Daratumumab Immunopolymersome-Enabled Safe and CD38-Targeted Chemotherapy and Depletion of Multiple Myeloma

Multiple myeloma (MM) is a second ranking hematological malignancy. Despite the fast advancement of new treatments such as bortezormib and daratumumab, MM patients remain incurable and tend to eventually become relapsed and drug-resistant. Development of novel therapies capable of depleting MM cells is strongly needed. Here, daratumumab immunopolymersomes carrying vincristine sulfate (Dar-IPs-VCR) are reported for safe and high-efficacy CD38-targeted chemotherapy and depletion of orthotopic MM in vivo. Dar-IPs-VCR made by postmodification via strain-promoted click reaction holds tailored antibody density (2.2, 4.4 to 8.7 Dar per IPs), superb stability, small size (43-49 nm), efficacious VCR loading, and glutathione-responsive VCR release. Dar_4.4 -IPs-VCR induces exceptional anti-MM activity with an IC₅₀ of 76 × 10^-12 m to CD38-positive LP-1 MM cells, 12- and 20-fold enhancement over nontargeted Ps-VCR and free VCR controls, respectively. Intriguingly, mice bearing orthotopic LP-1-Luc MM following four cycles of i.v. administration of Dar_4.4 -IPs-VCR at 0.25 mg VCR equiv. kg^-1 reveal complete depletion of LP-1-Luc cells, superior survival rate to all controls, and no body weight loss. The bone and histological analyses indicate bare bone and organ damage. Dar-IPs-VCR appears as a safe and targeted treatment for CD38-overexpressed hematological malignancies.

Rapid scale-up and production of active-loaded PEGylated liposomes

Manufacturing of liposomal nanomedicines (e.g. Doxil®/Caelyx®) is a challenging and slow process based on multiple-vessel and batch processing techniques. As a result, the translation of these nanomedicines from bench to bedside has been limited. Microfluidic-based manufacturing offers the opportunity to address this issue, and de-risk the wider adoption of nanomedicines. Here we demonstrate the applicability of microfluidics for continuous manufacturing of PEGylated liposomes encapsulating ammonium sulfate (250 mM). Doxorubicin was subsequently active-loaded into these pre-formed liposomes. Critical process parameters and material considerations demonstrated to influence the liposomal product attributes included solvent selection and lipid concentration, flow rate ratio, and temperature and duration used for drug loading. However, the total flow rate did not affect the liposome product characteristics, allowing high production speeds to be adopted. The final liposomal product comprised of 80-100 nm vesicles (PDI < 0.2) encapsulating ≥ 90% doxorubicin, with matching release profiles to the innovator product and is stable for at least 6 months. Additionally, vincristine and acridine orange were active-loaded into these PEGylated liposomes (≥ 90% and ~100 nm in size) using the same process. These results demonstrate the ability to produce active-loaded PEGylated liposomes with high encapsulation efficiencies and particle sizes which support tumour targeting.

Ecotoxicity risk of presence of two cytostatic drugs: Bleomycin and vincristine and their binary mixture in aquatic environment

Cytostatic drugs have become one of the greatest environmental threats. They occur in surface, ground and even drinking water. Their key emission sources are hospital effluents, municipal wastewater, as well as drug manufacturers and their effluents. These compounds are extremely stable in natural waters and they are not significantly removed during wastewater treatment, because they are resistant to biodegradation. The aim of this work was to establish possible negative effects of chosen cytostatics: bleomycin and vincristine on the three trophic levels of surface waters. A single agent acute toxicity test was conducted on representatives of the producer - an aquatic freshwater plant Lemna minor, the consumer - crustaceans Daphnia magna, and the decomposer - bacteria Pseudomonas putida. Binary mixture tests were performed according to the Concentration Addition, Response Additivity, and Independent Action models. Both substances had a different effect on the tested organisms; bleomycin could be classified as a very toxic, while vincristine as a toxic water pollutant. Half maximal effective concentration (EC50) values designed in the presented single agent acute toxicity studies are < 10 mg/L in all the tests with bleomycin as well as vincristine conducted on L. minor. In tests with vincristine performed on D. magna and P. putida EC50 > 100 mg/L. The highest toxicity is demonstrated by bleomycin towards the aquatic freshwater plant (EC50 = 0.2 mg/L). The binary mixture of the tested chemicals showed antagonistic effects of environmental concern.

Safe and Effective Delivery of Antitumor Drug Using Mesenchymal Stem Cells Impregnated with Submicron Carriers

An important area in modern malignant tumor therapy is the optimization of antitumor drugs pharmacokinetics. The use of some antitumor drugs is limited in clinical practice due to their high toxicity. Therefore, the strategy for optimizing the drug pharmacokinetics focuses on the generation of high local concentrations of these drugs in the tumor area with minimal systemic and tissue-specific toxicity. This can be achieved by encapsulation of highly toxic antitumor drug (vincristine (VCR) that is 20-50 times more toxic than widely used the antitumor drug doxorubicin) into nano- and microcarriers with their further association into therapeutically relevant cells that possess the ability to migrate to sites of tumor. Here, we fundamentally examine the effect of drug carrier size on the behavior of human mesenchymal stem cells (hMSCs), including internalization efficiency, cytotoxicity, cell movement, to optimize the conditions for the development of carrier-hMSCs drug delivery platform. Using the malignant tumors derived from patients, we evaluated the capability of hMSCs associated with VCR-loaded carriers to target tumors using a three-dimensional spheroid model in collagen gel. Compared to free VCR, the developed hMSC-based drug delivery platform showed enhanced antitumor activity regarding those tumors that express CXCL12 (stromal cell-derived factor-1 (SDF-1)) gene, inducing directed migration of hMSCs via CXCL12 (SDF-1)/CXCR4 pathway. These results show that the combination of encapsulated antitumor drugs and hMSCs, which possess the properties of active migration into tumors, is therapeutically beneficial and demonstrated high efficiency and low systematic toxicity, revealing novel strategies for chemotherapy in the future.

