Biodegradable polymeric matrix for long-acting and zero-order release drug delivery systems

Three types of biodegradable triblock copolymers, ABA, ABC and ACB, where A is polycaprolactone (PCL), B is polylactide (PLA) and C is polyglycolide (PGA), were used as matrix to test their controlled release behavior of Levo-Norgestrel in the form of microsphere. It was verified that the overall release kinetics changes from in vitro first order to zero order when the percentage of PCL segments in all of the block copolymers decreases from 85 % to 60 −65 % with a long-acting release time of 5 months or more. It is ascribed to the two release mechanisms, the diffusion release, contributed by the PCL segment, and the erosion-caused release by PLA or PGA segment. At a certain ratio of segments the two release ways make a compromise to a constant rate of release, i. e. a zero-order kinetics in these multiphase block copolymers.     

Biodegradable and thermosensitive micelles of amphiphilic polyaspartamide derivatives containing aromatic groups for drug delivery

The preparation, characterization, release, and in vitro cytotoxicity of a biodegradable polymeric micellar formulation of paclictaxel (PTX) were investigated. The micelles based on thermosensitive and degradable amphiphilic polyaspartamide derivatives containing pendant aromatic structures (phe‐g‐PHPA‐g‐mPEG) were prepared by a quick heating method without using toxic organic solvent. Dynamic light‐scattering results show that the micelles are stable upon dilution under physiological conditions and the destabilization of the micelles is pH‐dependent and the phe‐g‐PHPA‐g‐mPEG polymers are biodegradable. PTX was loaded into the phe‐g‐PHPAs‐g‐mPEG micelles with encapsulation efficiency of >90%, resulting in a high drug loading content (up to 29%). PTX‐loaded micelles had a mean size around 70 nm with narrow size distribution (polydispersity index, <0.1). The PTX‐loaded micelles showed sustained drug release and obvious anticancer activity similar to Taxol against HepG2 cells, whereas blank micelles were nontoxic. The present results suggest that the thermosensitive and biodegradable phe‐g‐PHPA‐g‐mPEG micelles are a promising delivery system for the hydrophobic drugs. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3917–3924     

Biodegradable thermo‐ and pH‐responsive hydrogels for oral drug delivery

In this article, novel smart hydrogels based on biodegradable pH sensitive poly(L ‐glutamic acid‐g‐2‐hydroxylethyl methacrylate) (PGH) chains and temperature‐sensitive hydroxypropylcellulose‐g‐acrylic acid (HPC‐g‐AA) segments were designed and synthesized. The influence of pH and temperature on the equilibrium swelling ratios of the hydrogels was discussed. The optical transmittance of the hydrogels was also changed as a function of temperature, which reflecting that the HPC‐g‐AA part of the hydrogels became hydrophobic at the temperature above the lower critical solution temperature (LCST). At the same time, the LCST of the hydrogels had a visible pH‐dependent behavior. Scanning electron microscopic analysis revealed the morphology of the hydrogels before and after enzymatic degradation. The biodegradation rate of the hydrogels was directly related to the PGH content and the pH value. The in vitro release of bovine serum albumin from the hydrogels were investigated. The release profiles indicated that both the HPC‐g‐AA and PGH contents played important roles in the drug release behaviors. These results show that the smart hydrogels seem to be of great promise in pH–temperature oral drug delivery systems. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Biodegradable polymeric nanoparticles based on amphiphilic principle: construction and application in drug delivery

The use of nanotechnology in drug-delivery systems (DDS) is attractive for advanced diagnosis and treatment of cancer diseases. Biodegradable polymeric nanoparticles, for example, have promising applications as advanced drug carriers in cancer treatment. In this review, we discuss the development of drug-delivery systems based on an amphiphilic principle mainly conducted by our group for anti-cancer drug delivery. We first briefly address the synthetic chemistry for amphiphilic biodegradable polymers. In the second part, we summarize progress in the application of self-assembled polymer micelles using amphiphilic biodegradable copolymers as anti-tumor drug carriers.     

