dissolution profiles in vitro and systemic toxicity. For this purpose, three types of CDDP-MS that release the CDDP for 1, 2 and 5 weeks without a large amount of initial release in phosphate buffered saline (pH 7.4) were prepared. The dissolution profiles of these formulations in vivo were well correlated with in vitro studies, and resulted in well-controlled plasma platinum concentration. The systemic toxicity of the CDDP-MS and CDDP dissolved in saline (CDDP-SOL) were assessed by intraperitoneal administration in mice. The maximal tolerable dose (MTD) of CDDP-SOL was 13.4 mg/kg, whereas the CDDP-MS of 1, 2 and 5-week types were 34.6, 44.2, 62.6 mg/kg, respectively. The MTD of CDDP increased proportionally when 50% of CDDP had been released from MS in vitro (MTD (mg/kg)=5.22 x T(50(day)) + 13.2, R(2)=0.9935). We demonstrate that the systemic toxicity of CDDP-MS can be predicted by evaluation of the dissolution rate in vitro since in vivo dissolution was correlated with the in vitro.

Radiation-mediated control of drug delivery

Clinical trials of radiotherapy to control drug delivery were initiated in 1999 at Vanderbilt University. The initial studies exploited the findings that platelets are activated in tumor blood vessels after high-dose irradiation as used in radiosurgery and high-dose-rate brachytherapy. Platelets labeled with 111In showed binding in tumor blood vessels. However, the platelet labeling process caused platelets to also accumulate in the spleen. That clinical trial was closed, and subsequent clinical trials targeted protein activation in irradiated tumor blood vessels. Preclinical studies showed that peptide libraries that bind within irradiated tumor blood vessels contained the peptide sequence Arg-Gln-Asp (RGD). RGD binds to integrin receptors (e.g., receptors for fibrinogen, fibronectin, and vitronectin). We found that the fibrinogen receptor (GPIIb/IIIa, alpha2bbeta3) is activated within irradiated tumor blood vessels. RGD peptidemimetics currently in clinical trials include GPIIb/IIIa antagonists and the platelet-imaging agent biapcitide. Biapcitide is an RGD mimetic that is labeled with 99Tc to allow gamma camera imaging of the biodistribution of the GPIIb/IIIa receptor in neoplasms of patients treated with radiosurgery. This study has shown that the schedule of administration of the RGD mimetic is crucial. The peptide mimetic must be administered immediately before irradiation, whereas the natural ligands to the receptor compete for biapcitide binding if biapcitide is administered after irradiation. The authors currently are conducting a dose deescalation study to determine the threshold dosage required for RGD mimetic binding to radiation activated receptor. Radiation-guided clinical trials have been initiated by use of high-dose-rate brachytherapy. In a separate trial, the pharmacokinetics of radiation-inducible gene therapy are being investigated. In this trial, the radiation-activated promoter Egr-1 regulates expression of the tumor necrosis factor alpha gene, which is administered by use of the attenuated adenovirus vector. The Ad.Egr-TNF (ADGV) gene is administered by intratumoral injection of vector followed by irradiation in patients with soft-tissue sarcomas. This review highlights recent findings in these phase I pharmacokinetic studies of radiation-controlled drug delivery systems.

Pharmacokinetic behaviour of cisplatin in peritoneal fluid after intraperitoneal administration of cisplatin-loaded microspheres

The objective of this study was to establish a pharmacokinetic model for the estimation of unchanged cis-dichlorodiammine-platinum (II) (CDDP) concentration in peritoneal fluid after intraperitoneal administration of cisplatin-loaded microspheres (CDDP-MS) and to elucidate the accuracy of this model by comparisons between actual and simulated values after intraperitoneal administration of CDDP-MS. We developed a method enabling the precise and quick assessment of the drug concentration in the peritoneal cavity. The pharmacokinetic parameters obtained after intravenous bolus injection at a dose of 2 mg kg(-1) were total body clearance (1026 mL h(-1) kg(-1)), elimination rate constant (3.24 h(-1)) and distribution volume of systemic circulation (316.7 mL kg(-1)). After an intraperitoneal bolus injection at a dose of 5 mg kg(-1), the absorption rate constant from the peritoneal cavity (3.64 h(-1)) and the distribution volume of the peritoneal cavity (13.5 mL kg(-1)) were determined. The protein-binding rate constant in ascites was 0.58 h(-1). Using these pharmacokinetic parameters, we established a pharmacokinetic model consisting of two compartments. Administration of CDDP-MS at a dose of 10 mg kg(-1), which released CDDP over 7 days in-vitro, yielded sustained concentrations of unchanged CDDP (1-2 mg mL(-1)) in the peritoneal cavity that persisted for 7 days, and that were predictable by applying the in-vitro dissolution profile to the pharmacokinetic model. The findings obtained from this study are useful for understanding the basic pharmacokinetic characteristics of unchanged CDDP in the peritoneal cavity and may also be important in the development of optimized CDDP-MS formulations.

