Biodegradable and pH-Responsive Amphiphilic Poly(succinimide) Derivatives for Triggered Release of Antibiotics for Management of Infected Wounds

Wound infection has become a healthy economic burden globally. Current wound management mainly relies on the use of antibiotics; however, the misuse and overuse of antibiotics can easily result in antibiotic resistance. This study proposes a biodegradable, biocompatible, and pH-responsive amphiphilic 11-aminoundecanoic acid-grafted polysuccinimide (AUA-PSI) as a nanocarrier for drug encapsulation via nanoprecipitation. The succinimide groups in the backbone of PSI allow facile postfunctionalization via an aminolysis reaction. The degree of substitution of AUA can be modulated to adjust the degradation rate, pH sensitivity, and drug-release profile. Antibiotic rifampicin was incorporated with AUA-PSI to form Rif-AUA-PSI nanoparticles and demonstrated pH-responsiveness and antimicrobial activity. Because of the elevation of the pH value from pH = ∼ 5.5 in healthy skin to pH > 7 in an infected wound, Rif-AUA-PSI nanoparticles begin to decompose and release Rif upon the hydrolysis of succinimide/amide and deprotonation of carboxyl groups. The effective suppression of bacterial growth by Rif-AUA-PSI nanoparticles was demonstrated using a plate count method. More importantly, Rif-AUA-PSI nanoparticles were physically deposited on cotton gauze bandages as an antibiotic wound dressing. The Rif-AUA-PSI-modified gauze was applied to infected wounds on rats for wound management. The results show fast wound healing and inhibition of bacterial growth, which demonstrate that the method promotes modulable amphiphilicity, biodegradability, biocompatibility, pH-responsiveness, and facile modification for nanomedicine and medical devices.

Preparation of protein-loaded nanoparticles based on poly(succinimide)-oleylamine for sustained protein release: a two-step nanoprecipitation method

Currently, the treatment for acute disease encompasses the use of various biological drugs (BDs). However, the utilisation of BDs is limited due to their rapid clearance and non-specific accumulation in unwanted sites, resulting in a lack of therapeutic efficacy together with adverse effects. While nanoparticles are considered good candidates to resolve this problem, some available polymeric carriers for BDs were mainly designed for long-term sustained release. Thus, there is a need to explore new polymeric carriers for the acute disease phase that requires sustained release of BDs over a short period, for example for thrombolysis and infection. Poly(succinimide)-oleylamine (PSI-OA), a biocompatible polymer with a tuneable dissolution profile, represents a promising strategy for loading BDs for sustained release within a 48-h period. In this work, we developed a two-step nanoprecipitation method to load the model protein (e.g. bovine serum albumin and lipase) on PSI-OA. The characteristics of the nanoparticles were assessed based on various loading parameters, such as concentration, stirring rate, flow rate, volume ratio, dissolution and release of the protein. The optimised NPs displayed a size within 200 nm that is suitable for vasculature delivery to the target sites. These findings suggest that PSI-OA can be employed as a carrier for BDs for applications that require sustained release over a short period.

Hypothermia-Triggered Mesoporous Silica Particles for Controlled Release of Hydrogen Sulfide to Reduce the I/R Injury of the Myocardium

Despite the fact that heart transplantation (HTx) is a relatively mature procedure, heart ischemic and reperfusion (I/R) injury during HTx remains a challenge. Even after a successful operation, the heart will be at risk of primary graft failure and mortality during the first year. In this study, temperature-sensitive polymer poly(N-n-propylacrylamide-co-N-tert-butyl acrylamide) (PNNTBA) was coated on diallyl trisulfide (DATS)-loaded mesoporous silica nanoparticles (DATS-MSN) to synthesize hypothermia-triggered hydrogen sulfide (H₂S) releasing particles (HT-MSN). Because the PNNTBA shell dissolves in phosphate-buffered saline at 4 °C, the loaded DATS could continuously release H₂S within 6 h when activated by glutathione (GSH). Furthermore, after co-culturing biocompatible HT-MSN with cardiomyocytes, H₂S released from HT-MSN at 4 °C was found to protect cardiomyocytes from ischemic and reperfusion (I/R) injury. In detail, the rate of cell apoptosis and lactate dehydrogenase activity was decreased, as manifested by increased BCL-2 expression and decreased BAX expression. More importantly, in an isolated heart preservation experiment, HT-MSN demonstrated potent protection against cardiac I/R injury and reduced expression of inflammatory factors TNF-α and IL-1β. This study provided a new method for the controlled release of H₂S by the donor and myocardial protection from I/R injury.

