In Vitro and In Vivo Studies on HPMA-Based Polymeric Micelles Loaded with Curcumin.

Curcumin-loaded polymeric micelles composed of poly(ethylene glycol)-b-poly(N-2-benzoyloxypropyl methacrylamide) (mPEG-b-p(HPMA-Bz)) were prepared to solubilize and improve the pharmacokinetics of curcumin. Curcumin-loaded micelles were prepared by a nanoprecipitation method using mPEG5kDa-b-p(HPMA-Bz) copolymers with varying molecular weight of the hydrophobic block (5.2, 10.0, and 17.1 kDa). At equal curcumin loading, micelles composed of mPEG5kDa-b-p(HPMA-Bz)17.1kDa showed better curcumin retention in both phosphate-buffered saline (PBS) and plasma at 37 °C than micelles based on block copolymers with smaller hydrophobic blocks. No change in micelle size was observed during 24 h incubation in plasma using asymmetrical flow field-flow fractionation (AF4), attesting to particle stability. However, 22-49% of the curcumin loading was released from the micelles during 24 h from formulations with the highest to the lowest molecular weight p(HPMA-Bz), respectively, in plasma. AF4 analysis further showed that the released curcumin was subsequently solubilized by albumin. In vitro analyses revealed that the curcumin-loaded mPEG5kDa-b-p(HPMA-Bz)17.1kDa micelles were internalized by different types of cancer cells, resulting in curcumin-induced cell death. Intravenously administered curcumin-loaded, Cy7-labeled mPEG5kDa-b-p(HPMA-Bz)17.1kDa micelles in mice at 50 mg curcumin/kg showed a long circulation half-life for the micelles (t1/2 = 42 h), in line with the AF4 results. In contrast, the circulation time of curcumin was considerably shorter than that of the micelles (t1/2α = 0.11, t1/2ß = 2.5 h) but ∼5 times longer than has been reported for free curcumin (t1/2α = 0.02 h). The faster clearance of curcumin in vivo compared to in vitro studies can be attributed to the interaction of curcumin with blood cells. Despite the excellent solubilizing effect of these micelles, no cytostatic effect was achieved in neuroblastoma-bearing mice, possibly because of the low sensitivity of the Neuro2A cells to curcumin.

Anti-GD2 Immunoliposomes for Targeted Delivery of the Survivin Inhibitor Sepantronium Bromide (YM155) to Neuroblastoma Tumor Cells.

PURPOSE: Sepantronium bromide (YM155) is a hydrophilic quaternary compound that cannot be administered orally due to its low oral bioavailability; it is furthermore rapidly eliminated via the kidneys. The current study aims at improving the pharmacokinetic profile of YM155 by its formulation in immunoliposomes that can achieve its enhanced delivery into tumor tissue and facilitate uptake in neuroblastoma cancer cells. METHODS: PEGylated YM155 loaded liposomes composed of DPPC, cholesterol and DSPE-PEG2000 were prepared via passive film-hydration and extrusion method. Targeted (i.e. immuno-)liposomes were prepared by surface functionalization with SATA modified monoclonal anti-disialoganglioside (GD2) antibodies. Liposomes were characterized based on their size, charge, antibody coupling and YM155 encapsulation efficiency, and stability. Flow cytometry analysis and confocal microscopy were performed on IMR32 and KCNR neuroblastoma cell lines. The efficacy of developed formulations were assessed by in-vitro toxicity assays. A pilot pharmacokinetic analysis was performed to assess plasma circulation and tumor accumulation profiles of the developed liposomal formulations. RESULTS: YM155 loaded immunoliposomes had a size of 170 nm and zeta potential of -10 mV, with an antibody coupling efficiency of 60% andYM155 encapsulation efficiency of14%. Targeted and control liposomal formulations were found to have similar YM155 release rates in a release medium containing 50% serum. An in-vitro toxicity study on KCNR cells showed less toxicity for immunoliposomes as compared to free YM155. In-vivo pharmacokinetic evaluation of YM155 liposomes showed prolonged blood circulation and significantly increased half-lives of liposomal YM155 in tumor tissue, as compared to a bolus injection of free YM155. CONCLUSIONS: YM155 loaded immunoliposomes were successfully formulated and characterized, and initial in-vivo results show their potential for improving the circulation time and tumor accumulation of YM155.

