Effect of stereotactic implantation of biodegradable 5-fluorouracil-loaded microspheres in healthy and C6 glioma-bearing rats

Toward chronopharmaceutical drug delivery patches and biomaterial coatings for the facilitation of wound healing

Implantation of a biomaterial entails a form of injury where the integration of the implant into the host tissue greatly depends on the proper healing of the wound. Wound healing, itself, consists of a number of physiological processes, each occurring within a characteristic time window. A composite, multilayered polymeric drug delivery carrier for adhesion to the wound site and its supply with molecules released at precise time windows at which the stages in the healing process that they target occur is conceptualized here. We also present a simplified version of one such multilayered composite fabricated by a combination of solvent casting and dip coating, comprising the base poly(ε-caprolactone) layer reinforced with hydroxyapatite nanoparticles, poly(glutamic acid) mesolayer and poly-l-lysine surface layer, each loaded with specific small molecules and released at moderately distinct timescales, partially matching the chronology of wound healing. To that end, the base layer proved suitable for the delivery of an anti-inflammatory molecule or an angiogenic agent, the mesolayer appeared appropriate for the delivery of an epithelialization promoter or a granulation factor, and the adhesive surface layer interfacing directly with the site of injury showed promise as a carrier of a vasodilator. The drug release mechanisms were diffusion-driven, suggesting that the drug/carrier interaction is a key determinant of the release kinetics, as important as the nature of the polymer and its hydrolytic degradation rate in the aqueous medium. Morphological and phase composition analyses were performed, along with the cell compatibility ones, demonstrating solid adhesion and proliferation of both transformed and primary fibroblasts on both surfaces of the composite films. The design of the multilayered composite drug delivery carriers presented here is prospective, but requires further upgrades to achieve the ideal of a perfect timing of the sequential drug release kinetics and a perfect resonance with the physiological processes defining the chronology of wound healing.

Dual-drug delivery by thermo-responsive Janus nanogel for improved cellular uptake, sustained release, and combination chemo-thermal therapy

The goal of this work was to examine the heat-sensitizing effects of Janus-coated magnetic nanoparticles (JMNPs) as a vehicle for 5-fluorouracil (5-Fu) and Quercetin (Qu) in C6 and OLN-93 cell lines. The cellular uptake of nanoparticles was evaluated using Prussian blue staining and ICP-OES after monolayer culturing of C6 (rat brain cancer cell) and OLN-93 (normal rat brain cell) cells. The cells were treated with free 5-Fu, Qu, and MJNPs loaded with Qu/5-Fu for 24 h, followed by magnetic hyperthermia under an alternating magnetic field (AMF) at a temperature of 43 °C. Using the MTT test and Flow cytometry, the C6 and OLN-93 cells were investigated after being subjected to hyperthermia with and without magnetic nanoparticles. The results of Prussian blue staining confirmed the potential of MJNPs as carriers that facilitate the uptake of drugs by cancer cells. The results showed that the combined application of Qu/5-Fu/MJNPs with hyperthermia significantly increased the amount of ROS production compared to interventions without MJNPs. The therapeutic results demonstrated that the combination of Qu/5-Fu/MJNPs with hyperthermia considerably enhanced the rate of apoptotic and necrotic cell death compared to that of interventions without MJNPs. Furthermore, MTT findings indicated that controlled exposure of Qu/5-Fu/MJNPs to AMF caused a synergistic effect. The advanced Janus magnetic nanoparticles in this study can be proposed as a promising dual drug carrier (Qu/5-Fu) and thermosensitizer platform for dual-modal synergistic cancer therapy.

Injectable local drug delivery systems for glioblastoma: a systematic review and meta-analysis of progress to date

Glioblastoma (GBM) is an aggressive malignant cancer associated with bleak prognosis and high mortality. The current standard of care for GBM is maximum surgical resection plus radiotherapy and temozolomide (TMZ) chemotherapy. The blood brain barrier (BBB) remains the main obstacle for chemotherapy and severely limits the choice of therapeutic agents. Local treatment allows drugs to circumvent the BBB and reduces systemic side effects. Despite much research effort, to date, no drug delivery system (DDS) designed to be directly injected into brain tumors has been clinically approved, and a systematic overview of the progress in this field, or lack thereof, is missing. In this review, a systematic search of pre-clinical literature was conducted which resulted in 36 original articles on injectable DDS for local treatment of GBM which met the inclusion criteria. A wide range of injectable DDS have been developed and tested pre-clinically which include nanoparticles, liposomes, microspheres, hydrogels and others. meta-Analyses of the included studies showed that, overall, local administration of injectable DDS was beneficial to increase the animal's survival time. Finally, this review summarized the therapeutic effect after local treatment and discussed the shortcomings of the experimental setting in in vivo studies.

Rationally designed drug delivery systems for the local treatment of resected glioblastoma

Glioblastoma (GBM) is a particularly aggressive brain cancer associated with high recurrence and poor prognosis. The standard of care, surgical resection followed by concomitant radio- and chemotherapy, leads to low survival rates. The local delivery of active agents within the tumor resection cavity has emerged as an attractive means to initiate oncological treatment immediately post-surgery. This complementary approach bypasses the blood-brain barrier, increases the local concentration at the tumor site while reducing or avoiding systemic side effects. This review will provide a global overview on the local treatment for GBM with an emphasis on the lessons learned from past clinical trials. The main parameters to be considered to rationally design fit-of-purpose biomaterials and develop drug delivery systems for local administration in the GBM resection cavity to prevent the tumor recurrence will be described. The intracavitary local treatment of GBM should i) use materials that facilitate translation to the clinic; ii) be characterized by easy GMP effective scaling up and easy-handling application by the neurosurgeons; iii) be adaptable to fill the tumor-resected niche, mold to the resection cavity or adhere to the exposed brain parenchyma; iv) be biocompatible and possess mechanical properties compatible with the brain; v) deliver a therapeutic dose of rationally-designed or repurposed drug compound(s) into the GBM infiltrative margin. Proof of concept with high translational potential will be provided. Finally, future perspectives to facilitate the clinical translation of the local perisurgical treatment of GBM will be discussed.