Biodegradable and self-fluorescent ditelluride-bridged mesoporous organosilica/polyethylene glycol-curcumin nanocomposite for dual-responsive drug delivery and enhanced therapy efficiency

Mesoporous organosilica as drug delivery carriers capable of achieving improved cargo release, enhanced biodegradation, and direct imaging with prolonged circulation time and tracking cargo distribution is highly in demand for biomedical applications. Herein, we report a ditelluride-bridged mesoporous organosilica nanoparticle (DTeMSN)/polyethylene glycol-curcumin (PEG-CCM) nanocomposite through coassembly with oxidative/redox and self-fluorescent response. Tellurium is introduced into the silica framework for the first time as a drug delivery vehicle. In this case, the DTeMSNs as an inner core enable disassembly under oxidative and redox conditions via the cleavage of ditelluride bond, facilitating the drug release of doxorubicin (DOX) in a matrix degradation controlled manner. Through the systematical comparison of diselenide-bridged MSNs and DTeMSNs, DTeMSNs exhibit remarkable advantages in loading capacity, drug release, and degradation behavior, thereby significantly affecting the cytotoxicity and antitumor efficacy. The self-fluorescent response of PEG-CCM shell coated on the surface of DTeMSNs can real-timely track the cellular uptake, DOX release, and biodistribution owing to the intrinsic and stable fluorescence of CCM. Moreover, PEG-CCM could prolong circulation time, provide preferable drug accumulation in tumors, and increase antitumor efficacy of DOX-loaded DTeMSNs. Our findings are likely to enrich the family of organosilica that served as fluorescence-guided drug delivery carriers.     

Mesoporous materials for drug delivery

Research on mesoporous materials for biomedical purposes has experienced an outstanding increase during recent years. Since 2001, when MCM-41 was first proposed as drug-delivery system, silica-based materials, such as SBA-15 or MCM-48, and some metal-organic frameworks have been discussed as drug carriers and controlled-release systems. Mesoporous materials are intended for both systemic-delivery systems and implantable local-delivery devices. The latter application provides very promising possibilities in the field of bone-tissue repair because of the excellent behavior of these materials as bioceramics. This Minireview deals with the advances in this field by the control of the textural parameters, surface functionalization, and the synthesis of sophisticated stimuli-response systems.     

Polymeric conjugates for drug delivery

The field of polymer therapeutics has evolved over the past decade and has resulted in the development of polymer-drug conjugates with a wide variety of architectures and chemical properties. Whereas traditional non-degradable polymeric carriers such as poly(ethylene glycol) (PEG) and N-(2-hydroxypropyl methacrylamide) (HPMA) copolymers have been translated to use in the clinic, functionalized polymer-drug conjugates are increasingly being utilized to obtain biodegradable, stimuli-sensitive, and targeted systems in an attempt to further enhance localized drug delivery and ease of elimination. In addition, the study of conjugates bearing both therapeutic and diagnostic agents has resulted in multifunctional carriers with the potential to both "see and treat" patients. In this paper, the rational design of polymer-drug conjugates will be discussed followed by a review of different classes of conjugates currently under investigation. The design and chemistry used for the synthesis of various conjugates will be presented with additional comments on their potential applications and current developmental status.     

Biodegradable and antibacterial poly(azomethine‐urethane)‐chitosan hydrogels for potential drug delivery application

In this study, biodegradable and antibacterial poly(azomethine‐urethane) (PAMU)‐ and chitosan (CS)‐based hydrogels have been prepared for controlled drug delivery applications. Structural and morphological characterizations of the hydrogels were performed via Fourier transform‐infrared and scanning electron microscopy analyses. Thermal stability, hydrophilicity, swelling, mechanical, biodegradation, protein absorption properties, and drug delivery application of PAMU‐ and CS‐based hydrogels were also investigated. The swelling performance of the hydrogels was studied in acidic, neutral, and alkaline media. Swelling results showed that the hydrogels have higher swelling capacity in acidic and alkaline media than neutral medium. Biodegradation experiments of the hydrogels were also studied via hydrolytic and enzymatic experiments. The drug release property of the hydrogel was carried out using 5‐fluoro uracil (5‐FU), and 5‐FU release capacity of the hydrogels was found in the range from 40.10% to 58.40% after 3 days.     

Carrier-free, functionalized drug nanoparticles for targeted drug delivery

We demonstrate a new concept of carrier-free functionalized drug nanoparticles for targeted drug delivery. It exhibits significantly enhanced drug efficacy to folate receptor-positive cells with high selectivity and a high drug loading content up to more than 78%.     

Dendritic supramolecular assemblies for drug delivery

Dendritic supramolecular assemblies were formed in water with Reichardt's dye or the anticancer drug 10-hydroxycamptothecin and the dendritic macromolecule, ([G4]-PGLSA-OH)2-PEG3400.     

