Improved dissolution and cytotoxicity of camptothecin incorporated into oxidized-cellulose microspheres prepared by spray drying

A Review on the Modification of Cellulose and Its Applications

The latest advancements in cellulose and its derivatives are the subject of this study. We summarize the characteristics, modifications, applications, and properties of cellulose. Here, we discuss new breakthroughs in modified cellulose that allow for enhanced control. In addition to standard approaches, improvements in different techniques employed for cellulose and its derivatives are the subject of this review. The various strategies for synthetic polymers are also discussed. The recent advancements in polymer production allow for more precise control, and make it possible to make functional celluloses with better physical qualities. For sustainability and environmental preservation, the development of cellulose green processing is the most abundant renewable substance in nature. The discovery of cellulose disintegration opens up new possibilities for sustainable techniques. Based on the review of recent scientific literature, we believe that additional chemical units of cellulose solubility should be used. This evaluation will evaluate the sustainability of biomass and processing the greenness for the long term. It appears not only crucial to dissolution, but also to the greenness of any process.

Preparation of camptothecin-loaded PCEC microspheres for the treatment of colorectal peritoneal carcinomatosis and tumor growth in mice

The aim of this study was to prepare PCL-PEG-PCL (PCEC) microspheres to protect camptothecin from hydrolysis, to extend its release time and to enhance its treatment efficacy on colorectal peritoneal carcinomatosis and tumor growth in mice. Camptothecin (CPT)-loaded PCL-PEG-PCL (PCEC) microspheres were prepared by oil-in-water emulsion solvent evaporation method. The particle size, morphological characteristics, encapsulation efficiency, in vitro drug release studies and in vitro cytotoxicity of CPT-loaded PCEC microspheres have been investigated. In vivo studies were carried out on Balb/c male mice bearing colorectal peritoneal carcinomatosis. CPT-loaded PCEC microspheres were applied to abdominal cavity of mice once a week. Free CPT was used as a positive control. On 14th day of treatment, mice were sacrificed and antitumor activities of CPT-loaded PCEC microspheres were evaluated. Compared with control group, a significant decrease in the number of tumor nodes was observed in group treated with CPT-loaded PCEC microspheres. Immunohistochemistry staining of tumor tissues with CD34 revealed that MVD positive cells were significantly reduced in CPT-loaded PCEC microspheres treated group in contrast to other groups (P<0.05). The CPT-loaded PCEC microspheres were considered potentially useful to treat the abdominal metastases of colon carcinoma.

Nanomicelle with long-term circulation and enhanced stability of camptothecin based on mPEGylated alpha,beta-poly (L-aspartic acid)-camptothecin conjugate

To enhance the stability and long-term circulation of camptothecin (CPT), mPEGylated alpha,beta-poly (L-aspartic acid)-CPT conjugates were synthesized, and used to fabricate nanomicelle. Firstly, alpha,beta-poly (L-aspartic acid) derivative (PAA-der) containing alkyne groups was synthesized via the ring-opening of PSI with propargyl amine. And then, azide-functionalized CPT derivatives (CPT-N(3)) and azide-terminated poly (ethylene glycol) methyl ether (mPEG-N(3)) were conjugated with PAA-der by click cycloaddition to give mPEG-graft-PAA-CPT conjugates. The formation of mPEG-graft-PAA-CPT nanomicelles was confirmed by fluorescence spectrophotoscopy and particle size measurements. It was found that all the nanomicelles showed spherical shapes with size about 178 nm. MPEG-graft-PAA-CPT nanomicelles showed good storage stability, even incubation at 37 degrees C for 60 days, and improved the stability of CPT lactone form in aqueous media. A steady release rate of CPT was kept for 72h, suggested the great potential of mPEG-graft-PAA-CPT nanomicelles as polymer prodrug of CPT.