Effect of Particle Size on Drug Loading and Release Kinetics of Gefitinib-Loaded PLGA Microspheres.

Polymeric microspheres have gained widespread application as drug eluting depots. Typically, drug-loaded polymeric microspheres are prepared by oil-in-water emulsification which yields a product with a broad size distribution. The aim of the present study was to investigate the properties of different size-fractions of drug-loaded microspheres, in order to delineate whether particle size governs drug loading efficiency and release profile. Gefitinib-loaded PLGA-based microspheres were prepared using an oil-in-water solvent evaporation method and wet-sieved to obtain well-defined size fractions of 5 ± 1, 32 ± 4, 70 ± 3, and 130 ± 7 µm, respectively. The average drug loading of unfractionated microspheres was 6.3 ± 0.4% w/w, while drug loading of sieved fractions ranged from 2.4 ± 0.3 to 7.6 ± 0.9% w/w for smallest to largest microparticles. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analysis demonstrated that gefitinib was amorphously dispersed in the PLGA matrix, with no apparent shift in the Tg of PLGA indicating the absence of direct molecular interactions of the drug and polymer due to the formation of small drug particles embedded in PLGA. In vitro drug release was studied with microspheres embedded in dextran hydrogels to avoid their aggregation during the incubation conditions. Microspheres smaller than 50 µm showed rapid diffusion-based release reaching completion within 2 days when particles have not degraded yet. Larger microspheres, however, showed a sigmoidal release pattern that continued for three months in which diffusion (early stage) as well as particle erosion (later stage) governed drug release. Scanning electron microscopy (SEM) and polymer degradation data showed that larger microspheres degraded faster than smaller ones, which is in line with autocatalytic PLGA degradation upon acidification within the core of microparticles. In conclusion, we showed that different size-fractions of drug-loaded microspheres showed quite distinct drug loading and release kinetics. Control of microparticle size by fractionation is therefore an important determinant for obtaining well-defined and reproducible sustained release depots.

Plasma CTGF is independently related to an increased risk of cardiovascular events and mortality in patients with atherosclerotic disease: the SMART study.

AIMS: Connective tissue growth factor (CTGF) plays a key role in tissue fibrogenesis and growing evidence indicates a pathogenic role in cardiovascular disease. Aim of this study is to investigate the association of connective tissue growth factor (CTGF/CCN2) with cardiovascular risk and mortality in patients with manifest vascular disease. METHODS AND RESULTS: Plasma CTGF was measured by ELISA in a prospective cohort study of 1227 patients with manifest vascular disease (mean age 59.0 ± 9.9 years). Linear regression analysis was performed to quantify the association between CTGF and cardiovascular risk factors. Results are expressed as beta (ß) regression coefficients with 95% confidence intervals (CI). The relation between CTGF and the occurrence of new cardiovascular events and mortality was assessed with Cox proportional hazard analysis. Adjustments were made for potential confounding factors. Plasma CTGF was positively related to total cholesterol (ß 0.040;95%CI 0.013-0.067) and LDL cholesterol (ß 0.031;95%CI 0.000-0.062) and inversely to glomerular filtration rate (ß -0.004;95%CI -0.005 to -0.002). CTGF was significantly lower in patients with cerebrovascular disease. During a median follow-up of 6.5 years (IQR 5.3-7.4) 131 subjects died, 92 experienced an ischemic cardiac complication and 45 an ischemic stroke. CTGF was associated with an increased risk of new vascular events (HR 1.21;95%CI 1.04-1.42), ischemic cardiac events (HR 1.41;95%CI 1.18-1.67) and all-cause mortality (HR 1.18;95%CI 1.00-1.38) for every 1 nmol/L increase in CTGF. No relation was observed between CTGF and the occurrence of ischemic stroke. CONCLUSIONS: In patients with manifest vascular disease, elevated plasma CTGF confers an increased risk of new cardiovascular events and all-cause mortality.