Multiparticulate chitosan-dispersed system for drug delivery

A multiparticulate chitosan-dispersed system (CDS), which is composed of the drug reservoir and the drug release-regulating layer, was developed for drug delivery. The drug release-regulating layer is a mixture of water-insoluble polymer and chitosan powder. The drug is released from CDS pellets in all regions of the gastrointestinal tract (from the stomach to the colon). CDS pellets containing chitosan powder were designed to dissolve chitosan powder partly in the release-regulating layer in the stomach and release part of drug. After passing through the stomach, the drug is released from CDS pellets at a constant speed in the small intestine. In the large intestine, CDS pellets were designed to disintegrate the remaining chitosan powder at an accelerated speed and the remaining drug in CDS pellets is released. The drug release rate can be controlled with the thickness of the chitosan-dispersed water-insoluble layer. Furthermore, for colon-specific drug delivery, an additional outer enteric coating is necessary to prevent drug release from CDS pellets in the stomach, because the chitosan-dispersed water-insoluble layer dissolves gradually under acidic conditions. The resulting enteric-coated CDS (E-CDS) pellets were found to permit colon-specific drug delivery. In this study, the multiparticulate CDS was adopted not only for colon-specific drug delivery but also for sustained drug release.     

Hydrogel-mediated drug delivery for treating stroke

Stroke is a common disease and is the major cause of death and disability. It occurs and generates devastating neurological deficits when cerebral blood vessel is blocked(ischemic stroke, IS) or ruptured(hemorrhagic stroke, HS). Hydrogel, being biodegradable and biocompatible, have shown attractive advantages in stroke therapy as a new biomaterial with desirable mechanical properties and tunability of structure,owing to special ability to load different cargoes for multiple treatment strategies,...     

Polymeric multilayer capsules for drug delivery

The advent of Layer-by-Layer (LbL) assembly to fabricate polymeric as well as hybrid multilayer thin films has opened exciting avenues for the design of multifunctional drug carriers with extreme control over their physico-chemical properties. These polymeric multilayer capsules (PMLC) are typically fabricated by sequential adsorption of polymers onto a spherical substrate with dimensions varying from 10 nm to several microns and larger. In this critical review, we give an overview of the recent advances in the field of PMLC with respect to drug delivery and point out how sophisticated capsule engineering can lead to well-defined drug carriers with unique properties (139 references).     

Hydrogel design strategies for drug delivery

Hydrogels are water-swollen three-dimensional networks made of polymers, proteins, small molecules or colloids. They constitute a versatile platform for drug delivery because of their capacity to encapsulate and protect drugs and provide sustained and/or remotely programmable spatial and temporal release and have thus generated a substantial amount of research for the delivery of either small active compounds or biopharmaceuticals. This article discusses the features that make hydrogels attractive as matrices for delivery and reviews a range of designs, focussing on studies from recent years, in particular: ‘smart’ hydrogels (responding to temperature, light, magnetic fields, ultrasounds or combined stimuli); recent technologies: 3D printing and microneedles; and closes by discussing polymer-free drug delivery systems: peptides, small molecules and colloids.     

Biodegradable poly(ethylene carbonate) nanoparticles as a promising drug delivery system with "stealth" potential

The goal of this study was to investigate the suitability of poly(ethylene carbonate) (PEC) nanoparticles as a novel drug delivery system, fulfilling the requirements for a long circulation time. Particles were obtained with a narrow size distribution and nearly neutral zeta potential. Adsorption studies with human plasma proteins revealed that PEC nanoparticles bind much less proteins in comparison to polystyrene (PS) nanoparticles. Cell experiments with fluorescently labeled PEC showed no uptake of the nanoparticles by macrophages. These novel PEC nanospheres with their unique surface properties are a promising candidate for long circulating drug delivery systems in vivo.     

Biodegradable silk-curcumin composite for sustained drug release and visual wound monitoring

The production of biodegradable dressing capable of sustained drug release, along with the monitoring of wound conditions, represents new heights of multifunctional platforms for wound care. The reported curcumin-loaded silk fibroin has shown sustained drug release over the time of 10 days through a non-Fickian diffusion process satisfying Korsmeyer-Peppas' model along with the visual monitoring of wound healing through notable color variation with pH as a biomarker. The superhydrophobic nature (water contact angle = 163.7) of the SF, along with the lipophilicity (CA = 0 (Blood)) and hygroscopic nature prevents wetting of wound surface, whereas the excess exudates from wounds are absorbed along with sufficient water and oxygen permeability. The pH responsiveness as a result of the keto-enol tautomerism in curcumin was utilized for wound monitoring through visual indication enabling even ordinary people to detect the state of the wound. The in-situ biodegradation studies verified using cow-dung slurry, the degradability of the material with 25.3% weight loss within 30 days following first-order kinetics (R² = 0.994), as a result of the attack of proteolytic enzymes on the amino acid units of SF, mitigating the concerns of medical wastes.