Role of Polymeric Local Drug Delivery in Multimodal Treatment of Malignant Glioma: A Review

Malignant gliomas (MGs) are the most common and devastating primary brain tumor. At present, surgical interventions, radiotherapy, and chemotherapy are only marginally effective in prolonging the life expectancy of patients with MGs. Inherent heterogeneity, aggressive invasion and infiltration, intact physical barriers, and the numerous mechanisms underlying chemotherapy and radiotherapy resistance contribute to the poor prognosis for patients with MGs. Various studies have investigated methods to overcome these obstacles in MG treatment. In this review, we address difficulties in MG treatment and focus on promising polymeric local drug delivery systems. In contrast to most local delivery systems, which are directly implanted into the residual cavity after intratumoral injection or the surgical removal of a tumor, some rapidly developing and promising nanotechnological methods—including surface-decorated nanoparticles, magnetic nanoparticles, and focused ultrasound assist transport—are administered through (systemic) intravascular injection. We also discuss further synergistic and multimodal strategies for heightening therapeutic efficacy. Finally, we outline the challenges and therapeutic potential of these polymeric drug delivery systems.

Frontiers in the treatment of glioblastoma: Past, present and emerging

Glioblastoma (GBM) is one of the most aggressive cancers of the brain. Despite extensive research over the last several decades, the survival rates for GBM have not improved and prognosis remains poor. To date, only a few therapies are approved for the treatment of GBM with the main reasons being: 1) significant tumour heterogeneity which promotes the selection of resistant subpopulations 2) GBM induced immunosuppression and 3) fortified location of the tumour in the brain which hinders the delivery of therapeutics. Existing therapies for GBM such as radiotherapy, surgery and chemotherapy have been unable to reach the clinical efficacy necessary to prolong patient survival more than a few months. This comprehensive review evaluates the current and emerging therapies including those in clinical trials that may potentially improve both targeted delivery of therapeutics directly to the tumour site and the development of agents that may specifically target GBM. Particular focus has also been given to emerging delivery technologies such as focused ultrasound, cellular delivery systems nanomedicines and immunotherapy. Finally, we discuss the importance of developing novel materials for improved delivery efficacy of nanoparticles and therapeutics to reduce the suffering of GBM patients.

Intratumoral temozolomide in spontaneous canine gliomas: feasibility of a novel therapy using implanted microcylinders

Entotherapy[Link] an image‐guided drug‐eluting microcylinder platform, has the potential to bypass the limitations of systemic chemotherapy use in the treatment of canine brain tumours. Gliomas, which are common in dogs and also represent the majority of fatal brain tumours in humans, can be amenable to chemotherapy with temozolomide. Biopolymer microcylinders conjugated with temozolomide and gadolinium were implanted into partially resected tumours of four client‐owned dogs with gliomas. All four dogs presented with generalized seizures and had mild to no neurologic deficits at the time of craniotomy. All dogs underwent craniotomy for implantation of the microcylinders into partially resected gliomas (glioblastoma multiforme {n = 1} or oligodendroglioma {n = 3}). All dogs recovered well from the craniotomy and implantation procedure. This novel procedure appears to be feasible and tolerated in tumour‐bearing dogs. A future controlled clinical study can now aim to evaluate the microcylinder implantation for long‐term efficacy.

Injection of Chemotherapeutic Microspheres and Glioma III: Parameters to Optimize Efficacy

Injectable microspheres may provide a means of providing local, sustained exposure of glioma to chemotherapeutics to improve patient survival. Using a rodent model of surgically resected glioma, we previously demonstrated that direct injections of chemotherapeutic microspheres into the tissue surrounding a resection cavity provide superior survival effects over injections of the same microspheres directly into the surgical cavity. The present experiments extended this novel observation by exploring several parameters related to the use of intraparenchymal injections of chemotherapeutic microspheres to treat glioma. Using a rat model of resected glioma, several principles regarding the use of local sustained release carboplatin microspheres were established. First, an inverted U dose–response was observed, wherein further dose escalation beyond the optimal dose was not efficacious and indeed produced significant local toxicity. Second, it was necessary to expose approximately 40% of the tumor margin to sustained release carboplatin in order to increase survival in this model. Survival was not enhanced when the proportion of the tumor margin exposed to carboplatin was only 20%. Third, the distribution of the chemotherapeutic microsphere injections along the tumor perimeter was shown to be important, requiring that the entire perimeter be proportionately exposed to the chemotherapeutic agent. Together, these data continue to support the development of chemotherapeutic microspheres for treating glioma. However, they also caution that a number of fundamental parameters can profoundly influence the efficacy that might be expected from local sustained delivery. Careful attention to these principles is not only required if chemotherapeutic microspheres are to be used efficaciously, but these principles should provide a foundation to further optimize the potential of this and other polymeric delivery systems under development for local, intraparenchymal drug delivery to glioma.