Polymer-Free Drug-Eluting Stents: An Overview of Coating Strategies and Comparison with Polymer-Coated Drug-Eluting Stents.

Clinical evaluations have proven the efficacy of drug-elution stents (DES) in reduction of in-stent restenosis rates as compared to drug-free bare metal stents (BMS). Typically, DES are metal stents that are covered with a polymer film loaded with anti-inflammatory or antiproliferative drugs that are released in a sustained manner. However, although favorable effects of the released drugs have been observed, the polymer coating as such has been associated with several adverse clinical effects, such as late stent thrombosis. Elimination of the polymeric carrier of DES may therefore potentially lead to safer DES. Several technologies have been developed to design polymer-free DES, such as the use of microporous stents and inorganic coatings that can be drug loaded. Several drugs, including sirolimus, tacrolimus, paclitaxel, and probucol have been used in the design of carrier-free stents. Due to the function of the polymeric coating to control the release kinetics of a drug, polymer-free stents are expected to have a faster drug elution rate, which may affect the therapeutic efficacy. However, several polymer-free stents have shown similar efficacy and safety as the first-generation DES, although the superiority of polymer-free DES has not been established in clinical trials.

Epac-Rap signaling reduces oxidative stress in the tubular epithelium.

Activation of Rap1 by exchange protein activated by cAMP (Epac) promotes cell adhesion and actin cytoskeletal polarization. Pharmacologic activation of Epac-Rap signaling by the Epac-selective cAMP analog 8-pCPT-2'-O-Me-cAMP during ischemia-reperfusion (IR) injury reduces renal failure and application of 8-pCPT-2'-O-Me-cAMP promotes renal cell survival during exposure to the nephrotoxicant cisplatin. Here, we found that activation of Epac by 8-pCPT-2'-O-Me-cAMP reduced production of reactive oxygen species during reoxygenation after hypoxia by decreasing mitochondrial superoxide production. Epac activation prevented disruption of tubular morphology during diethyl maleate-induced oxidative stress in an organotypic three-dimensional culture assay. In vivo renal targeting of 8-pCPT-2'-O-Me-cAMP to proximal tubules using a kidney-selective drug carrier approach resulted in prolonged activation of Rap1 compared with nonconjugated 8-pCPT-2'-O-Me-cAMP. Activation of Epac reduced antioxidant signaling during IR injury and prevented tubular epithelial injury, apoptosis, and renal failure. Our data suggest that Epac1 decreases reactive oxygen species production by preventing mitochondrial superoxide formation during IR injury, thus limiting the degree of oxidative stress. These findings indicate a new role for activation of Epac as a therapeutic application in renal injury associated with oxidative stress.

Uniting education, research, healthcare, and society to advance women's heart health.

Complex health challenges require professionals to operate across disciplines and to better connect with society. Here, we showcase a community-engaged and challenge-based educational model in which undergraduate students conduct transdisciplinary research on authentic complex biomedical problems. This concept reinforces translational medicine, human capital, and exemplifies synergy between education, research, healthcare, and society.

Inhibition of tumor growth by targeted anti-EGFR/IGF-1R nanobullets depends on efficient blocking of cell survival pathways.

The clinical efficacy of epidermal growth factor receptor (EGFR)-targeted inhibitors is limited due to resistance mechanisms of the tumor such as activation of compensatory pathways. Crosstalk between EGFR and insulin-like growth factor 1 (IGF-1R) signaling has been frequently described to be involved in tumor proliferation and resistance. One of the attractive features of nanomedicines is the possibility to codeliver agents that inhibit different molecular targets in one nanocarrier system, thereby strengthening the antitumor effects of the individual agents. Additionally, exposure to healthy tissues and related unwanted side-effects can be reduced. To this end, we have recently developed anti-EGFR nanobody (Nb)-liposomes loaded with the anti-IGF-1R kinase inhibitor AG538, which showed promising antiproliferative effects in vitro. In the present study, we have further evaluated the potential of this dual-active nanomedicine in vitro and for the first time in vivo. As intended, the nanomedicine inhibited EGFR and IGF-1R signaling and subsequent activation of downstream cell proliferation and survival pathways. The degree of inhibition induced by the nanomedicine on a molecular level correlated with cytotoxicity in tumor cell proliferation assays and may even be predictive of the response to nanomedicine treatment in tumor xenograft models. Combination therapy with kinase inhibitor-loaded Nb-liposomes is therefore an appealing strategy for inhibiting the proliferation of tumors that are highly dependent on EGFR and IGF-1R signaling.

