Local delivery to malignant brain tumors: potential biomaterial-based therapeutic/adjuvant strategies

Glioblastoma (GBM) is the most aggressive malignant brain tumor and is associated with a very poor prognosis. The standard treatment for newly diagnosed patients involves total tumor surgical resection (if possible), plus irradiation and adjuvant chemotherapy. Despite treatment, the prognosis is still poor, and the tumor often recurs within two centimeters of the original tumor. A promising approach to improving the efficacy of GBM therapeutics is to utilize biomaterials to deliver them locally at the tumor site. Local delivery to GBM offers several advantages over systemic administration, such as bypassing the blood-brain barrier and increasing the bioavailability of the therapeutic at the tumor site without causing systemic toxicity. Local delivery may also combat tumor recurrence by maintaining sufficient drug concentrations at and surrounding the original tumor area. Herein, we critically appraised the literature on local delivery systems based within the following categories: polymer-based implantable devices, polymeric injectable systems, and hydrogel drug delivery systems. We also discussed the negative effect of hypoxia on treatment strategies and how one might utilize local implantation of oxygen-generating biomaterials as an adjuvant to enhance current therapeutic strategies. © 2021 The Royal Society of Chemistry

Self-emulsifying drug delivery system: mucus permeation and innovative quantification technologies

Mucus is a dynamic barrier which covers and protects the underlying mucosal epithelial membrane against bacteria and foreign particles. This protection mechanism extends to include therapeutic macromolecules and nanoparticles (NPs) through trapping of these particles. Mucus is not only a physical barrier that limiting particles movements based on their sizes but it selectively binds with particles through both hydrophilic and lipophilic interactions. Therefore, nano-carriers for mucosal delivery should be designed to eliminate entrapment by the mucus barrier. For this reason, different strategies have been approached for both solid nano-carriers and liquid core nano-carriers to synthesise muco-diffusive nano-carrier. Among these nano-strategies, Self-Emulsifying Drug Delivery System (SEDDS) was recognised as very promising nano-carrier for mucus delivery. The system was introduced to enhance the dissolution and bioavailability of orally administered insoluble drugs. SEDDS has shown high stability against intestinal enzymatic activity and more importantly, relatively rapid permeation characteristics across mucus barrier. The high diffusivity of SEDDS has been tested using various in vitro measurement techniques including both bulk and individual measurement of droplets diffusion within mucus. The selection and processing of an optimum in vitro technique is of great importance to avoid misinterpretation of the diffusivity of SEDDS through mucus barrier. In conclusion, SEDDS is a system with high capacity to diffuse through intestinal mucus even though this system has not been studied to the same extent as solid nano-carriers

Caveolin-1 in renal cell carcinoma promotes tumour cell invasion, and in co-operation with pERK predicts metastases in patients with clinically confined disease

Background: Up to 40% of patients initially diagnosed with clinically-confined renal cell carcinoma (RCC) and who undergo curative surgery will nevertheless relapse with metastatic disease (mRCC) associated with poor long term survival. The discovery of novel prognostic/predictive biomarkers and drug targets is needed and in this context the aim of the current study was to investigate a putative caveolin-1/ERK signalling axis in clinically confined RCC, and to examine in a panel of RCC cell lines the effects of caveolin-1 (Cav-1) on pathological processes (invasion and growth) and select signalling pathways. Methods: Using immunohistochemistry we assessed the expression of both Cav-1 and phosphorylated-ERK (pERK) in 176 patients with clinically confined RCC, their correlation with histological parameters and their impact upon disease-free survival. Using a panel of RCC cell lines we explored the functional effects of Cav-1 knockdown upon cell growth, cell invasion and VEGF-A secretion, as well Cav-1 regulation by cognate cell signalling pathways. Results: We found a significant correlation (P = 0.03) between Cav-1 and pERK in a cohort of patients with clinically confined disease which represented a prognostic biomarker combination (HR = 4.2) that effectively stratified patients into low, intermediate and high risk groups with respect to relapse, even if the patients’ tumours displayed low grade and/or low stage disease. In RCC cell lines Cav-1 knockdown unequivocally reduced cell invasive capacity while also displaying both pro-and anti-proliferative effects; targeted knockdown of Cav-1 also partially suppressed VEGF-A secretion in VHL-negative RCC cells. The actions of Cav-1 in the RCC cell lines appeared independent of both ERK and AKT/mTOR signalling pathways. Conclusion: The combined expression of Cav-1 and pERK serves as an independent biomarker signature with potential merit in RCC surveillance strategies able to predict those patients with clinically confined disease who will eventually relapse. In a panel of in-vitro RCC cells Cav-1 promotes cell invasion with variable effects on cell growth and VEGF-A secretion. Cav-1 has potential as a therapeutic target for the prevention and treatment of mRCC