Poly(aspartic acid) Biohydrogel as the Base of a New Hybrid Conducting Material

In the present study, a composite made of conducting polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), and a biodegradable hydrogel of poly(aspartic acid) (PASP) were electrochemically interpenetrated with poly(hydroxymethyl-3,4-ethylenedioxythiophene) (PHMeDOT) to prepare a new interpenetrated polymer network (IPN). Different cross-linker and PEDOT MPs contents, as well as different electropolymerization times, were studied to optimize the structural and electrochemical properties. The properties of the new material, being electrically conductive, biocompatible, bioactive, and biodegradable, make it suitable for possible uses in biomedical applications.

Mixed micelles for enhanced oral bioavailability and hypolipidemic effect of liquiritin: preparation, in vitro and in vivo evaluation

OBJECTIVES

Liquiritin, as one of the main flavonoids in Glycyrrhiza, exhibits extensive pharmacological effects, such as the anti-oxidant, anti-inflammatory, anti-tumor and so on. Herein, the aqueous solubility and oral bioavailability of liquiritin was purposely enhanced via the preparation of the mixed micelles.

METHODS

The liquiritin-loaded micelles (LLM) were fabricated via thin-film dispersion method. The optimal LLM formulation was evaluated through physical properties including particle size (PS), encapsulation efficiency (EE) and drug loading (DL). In vitro accumulate release as well as in vivo pharmacokinetics were also evaluated. Moreover, the hypolipidemic activity of LLM was observed in the hyperlipidemia mice model.

RESULTS

The LLM exhibited a homogenous spherical shape with small mean PS, good stability and high encapsulation efficiency. The accumulate release rates in vitro of the LLM were obviously higher than free liquiritin. The oral bioavailability of the formulation was heightened by 3.98 times in comparison with the free liquiritin. More importantly, LLM increased the hypolipidemic and effect of alleviating lipid metabolism disorder in hepatocytes of liquiritin in hyperlipidemia mice model.

CONCLUSIONS

Collectively, the improved solubility of liquiritin in water coupled with its enhanced oral bioavailability and concomitant hypolipidemic activity could be attributed to the incorporation of the drug into the mixed micelles.

Amphiphilic Block Copolymer Poly (Acrylic Acid)-B-Polycaprolactone as a Novel pH-sensitive Nanocarrier for Anti-Cancer Drugs Delivery: In-vitro and In-vivo Evaluation

Gambogenic acid (GNA) has been demonstrated with outstanding antitumor activity as a potential antitumor drug in recent years. However, the low solubility and deficient bioavailability of GNA seriously hinder its practical application in the clinic area. In this study, a novel amphiphilic block copolymer, poly (acrylic acid)-b-polycaprolactone (PAA-b-PCL) is prepared and assembled into pH-responsive polymeric micelles (PMs) as one mold of drug delivery system (DDS) with unique properties. Relevant investigation on PMs exhibits excellent carrying potential and pH-dependent release performance for GNA. The drug loading capacity (DLC) and drug loading efficiency (DLE) for GNA-loaded PMs can be achieved as high as 15.20 ± 0.07% and 83.67 ± 0.49%, respectively. The in vitro experiments indicate that the GNA releasing time, cytotoxicity, and cellular uptake are significantly enhanced. Especially, the peak concentration (Cmax) and area under the curve (AUC) are promoted sharply in the GNA-loaded PMs concentration-time curve. This study not only provides a novel way to widen the application of anticancer GNA in the future, but also extends the potential of stimuli-responsive copolymers to biomedical applications.