Effect of GFR on plasma N-terminal connective tissue growth factor (CTGF) concentrations.

BACKGROUND: Connective tissue growth factor (CTGF) has a key role in the pathogenesis of renal and cardiac fibrosis. Its amino-terminal fragment (N-CTGF), the predominant form of CTGF detected in plasma, has a molecular weight in the middle molecular range (18 kDa). However, it is unknown whether N-CTGF is a uremic retention solute that accumulates in chronic kidney disease (CKD) due to decreased renal clearance and whether it can be removed by hemodiafiltration. STUDY DESIGN: 4 observational studies in patients and 2 pharmacokinetic studies in rodents. SETTING & PARTICIPANTS: 4 single-center studies. First study (cross-sectional): 88 patients with CKD not receiving kidney replacement therapy. Second study (cross-sectional): 23 patients with end-stage kidney disease undergoing low-flux hemodialysis. Third study: 9 kidney transplant recipients before and 6 months after transplant. Fourth study: 11 low-flux hemodialysis patients and 12 hemodiafiltration patients before and after one dialysis session. PREDICTOR: First, second, and third study: (residual) glomerular filtration rate (GFR). Fourth study: dialysis modality. OUTCOMES & MEASUREMENTS: Plasma (N-)CTGF concentrations, measured by enzyme-linked immunosorbent assay. RESULTS: In patients with CKD, we observed an independent association between plasma CTGF level and estimated GFR (ß = -0.72; P < 0.001). In patients with end-stage kidney disease, plasma CTGF level correlated independently with residual kidney function (ß = -0.55; P = 0.046). Successful kidney transplant resulted in a decrease in plasma CTGF level (P = 0.008) proportional to the increase in estimated GFR. Plasma CTGF was not removed by low-flux hemodialysis, whereas it was decreased by 68% by a single hemodiafiltration session (P < 0.001). Pharmacokinetic studies in nonuremic rodents confirmed that renal clearance is the major elimination route of N-CTGF. LIMITATIONS: Observational studies with limited number of patients. Fourth study: nonrandomized, evaluation of the effect of one session; randomized longitudinal study is warranted. CONCLUSION: Plasma (N-)CTGF is eliminated predominantly by the kidney, accumulates in CKD, and is decreased substantially by a single hemodiafiltration session.

Controlled release of octreotide and assessment of peptide acylation from poly(D,L-lactide-co-hydroxymethyl glycolide) compared to PLGA microspheres.

PURPOSE: To investigate the in vitro release of octreotide acetate, a somatostatin agonist, from microspheres based on a hydrophilic polyester, poly(D,L-lactide-co-hydroxymethyl glycolide) (PLHMGA). METHODS: Spherical and non-porous octreotide-loaded PLHMGA microspheres (12 to 16 µm) and loading efficiency of 60-70% were prepared by a solvent evaporation. Octreotide release profiles were compared with commercial PLGA formulation (Sandostatin LAR(®)); possible peptide modification with lactic, glycolic and hydroxymethyl glycolic acid units was monitored. RESULTS: PLHMGA microspheres showed burst release (~20%) followed by sustained release for 20-60 days, depending on the hydrophilicity of the polymer. Percentage of released loaded peptide was high (70-90%); > 60% of released peptide was native octreotide. PLGA microspheres did not show peptide release for the first 10 days, after which it was released in a sustained manner over the next 90 days; > 75% of released peptides were acylated adducts. CONCLUSIONS: PLHMGA microspheres are promising controlled systems for peptides with excellent control over release kinetics. Moreover, substantially less peptide modification occurred in PLHMGA than in PLGA microspheres.