Incorporation methods for cholic acid chitosan-g-mPEG self-assembly micellar system containing camptothecin

A water-insoluble anticancer agent, camptothecin (CPT) was incorporated to a polymeric micelle carrier system preparing from cholic acid chitosan-grafted poly (ethylene glycol) methyl ether (CS-mPEG-CA). CS-mPEG-CA formed a core-shell micellar structure with a critical micelle concentration (CMC) of 7.08 microg/ml. Incorporation efficiency was investigated by varying physical incorporation method and initial drug loading. Among three incorporation methods (dialysis, emulsion and evaporation methods), an emulsion method showed the highest CPT incorporation efficiency. Increasing the initial CPT loading from 5 to 40%, the incorporation efficiency decreased. In all examined CPT-loaded CS-mPEG-CA micelles, 5% initial drug loading showed the highest drug incorporation efficiency. Release of CPT from the micelles was sustained when increasing the initial CPT loading. This indicates the importance of incorporation method and the initial drug loading to obtain the optimum particle size with high drug loading and sustained drug release. When compared to the unprotected CPT, CPT-loaded CS-mPEG-CA micelles were able to prevent the hydrolysis of the lactone group of the drug. This novel CS-mPEG-CA polymer presents considerable potential interest in the further development of CPT carrier.

Poly(omega-pentadecalactone-co-butylene-co-succinate) nanoparticles as biodegradable carriers for camptothecin delivery

In this study, we show that degradable particles of a hydrophobic polymer can effectively deliver drugs to tumors after i.v. administration. Free-standing nanoparticles with diameters of 100-300 nm were successfully fabricated from highly hydrophobic, biodegradable poly(omega-pentadecalactone-co-butylene-co-succinate) (PPBS) copolyesters. PPBS copolymers with various compositions (20-80 mol% PDL unit contents) were synthesized via copolymerization of omega-pentadecalactone (PDL), diethyl succinate (DES), and 1,4-butanediol (BD) using Candida antarctica lipase B (CALB) as the catalyst. Camptothecin (CPT, 12-22%) was loaded into PPBS nanoparticles with high encapsulation efficiency (up to 96%) using a modified oil-in-water single emulsion technique. The CPT-loaded nanoparticles had a zeta potential of about -10 mV. PPBS particles were non-toxic in cell culture. Upon encapsulation, the active lactone form of CPT was remarkably stabilized and no lactone-to-carboxylate structural conversion was observed for CPT-loaded PPBS nanoparticles incubated in both phosphate-buffered saline (PBS, pH=7.4) and DMEM medium for at least 24 h. In PBS at 37 degrees C, CPT-loaded PPBS nanoparticles showed a low burst CPT release (20-30%) within the first 24 h followed by a sustained, essentially complete, release of the remaining drug over the subsequent 40 days. Compared to free CPT, CPT-loaded PPBS nanoparticles showed a significant enhancement of cellular uptake, higher cytotoxicity against Lewis lung carcinoma and 9L cell lines in vitro, a longer circulation time, and substantially better antitumor efficacy in vivo. These results demonstrate the potential of PPBS nanoparticles as long-term stable and effective drug delivery systems in cancer therapy.

Camptothecin-incorporating N-phthaloylchitosan-g-mPEG self-assembly micellar system: Effect of degree of deacetylation

Amphiphilic grafted copolymers, N-phthaloylchitosan-grafted poly (ethylene glycol) methyl ether (PLC-g-mPEG), were synthesized from chitosan with different degree of deacetylation (DD=80%, 85%, 90% and 95%). Due to their amphiphilic characteristic, these copolymers could form micelle-like nanoparticles. The critical micelle concentration (CMC) of these nanoparticles with different DD in water was similar (28microg/ml). Under transmission electron microscope (TEM), the nanoparticles exhibited a regular spherical shape with core-shell structure. The particle sizes determined by dynamic light scattering were in the range of 100-250nm, and increased as the %DD of chitosan increased. The cytotoxicity of phthaloylchitosans (PLC) and PLC-g-mPEG in Hela cells line were evaluated. The results showed that cytotoxicity of PLC and PLC-g-mPEG increased with increasing %DD of chitosan. The cytotoxicity of PLC-g-mPEG was significantly lower than that of PLC. Camptothecin as a model drug was loaded into the inner core of the micelles by dialysis method. It was found that %DD of chitosan, corresponding to the N-phthaloyl groups in the inner core of the nanoparticle obtained, was a key factor in controlling %yield, stability of the drug-loaded micelles, and drug release behavior. As the %DD increased, the CPT-loaded micelles stability increased. Release of CPT from the micelles was dependent on the %DD and a sustained release was obtained in high %DD.