Destabilization of α-helical structure in solution improves bactericidal activity of antimicrobial peptides: Opposing effects on bacterial and viral targets

We have previously examined the mechanism of antimicrobial peptides on the outer membrane of vaccinia virus. Here we show that the formulation of peptides LL37 and magainin-2B amide in polysorbate 20 (Tween-20™) results in greater reductions in virus titre than formulation without detergent, and the effect is replicated by substitution of polysorbate 20 with high ionic strength buffer. In contrast, formulation with polysorbate 20 or high ionic strength buffer has the opposite effect on bactericidal activity of both peptides, resulting in lesser reductions in titre for both gram-positive and gram-negative bacteria. Circular dichroism spectroscopy shows that the differential action of polysorbate 20 and salt on the virucidal and bactericidal activities correlates with the α-helical content of peptide secondary structure in solution, suggesting that the virucidal and bactericidal activities are mediated through distinct mechanisms. The correlation of a defined structural feature with differential activity against a host-derived viral membrane and the membranes of both gram-positive and gram-negative bacteria suggests that overall helical content in solution under physiological conditions is an important feature for consideration in the design and development of candidate peptide-based antimicrobial compounds

Caveolin-1 implicated as a pro-invasive gene in high-grade glioma cell models: implementation of a 3d spheroid matrix invasion assay

INTRODUCTION: The poor prognosis associated with Glioblastoma multiforme (GBM) is multifactorial but includes the capacity of residual tumour cells not removed by surgery and resistant to radio-/chemo-therapy undergoing diffuse invasion into the surrounding brain tissue. Caveolin-1 (Cav-1) is the major structural and functional component of caveolae. In a number of tumour types Cav-1 is recognised to participate in cytoskeletal rearrangement, integrin-mediated adhesion and/or matrix remodelling. We proposed Cav-1 serves to promote invasion of GBM cells. To investigate this we have employed in an in-vitro 3D cellular invasion assay. METHOD: The human GBM cell lines, UP007 and UP029 established from primary cultures of biopsy-derived brain tumours (University of Portsmouth), U-87 MG (ECACC) and U-373 MG (ECACC) were genetically modified to stably knock-out Cav-1 using a Lentiviral Cav-1 shRNA approach; corresponding stably transfected non-target (NT) shRNA cell lines were generated as controls. Neuropheres were formed and embedded within an extracellular matrix (Matrigel™). Over a two-/four-day period (depending on cell line) the migration of cells away from the neurophere core (CORE) was quantified by image capture and processing (Image J) using a custom-developed MatLab script for pixel density analysis indicative of the density of migrating cellular material. RESULTS: Cav-1 knockout resulted in significant (P0.05) towards reduced invasion. Depending upon the cell line the Cav-1 knockdown also resulted in reduced size and cellular density of the neurosphere core (UP007 and UP029) indicative of reduced proliferation and/or cell survival capacity. CONCLUSION: Using an in-vitro 3D cellular invasion assay we have found Cav-1 expression in a series of three GBM cell lines to promote cellular invasion capacity. Ongoing studies are addressing signalling mechanisms and the influence of the microenvironment