Quantitative analysis of intratumoral infusion of color molecules

Intratumoral infusion has a potential for improving distribution of drugs. To optimize the infusion, we developed a novel technique to quantify the distribution volume of color molecules (Vd) in solid tumors. Evans blue-labeled albumin was infused locally with the use of a needle into a rat fibrosarcoma ex vivo under different pressures. After the infusion, tumor tissues were sectioned serially into thin slices. The blue area in each slice was quantified with the use of the newly developed technique. The Vd was calculated based on the blue area and the slice thickness. Our data showed that infusion pressure and volume (V(i)) had significant effects on Vd. The median of Vd/V(i) decreased from 2.99 to 1.79 when infusion pressure was increased from 50 to 163 cmH2O, presumably due to retardation of convective transport. In addition, the coefficient of variation in Vd/V(i) was increased from 0.13 at 50 cmH2O to 0.64 at 163 cmH2O. The dependence of Vd/V(i) and its variation on infusion pressure suggests that 1) infusion-induced tissue deformation is unpredictable and 2) both the unpredictability and the interstitial retardation of convective transport increase with infusion pressure.

Targeting drug delivery to radiation-induced neoantigens in tumor microvasculature

Radiation can be used to guide drugs to specific sites such as neoplasms or aberrant blood vessels. When blood vessels are treated with ionizing radiation, they respond by expressing a number of cell adhesion molecules and receptors that participate in homeostasis. Examples of radiation-induced molecules in blood vessels include ICAM-1, E-selectin, P-selectin and the beta(3) integrin. We have observed that the endothelium and blood components respond to oxidative stress in a similar, if not identical manner in all tumor models. Although we have identified several other radiation-induced molecules within tumor blood vessels, the beta(3) target for drug delivery achieves the greatest site-specific peptide binding within irradiated tumor blood vessels. We have focused on peptides and antibodies that bind to integrin beta(3). beta(3)-binding proteins have been conjugated to fluorochromes and radionuclides to study the site specificity and microscopic distribution. We have found immunofluorescent and immunohistochemical staining of beta(3) within the lumen of blood vessels immediately following irradiation. To determine whether it is feasible to guide drug delivery to irradiated tumors, we studied ligands to alpha(2b)beta(3) (fibrinogen). Peptides within fibrinogen that bind to alpha(2b)beta(3) includes the dodecapeptide, HHLGGAKQAGDV and the RGD peptide. We utilized 131I conjugation to these ligands to study the biodistribution in tumor bearing mice. Our clinical trial consists of the RGD peptidomimetic, biapcitide, labeled with 99mTc. This study shows that it is feasible to guide drugs to human neoplasms by use of radiation-guided peptides. These studies have shown that peptides that bind to these integrins bind to tumors following exposure to ionizing radiation.

Fluorine ion-implanted polystyrene improves growth and viability of vascular smooth muscle cells in culture

Vascular smooth muscle cells derived from the rat aorta were cultured on unmodified or F(+) ion-implanted polystyrene (5 x 10(12) or 5 x 10(14) ions/cm(2), energy 150 keV). In 1-day-old cultures, the cells adhered to the modified polystyrene in higher numbers and over larger contact areas. Increased resistance of the cells to trypsin-mediated detachment from the growth support indicated an improved adhesion of cells to the modified polymer at later culture intervals. The cells cultured on ion-modified polymers also were larger and had a higher total protein content. By use of immunocytochemistry, several specific protein species were increased, including the cytoskeletal alpha-actin and vimentin and the plasma membrane-associated vinculin, talin, alpha-v integrins, ICAM-1, and VCAM-1, which account for stronger cell-cell and cell-extracellular matrix adhesion. The lower number of cells found floating in the medium suggests that the spontaneous detachment of cells from the modified polystyrene was lower and that the viability of the adhered cell population was higher. As was shown by the two-parameter flow-cytometric measurements of BrdU incorporation and DNA content, as well as by (3)H-thymidine autoradiography, the cell proliferation on samples modified by the dose of 5 x 10(12) ions/cm(2) was similar to that in controls; and at the dose of 5 x 10(14) ions/cm(2), it tended to be even lower. The cells grown on the polymer implanted with the dose of 5 x 10(12) ions/cm(2) responded to a new artificially created cell-free area in a confluent cell layer by more intense migration whereas at the dose of 5 x 10(14) ions/cm(2), the migration ability of cells was similar to that on the unmodified polymer. The data revealed a higher biocompatibility of ion-implanted polystyrene with vascular smooth muscle cells in culture. There was better adhesion, differentiation, and survival, and there was neither excessive migration nor proliferation.