Ajmaline, Oxindole, and Cytotoxic Macroline-Akuammiline Bisindole Alkaloids from Alstonia penangiana

Examination of the EtOH extract of the Malayan Alstonia penangiana resulted in the isolation of 10 new alkaloids, comprising two ajmaline (1, 2), four macroline oxindole (3-6), and four macroline-akuammiline bisindole alkaloids (7-10). The structures of these alkaloids were determined based on analysis of the spectroscopic data and, in the case of the oxindole 6 and the bisindole alkaloid 7, also confirmed by X-ray diffraction analysis. The bisindole alkaloids 7 and 8 showed pronounced in vitro growth inhibitory activity against an array of human cancer cell lines, including KB, vincristine-resistant KB, PC-3, LNCaP, MCF7, MDA-MB-231, HT-29, HCT 116, and A549 cells with IC₅₀ values in the 0.3-8.3 μM range.

Biodegradable Self-Assembled Micelles Based on MPEG-PTMC Copolymers: An Ideal Drug Delivery System for Vincristine

Despite advantageous properties, micelles using methoxy poly(ethylene glycol)-poly(trimethylene carbonate) (MPEGPTMC) have not been widely studied. In this work, we aim to develop a novel vehicle for vincristine (VCR) based on a MPEG-PTMC micelle system. MPEG-PTMC with a series of molecular weights were synthesized and screened for the appropriate range for forming stable VCR micelles. The prepared micelles were then characterized in vitro and in vivo . VCR micelles presented high stability and ideal sustained release profile. The passive targeting effect was also enhanced compared with liposomal VCR. These results provide critical data to give the first clues regarding novel VCR micelles which exhibit potential for clinical application.

Interactions of Bovine Serum Albumin with Anti-Cancer Compounds Using a ProteOn XPR36 Array Biosensor and Molecular Docking

The aim of the work was to determine the interactions of a set of anti-cancer compounds with bovine serum albumin (BSA) using a ProteOn XPR36 array biosensor and molecular docking studies. The results revealed that a total of six anti-cancer compounds: gallic acid, doxorubicin, acteoside, salvianolic acid B, echinacoside, and vincristine were able to reversibly bind to the immobilized BSA. The sensorgrams of these six compounds were globally fit to a Langmuir 1:1 interaction model for binding kinetics analysis. There were significant differences in their affinity for BSA, with doxorubicin, the weakest binding compound having 1000-fold less affinity than salvianolic acid B, the strongest binding compound. However, compounds with a similar KD often exhibited markedly different kinetics due to the differences in k_a and k_d. Molecular docking experiments demonstrated that acteoside was partially located within sub-domain IIA of BSA, whereas gallic acid bound to BSA deep within its sub-domain IIIA. In addition, the interactions between these compounds and BSA were dominated by hydrophobic forces and hydrogen bonds. Understanding the detailed information of these anti-cancer compounds can provide important insights into optimizing the interactions and activity of potential compounds during drug development.

Fungal vincristine from Eutypella spp - CrP14 isolated from Catharanthus roseus induces apoptosis in human squamous carcinoma cell line -A431

BACKGROUND

Catharanthus roseus, a medicinal plant, is known to produce secondary metabolites, vincristine and vinblastine, which are terpenoid indole alkaloids. Previously we have reported that Eutypella spp - CrP14 isolated from stem cutting of this plant had shown significant antiproliferative activity when tested in vitro against HeLa cell line. The present study was conducted to identify the anticancer compound responsible for the anti-proliferative activity of the fungal extract and to evaluate its in vitro anticancer and apoptotic effects.

METHODS

The anti-proliferative activity of the fungal anticancer compound, vincristine was analyzed by MTT assay against different cancer cell lines. We examined its efficacy of apoptotic induction on A431 cells. The parameters examined included cell cycle distribution, loss of mitochondrial membrane potential (MMP), DNA fragmentation and reactive oxygen species (ROS) generation.

RESULTS

The presence of vincristine in fungal culture filtrate was confirmed through chromatographic and spectroscopic analyses, and the amount was estimated to be 53 ± 5.0 μg/l. The partially purified fungal vincristine had strong cytotoxic activity towards human squamous carcinoma cells - A431 in the MTT assay. Furthermore, we showed that the fungal vincristine was capable of inducing apoptosis in A431 cells through generation of reactive oxygen species and activation of the intrinsic pathway leading to loss of MMP.

CONCLUSIONS

We have demonstrated for the first time that the vincristine from Eutypella spp - CrP14 is an efficient inducer of apoptosis in A431 cells, meriting its further evaluation in vivo.

Sustained release of active chemotherapeutics from injectable-solid β-hairpin peptide hydrogel

MAX8 β-hairpin peptide hydrogel is a solid, preformed gel that can be syringe injected due to shear-thinning properties and can recover solid gel properties immediately after injection. This behavior makes the hydrogel an excellent candidate as a local drug delivery vehicle. In this study, vincristine, a hydrophobic and commonly used chemotherapeutic, is encapsulated within MAX8 hydrogel and shown to release constantly over the course of one month. Vincristine was observed to be cytotoxic in vitro at picomolar to nanomolar concentrations. The amounts of drug released from the hydrogels over the entire time-course were in this concentration range. After encapsulation, release of vincristine from the hydrogel was observed for four weeks. Further characterization showed the vincristine released during the 28 days remained biologically active, well beyond its half-life in bulk aqueous solution. This study shows that vincristine-loaded MAX8 hydrogels are excellent candidates as drug delivery vehicles, through sustained, low, local and effective release of vincristine to a specific target. Oscillatory rheology was employed to show that the shear-thinning and re-healing, injectable-solid properties that make MAX8 a desirable drug delivery vehicle are unaffected by vincristine encapsulation. Rheology measurements also were used to monitor hydrogel nanostructure before and after drug encapsulation.

Non-covalent carriage of anticancer agents by humanized antibody trastuzumab

This article explores the internalization and non-covalent carriage of small molecule anticancer agents like vinca alkaloids by humanized monoclonal antibody trastuzumab. Such carriage is marked by significant reduction in side effects and increased therapeutic value of these anticancer agents. This study is coherent with few clinical observations of enhanced efficiency of these anticancer agents when co-administered with therapeutic antibodies. This study will also serve as the foundation for screening a database of anticancer agents for possible compounds that may be co-delivered alongwith the antibody. Based on this study vincristine conformation inside antibody and its charge environment may be used as descriptors for screening purposes.