Local delivery to malignant brain tumors: potential biomaterial-based therapeutic/adjuvant strategies

Glioblastoma (GBM) is the most aggressive malignant brain tumor and is associated with a very poor prognosis. The standard treatment for newly diagnosed patients involves total tumor surgical resection (if possible), plus irradiation and adjuvant chemotherapy. Despite treatment, the prognosis is still poor, and the tumor often recurs within two centimeters of the original tumor. A promising approach to improving the efficacy of GBM therapeutics is to utilize biomaterials to deliver them locally at the tumor site. Local delivery to GBM offers several advantages over systemic administration, such as bypassing the blood–brain barrier and increasing the bioavailability of the therapeutic at the tumor site without causing systemic toxicity. Local delivery may also combat tumor recurrence by maintaining sufficient drug concentrations at and surrounding the original tumor area. Herein, we critically appraised the literature on local delivery systems based within the following categories: polymer-based implantable devices, polymeric injectable systems, and hydrogel drug delivery systems. We also discussed the negative effect of hypoxia on treatment strategies and how one might utilize local implantation of oxygen-generating biomaterials as an adjuvant to enhance current therapeutic strategies

The differential absorption of a series of P-glycoprotein substrates in isolated perfused lungs from Mdr1a/1b genetic knockout mice can be attributed to distinct physico-chemical properties: an insight into predicting transporter-mediated, pulmonary specific disposition

Purpose To examine if pulmonary P-glycoprotein (P-gp) is functional in an intact lung; impeding the pulmonary absorption and increasing lung retention of P-gp substrates administered into the airways. Using calculated physico-chemical properties alone build a predictive Quantitative Structure-Activity Relationship (QSAR) model distinguishing whether a substrate’s pulmonary absorption would be limited by P-gp or not. Methods A panel of 18 P-gp substrates were administered into the airways of an isolated perfused mouse lung (IPML) model derived from Mdr1a/Mdr1b knockout mice. Parallel intestinal absorption studies were performed. Substrate physico-chemical profiling was undertaken. Using multivariate analysis a QSAR model was established. Results A subset of P-gp substrates (10/18) displayed pulmonary kinetics influenced by lung P-gp. These substrates possessed distinct physico-chemical properties to those P-gp substrates unaffected by P-gp (8/18). Differential outcomes were not related to different intrinsic P-gp transporter kinetics. In the lung, in contrast to intestine, a higher degree of non-polar character is required of a P-gp substrate before the net effects of efflux become evident. The QSAR predictive model was applied to 129 substrates including eight marketed inhaled drugs, all these inhaled drugs were predicted to display P-gp dependent pulmonary disposition. Conclusions Lung P-gp can affect the pulmonary kinetics of a subset of P-gp substrates. Physico-chemical relationships determining the significance of P-gp to absorption in the lung are different to those operative in the intestine. Our QSAR framework may assist profiling of inhaled drug discovery candidates that are also P-gp substrates. The potential for P-gp mediated pulmonary disposition exists in the clinic

A human co‐culture cell model incorporating microglia supports glioblastoma growth and migration, and confers resistance to cytotoxics

Despite the importance of the tumor microenvironment in regulating tumor progression, few in vitro models have been developed to understand the effects of non‐neoplastic cells and extracellular matrix (ECM) on drug resistance in glioblastoma (GBM) cells. Using CellTrace‐labeled human GBM and microglial (MG) cells, we established a 2D co‐culture including various ratios of the two cell types. Viability, proliferation, migration, and drug response assays were carried out to assess the role of MG. A 3D model was then established using a hyaluronic acid‐gelatin hydrogel to culture a mixture of GBM and MG and evaluate drug resistance. A contact co‐culture of fluorescently labeled GBM and MG demonstrated that MG cells modestly promoted tumor cell proliferation (17%‐30% increase) and greater migration of GBM cells (>1.5‐fold increase). Notably, the presence of MG elicited drug resistance even when in a low ratio (10%‐20%) relative to co‐cultured tumor cells. The protective effect of MG on GBM was greater in the 3D model (>100% survival of GBM when challenged with cytotoxics). This new 3D human model demonstrated the influence of non‐neoplastic cells and matrix on chemoresistance of GBM cells to three agents with different mechanisms of action suggesting that such sophisticated in vitro approaches may facilitate improved preclinical testing

A systematic review and meta-analysis reveals altered drug pharmacokinetics in humans during acute exposure to terrestrial high altitude- clinical justification for dose adjustment?