Injection of Chemotherapeutic Microspheres and Glioma IV: Eradicating Tumors in Rats

Polymer microspheres can be easily injected into the brain to provide a local and sustained delivery of chemotherapeutics to a tumor or surrounding tissue subject to high rates of tumor recurrence following surgery. Building on previous studies that established the clear advantage of local, peritumoral injections of sustained release microspheres, the following experiments utilized two different approaches for maximizing the survival benefit in glioma-bearing rats. In the first experiment, a previously grown cortical tumor was debulked and animals received either one or two treatments with carboplatin-loaded microspheres (either 200 or 800 μg total carboplatin per treatment). In each case, the microspheres were injected along the perimeter of the resection cavity with each treatment separated by 20 days. Survival studies clearly demonstrated that two, temporally spaced injections were superior to a single series of injections. At the lowest dose tested (200 μg), median survival was increased an additional 40% over that in animals receiving one treatment. At the higher dose (800 μg), one third of the animals receiving two separate treatments were long-term survivors (>150 days) and showed complete eradication of the tumor on histological examination. In the second experiment, we directly compared the efficacy produced by sustained release carboplatin or 1,3-bis[2-chloroethyl]-1-nitrourea (BCNU) alone versus injecting carboplatin and BCNU-loaded micro-spheres blended together as a single suspension. Carboplatin and BCNU both enhanced survival, with BCNU being significantly less effective than carboplatin. However, the greatest improvements in survival were seen when a blended suspension of carboplatin and BCNU microspheres was injected around the surgical cavity. In contrast, spatially alternating injections of BCNU and carboplatin microspheres was significantly less effective and the increase in survival was no greater than that achieved with BCNU alone. These data offer further support for the potential utility of local, sustained release chemotherapeutic microspheres for treating glioma. Moreover, they suggest that injectable chemotherapeutic microspheres may offer important advantages by (a) permitting multiple, temporally spaced injections to be made, as needed, and (b) providing the opportunity to deliver combinations of several different efficacious drugs directly to the tumor site to enhance survival beyond what can be achieved with delivery of any single chemotherapeutic agent.

Drug encapsulated aerosolized microspheres as a biodegradable, intelligent glioma therapy

The grim prognosis for patients diagnosed with malignant gliomas necessitates the development of new therapeutic strategies for localized and sustained drug delivery to combat tumor drug resistance and regrowth. Here we introduce drug encapsulated aerosolized microspheres as a biodegradable, intelligent glioma therapy (DREAM BIG therapy). DREAM BIG therapy is envisioned to deliver three chemotherapeutics, temporally staged over one year, via a bioadhesive, biodegradable spray directly to the brain surgical site after tumor excision. In this proof-of-principle article exploring key components of the DREAM BIG therapy prototype, rhodamine B (RB) encapsulated poly(lactic-co-glycolic acid) and immunoglobulin G (IgG) encapsulated poly(lactic acid) microspheres were formulated and characterized. The encapsulation efficiency of RB and IgG and the release kinetics of the model drugs from the microspheres were elucidated in addition to the release kinetics of RB from poly(lactic-co-glycolic acid) microspheres formulated in a degradable poly(N-isopropylacrylamide) solution. The successful aerosolized application onto brain tissue ex-vivo demonstrated the conformal adhesion of the RB encapsulated poly(lactic-co-glycolic acid) microspheres to the convoluted brain surface mediated by the thermoresponsive carrier, poly(N-isopropylacrylamide). These preliminary results suggest the potential of the DREAM BIG therapy for future use with multiple chemotherapeutics and microsphere types to combat gliomas at a localized site.

Drug encapsulated polymeric microspheres for intracranial tumor therapy: A review of the literature

Despite intensive surgical excision, radiation therapy, and chemotherapy, the current life expectancy for patients diagnosed with glioblastoma multiforme is only 12 to 15months. One of the approaches being explored to increase chemotherapeutic efficacy is to locally deliver chemotherapeutics encapsulated within degradable, polymeric microspheres. This review describes the techniques used to formulate drug encapsulated microspheres targeted for intracranial tumor therapy and how microsphere characteristics such as drug loading and encapsulation efficiency can be tuned based on formulation parameters. Further, the results of in vitro studies are discussed, detailing the varied drug release profiles obtained and validation of drug efficacy. Finally, in vivo results are summarized, highlighting the study design and the effectiveness of the drug encapsulated microspheres applied intracranially.

Preparation and characterization of Δ(9)-tetrahydrocannabinol-loaded biodegradable polymeric microparticles and their antitumoral efficacy on cancer cell lines

Cannabinoids present an interesting therapeutic potential as antiemetics, appetite stimulants in debilitating diseases (cancer, AIDS and multiple sclerosis), analgesics, and in the treatment of multiple sclerosis and cancer, among other conditions. However, despite their high clinical potential, only few dosage forms are available to date. In this paper, the development of Δ(9)-tetrahydrocannabinol (THC) biodegradable microspheres as an alternative delivery system for cannabinoid parenteral administration is proposed. Tetrahydrocannabinol was encapsulated into biodegradable microspheres by the oil-in-water (o/w) emulsion solvent evaporation method. Several formulations were prepared using different drug:polymer ratios. The influence of antioxidant (α-tocopherol acetate) concentration on the release of THC from the microparticles was studied. Elevated process yield and entrapment efficiencies were achieved. The in vitro drug release studies showed that the encapsulated drug was released over a two week period. As THC has shown therapeutic potential as anticancer drug, the efficacy of the microspheres was tested on different cancer cell lines. Interestingly, the microspheres were able to inhibit cancer cell proliferation during the nine-day study period. All the above results suggest that the use of biodegradable microspheres would be a suitable alternative delivery system for THC administration.