Nonspecifically enhanced therapeutic effects of vincristine on multidrug-resistant cancers when coencapsulated with quinine in liposomes

The use of vincristine (VCR) to treat cancer has been limited by its dose-dependent toxicity and development of drug resistance after repeated administrations. In this study, we investigated the mechanism by which quinine hydrochloride (QN) acts as a sensitizer for VCR. Our experiments used three kinds of multidrug-resistant cancer cells and demonstrated that QN worked by inducing intracellular depletion of adenosine triphosphate, increasing adenosine triphosphatase activity, and decreasing P-glycoprotein expression. Based on these results, we designed and prepared a VCR and QN codelivery liposome (VQL) and investigated the effect of coencapsulated QN on the in vitro cytotoxicity of VCR in cells and three-dimensional multicellular tumor spheroids. The antitumor effects of the formulation were also evaluated in multidrug-resistant tumor-bearing mice. The results of this in vivo study indicated that VQL could reverse VCR resistance. In addition, it reduced tumor volume 5.4-fold when compared with other test groups. The data suggest that VQL could be a promising nanoscaled therapeutic agent to overcome multidrug resistance, and may have important clinical implications for the treatment of cancer.

Effect of chromium on antioxidant potential of Catharanthus roseus varieties and production of their anticancer alkaloids: vincristine and vinblastine

Catharanthus roseus (L.) G. Don, a medicinal plant, has a very important place in the traditional as well as modern pharmaceutical industry. Two common varieties of this plant rosea and alba are named so because of pink and white coloured flowers, respectively. This plant comprises of about 130 terpenoid indole alkaloids and two of them, vincristine and vinblastine, are common anticancer drugs. The effect of chromium (Cr) on enzymatic and non-enzymatic antioxidant components and on secondary metabolites vincristine and vinblastine was studied under pot culture conditions of both varieties of C. roseus. Antioxidant responses of these varieties were analyzed under 0, 10, 50, and 100  μM chromium (Cr) level in order to investigate the plant's protective mechanisms against Cr induced oxidative stress. The results indicated that Cr affects all the studied parameters and decreases growth performance. However, vincristine and vinblastine contents were increased under Cr stress. Results are quite encouraging, as this plant shows good antioxidant potential and increased the level of active constituents under Cr stress.

Isolation, purification and characterization of vinblastine and vincristine from endophytic fungus Fusarium oxysporum isolated from Catharanthus roseus

Endophytic fungi reside in a symbiotic fashion inside their host plants, mimic their chemistry and interestingly, produce the same natural products as their hosts and are thus being screened for the production of valuable compounds like taxol, camptothecin, podophyllotoxin, etc. Vinblastine and vincristine are excellent anti-cancer drugs but their current production using plants is non-abundant and expensive. In order to make these drugs readily available to the patients at affordable prices, we isolated the endophytic fungi from Catharanthus roseus plant and found a fungus AA-CRL-6 which produces vinblastine and vincristine in appreciable amounts. These drugs were purified by TLC and HPLC and characterized using UV-Vis spectroscopy, ESI-MS, MS/MS and ¹H NMR. One liter of culture filtrate yielded 76 µg and 67 µg of vinblastine and vincristine respectively. This endophytic fungal strain was identified as Fusarium oxysporum based upon its cultural and morphological characteristics and internal transcribed spacer (ITS) sequence analysis.

Innovative in vitro chemo-hormonal drug therapy for refractory thyroid carcinomas

More than 95% of the thyroid carcinomas are well differentiated types showing favorable prognosis. However, only a few therapeutic options are available to treat the patients with undifferentiated thyroid carcinomas, especially with refractory thyroid carcinomas that are not amenable to surgery or radioiodine ablation. We investigated the anticancer effects of 20 chemotherapy and hormonal therapy drugs on 8 thyroid carcinoma cell lines. In vitro chemosensitivity was tested using the adenosine-triphosphate-based chemotherapy response assay (ATP-CRA). The tumor inhibition rate (TIR; or cell death rate) or half maximal inhibitory concentration (IC(50)) was analyzed to interpret the results. Of the 12 chemotherapy drugs, etoposide (178.9 index value in follicular carcinoma cell line) and vincristine (211.7 in Hürthle cell carcinoma cell line) were the most active drugs showing the highest chemosensitivity, and of the 8 additional drugs, trichostatin A (0.03 µg/mL IC(50) in follicular carcinoma cell line) showed favorable outcome having the anticancer effect. In our study, the result of etoposide and vincristine show evidence as active anticancer drugs in thyroid carcinoma cell lines and trichostatin A seems be the next promising drug. These drugs may become an innovative therapy for refractory thyroid carcinomas in near future.

Modifications on the basic skeletons of vinblastine and vincristine

The synthetic investigation of biologically active natural compounds serves two main purposes: (i) the total synthesis of alkaloids and their analogues; (ii) modification of the structures for producing more selective, more effective, or less toxic derivatives. In the chemistry of dimeric Vinca alkaloids enormous efforts have been directed towards synthesizing new derivatives of the antitumor agents vinblastine and vincristine so as to obtain novel compounds with improved therapeutic properties.

Replacement of conventional doxorubicin by pegylated liposomal doxorubicin is a safe and effective alternative in the treatment of non-Hodgkin's lymphoma patients with cardiac risk factors

Anthracyclines are a major component in the therapy of non-Hodgkin's lymphoma. However, due to their cardiac toxicity potential, curative and palliative treatment is often limited in patients with preexisting cardiac dysfunction. Liposomal doxorubicin formulations have been described to be less cardiotoxic than conventional doxorubicin. In the current study, we analyzed the efficacy and toxicity of pegylated liposomal doxorubicin (PLD) as constituent of the cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) regimen replacing conventional doxorubicin in 21 patients with impaired cardiac left ventricular ejection fraction or preexisting cardiac risk factors and established diagnosis of diffuse large B cell lymphoma (n = 15), mantle cell lymphoma (n = 3), follicular lymphoma (n = 1), and T cell lymphoma (n = 2). Overall and complete response rate were 85% and 40%, respectively. Event-free survival and overall survival after 2 years were 58%. One lethal event of acute cardiac death occurred during the first cycle in a patient with transposition of the big arteries, atrial flutter, and mitral valve regurgitation. In the remaining 20 patients, no deterioration of myocardial function was observed in echocardiography performed before and after treatment. Seven cases of grade III-IV hematological toxicity were observed as well as four episodes of neutropenic fever leading to hospitalization. No infection-related death occurred. However, 25% of patients developed a hand-foot syndrome (HFS) leading to discontinuation of treatment. Importantly, the incidence of HFS increased considerably when PLD doses of 15 mg/m(2)/week were exceeded. We conclude that replacing conventional doxorubicin with PLD in polychemotherapy regimens such as CHOP is an efficient alternative in the treatment of patients with preexisting cardiac dysfunction. However, we recommend that PLD dose should not exceed 15 mg/m(2)/week. The rationale for the use of non-pegylated liposomal doxorubicin formulations should be evaluated in further studies.