Reduction of advanced liver fibrosis by short-term targeted delivery of an angiotensin receptor blocker to hepatic stellate cells in rats.

UNLABELLED: There is no effective therapy for advanced liver fibrosis. Angiotensin type 1 (AT1) receptor blockers attenuate liver fibrogenesis, yet their efficacy in reversing advanced fibrosis is unknown. We investigated whether the specific delivery of an AT1 receptor blocker to activated hepatic stellate cells (HSCs) reduces established liver fibrosis. We used a platinum-based linker to develop a conjugate of the AT1 receptor blocker losartan and the HSC-selective drug carrier mannose-6-phosphate modified human serum albumin (losartan-M6PHSA). An average of seven losartan molecules were successfully coupled to M6PHSA. Rats with advanced liver fibrosis due to prolonged bile duct ligation or carbon tetrachloride administration were treated with daily doses of saline, losartan-M6PHSA, M6PHSA or oral losartan during 3 days. Computer-based morphometric quantification of inflammatory cells (CD43), myofibroblasts (smooth muscle alpha-actin [alpha-SMA]) and collagen deposition (Sirius red and hydroxyproline content) were measured. Hepatic expression of procollagen alpha2(I) and genes involved in fibrogenesis was assessed by quantitative polymerase chain reaction. Losartan-M6PHSA accumulated in the fibrotic livers and colocalized with HSCs, as assessed by immunostaining of anti-HSA and anti-alpha-SMA. Losartan-M6PHSA, but not oral losartan, reduced collagen deposition, accumulation of myofibroblasts, inflammation and procollagen alpha2(I) gene expression. Losartan-M6PHSA did not affect metalloproteinase type 2 and 9 activity and did not cause apoptosis of activated HSCs. CONCLUSION: Short-term treatment with HSC-targeted losartan markedly reduces advanced liver fibrosis. This approach may provide a novel means to treat chronic liver diseases.

Development of a cell-selective and intrinsically active multikinase inhibitor bioconjugate.

Multikinase inhibitors are potent anticancer drugs that simultaneously intervene in multiple related signaling cascades, thus being capable of blocking salvage pathways that may play a role in the development of drug resistance. Multikinase inhibitors are increasingly evaluated for indications other than cancer, but long-term safety risks dictated by off-organ toxicities of these agents may prevent their safe and effective use. Here, we describe a new approach in which platinum coordination chemistry is applied for the development of a cell-selective multikinase inhibitor bioconjugate. The platinum(II) kinase inhibitor bioconjugate was designed to be active with the linker attached to the inhibitor and displayed improved activity by enhanced cell specificity as well as enhanced intracellular retention, thereby prolonging its pharmacological activity. In addition, the utilized platinum-based linkage technology potentiated the inhibitory activity of the multikinase inhibitor. These features in combination with carrier-mediated uptake in the target cells may revolutionize dosing regimens and safety profiles of (multi)kinase inhibitors.

Connective tissue growth factor (CTGF/CCN2) ELISA: a novel tool for monitoring fibrosis.

BACKGROUND: Connective tissue growth factor (CTGF) has been identified as a key factor in the pathogenesis of diseases with significant fibrosis-related complications such as hepatitis, diabetes and renal transplantation. Increasing evidence shows that CTGF levels in plasma, serum and urine have promising biomarker applicability in these disorders. OBJECTIVE: To present an overview of current knowledge on CTGF in various patient populations and the technical aspects of CTGF measurement by enzyme-linked immunosorbent assay (ELISA). METHOD: We performed a comprehensive literature search by using electronic bibliographic databases. CONCLUSION: CTGF is associated with disease severity parameters and outcome in fibrotic disease and may have diagnostic and prognostic values. However, CTGF ELISA needs standardization.

Post-loading of proangiogenic growth factors in PLGA microspheres.