Convection-enhanced delivery improves distribution and efficacy of tumor-selective retroviral replicating vectors in a rodent brain tumor model

In the present study, we compared the therapeutic effect of tumor-selective retroviral replicating vectors (RRV) expressing the yeast cytosine deaminase (CD) delivered by CED or simple injection, followed by systemic administration of the pro-drug, 5-fluorocytosine (5-FC). Treatment with RRV-CD and systemic 5-FC significantly increased survival in rodent U87MG glioma model in comparison to controls (p<0.01). Interestingly, CED of RRV-CD followed by 5-FC further enhanced survival in this animal model in comparison to intra-tumoral injection of RRV-CD followed by systemic 5-FC (p<0.05). High expression levels of Ki-67 were found in untreated tumors compared to treated. Untreated tumors were also much larger than treated. CED resulted in excellent distribution of RRV while only partial distribution of RRV was obtained after injection. Furthermore, RRV-CD and cytosine deaminase were also found in tumors from treated rats at study end-points. These results demonstrated that RRV vectors may efficiently transduce and stably propagate in malignant human glioma, thereby achieving a significant in-situ amplification effect after initial administration. We conclude that delivery of RRV into the glioma by CED provides much wider vector distribution than simple, injection, and this correlated with better therapeutic outcomes.

Hemostatic absorbable gelatin sponge loaded with 5-fluorouracil for treatment of tumors

BACKGROUND

Surgical tumor resection is the main treatment for tumors however the treatment process often results in massive bleeding and tumor cell residue. The main aim of this research was to address problems such as bleeding, systemic chemotherapy side effects while enhancing quality of life, and increasing drug concentrations at the tumor site by developing a novel formulation with local long-term efficacy for treatment of tumors and to stop bleeding.

METHODS

5-Fluorouracil (5-FU) was suspended in an ethyl acetate solution of poly D,L-lactide-co-glycolic acid (PLGA) and a vacuum drying method was applied. The hemostatic gelatin sponge loaded with 5-FU was prepared by absorption of the suspension. The in vitro and in vivo characteristics of the hemostatic gelatin sponge loaded with 5-FU (5-FU-HAGS) were investigated.

RESULTS

5-FU-HAGS (hemostatic absorbable gelatin sponge loaded with 5-fluorouracil) was successfully produced with controlled release of the content and was reproducibly suitable for local tumor treatment as an implant to stop bleeding. The encapsulation efficiency of 5-FU-HAGS was above 98%. The in vitro 5-FU release kinetic profile matched a near zero-order equation for 20 days. The in vivo 5-FU plasma concentration was at a more stable level than when 5-FU solution was administered by subcutaneous injection. Bleeding can be stopped more effectively by coating a piece of blank gelatin sponge. The survival ratio of tumor-bearing mice using a 5-FU-HAGS subcutaneous implant was higher when compared to mice given a subcutaneous injection of 5-FU solution.

CONCLUSION

The 5-FU-HAGS system is a potential and effective way of enhancing the survival ratio and improving the quality of life of tumor-bearing mice.

5-Fluorouracil encapsulated HA/PLGA composite microspheres for cancer therapy

5-Fluorouracil (5FU) was successfully entrapped within poly(lactide-co-glycolide) (PLGA) and hydroyapatite (HA) composite microspheres using the emulsification/solvent extraction technique. The effects of HA to PLGA ratio, solvent ratio as well as polymer inherent viscosity (IV) on encapsulation efficiency were investigated. The degradation and drug release rates of the microspheres were studied for 5 weeks in vitro in phosphate buffered solution of pH 7.4 at 37 °C. The drug release profile followed a biphasic pattern with a small initial burst followed by a zero-order release for up to 35 days. The initial burst release decreased with increasing HA content. The potential of HA in limiting the initial burst release makes the incorporation of HA into PLGA microspheres advantageous since it reduces the risk of drug overdose from high initial bursts. The linear sustained drug release profile over the course of 5 weeks makes these 5-FU-loaded HA/PLGA composite microparticles a promising delivery system for the controlled release of chemotherapy drugs in the treatment of cancer.

Drug delivery strategies for the treatment of malignant gliomas

As primary brain tumors, malignant gliomas are known to be one of the most insidious types of brain cancer afflicting the humans. The current standard strategy for the treatment of malignant gliomas includes the surgical resection of the tumor when possible, followed by a combination of radiotherapy and/or a certain chemotherapeutic protocol. However, due to the short mean survival, frequent recurrences, and poor prognosis associated with the tumors, new therapeutic strategies are investigated consecutively. These novel drug delivery approaches can be subdivided as systemic and local drug administration. This review focuses on localized drug delivery strategies for the treatment of malignant gliomas, including the injections, infusions, trans-nasal delivery systems, convection enhanced delivery (CED) systems, and various types of polymeric implants. Furthermore, systemic strategies to increase the drug penetration into the brain, such as temporary disruption of the blood brain barrier (BBB), chemical modification of the available therapeutic substances, and utilization of endogenous transport systems will be briefly discussed.

Biological evaluation of 5-fluorouracil nanoparticles for cancer chemotherapy and its dependence on the carrier, PLGA

Nanoscaled devices have great potential for drug delivery applications due to their small size. In the present study, we report for the first time the preparation and evaluation of antitumor efficacy of 5-fluorouracil (5-FU)-entrapped poly (D, L-lactic-co-glycolic acid) (PLGA) nanoparticles with dependence on the lactide/glycolide combination of PLGA. 5-FU-loaded PLGA nanoparticles with two different monomer combinations, 50-50 and 90-10 were synthesized using a modified double emulsion method, and their biological evaluation was done in glioma (U87MG) and breast adenocarcinoma (MCF7) cell lines. 5-FU-entrapped PLGA 50-50 nanoparticles showed smaller size with a high encapsulation efficiency of 66%, which was equivalent to that of PLGA 90-10 nanoparticles. Physicochemical characterization of nanoparticles using differential scanning calorimetry and X-ray diffraction suggested the presence of 5-FU in molecular dispersion form. In vitro release studies showed the prolonged and sustained release of 5-FU from nanoparticles with both the PLGA combinations, where PLGA 50-50 nanoparticles showed faster release. Nanoparticles with PLGA 50-50 combination exhibited better cytotoxicity than free drug in a dose- and time-dependent manner against both the tumor cell lines. The enhanced efficiency of PLGA 50-50 nanoparticles to induce apoptosis was indicated by acridine orange/ethidium bromide staining. Cell cycle perturbations studied using flow cytometer showed better S-phase arrest by nanoparticles in comparison with free 5-FU. All the results indicate that PLGA 50-50 nanoparticles possess better antitumor efficacy than PLGA 90-10 nanoparticles and free 5-FU. Since, studies have shown that long-term exposure of ailing tissues to moderate drug concentrations is more favorable than regular administration of higher concentration of the drug; our results clearly indicate the potential of 5-FU-loaded PLGA nanoparticles with dependence on carrier combination as controlled release formulation to multiplex the therapeutic effect of cancer chemotherapy.