[Preparation and in vitro release characteristics of vincristine sulphate loaded poly (butylcyanoacrylate) nanoparticles]

OBJECTIVE

To prepare vincristine sulphate loaded poly (butylcyanoacrylate) nanoparticles (VCR-PBCA-NPs) and to investigate the in vitro release charactersitics.

METHOD

VCR-PBCA-NPs were prepared by emulsion polymerization method, and characterized for morphology, particle size, drug encapsulation efficiency and loading efficiency. The formulation was optimized using central composite design and response surface methodology. In vitro release study of VCR-PBCA-NPs was performed by dialysis technique. Model fitting was used to determine the kinetics and to discuss the mechanism.

RESULT

The nanoparticles were spherical and uniform with a mean diameter of (98.9 +/- 3.05) nm. The drug encapsulation efficiency and loading efficiency were (55.23 +/- 0.96)% and (7.87 +/- 0.11)%, respectively. In vitro release results showed that 63.66% of VCR was released from VCR-PBCA-NPs in 4 h, and the Weibull model fitted VCR release pattern best.

CONCLUSION

The VCR-PBCA-NPs prepared in this study showed sustained release compared with VCR solution.

Atomic force microscopy studies on circular DNA structural changes by vincristine and aspirin

In this chapter, we have presented materials and methods to study the interaction between DNA and small molecule drugs by AFM. The detailed AFM imaging of the circular DNA after incubation with -various concentrations of vincristine and aspirin have been demonstrated. The immobilization of DNA fragments on mica surface as well as the force between tip and sample plays an important role for successful imaging of DNA-drug complexes. How to quantitatively describe the conformations and structures of circular DNA molecules and their changes is also introduced. Our work indicates that the AFM is a powerful tool in studying the interaction between DNA and small molecules.

Competitive mass spectrometry binding assay for characterization of three binding sites of tubulin

Tubulin is an attractive and established target for anticancer therapy. To date, the only method to determine the binding of inhibitor to tubulin has been competitive radioligand binding assays. We developed a non-radioactive mass spectrometry (MS) binding assay to study the tubulin binding of colchicine, vinblastine and paclitaxel and to identify which of these three binding sites that a novel inhibitor binds. The method involves a very simple step of separating the unbound ligand from macromolecules using ultrafiltration. The unbound ligand in the filtrate can be accurately determined using highly sensitive and specific liquid chromatography tandem mass spectrometry (LC-MS/MS) method using multiple reaction monitoring (MRM) mode. The assay was validated using podophyllotoxin, vincristine and docetaxel, drugs that compete to the colchicine-, vinblastine- and paclitaxel-binding sites in tubulin, respectively. This competitive binding assay allowed the reliable detection of interactions of these drugs with three binding sites on tubulin. This method was subsequently applied to determine the tubulin-binding site of 4-substituted methoxylbenzoyl-aryl-thiazoles (SMART-H), a potent antitubulin agent developed in our laboratory. The results indicated that SMART-H specifically and reversibly bound only to the colchicine-binding site, but not to vinblastine- or paclitaxel sites. This new non-radioligand binding method to determine the binding site on tubulin will function as a useful tool to study the binding sites of tubulin inhibitors.

Characteristics and anti-proliferative activity of azelaic acid and its derivatives entrapped in bilayer vesicles in cancer cell lines

The hydrophilicity and lipophilicity of azelaic acid (AA) were modified to diethyl azelate (DA) which was synthesized by Fisher esterification reaction and identified by IR, MS and (1)H NMR and to azelaic acid-beta-cyclodextrin complex (AACD) which was prepared by inclusion complexation and identified by IR, DSC and XRD respectively. AA, DA and AACD were entrapped in liposomes and niosomes comprising of L-alpha-dipalmitoyl phosphatidylcholine (DPPC)/cholesterol at 7:3 molar ratio and Tween61/cholesterol at 1:1 molar ratio, respectively, using a thin-film hydration method with sonication. The size and morphology of these bilayer vesicles were determined by optical and transmission electron microscopy. The particle size was found to be in the range of 90-190 nm. The entrapment efficiency of AA, DA and AACD in all vesicular formulations was more than 80%, as analyzed by HPLC for AA and AACD, and GC for DA. Anti-proliferative activity of AA and its derivatives (DA and AACD) both entrapped and not entrapped in bilayer vesicles, using MTT assay in three cancer cell lines (HeLa, KB and B(16)F(10)) comparing with vincristine, were investigated. AACD showed the highest potency comparing to AA in HeLa, KB and B(16)F(10) of 1.48, 1.6 and 1.5 times, respectively. AA entrapped in liposomes was about 90 times more potent than the free AA, and about 1.5 times less potent than vincristine. When entrapped in bilayer vesicles, DA and AACD were more effective than AA in killing cancer cells. AACD entrapped in liposomes gave the highest anti-proliferation activity in HeLa cell lines with the IC(50) of 2.3 and 327 times more potent than vincristine and AA, respectively. DA in liposomes demonstrated the IC(50) of 0.03 times less potent than vincristine in KB cell lines, while in B(16)F(10) AACD in niosomes showed the IC(50) of 0.05 times less potent than vincristine. This study has suggested that the modification of AA by derivatization and complexation as well as the entrapment in bilayer vesicles can enhance its therapeutic efficacy.

[Study on the interaction between vincristine and bovine serum albumin]

The interaction between vincristine (VCR) and bovine serum albumin (BSA) was investigated by UV-Vis absorption, fluorescence and circular dichroism (CD) spectra at 296, 303 and 310 K, respectively. With fluorescence quenching method, the binding constants Ka were determined to be 1.5 x 10(4) L x mol(-1), 9.5 x 10(3) L x mol(-1), 4.9 x 10(3) L x mol(-1) and the number of binding site was 1 at three temperatures, respectively. The conformation of BSA was altered (CD data) with the reductions of alpha-helices from 33.5% for free BSA to 29.7%, and with increases of beta-sheet from 13.6% for free BSA to 18.4% in the presence of VCR. The thermodynamic parameters, enthalpy change (deltaH) and entropy change (deltaS), were calculated to be -62.07 kJ x mol(-1) and -129.38 J x (mol x K)(-1) respectively, according to van't Hoff equation, which indicated that hydrogen bonds and van der walls interactions played major roles in the binding process.