Active self-encapsulation (ASE) is a recently developed post-loading method based on absorption of (positively charged) proteins in microporous PLGA microspheres loaded with negatively charged polysaccharides (trapping agents). The aim of this study was to investigate ASE for simultaneous loading and controlled release of multiple growth factors. For this purpose, vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF) and insulin-like growth factor (IGF) were loaded in microspheres containing high molecular weight dextran sulfate (HDS) as trapping agent; loading was performed in a concentrated growth factor solution of low ionic strength and of pH 5 under conditions at which the proteins are positively charged. Subsequent pore closure was induced by incubation of the growth factor-loaded microspheres at 42.5 °C, i.e. above the Tg of (hydrated) PLGA (~30 °C). A 1:1:1 combination of VEGF, FGF and IGF was loaded with high loading (4.3%) and loading efficiency (91%). The in vitro release kinetics and bioactivity of loaded growth factors were studied for 4 weeks using ELISA and an endothelial cell proliferation assay, respectively. While IGF was released quickly, VEGF and FGF were continuously released for 4 weeks in their bioactive form, whereby a growth factor combination had a synergistic angiogenic effect. Therefore, ASE is a suitable method for co-loading growth factors which can provide sustained release profiles of bioactive growth factors, which is attractive for vascularization of biomaterial implants.

Assessing the Effects of VEGF Releasing Microspheres on the Angiogenic and Foreign Body Response to a 3D Printed Silicone-Based Macroencapsulation Device.

Macroencapsulation systems have been developed to improve islet cell transplantation but can induce a foreign body response (FBR). The development of neovascularization adjacent to the device is vital for the survival of encapsulated islets and is a limitation for long-term device success. Previously we developed additive manufactured multi-scale porosity implants, which demonstrated a 2.5-fold increase in tissue vascularity and integration surrounding the implant when compared to a non-textured implant. In parallel to this, we have developed poly(ε-caprolactone-PEG-ε-caprolactone)-b-poly(L-lactide) multiblock copolymer microspheres containing VEGF, which exhibited continued release of bioactive VEGF for 4-weeks in vitro. In the present study, we describe the next step towards clinical implementation of an islet macroencapsulation device by combining a multi-scale porosity device with VEGF releasing microspheres in a rodent model to assess prevascularization over a 4-week period. An in vivo estimation of vascular volume showed a significant increase in vascularity (* p = 0.0132) surrounding the +VEGF vs. -VEGF devices, however, histological assessment of blood vessels per area revealed no significant difference. Further histological analysis revealed significant increases in blood vessel stability and maturity (** p = 0.0040) and vessel diameter size (*** p = 0.0002) surrounding the +VEGF devices. We also demonstrate that the addition of VEGF microspheres did not cause a heightened FBR. In conclusion, we demonstrate that the combination of VEGF microspheres with our multi-scale porous macroencapsulation device, can encourage the formation of significantly larger, stable, and mature blood vessels without exacerbating the FBR.

Renal proximal tubular dysfunction is a major determinant of urinary connective tissue growth factor excretion.

Connective tissue growth factor (CTGF) plays a key role in renal fibrosis. Urinary CTGF is elevated in various renal diseases and may have biomarker potential. However, it is unknown which processes contribute to elevated urinary CTGF levels. Thus far, urinary CTGF was considered to reflect renal expression. We investigated how tubular dysfunction affects urinary CTGF levels. To study this, we administered recombinant CTGF intravenously to rodents. We used both full-length CTGF and the NH(2)-terminal fragment, since the NH(2)-fragment is the predominant form detected in urine. Renal CTGF extraction, determined by simultaneous arterial and renal vein sampling, was 18 +/- 3% for full-length CTGF and 21 +/- 1% for the NH(2)-fragment. Fractional excretion was very low for both CTGFs (0.02 +/- 0.006% and 0.10 +/- 0.02%, respectively), indicating that >99% of the extracted CTGF was metabolized by the kidney. Immunohistochemistry revealed extensive proximal tubular uptake of CTGF in apical endocytic vesicles and colocalization with megalin. Urinary CTGF was elevated in megalin- and cubilin-deficient mice but not in cubilin-deficient mice. Inhibition of tubular reabsorption by Gelofusine reduced renal uptake of CTGF and increased urinary CTGF. In healthy volunteers, Gelofusine also induced an increase of urinary CTGF excretion, comparable to the increase of beta(2)-microglobulin excretion (r = 0.99). Furthermore, urinary CTGF correlated with beta(2)-microglobulin (r = 0.85) in renal disease patients (n = 108), and only beta(2)-microglobulin emerged as an independent determinant of urinary CTGF. Thus filtered CTGF is normally reabsorbed almost completely in proximal tubules via megalin, and elevated urinary CTGF may largely reflect proximal tubular dysfunction.