Nano to micro delivery systems: targeting angiogenesis in brain tumors

Treating brain tumors using inhibitors of angiogenesis is extensively researched and tested in clinical trials. Although anti-angiogenic treatment holds a great potential for treating primary and secondary brain tumors, no clinical treatment is currently approved for brain tumor patients. One of the main hurdles in treating brain tumors is the blood brain barrier - a protective barrier of the brain, which prevents drugs from entering the brain parenchyma. As most therapeutics are excluded from the brain there is an urgent need to develop delivery platforms which will bypass such hurdles and enable the delivery of anti-angiogenic drugs into the tumor bed. Such delivery systems should be able to control release the drug or a combination of drugs at a therapeutic level for the desired time. In this mini-review we will discuss the latest improvements in nano and micro drug delivery platforms that were designed to deliver inhibitors of angiogenesis to the brain.

Doxorubicin and irinotecan drug-eluting beads for treatment of glioma: a pilot study in a rat model

Despite some progress in therapy, the prognosis of patients with malignant gliomas remains poor. Local delivery of cytostatics to the tumour has been proven to be an efficacious therapeutic approach but which nevertheless needs further improvements. Drug Eluting Beads (DEB), have been developed as drug delivery embolisation systems for use in trans-arterial chemoembolisation. We tested in a rat model of malignant glioma, whether DEB, loaded with doxorubicin or irinotecan, may be used for local treatment of brain tumours. Unloaded and drug loaded DEB were implanted into the brains of healthy and tumour bearing BD IX rats followed by histological investigations and survival assessment. Intracerebral implantation of unloaded DEB caused no significant local tissue damage, whilst both doxorubicin and irinotecan DEB improved survival time significantly. However, a significant local toxicity was found after the implantation of doxorubicin DEB but not with irinotecan DEB. We concluded that irinotecan appears to be superior in terms of the risk-benefit ratio and that DEB may be used for local treatment of brain tumours.

Novel technologies for antiangiogenic drug delivery in the brain

Antiangiogenic therapies aimed at inhibiting the formation of tumor vasculature hold great promise for cancer therapy, with multiple compounds currently undergoing clinical trials. As with many forms of chemotherapy, antiangiogenic drugs face numerous hurdles in their translation to clinical use. Many such promising agents exhibit a short half-life, low solubility, poor bioavailability and multiple toxic side effects. Furthermore, when targeting malignant brain tumors the blood-brain barrier represents a formidable obstacle, preventing drugs from penetrating into the central nervous system (CNS). In this review, we discuss several preclinical antiangiogenic therapies and describe issues related to the unique conditions in the brain with regard to cancer treatment and neurotoxicity. We focus on the limitations of antiangiogenic drugs in the brain, along with numerous solutions that involve novel biomaterials and nanotechnological approaches. We also discuss an example in which modifying the properties of an antiangiogenic compound enhanced its clinical efficacy in treating tumors while simultaneously mitigating undesirable neurological side-effects.

Biomaterials for the central nervous system

Biomaterials are widely used to help treat neurological disorders and/or improve functional recovery in the central nervous system (CNS). This article reviews the application of biomaterials in (i) shunting systems for hydrocephalus, (ii) cortical neural prosthetics, (iii) drug delivery in the CNS, (iv) hydrogel scaffolds for CNS repair, and (v) neural stem cell encapsulation for neurotrauma. The biological and material requirements for the biomaterials in these applications are discussed. The difficulties that the biomaterials might face in each application and the possible solutions are also reviewed in this article.

Novel strategies to improve the anticancer action of 5-fluorouracil by using drug delivery systems

Because of the fundamental importance of new therapeutic routes for cancer treatment, a number of systems based on colloidal particles as vehicles for the delivery of the anticancer drug 5-fluorouracil have been devised. The target is always to provide the proper dose of the antitumor agent only at the desired locus of action, thus reducing the unwanted side effects. In this review, the main strategies and the more significant results in the development of 5-fluorouracil carriers for cancer treatment are discussed.

In vivo fate and therapeutic efficacy of PF‐4/CTF microspheres in an orthotopic human glioblastoma model

The correlation between glioma grade and angiogenesis suggests that antiangiogenic therapies are potentially therapeutically effective for these tumors. However, to achieve tumor suppression, antiangiogenic therapies need to be administered daily using high systemic quantities. We designed a biodegradable polymeric device that overcomes those barriers by providing sustained local delivery of a C-terminal fragment of platelet factor 4 (PF-4/CTF), an antiangiogenic agent. Fluorescent-labeled microspheres composed of poly lactic-coglycolic acid (PLGA) were loaded with rhodamine-labeled PF-4/CTF and formulated to release their contents over time. Fluorescent labeling enabled the correlation between the in vitro to the in vivo kinetic and release studies. PF-4/CTF microspheres were injected into established intracranial human glioma tumors in nude mice. Noninvasive magnetic resonance imaging (MRI) was used to assess the therapeutic response. Tumor size, microvessel density, proliferation, and apoptosis rate were measured by histological analysis. Intracranially, the microspheres were located throughout the tumor bed and continuously released PF-4/CTF during the entire experimental period. MRI and histological studies showed that a single injection of microspheres containing PF-4/CTF caused a 65.2% and 72% reduction in tumor volume, respectively, with a significant decrease in angiogenesis and an increase in apoptosis. Our data demonstrate that polymeric microspheres are an effective therapeutic approach for delivering antiangiogenic agents that result in the inhibition of glioma tumor growth.