PLGA nanoparticles simultaneously loaded with vincristine sulfate and verapamil hydrochloride: systematic study of particle size and drug entrapment efficiency

PLGA nanoparticles simultaneously loaded with vincristine sulfate (VCR) and verapamil hydrochloride (VRP) were prepared via combining O/W emulsion solvent evaporation and salting-out method. Ten independent processing parameters and two materials characteristics were assessed systematically to enhance the incorporation of the two hydrophilic low molecular weight drugs into PLGA nanoparticles and minimize nanoparticles size. Approaches investigated for the enhancement of drug entrapment efficiencies and the minimization of particle size included the influence of the molecular weight (MW) of PLGA and the lactide to glycolide (L:G) ratio of PLGA, PLGA concentration, the degrees of hydrolyzation and polymerization of PVA, PVA concentration, initial VCR and VRP content, acetone to dichloromethane volume ratio, aqueous phase pH, salt concentration of aqueous phase, aqueous to organic phase volume ratio, sonication time, sonication energy and removal rate of organic solvents. The nanoparticles produced by optimal formulation were submicron size (111.4+/-2.35nm, n=3) and of low polydispersity (0.062+/-0.023, n=3). Nanoparticles observed by transmission electron microscopy (TEM) showed extremely spherical shape. The entrapment efficiencies determined with high performance liquid chromatogram (HPLC) by ultracentrifuge method were 55.35+/-4.22% for VCR and 69.47+/-5.34% for VRP, respectively (n=3).

[Preparation and characterization of vincristine sulfate-loaded PLGA microspheres]

OBJECTIVE

To prepare the vincristine sulfate (VCR) microspheres by W/O/O solvent evaparation method and evaluate the effect of zinc carbonate (ZnCO3) on the morphology and release kinetics of the microspheres.

METHODS

Degradation kinetic of VCR was tested in PBS of four different pH values at 37TC to select the optimal incubation medium for in vitro release. Microspheres were made with or without Zn-CO3 (w/w 5% and 10%) in the polymeric phase. The properties and in vitro release profiles of the microspheres were examed.

RESULTS

ZnCO3 increased the stability of VCR in the PLGA microspheres. During the 36 days of in vitro release, the accumulative release of VCR from the microspheres reached > 70% when added with ZnCO3, and was (54.2 +/- 1.1)% when no ZnCO3 was added. 10% ZnCO3 showed superior effect than 5% ZnCO3 in the stabilization of microspheres.

CONCLUSIONS

Adding ZnCO3 is essential during the preparation of PLGA microspheres. It can remarkably improve the stability of drugs in the acid microenvironment inside PL-GA microspheres and decrease the VCR degradation during incubation.

[Preparation of liposome entrapped vincristine sulfate and mitoxantrone chlorhydric acid]

OBJECTIVE

To investigate the prepation of the liposome carried with vincristine sulfate (VCR) and mitoxantrone chlorhydric acid (MTO) and to evaluate the quality of the liposome.

METHOD

The liposome carried with VCR and MIT was prepared by pH-gradients method and reverse evaporation technique. HPLC was employed to determine VCR and MIT entrapping efficiency of liposomal. Laser particle analyzer was applied to determine the size and zeta potential of the liposomes carried with VCR and MTO.

RESULT

The mean diameter of the liposome carried with MIT and VCR was 72.22 nm, with the entrapping rate of 95.77% for VCR and 99.53% for MTO. The liposome had perfect shape.

CONCLUSION

The liposomes with high entrapping rate and small particle size had been prepared by pH-gradient method and reverse evaporation technique.

Release of Drugs from Liposomes Varies with Particle Size

The efficacy of many drugs is improved by liposomal formulations. The greatest improvements in therapeutic benefits are achieved if the drug is retained in the liposomes for several hours after administration. Many basic drugs can be concentrated efficiently into liposomes in response to a transmembrane pH gradient. However, the rate of release from liposomal formulations is drug-dependent; for example, doxorubicin is released slowly from liposomes whereas vincristine leaks out rapidly. The aim of this study was to identify the causes of the rapid release of drugs from liposomes and then to apply this knowledge to the development of more stable formulations. Our initial focus was to explore the influence of liposomal size on the rate of release of drugs. The retention of doxorubicin within liposomes was independent of the particle size as far as this experimental condition was concerned. However, the rate of release of vincristine varied in relation to the particle size of the liposomes; vincristine was retained more effectively in larger liposomes. Experimental data generated using (31)P-NMR analysis and trap volume measurements, indicated that the number of lipid bilayers in liposomes increased as the particle size was increased. Additional lipid bilayers are likely to present a more effective barrier thereby slowing the release of drugs.

[Release profile of compound liposomes entrapped with vincristine sulfate and mitoxantrone chlorhydric acid in vitro and their distribution in mice]

AIM

To study on the release profile in vitro and biodistribution in mice of the compound liposomes carried with vincristine sulfate (VCR) and mitoxantrone chlorhydric acid (MTO).

METHODS

The release behaviors of the VCR and MTO from compound liposomes were studied in vitro. HPLC was developed for the determination of the contents of VCR and MTO in tissues in mice.

RESULTS

The release time of VCR from compound liposome was 24 h and that from free drug (in control solution) was 6 h. The release of MTO from compound liposome was 0.05% after 288 h and release time of MTO from free drug (in control solution) was 12 h. The liposomes and free drugs were injected intravenously at same dose to mice. The elimination half-life time (T 1/2) in plasma of liposomal and free VCR were 0.16 h and 0.14 h, and the AUCs (0 - 48 h) of them were 2.69 (ug x g(-1)) x h and 1.58 (ug x g(-1)) x h, respectively. The elimination half-life times (T 1/2) in plasma of liposomal and free MTO were 21.6 h and 0.05 h and the AUCs (0 - 48 h) of them were 17.06 (ug x g(-1)) x h and 0.42 (ug x g(-1)) x h, respectively.

CONCLUSION

The compound liposome with high entrapping efficiency and small particle size could be prepared by pH-gradients method and reverse evaporation technique. Two drugs were sustained-released from the compound liposome. Mice tail intravenous injection of compound liposomes showed that compound liposome prolonged the retention time and improved the concentration of MTO and VCR in the blood circulation system compared to control. In the mean time, compound liposome reduced the concentration of the MTO and VCR in heart, lung, kidney etc. These observations indicated that compound liposome could improve anticancer activity and reduce side effect.