Antitumor activity of poly(ethylene glycol)-camptothecin conjugate: the inhibition of tumor growth in vivo

Antitumor effect of poly(ethylene glycol)-camptothecin conjugate (PEG-CPT) was studied in the nude mouse model of human colon cancer xenografts. The animals were treated intravenously with 15 mg/kg of camptothecin (CPT) or PEG-CPT conjugate at equivalent CPT dose. Antitumor activity, apoptosis induction and caspase-dependent signaling pathways were studied 12, 24, 48 and 96 h after single injection. In addition, pharmacokinetics, tumor distribution and accumulation of PEG polymer labeled with green fluorescence protein (GFP) were studied. The data obtained showed that the conjugation of low molecular weight anticancer drug CPT with low solubility to high molecular weight water-soluble PEG polymer provides several advantages over the native drug. First, the conjugation improves drug pharmacokinetics in the blood and tumor. Second, such conjugation provides passive tumor targeting by the Enhanced Permeability and Retention (EPR) effect, increasing drug concentration in the tumor. Third, the coupling increases the bioavailability of CPT, induces apoptosis in tumor and, therefore, enhances anticancer activity of PEG-CPT. Thus, the use of macromolecular conjugate provided passive tumor targeting of the drug, improved pharmacokinetics and increased the stability of the drug during circulation. It offered better uptake by the targeted tumor cells and substantially enhanced apoptosis and antitumor activity of the conjugated drug in the tumor and decreased apoptosis in liver and kidney as compared with the native drug. All these characteristics make PEG-CPT conjugate an attractive anticancer drug for the effective chemotherapy of solid tumors.

Block copolymer design for camptothecin incorporation into polymeric micelles for passive tumor targeting

PURPOSE

Polymeric micelles were designed for targeting of a water-insoluble anticancer agent, camptothecin (CPT). Chemical structures of inner core segment were optimized to achieve high incorporation efficiency and stable CPT-loaded micelles.

METHODS

Poly(ethylene glycol)-poly(beta-benzyl L-aspartate) block copolymer (PEG-PBLA) was synthesized. The PBLA chain was modified by alkaline hydrolysis of its benzyl group followed by esterification with benzyl, n-butyl, and lauryl groups. Incorporation of CPT into micelles was carried out by an evaporation method. The stability of drug-loaded micelles was studied by gel-permeation chromatography (GPC), and their in vitro release behaviors were analyzed.

RESULTS

CPT was incorporated into polymeric micelles constructed by various block copolymers. Among the esterified groups, block copolymers with high benzyl ester contents showed high CPT loading efficiency and stable CPT-loaded micelles. In chain lengths, 5-27 Bz-69 showed the highest incorporation efficiency. In contrast, 5-52 Bz-67, which had a longer hydrophobic chain, showed low incorporation efficiency. Release of CPT from the micelles was dependent on the benzyl contents and chain lengths. Sustained release was obtained when the benzyl content was high.

CONCLUSIONS

CPT was successfully incorporated into polymeric micelles with high efficiency and stability by optimizing chemical structures of the inner core segment.

Camptothecin delivery methods

Camptothecin has shown significant antitumor activity to lung, ovarian, breast, pancreas, and stomach cancers. Camptothecin, however, like a number of other potent anticancer agents such as paclitaxel, is extremely water insoluble. Furthermore, pharmacology studies have determined that prolonged schedules of administration given continuously are required. Thus, this insolubility has restricted its clinical application. For these reasons, a number of water-soluble analogs have been synthesized and a number of different formulation approaches have been investigated. In this review, we examine each of these approaches and discuss their advantages and limitations.