Discriminating healthy from tumor and necrosis tissue in rat brain tissue samples by Raman spectral imaging

The purpose of this study was to investigate molecular changes associated with glioma tissues by Raman microspectroscopy in order to develop its use in clinical practice. Spectroscopic markers obtained from C6 glioma tissues were compared to conventional histological and histochemical techniques. Cholesterol and phospholipid contents were highest in corpus callosum and decreased gradually towards the cortex surface as well as in the tumor. Two different necrotic areas have been identified: a fully necrotic zone characterized by the presence of plasma proteins and a peri-necrotic area with a high lipid content. This result was confirmed by Nile Red staining. Additionally, one structure was detected in the periphery of the tumor. Invisible with histopathological hematoxylin and eosin staining, it was revealed by immunohistochemical Ki-67 and MT1-MMP staining used to visualize the proliferative and invasive activities of glioma, respectively. Hierarchical cluster analysis on the only cluster averaged spectra showed a clear distinction between normal, tumoral, necrotic and edematous tissues. Raman microspectroscopy can discriminate between healthy and tumoral brain tissue and yield spectroscopic markers associated with the proliferative and invasive properties of glioblastoma. Development of in vivo Raman spectroscopy could thus accurately define tumor margins, identify tumor remnants, and help in the development of novel therapies for glioblastoma.

5-Fluorouracil plasma levels and biodegradation of subcutaneously injected drug-loaded microspheres prepared by spray-drying poly(d,l-lactide) and poly(d,l-lactide-co-glycolide) polymers

Microspheres (MS) of 5-fluorouracil-loaded poly(D,L-lactide) (PLA), poly(D,L-lactide-co-glycolide) 75/25 (PLGA 75/25) and poly(D,L-lactide-co-glycolide) 50/50 (PLGA 50/50) prepared by the spray-drying technique were subcutaneously injected in the back of Wistar rats in order to evaluate the 5-fluorouracil (5-FU) release and the biodegradation characteristics. Determination of plasma 5-FU concentration by HPLC with analysis of data using a non-compartmental model showed drug in plasma between 9 and 14 days after administration of drug-loaded PLGA 50/50 or PLA and PLGA 75/25 microspheres, respectively, with a maximum drug concentration of 2.4+/-0.2microg/mL at 24h (5-FU-loaded PLGA 50/50 MS), 2.5+/-0.1microg/mL at 48h (5-FU-loaded PLGA 75/25 MS), and 2.3+/-0.1microg/mL at 24h (5-FU-loaded PLA MS). Pharmacokinetically, a significant increase of AUC (up to 50 times) and MRT (up to 196 times) of 5-FU with regard to the administration of the drug in solution was observed. Scanning electron microscopy and histological studies indicated that a small fibrous capsule was observed around the microspheres in the site of injection. One month after the injection of PLGA 50/50 MS and 2 months after the injection of PLGA 75/25 and PLA MS, masses of polymers, instead of single microspheres, were observed. Close to them, macrophagic cells were present, and blood vessels were observed in the connective tissue. Total absence of fibrous capsule and injected microspheres was observed after 2 (for PLGA 50/50 MS) or 3 (PLGA 75/25 and PLA MS) months.

Pharmacologically active microcarriers releasing glial cell line – derived neurotrophic factor: Survival and differentiation of embryonic dopaminergic neurons after grafting in hemiparkinsonian rats

To improve the outcome of foetal dopaminergic cell transplantation for the treatment of Parkinson's disease, pharmacologically active microcarriers (PAM) were developed. PAM are able to convey cells on their surface and release a growth factor to improve cell survival, differentiation and integration after brain implantation. Lysozyme-releasing PAM were first produced and characterized. They served as a model system for the development of glial cell line-derived neurotrophic factor (GDNF)-releasing PAM conveying foetal ventral mesencephalic (FVM) cells. The effects of the intrastriatal implantation of this system were studied in hemiparkinsonian rats during a 6-week period. This study reports on the degradation of coated and non-coated PAM and the release of lysozyme and of biologically active GDNF for 42 days. Unloaded and GDNF-loaded PAM conveying FVM cells allowed a high improvement of the grafted cell survival and of fibre outgrowth, when compared to the cells transplanted alone. The animals receiving the PAM showed an earlier improvement in amphetamine-induced rotational behaviour compared to animals receiving FVM cells only; behaviour that appears to be more regular and stable with the GDNF-releasing PAM. The use of PAM to convey foetal cells is thus an efficient strategy for cell therapy in neurodegenerative diseases, as it allows improvement of cell survival and fibre outgrowth inducing a rapid recovery of behaviour using only low amounts of cells.