Objective: While physiological responses during acute ascent to terrestrial high altitude (HA) have the potential to alter the pharmacokinetics (PKs) that define absorption and disposition of medicinal drugs, there have been no systematic reviews and meta-analyses performed to date. Methods: We conducted a systematic literature search in June 2017 using NCBI PubMed, EMBASE, Web of Science, and Ovid MEDLINE databases to identify relevant observational studies. Studies were deemed eligible based on the following criteria: (1) participants: healthy, nonacclimatized male or female lowlanders (born and bred at sea level) and (2) environment: exposure to low altitude (LA, ≤600 m), followed by terrestrial high altitude (HA, ≤24 hours to ≥2500 m), the time course specifically selected to avoid interpretive complications associated with erythrocytosis. All PK parameters were standardized to be in the same units and the weighted standardized mean difference (SMD) calculated using a combination of fixed and random effects models with heterogeneity evaluated using χ2 and I2 statistics. Results: Of 20,840 studies reviewed, 6 prospective cohort studies (n = 75) qualified for inclusion, with participants exposed to a mean altitude of 4025 (mean) ± 380 (SD) m. We observed increases for absorption half-life (SMD: 0.40, 95% CI: 0.01–0.80, p = 0.04], elimination half-life (SMD: 0.89, 95% CI: 0.30–1.48, p = 0.003), and erythrocyte binding (SMD: 0.52, 95% CI: 0.16–0.88, p = 0.004) and reduction in clearance (SMD: −0.56, 95% CI: −1.13 to 0.00, p = 0.05). Conclusions: Collectively, these findings reveal impairments in both oral absorption and corresponding clearance of the, although limited, sample of drugs at HA that may potentially require closer patient monitoring and dose adjustments to maintain therapeutic efficacy and avoid incidental toxicity

Oral immunogenicity in mice and sows of enterotoxigenic escherichia coli outer-membrane vesicles incorporated into zein-based nanoparticles

Enterotoxigenic Escherichia coli (ETEC) strains are a major cause of illness and death in neonatal and recently weaned pigs. The immune protection of the piglets derives from maternal colostrum, since this species does not receive maternal antibodies through the placenta. In the present study, outer membrane vesicles (OMVs) obtained from main ETEC strains involved in piglet infection (F4 and F18 serotypes), encapsulated into zein nanoparticles coated with Gantrez®® AN-mannosamine conjugate, were used to orally immunize mice and pregnant sows. Loaded nanoparticles were homogeneous and spherical in a shape, with a size of 220–280 nm. The diffusion of nanoparticles through porcine intestinal mucus barrier was assessed by a Multiple Particle Tracking technique, showing that these particles were able to diffuse efficiently (1.3% diffusion coefficient), validating their oral use. BALB/c mice were either orally immunized with free OMVs or encapsulated into nanoparticles (100 µg OMVs/mouse). Results indicated that a single dose of loaded nanoparticles was able to elicit higher levels of serum specific IgG1, IgG2a and IgA, as well as intestinal IgA, with respect to the free antigens. In addition, nanoparticles induced an increase in levels of IL-2, IL-4 and IFN-γ with respect to the administration of free OMVs. Orally immunized pregnant sows with the same formulation elicited colostrum-, serum- (IgG, IgA or IgM) and fecal- (IgA) specific antibodies and, what is most relevant, offspring suckling piglets presented specific IgG in serum. Further studies are needed to determine the infection protective capacity of this new oral subunit vaccin