Sphingomyelin/cholesterol liposomal vincristine: a new formulation for an old drug

Sphingomyelin/cholesterol liposomal vincristine (SV) is a novel formulation of vincristine encapsulated in the aqueous interior of liposomes composed of sphingomyelin and cholesterol. Benefits of the liposomal formulation include prolongation of the circulation half-life of total vincristine and an increase in drug delivery to sites of tumour growth resulting in enhanced efficacy. In addition, higher doses of vincristine than ordinarily administered can be prescribed without significant toxicity. Phase II studies have demonstrated that SV is active and well tolerated in relapsed diffuse large B cell lymphoma (DLBCL), including patients who have relapsed following an autologous stem cell transplant. SV has been successfully substituted for free vincristine in the CHOP regimen for those with previously untreated aggressive B cell non-Hodgkin's lymphoma, and is undergoing study in other settings. The achievement of responses in heavily pretreated patients with DLBCL and its low toxicity profile make SV a potential therapy for the palliative treatment of patients with multiply relapsed DLBCL. Ultimately, it is likely to be incorporated into combination chemotherapy regimens for use in untreated or relapsed patients. Its true value both as a single agent in heavily pretreated patients and in combination regimens will need to be established in Phase III trials.

[Preparation and characterization of transfersomes of three drugs in vitro]

OBJECTIVE

To investigate the influence of drug properties on the encapsulation effiency (EE) and drug release of transfersomes for a proper transfersome preparation.

METHOD

To prepare the transfersomes of colchicines (CLC), vincristine sulfate (VCR) and mitoxantrone hydrochloride (DHAD) with the same materials and methods, and then measure their EE. To find out the relationship between drug properties like solubility, molecular weight and charges, and EE. To performe the drug release experiments of various types of transfersomes in vitro, and compare their differences.

RESULT

VCR and DHAD are lipophilic or hydrophilic, owing positive charges and large molecular weight, as a result, their EE are high, while CLC is amphipathic, neutral, and of small molecular weight, its EE is very low. As DHAD can insert into the membrane of transfersome, the drug release of DHAD-T in vitro is much slower than that of VCR-T.

CONCLUSION

To prepare transfersomes with high EE, drugs that are lipophilic or hydrophilic, high molecular weight and opposite charges to the membrane should be chosen. Interaction between drugs and membrane will influnce the rate of drug release.

Therapeutically optimized rates of drug release can be achieved by varying the drug-to-lipid ratio in liposomal vincristine formulations

The anti-tumor efficacy of liposomal formulations of cell cycle dependent anticancer drugs is critically dependent on the rates at which the drugs are released from the liposomes. Previous work on liposomal formulations of vincristine have shown increasing efficacy for formulations with progressively slower release rates. Recent work has also shown that liposomal formulations of vincristine with higher drug-to-lipid (D/L) ratios exhibit reduced release rates. In this work, the effects of very high D/L ratios on vincristine release rates are investigated, and the antitumor efficacy of these formulations characterized in human xenograft tumor models. It is shown that the half-times (T(1/2)) for vincristine release from egg sphingomyelin/cholesterol liposomes in vivo can be adjusted from T(1/2) = 6.1 h for a formulation with a D/L of 0.025 (wt/wt) to T(1/2) = 117 h (extrapolated) for a formulation with a D/L ratio of 0.6 (wt/wt). The increase in drug retention at the higher D/L ratios appears to be related to the presence of drug precipitates in the liposomes. Variations in the D/L ratio did not affect the circulation lifetimes of the liposomal vincristine formulations. The relationship between drug release rates and anti-tumor efficacy was evaluated using a MX-1 human mammary tumor model. It was found that the antitumor activity of the liposomal vincristine formulations increased as D/L ratio increased from 0.025 to 0.1 (wt/wt) (T(1/2) = 6.1-15.6 h respectively) but decreased at higher D/L ratios (D/L = 0.6, wt/wt) (T(1/2) = 117 h). Free vincristine exhibited the lowest activity of all formulations examined. These results demonstrate that varying the D/L ratio provides a powerful method for regulating drug release and allows the generation of liposomal formulations of vincristine with therapeutically optimized drug release rates.

Reliability of preparation procedure for sphingosomal vincristine

PURPOSE

The reliability of the preparation procedure for sphingosomal vincristine was studied. The effect of minor variations in the constitution conditions on the integrity of the drug product was also examined.

METHODS

Two studies were conducted. The laboratory study, which had two parts, was conducted to determine the effects of deliberately varying the constitution conditions, including such key parameters as incubation time and incubation temperature. In the field study, 20 pharmacists unfamiliar with sphingosomal vincristine were asked to constitute the product using the written instructions provided in the package insert as their sole guidance. All samples in both studies were evaluated by measuring key product characteristics, including free (un-encapsulated) vincristine sulfate, total vincristine sulfate, vincristine degradation products, and in vitro release rate. Vincristine loading into sphingosomes was considered acceptable if the percentage of free vincristine sulfate did not exceed 10%.

RESULTS

In the laboratory study, samples that were incubated at 60-75 degrees C for 5-60 minutes met all the acceptance criteria. However, acceptable loading was not achieved for samples that were incubated at 55 degrees C for 10 minutes or less. In the field study, all the pharmacist-prepared samples met the acceptance criteria, with the results for free vincristine sulfate demonstrating a high degree of statistical confidence in the reliability of the loading procedure.

CONCLUSION

The recommended constitution procedure of sphingosomal vincristine from a three-vial kit can be reliably performed in pharmacies with a high degree of confidence. Small variations in temperature and incubation time had no effects on the quality of the product.