Fibrin glue system for adjuvant brachytherapy of brain tumors with 188Re and 186Re-labeled microspheres

Brain tumors such as glioblastoma reappear in their original location in almost 50% of cases. To prevent this recurrence, we developed a radiopharmaceutical system that consists of a gel applied immediately after surgical resection of a brain tumor to deliver local radiation booster doses. The gel, which strongly adheres to tissue in the treatment area, consists of fibrin glue containing the beta-emitters rhenium-188 and rhenium-186 in microsphere-bound form. Such microspheres can be prepared by short (2 h or less) neutron activation even in low neutron flux reactors, yielding a mixture of the two beta-emitters rhenium-188 (E(max)=2.1 MeV, half life=17 h) and rhenium-186 (E(max)=1.1 MeV, half life=90.6h). The dosimetry of this rhenium-188/rhenium-186 fibrin glue system was determined using gafchromic film measurements. The treatment efficacy of the radioactive fibrin glue was measured in a 9L-glioblastoma rat model. All animals receiving the non-radioactive fibrin glue died within 17+/-3 days, whereas 60% of the treated animals survived 36 days, the final length of the experiment. Control animals that were treated with the same amount of radioactive fibrin glue, but had not received a previous tumor cell injection, showed no toxic effects over one year. The beta-radiation emitting rhenium-188/rhenium-186-based gel thus provides an effective method of delivering high doses of local radiation to tumor tissue, particularly to wet areas where high adhesive strength and long-term radiation (with or without drug) delivery are needed.

Treatment of malignant gliomas with mitoxantrone-loaded poly (lactide-co-glycolide) microspheres

OBJECTIVE

Mitoxantrone (MTZ) has potent in vitro activity against malignant glioma cell lines, but it cannot be used effectively as a systemic agent for the treatment of brain tumors because of its poor central nervous system penetration. However, MTZ-loaded poly(lactide-co-glycolide) (PLGA) microspheres may be injected into the peritumoral area and into tumor tissue to provide effective and sustained local drug concentrations without causing systemic side effects.

METHODS

Fisher rats were randomized into three groups. The first group (n = 9) was concomitantly implanted with rat glioma (RG2) cells and blank PLGA microspheres. The second group (n = 6) was implanted with RG2 cells and MTZ-loaded PLGA microspheres. The third group (n = 9) was implanted with RG2 cells, and MTZ-loaded PLGA microspheres were injected into the same area after 7 days. Animals were sacrificed on Day 15 or 35. Tumor volumes were measured after hematoxylin and eosin staining. Distribution kinetics of MTZ in the brain was determined by high-performance liquid chromatography in nine rats injected with MTZ-loaded microspheres.

RESULTS

The tumor volumes were 76 +/- 11 and 107 +/- 11 mm (mean +/- standard error) on Days 15 (n = 6) and 35 (n = 3), respectively, in the control group. In rats treated with MTZ-loaded microspheres on Day 7, tumor volumes were significantly reduced to 17 +/- 4 and 23 +/- 2 mm on Days 15 (n = 6) and 35 (n = 3), respectively. No tumor formation was observed when glioma cells and MTZ-loaded PLGA microspheres were implanted concomitantly (n = 6). No systemic side effects or parenchymal inflammatory infiltration were observed in either group of rats. Brain MTZ concentration was highest at the injection site and declined with time and distance from the injection site and with time.

CONCLUSION

These data demonstrate that MTZ-loaded PLGA microspheres can deliver therapeutic concentrations of drug to the tumor and prevent glioma growth without causing side effects. This treatment method may increase the efficiency of antineoplastic therapy and positively impact survival.

Local and sustained delivery of 5-fluorouracil from biodegradable microspheres for the radiosensitization of malignant glioma: a randomized phase II trial

OBJECTIVE

This study was a randomized, multicenter Phase II trial comparing the effect of perioperative implantation of 5-fluorouracil-releasing microspheres followed by early radiotherapy (Arm A) and early radiotherapy alone (Arm B) in patients with gross total resection of high-grade glioma.

METHODS

Patients were randomized on clinical and radiological assumption of supratentorial high-grade glioma. All patients underwent surgery, and after resection and histological confirmation, patients randomized to Arm A received multiple injections of microsphere suspension (130 mg of 5-fluorouracil). Conventional fractionated radiotherapy (59.4 Gy) was initiated between the second and the seventh day after surgery for both arms.

RESULTS

A total of 95 patients were randomized. Seventy-seven patients were treated and analyzed in intention to treat for efficacy and safety. Overall survival was 15.2 months in Arm A and 13.5 months in Arm B. In the subpopulation of patients with complete resection, overall survival was 15.2 months in Arm A versus 12.3 months in Arm B. However, these differences were not significant. Safety was acceptable with prophylactic high doses of corticosteroids.

CONCLUSION

It may be hypothesized that the implantation of 5-fluorouracil-loaded microspheres in the wall of the cavity resection did increase the overall survival, but the present study was not designed and sufficiently powered to demonstrate this.

Local fluorouracil chemotherapy interferes with neural and behavioral recovery after brain tumor-like mass compression

In this study, we investigated the impact of intracerebral delivery of chemotherapy on functional recovery from focal cortical tissue displacement, characteristic of brain tumors. Unilateral focal brain compression was induced by epidural implantation of an inverted hemisphere-shaped bead over the sensorimotor cortex. Microinjections of a total of 1mg chemoagent fluorouracil or the same volume of saline were made into the compressed cortex. Behavioral tests of forelimb sensorimotor function were conducted during 4 weeks' observation. Rats subjected to any of the three types of lesions, saline microinjection plus cortical compression, chemoagent microinjection alone, or chemoagent microinjection combined with cortical compression, demonstrated significant behavioral deficits in several sensorimotor tasks, compared with saline-microinjected control animals. In placing tests, behavioral deficits elicited by each single treatment were worsened by combined treatment with chemoagent microinjection and focal cortical compression. Concurrently, local delivery of chemoagent into the compressed cortex induced increased cortical tissue loss, necrosis and apoptosis. These data indicate that local chemotherapy exacerbates compression-induced neurological impairment, and a model of controlled focal cortical compression may provide a valuable means to improve anti-cancer therapeutic designs with reduced deterioration of brain function.