Folate decorated polymeric micelles for targeted delivery of the kinase inhibitor dactolisib to cancer cells.

One of the main challenges in clinical translation of polymeric micelles is retention of the drug in the nanocarrier system upon its systemic administration. Core crosslinking and coupling of the drug to the micellar backbone are common strategies to overcome these issues. In the present study, polymeric micelles were prepared for tumor cell targeting of the kinase inhibitor dactolisib which inhibits both the mammalian Target of Rapamycin (mTOR) kinase and phosphatidylinositol-3-kinase (PI3K). We employed platinum(II)-based linker chemistry to couple dactolisib to the core of poly(ethylene glycol)-b-poly(acrylic acid) (PEG-b-PAA) polymeric micelles. The formed dactolisib-PEG-PAA unimers are amphiphilic and self-assemble in an aqueous milieu into core-shell polymeric micelles. Folate was conjugated onto the surface of the micelles to yield folate-decorated polymeric micelles which can target folate receptor over-expressing tumor cells. Fluorescently labeled polymeric micelles were prepared using a lissamine-platinum complex linked in a similar manner as dactolisib. Dactolisib polymeric micelles showed good colloidal stability in water and released the coupled drug in buffers containing chloride or glutathione. Folate decorated micelles were avidly internalized by folate-receptor-positive KB cells and displayed targeted cellular cytotoxicity at 50-75 nM IC50. In conclusion, we have prepared a novel type of folate-receptor targeted polymeric micelles in which platinum(II) linker chemistry modulates drug retention and sustained release of the coupled inhibitor dactolisib.

Vascular Endothelial Growth Factor-Releasing Microspheres Based on Poly(ε-Caprolactone-PEG-ε-Caprolactone)-b-Poly(L-Lactide) Multiblock Copolymers Incorporated in a Three-Dimensional Printed Poly(Dimethylsiloxane) Cell Macroencapsulation Device.

Pancreatic islet transplantation is a promising advanced therapy that has been used to treat patients suffering from diabetes type 1. Traditionally, pancreatic islets are infused via the portal vein, which is subsequently intended to engraft in the liver. Severe immunosuppressive treatments are necessary, however, to prevent rejection of the transplanted islets. Novel approaches therefore have focused on encapsulation of the islets in biomaterial implants which can protect the islets and offer an organ-like environment. Vascularization of the device's surface is a prerequisite for the survival and proper functioning of transplanted pancreatic islets. We are pursuing a prevascularization strategy by incorporation of vascular endothelial growth factor (VEGF)-loaded microspheres in 3-dimensional printed poly(dimethylsiloxane)-based devices prior to their prospective loading with transplanted cells. Microspheres (~50 µm) were based on poly(ε-caprolactone-PEG-ε-caprolactone)-b-poly(L-lactide) multiblock copolymers and were loaded with 10 µg VEGF/mg microspheres, and subsequently dispersed in a hyaluronic acid carrier liquid. In vitro release studies at 37°C demonstrated continuous release of fully bioactive VEGF for 4 weeks. In conclusion, our results demonstrate that incorporation of VEGF-releasing microspheres ensures adequate release of VEGF for a time window of 4 weeks, which is attractive in view of the vascularization of artificial pancreas implants.

Correlation between in vitro stability and pharmacokinetics of poly(ε-caprolactone)-based micelles loaded with a photosensitizer.