Liposome-encapsulated vincristine, vinblastine and vinorelbine: A comparative study of drug loading and retention

A comparative study of the loading and retention properties of three structurally very closely related vinca alkaloids (vincristine, vinorelbine and vinblastine) in liposomal formulations has been performed. All three vinca alkaloids showed high levels of encapsulation when accumulated into egg sphingomyelin/cholesterol vesicles in response to a transmembrane pH gradient generated by the use of the ionophore A23187 and encapsulated MgSO4. However, despite the close similarities of their structures the different vinca drugs exhibited very different release behavior, with vinblastine and vinorelbine being released faster than vincristine both in vitro and in vivo. The differences in loading and retention can be related to the lipophilicity of the drugs tested, where the more hydrophobic drugs are released more rapidly. It was also found that increasing the drug-to-lipid ratio significantly enhanced the retention of vinca alkaloids when the ionophore-based method was used for drug loading. In contrast, drug retention was not dependent on the initial drug-to-lipid ratio for vinca drugs loaded into liposomes containing an acidic citrate buffer. The differences in retention can be explained on the basis of differences in the physical state of the drug inside the liposomes. The drug-to-lipid ratio dependence of retention observed for liposomes loaded with the ionophore technique may provide a way to improve the retention characteristics of liposomal formulations of vinca drugs.

Preparation, characterization, and biological analysis of liposomal formulations of vincristine

Vincristine is a dimeric Catharanthus alkaloid derived from the Madagascan periwinkle that acts by binding to tubulin and blocking metaphase in actively dividing cells. While vincristine is widely used in the treatment of a number of human carcinomas, its use is associated with dose-limiting neurotoxicity, manifested mainly as peripheral neuropathy. It is known that the therapeutic activity of vincristine can be significantly enhanced after its encapsulation in appropriately designed liposomal systems. Enhanced efficacy is also associated with a slight decrease in drug toxicity. Thus, the therapeutic index of vincristine can be enhanced significantly through the use of a liposomal delivery system. Vincristine may be encapsulated into liposomes of varying lipid composition by several techniques, including passive loading, pH gradient loading, and ionophore-assisted loading. However, most research has focused on the encapsulation of vincristine in response to a transbilayer pH gradient, which actively concentrates the drug within the aqueous interior of the liposome. This chapter details the preparation and evaluation of liposomal vincristine. Specifically, we elaborate on the components (choice of lipids, molar proportions, etc.), methods (preparation of liposomes, drug loading methods, etc.), critical design features (size, surface charge, etc.), and key biological endpoints (circulation lifetime, bioavailability, efficacy measurements) important to the development of a formulation of vincristine with enhanced therapeutic properties.

Novel bisindole derivatives of Catharanthus alkaloids with potential cytotoxic properties

Pantropical plant Catharanthus roseus (L) G. Don is known as a source of valuable bisindole alkaloids: vinblastine (VBL) and vincristine (VCR), oncolytics widely used as sulfates in therapy of malignant diseases. They are biosynthesized in the plant from monoindolic vindoline and catharanthine, both derived from L-tryptophan and loganine units. In the course of phytochemical screening of this plant cultivated in Poland and considered as a home source of VBL and VCR we developed a new isolation method based on the solid phase extraction. Mild conditions used during the isolation procedure enabled the isolation of some labile compounds and so the monomeric alkaloids with high yields. Vindoline and so its congeners and subjected to various oxidative conditions gave 15,15'-bisindolic derivatives in quite good yield. Biological activities of the above mentioned bisindolic compounds are under study.

Stereocontrolled total synthesis of (+)-vincristine

An efficient total synthesis of (+)-vincristine has been accomplished through a stereoselective coupling of demethylvindoline and the eleven-membered carbomethoxyverbanamine presursor. Demethylvindoline was prepared by oxidation of 17-hydroxy-11-methoxytabersonine, followed by regioselective acetylation with mixed anhydride method. Although an initial attempt of coupling by using demethylvindoline formamide was not successful and resulted in recovery of the starting compounds, the reaction using demethylvindoline took place smoothly to furnish the desired bisindole product with the correct stereochemistry at C18'. After formation of the piperidine ring by sequential removal of the protective groups and intramolecular nucleophilic cyclization, the total synthesis of vincristine was completed by formylation of N1.

Reversal of P-glycoprotein mediated vincristine resistance of L1210/VCR cells by analogues of pentoxifylline

In our previous papers we described the ability of methylxanthine pentoxifylline (PTX) to depress the P-glycoprotein (P-gp) mediated multidrug resistance (MDR) of the mouse leukemic cell line L1210/VCR. Other methylxanthines like caffeine and theophylline were found to be ineffective in this respect. In the present paper we have analysed the capability of 25 methylxanthines to depress MDR of L1210/VCR cells. These methylxanthines structurally differ in substituents located in positions N1, N3, N7 and C8. The results indicate that for an effective reversal of P-gp mediated MDR of our cells the existence of a longer polar substituent in the position N1 plays a crucial role. The elongation of the substituent in the positions N3 and N7 (from methyl to propyl) increases and in the position C8 (from H to propyl) decreases the efficacy of xanthines to reverse the vincristine resistance of L1210/VCR cells. The multiple linear regression for effectiveness of methylxanthines in reversal of P-gp mediated MDR of L1210/VCR cells (expressed as respective IC(50r) values) has been computed, with molar weight: M(w), molar volume: V(M), molar refractivity: R(M), crystal density: d and partition coefficient n-octanol/water: logP as descriptors. A high intercorrelation of M(W), V(M) and R(M) was found for the tested group of methylxanthines indicating that only one of these parameters is necessary for testing a potential correlation. The best fit in the multiple linear regression was obtained for R(M) applied together with d and logP and resulted in a QSAR model given by the following equation: IC(50r)=-[(32.3+/-7.2)x10(-3)xR(M)]+[(10.1+/-2.3)xd]+[(0.74+/-0.10)xlogP]-[10.5+/-3.2]. Model revealed that: (i) the molar refractivity influences the effectiveness of xanthine positively; (ii) the crystal density and partition coefficient influence the MDR reversal effectiveness of xanthine negatively.

Stabilization of vinca alkaloids encapsulated in poly(lactide-co-glycolide) microspheres

PURPOSE

The purpose of this study was to stabilize the vinca alkaloids, vincristine sulfate (VCR) and vinblastine sulfate (VBL), in poly(lactide-co-glycolide) (PLGA) microspheres and to release the drugs in a sustained manner for more than a month.

METHODS

An oil-in-oil emulsion-solvent extraction method was used to encapsulate VCR and VBL in PLGA50/50 microspheres. Stability and release kinetics of the drugs during the incubation at 37 degrees C in PBS/Tween 80 were assessed by HPLC. Degradation products were identified with HPLC-MS.