Single-shot, multicycle suicide gene therapy by replication-competent retrovirus vectors achieves long-term survival benefit in experimental glioma

Achieving therapeutically efficacious levels of gene transfer in tumors has been a major obstacle for cancer gene therapy using replication-defective virus vectors. Recently, replicating viruses have emerged as attractive tools for cancer therapy, but generally achieve only transitory tumor regression. In contrast to other replicating virus systems, transduction by replication-competent retrovirus (RCR) vectors is efficient, tumor-selective, and persistent. Correlating with its efficient replicative spread, RCR vector expressing the yeast cytosine deaminase suicide gene exhibited remarkably enhanced cytotoxicity in vitro after administration of the prodrug 5-fluorocytosine. In vivo, RCR vectors replicated throughout preestablished primary gliomas without spread to adjacent normal brain, resulting in profound tumor inhibition after a single injection of virus and single cycle of prodrug administration. Furthermore, stable integration of the replicating vector resulted in persistent infection that achieved complete transduction of ectopic glioma foci that had migrated away from the primary tumor site. Thus, efficient and stable integration of suicide genes represents a unique property of the RCR vector that achieved multiple cycles of synchronous cell killing upon repeated prodrug administration, resulting in chronic suppression of tumor growth and prolonged survival.

New Delivery Approaches for Pediatric Brain Tumors

For many types of childhood brain tumors, including malignant gliomas, disease progression at the primary site is the predominant mode of treatment failure. Accordingly, interest has been directed during the last decade on exploring strategies to enhance the delivery of therapeutically active agents into the tumor microenvironment. Two approaches that have been the focus of considerable attention in the treatment of adult malignant brain tumors include interstitial administration of chemotherapeutic agents using time-release polymers and convection-enhanced delivery of immunotoxin conjugates targeted to receptors overexpressed in brain tumors relative to normal brain cells. Although it remains to be determined whether these approaches will lead to meaningful improvements in disease control and long-term prognosis in children with brain tumors, the encouraging results from studies in adults support the rationale for further exploring these strategies in the pediatric setting.

Novel advances in drug delivery to brain cancer

The therapy of brain tumors has been limited by a lack of effective methods of drug delivery to the brain. Systemic administration is often associated with toxic side effects and ultimately fails to achieve therapeutic concentrations within a tumor. An attractive strategy that has gained importance in brain tumor therapy has relied on local and controlled delivery of chemotherapeutic agents by biodegradable polymers. This technique allows direct exposure of tumor cells to a therapeutic agent for a prolonged period of time and has been shown to prolong the survival of patients with malignant brain tumors. The use of polymers for local drug delivery greatly expands the spectrum of drugs available for the treatment of malignant brain tumors. This review discusses the rationale for local drug delivery, describes the development of currently available polymer-based therapeutic agents, and highlights examples of promising non-polymer based drug delivery methods for use in the treatment of malignant brain tumors.

Drug delivery into the brain using poly(lactide-co-glycolide) microspheres

Among the strategies developed for drug delivery into the CNS, locally controlled drug release by the way of an implantable polymeric device has been developed in recent years. The first polymeric devices developed were macroscopic implants needing open surgery for implantation. Over the last few years, poly(lactide-co-glycolide) microspheres have been shown to be safe and promising for drug delivery into the brain. Poly(lactide-co-glycolide) is biodegradable and biocompatible with brain tissue. Due to their size, these microspheres can be easily implanted by stereotaxy in discrete, precise and functional areas of the brain without causing damage to the surrounding -tissue. Brain tumour treatments have been developed using this approach and clinical trials have been performed. Potential applications in neurodegenerative diseases have also been explored, particularly neurotrophic factor delivery and cell therapy.

Local delivery of antineoplastic agents by controlled-release polymers for the treatment of malignant brain tumours

Recent advances in the treatment of malignant brain tumours have focused on the development of targeted local delivery of therapeutic agents, which combine various antineoplastic strategies that include cytotoxic, anti-angiogenic and immunomodulatory mechanisms, among others. The introduction of local delivery devices for sustained administration of antineoplastic agents represents a new opportunity to effectively treat these malignancies by facilitating the intracranial administration of safe and clinically efficacious doses for prolonged periods of time in a controlled fashion. This technology circumvents the need for high systemic doses with potentially harmful toxicities, bypasses the blood-brain barrier and can be tailored to deliver new agents with complex pharmacological properties. Based on local delivery strategies, new delivery systems, including convection-enhanced delivery and microchips, have been developed. As a result, recent advances in tumour biology have been adopted as potentially translatable treatments and are undergoing preclinical and clinical evaluation at present. These novel approaches could improve the prognosis of patients with these tumours.

Evaluation of in vitro and in vivo antitumor activity of BCNU-loaded PLGA wafer against 9L gliosarcoma

The purpose of the present study was to develop implantable BCNU-loaded poly(D,L-lactide-co-glycolide) (PLGA) wafer for the controlled release of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and to evaluate its in vitro and in vivo antitumor activity. The release rate of BCNU from PLGA wafer increased with the increase of BCNU amount loaded and the release was continued until 7 days. In vitro and in vivo antitumor activity of BCNU-loaded PLGA wafer was investigated using in vitro cytotoxicity against 9L gliosarcoma cells and a subcutaneous (s.c.) solid tumor model of 9L gliosarcoma, respectively. The wafers containing BCNU showed more effective cytotoxicity than BCNU powder due to its short half-life and inhibited the proliferation of 9L gliosarcoma cells. BCNU-loaded PLGA wafer delayed the growth of the tumors significantly and increasing the dose of BCNU in the wafer resulted in a substantial regression of the tumor. These results of antitumor activity of BCNU-loaded PLGA wafer demonstrate the feasibility of the wafers for clinical application.