Polymeric micelles are extensively investigated as drug delivery systems for hydrophobic drugs including photosensitizers (PSs). In order to benefit from micelles as targeted delivery systems for PS, rather than only solubilizers, the stability and cargo retention of the (PS-loaded) micelles should be properly assessed in biologically relevant media to get insight into the essential parameters predicting their in vivo performance (i.e., pharmacokinetics). In the present study, asymmetric flow field-flow fractionation (AF4) was used to investigate the in vitro stability in human plasma of empty and meta-tetra(hydroxyphenyl)chlorin (mTHPC)-loaded dithiolane-crosslinked micelles based on poly(ɛ-caprolactone)-co-poly(1,2-dithiolane­carbonate)-b-poly(ethylene glycol) (p(CL-co-DTC)-PEG) and non (covalently)-crosslinked micelles composed of poly(ε-caprolactone)-b-poly(ethylene glycol) (pCL-PEG). AF4 allows separation of the micelles from plasma proteins, which showed that small non (covalently)-crosslinked pCL9-PEG (17 nm) and pCL15-PEG (22 nm) micelles had lower stability in plasma than pCL23-PEG micelles with larger size (43 nm) and higher degree of crystallinity of pCL, and had also lower stability than covalently crosslinked p(CL9-DTC3.9)-PEG and p(CL18-DTC7.5)-PEG micelles with similar small sizes (~20 nm). In addition, PS (re)distribution to specific plasma proteins was observed by AF4, giving strong indications for the (in)stability of PS-loaded micelles in plasma. Nevertheless, fluorescence spectroscopy in human plasma showed that the retention of mTHPC in non (covalently)-crosslinked but semi-crystalline pCL23-PEG micelles (>8 h) was much longer than that in covalently crosslinked p(CL18-DTC7.5)-PEG micelles (~4 h). In line with this, in vivo circulation kinetics showed that pCL23-PEG micelles loaded with mTHPC had significantly longer half-life values (t½-ß of micelles and mTHPC was 14 and 18 h, respectively) than covalently crosslinked p(CL18-DTC7.5)-PEG micelles (t½-ß of both micelles and mTHPC was ~2 h). As a consequence, long circulating pCL23-PEG micelles resulted in significantly higher tumor accumulation of both the micelles and loaded mTHPC as compared to short circulating p(CL18-DTC7.5)-PEG micelles. These in vivo data were in good agreement with the in vitro stability studies. In conclusion, the present study points out that AF4 and fluorescence spectroscopy are excellent tools to evaluate the (in)stability of nanoparticles in biological media and thus predict the (in)stability of drug loaded nanoparticles after i.v. administration, which is favorable to screen promising delivery systems with reduced experimental time and costs and without excessive use of animals.

π-π-Stacked Poly(ε-caprolactone)-b-poly(ethylene glycol) Micelles Loaded with a Photosensitizer for Photodynamic Therapy.

To improve the in vivo stability of poly(-caprolactone)-b-poly(ethylene glycol) (PCL-PEG)-based micelles and cargo retention by π-π stacking interactions, pendant aromatic rings were introduced by copolymerization of -caprolactone with benzyl 5-methyl-2-oxo-1,3-dioxane-5-carboxylate (TMC-Bz). It was shown that the incorporation of aromatic rings yielded smaller micelles (18-30 nm) with better colloidal stability in PBS than micelles without aromatic groups. The circulation time of i.v. injected micelles containing multiple pendant aromatic groups was longer (t½-α: ~0.7 h; t½-ß: 2.9 h) than that of micelles with a single terminal aromatic group (t½ < 0.3 h). In addition, the in vitro partitioning of the encapsulated photosensitizer (meta-tetra(hydroxyphenyl)chlorin, mTHPC) between micelles and human plasma was favored towards micelles for those that contained the pendant aromatic groups. However, this was not sufficient to fully retain mTHPC in the micelles in vivo, as indicated by similar biodistribution patterns of micellar mTHPC compared to free mTHPC, and unequal biodistribution patterns of mTHPC and the host micelles. Our study points out that more detailed in vitro methods are necessary to more reliably predict in vivo outcomes. Furthermore, additional measures beyond π-π stacking are needed to stably incorporate mTHPC in micelles in order to benefit from the use of micelles as targeted delivery systems.