RESULTS

VCR and VBL were encapsulated in PLGA microspheres unchanged. During the microsphere incubation, however, VCR degraded inside the particles with a t1/2 approximately 7.5 days. The degradation product was identified by LC-MS as the deformyl derivative, commonly formed at acidic pH. VBL, which differs only by a stable methyl group in place of the N-formyl group in VCR, was completely stable in the PLGA microclimate. The neutralization of acidic PLGA microclimate by addition of 3-10% Mg(OH)2 completely inhibited deformylation of VCR during release. but introduced a new degradation product formed under the more alkaline conditions used during the preparation. The substitution of Mg(OH)2 with a weaker base, ZnCO3, inhibited the formation of both degradation products resulting in VCR stabilization of >92% for 4 weeks. The optimal formulations of VCR (containing ZnCO3) and VBL (no additives) slowly and continuously released stable drugs for over a month.

CONCLUSIONS

VCR and VBL were successfully stabilized and released in a sustained manner from PLGA microspheres. Co-encapsulation of ZnCO3 stabilizes VCR against acid-catalyzed degradation during release from the polymer and minimizes VCR decomposition during encapsulation.

Factors influencing uptake and retention of amino-containing drugs in large unilamellar vesicles exhibiting transmembrane pH gradients

The level of uptake and retention of amino-containing drugs in large unilamellar vesicles (LUVs) following uptake in response to a transmembrane pH gradient (DeltapH) can vary dramatically depending on the drug. For example, the anticancer drugs doxorubicin and epirubicin can be readily retained, whereas the anticancer drug vincristine and the antibiotic ciprofloxacin tend to leak out rapidly. In this investigation, we examine the influence of the hydrophobicity of the entrapped amines (that induce the DeltapH) and the anionic lipid content of the LUV on drug retention. It is shown that entrapment of increasingly hydrophobic monoamines (methylamine to amylamine) all lead to an induced DeltapH of 3 units and essentially complete drug uptake under the conditions employed, but do not lead to improved retention of vincristine and ciprofloxacin. However, significantly improved retention could be achieved by substitution of the anionic lipid distearoylphosphatidylglycerol (DSPG) for distearoylphosphatidylcholine (DSPC) in the LUV bilayer. Further, it is shown that if the induced DeltapH is reduced to 1.4 units (driven by entrapped diamine) nearly 100% accumulation of doxorubicin and epirubicin could be achieved, whereas only 25% loading for vincristine and ciprofloxacin was observed. Taken together these results provide methodology for improving (weak base) drug retention in liposomes and indicate that drugs that can partition into the lipid bilayer exhibit improved uptake and retention characteristics.

Ionophore-mediated uptake of ciprofloxacin and vincristine into large unilamellar vesicles exhibiting transmembrane ion gradients

A new method, based on the ion-translocating properties of the ionophores nigericin and A23187, is described for loading large unilamellar vesicles (LUVs) with the drugs vincristine and ciprofloxacin. LUVs composed of distearoylphosphatidylcholine/cholesterol (DSPC/Chol) (55:45 mol/mol) or sphingomyelin (SPM)/Chol (55:45 mol/mol) exhibiting a transmembrane salt gradient (for example, internal solution 300 mM MnSO4 or K2SO4; external solution 300 mM sucrose) are incubated in the presence of drug and, for experiments involving divalent cations, the chelator EDTA. The addition of ionophore couples the outward movement of the entrapped cation to the inward movement of protons, thus acidifying the vesicle interior. External drugs that are weak bases can be taken up in response to this induced transmembrane pH gradient. It is shown that both nigericin and A23187 facilitate the rapid uptake of vincristine and ciprofloxacin, with entrapment levels approaching 100% and excellent retention in vitro. Following drug loading, the ionophores can be removed by gel exclusion chromatography, dialysis, or treatment with biobeads. In vitro leakage assays (addition of 50% mouse serum) and in vivo pharmacokinetic studies (in mice) reveal that the A23187/Mn2+ system exhibits superior drug retention over the nigericin/K+ system, and compares favorably with vesicles loaded by the standard DeltapH or amine methods. The unique features of this methodology and possible benefits are discussed.

Structural studies of vinblastine alkaloids by exciton coupled circular dichroism

SCF-CI-dipole velocity MO calculations have shown that the bisignate circular dichroic curves of vinblastine/vincristine alkaloids at ca 210 and 220-230 nm are due to exciton coupling between the indoline and indole moieties. Furthermore, a combination of X-ray crystal structure data with MM2 local energy minimization provides a convenient means for estimation of the preferred solution conformation.

Visual hallucinations following treatment with vincristine

Peripheral neuropathy is a common side effect of vincristine therapy. However, side effects due to central nervous system (CNS) toxicity following intravenous administration are rare. We report two patients who developed visual hallucinations during treatment with vincristine.

Potential strategies for circumventing myeloperoxidase-catalyzed degradation of vinca alkaloids

Myeloperoxidase (MPO) has recently been shown in an in vitro, cell-free system to catalyze the peroxidative degradation of vincristine (VCR). Oxidation of VCR involves a ring fission between positions 20' and 21', and is thought to be facilitated by the presence of an hydroxyl (-OH) group at position 20'. We report here two different approaches, both with potential clinical application, to decrease MPO-catalyzed vinca degradation. Firstly, we tested the hypothesis that -OH substitution at position 20' increases vinca susceptibility to peroxidation by comparing the relative extent of degradation of vinorelbine (Navelbine or NVB), which lacks a 20' hydroxyl substitution, with that of VCR. As anticipated, NVB was significantly less susceptible to MPO-catalyzed peroxidation than was VCR (p < 0.01). Secondly, we screened an array of compounds that are in current clinical use for their ability to inhibit MPO. Acetaminophen, N-acetylcysteine, propylthiouracil, D-penicillamine, mefenamic acid, dapsone, and methimazole all inhibited MPO at clinically achievable concentrations. Insofar as increased MPO activity has been observed in patients with acute myeloid leukemia, these findings suggest potential strategies for improving the activity of vinca alkaloids in this disease.

Alteration of the inner surface of venous catheters by antineoplastic drugs

Septic complications and thrombosis are frequent causes of long-term venous catheter implantation failure and tend to occur more frequently in oncology than in patients using catheters for hyperalimentation only. The purpose of this in vitro study was to study extensively the inner surface behaviour and the possible changes in their mechanical properties of various silicone and polyurethane catheters after exposure to a flow of the most common antineoplastic drugs. Silicone catheters appeared to be the best choice for cytostatic drug infusions because of their chemical stability, but the addition of an opacifier imposes a protective inner and outer layer to improve their surface properties for biocompatibility.