In Situ Drug Delivery to Breast Cancer-Associated Extracellular Matrix

The extracellular matrix (ECM) contributes to tumor progression through changes induced by tumor and stromal cell signals that promote increased ECM density and stiffness. The increase in ECM stiffness is known to promote tumor cell invasion into surrounding tissues and metastasis. In addition, this scar-like ECM creates a protective barrier around the tumor that reduces the effectiveness of innate and synthetic antitumor agents. Herein, clinically approved breast cancer therapies as well as novel experimental approaches that target the ECM are discussed, including in situ hydrogel drug delivery systems, an emerging technology the delivers toxic chemotherapeutics, gene-silencing microRNAs, and tumor suppressing immune cells directly inside the tumor. Intratumor delivery of therapeutic agents has the potential to drastically reduce systemic side effects experienced by the patient and increase the efficacy of these agents. This review also describes the opposing effects of ECM degradation on tumor progression, where some studies report improved drug delivery and delayed cancer progression and others report enhanced metastasis and decreased patient survival. Given the recent increase in ECM-targeting drugs entering preclinical and clinical trials, understanding and addressing the factors that impact the effect of the ECM on tumor progression is imperative for the sake of patient safety and survival outcome.

Influence of Block versus Random Monomer Distribution on the Cellular Uptake of Hydrophilic Copolymers

The use of polymers has revolutionized the field of drug delivery in the past two decades. Properties such as polymer size, charge, hydrophilicity, or branching have all been shown to play an important role in the cellular internalization of polymeric systems. In contrast, the fundamental impact of monomer distribution on the resulting biological properties of copolymers remains poorly studied and is always only investigated for biologically active self-assembling polymeric systems. Here, we explore the fundamental influence of monomer distribution on the cellular uptake of nonaggregating and biologically passive copolymers. Reversible addition-fragmentation chain-transfer (RAFT) polymerization was used to prepare precisely defined copolymers of three hydrophilic acrylamide monomers. The cellular internalization of block copolymers was compared with the uptake of a random copolymer where monomers are statistically distributed along the chain. The results demonstrate that monomer distribution in itself has a negligible impact on copolymer uptake.

Temperature-Responsive Smart Nanocarriers for Delivery Of Therapeutic Agents: Applications and Recent Advances

Smart drug delivery systems (DDSs) have attracted the attention of many scientists, as carriers that can be stimulated by changes in environmental parameters such as temperature, pH, light, electromagnetic fields, mechanical forces, etc. These smart nanocarriers can release their cargo on demand when their target is reached and the stimulus is applied. Using the techniques of nanotechnology, these nanocarriers can be tailored to be target-specific, and exhibit delayed or controlled release of drugs. Temperature-responsive nanocarriers are one of most important groups of smart nanoparticles (NPs) that have been investigated during the past decades. Temperature can either act as an external stimulus when heat is applied from the outside, or can be internal when pathological lesions have a naturally elevated termperature. A low critical solution temperature (LCST) is a special feature of some polymeric materials, and most of the temperature-responsive nanocarriers have been designed based on this feature. In this review, we attempt to summarize recent efforts to prepare innovative temperature-responsive nanocarriers and discuss their novel applications.

Biomaterial Applications in Cell-Based Therapy in Experimental Stroke

Stroke is an important health issue corresponding to the second cause of mortality and first cause of severe disability with no effective treatments after the first hours of onset. Regenerative approaches such as cell therapy provide an increase in endogenous brain structural plasticity but they are not enough to promote a complete recovery. Tissue engineering has recently aroused a major interesting development of biomaterials for use into the central nervous system. Many biomaterials have been engineered based on natural compounds, synthetic compounds, or a mix of both with the aim of providing polymers with specific properties. The mechanical properties of biomaterials can be exquisitely regulated forming polymers with different stiffness, modifiable physical state that polymerizes in situ, or small particles encapsulating cells or growth factors. The choice of biomaterial compounds should be adapted for the different applications, structure target, and delay of administration. Biocompatibilities with embedded cells and with the host tissue and biodegradation rate must be considerate. In this paper, we review the different applications of biomaterials combined with cell therapy in ischemic stroke and we explore specific features such as choice of biomaterial compounds and physical and mechanical properties concerning the recent studies in experimental stroke.

Stable micelles formed through a stereocomplex of amphiphilic copolymers zwitterionic-(PLLA)2 and MPEG-(PDLA)2 for controlled drug delivery

Y-Shaped amphiphilic copolymers (zwitterionic-(PLLA_2.5K)₂ and MPEG-(PDLA_2.5K)₂) were synthesized through click reaction. The aggregation behavior of the polymers and their stereocomplexes and the DOX release profile from the aggregates were studied.