Strategies for Liposome Drug Delivery Systems to Improve Tumor Treatment Efficacy.

In the advancement of tumor therapy, in addition to the search for new antitumor compounds, the development of nano-drug delivery systems has opened up new pathways for tumor treatment by addressing some of the limitations of traditional drugs. Liposomes have received much attention for their high biocompatibility, low toxicity, high inclusivity, and improved drug bioavailability. They are one of the most studied nanocarriers, changing the size and surface characteristics of liposomes to better fit the tumor environment by taking advantage of the unique pathophysiology of tumors. They can also be designed as tumor targeting drug delivery vehicles for the precise delivery of active drugs into tumor cells. This paper reviews the current development of liposome formulations, summarizes the characterization methods of liposomes, and proposes strategies to improve the effectiveness of tumor treatment. Finally, it provides an outlook on the challenges and future directions of the field. Graphical abstract.

Progress and Principle of Drug Nanocrystals for Tumor Targeted Delivery.

Drugs are referred to as drug nanocrystals when they exist as nanoscale crystal structures. This kind of nanocarrier has been widely utilized to increase the solubility and absorption for poorly aqueous soluble drugs after oral administration, or prolong the drug circulation when intravenous administration. The systemic cytotoxicity caused by antitumor drugs usually come from the nonspecific drug distribution. To solve the disadvantage of poor targetability, drug nanocrystals for tumor targeted delivery have been developed in recent years. In this review, the targeting mechanisms of various surface modified drug nanocrystals are introduced with the focus on passive targeting, active targeting and stimuli-responsive targeting in details. Function and application of common surface modified materials are also discussed.

Porous Core/Dense Shell PLA Microspheres Embedded with High Drug Loading of Bupivacaine Crystals for Injectable Prolonged Release.

Objective of the study was to design an injectable microsphere preparation with high drug loading of bupivacaine for prolonged release and local anesthetic. PLA or PLGA was used as the biodegradable matrix material to fabricate microspheres with the o/w emulsification-solvent evaporation method. The characterization of bupivacaine microspheres was observed by SEM, DSC, and XRPD. The microsphere preparation and extended drug release, as well as the plasma drug concentration and sciatic nerve blockade after injection of the microsphere formulation to rats were investigated. High drug-loading microspheres of more than 70% were successfully obtained with extended drug release over 5 days in vitro depending on the type of matrix and the feed ratio of drug to polymer. SEM, DSC, and XRPD results verified a novel microsphere structure characterized as the porous core composed of PLA material and form II bupivacaine crystals and dense shell formed of PLA layer. The mechanism that bupivacaine was dissolved inside the microsphere and diffused across the dense shell was suggested for drug release in vitro. The optimized PLA microsphere formulation showed low and steady plasma drug concentration over 5 days and prolonged duration of sensory and motor blockade of sciatic nerve lasted more than 3 days. Results indicated that the porous core-shell structure of PLA microsphere formulation would provide enormous potential as an injectable depot for locally prolonged delivery of bupivacaine and control of postoperative pain.

The relationship between serum triglyceride levels and acute pancreatitis in an animal model and a 14-year retrospective clinical study.

OBJECTIVES: The aim of the current study was to evaluate influence of serum triglyceride levels on the course of acute pancreatitis (AP). METHODS: Rats models of hypertriglyceridemic were used in animal experiments. Following induction of acute pancreatitis, amylase, and pancreas histological scores were all compared. In addition, in a clinical study, clinical data were collected from 1681 AP patients admitted from 2003 to 2016 who were divided into 4 groups based on their serum triglyceride (TG) levels. The clinical features among these 4 groups were compared, and a receiver operating characteristic (ROC) curve analysis was also performed on TG values to estimate their relationship with severity. RESULTS: In animal experiments, the hypertriglyceridemic pancreatitis (HTGP) group had markedly higher serum amylase, and histological scores relative to the other animal groups. In the clinical study, we identified significant differences in gender, age, body mass index (BMI), cost, and incidence of partial complications among the 4 TG-based groups. Importantly, the TG levels on day 3-4 after admission could be used to accurately predict disease severity. CONCLUSIONS: Hypertriglyceridemia (HTG) can aggravate pancreatic injury, and hypertriglyceridemia patients are more likely to suffer from severe pancreatic injury with a higher possibility of complications. In addition, triglyceride levels are correlated with the severity of AP positively.

Biomaterial-based microstructures fabricated by two-photon polymerization microfabrication technology.

Two-photon polymerization (TPP) microfabrication technology can freely prepare micro/nano structures with different morphologies and high accuracy for micro/nanophotonics, micro-electromechanical systems, microfluidics, tissue engineering and drug delivery. With the broad application of 3D microstructures in the biomedical field, people have paid more attention to the physicochemical properties of the corresponding materials such as biocompatibility, biodegradability, stimuli responsiveness and immunogenicity. Therefore, microstructures composed of biocompatible synthetic polymers, polysaccharides, proteins and their complexes have been widely studied. In this review, we briefly summarize the TPP mechanism, the photoinitiators for TPP microfabrication, photoresist based on biomaterials, their corresponding microstructures and subsequently their biomedical applications. We will point out the issues in previous research and provide a useful perspective on the future development of TPP microfabrication technology.

A Comparative Study on Dissolution Enhancement of Acetaminophen by Cooling, Anti-solvent, and Solvent Evaporation Crystallization.

The aim of this study was to prepare APAP crystals by cooling, anti-solvent, and solvent evaporation crystallization to enhance its dissolution rate and to make comparisons of the three methods. Agitating speeds and types were regarded as factors affecting crystallization procedure. Samples were made with different ratios of PEG4000. They were characterized by X-ray diffraction and scanning electron microscopy. Dissolution tests were conducted to assess their dissolution property. The proportions of carriers existing in crystals by cooling and anti-solvent crystallization ranged from 1.3 to 5.1%. Mean dissolution time (MDT) of samples by the two methods was about 3 min, which was 17.2 min for untreated APAP. Addition of too much PEG4000 in solvent evaporation crystallization could decrease dissolution rate of APAP. Samples agitated by a rotor with speed of 100, 500, and 1000 rpm dissolved faster than those by a high shear mixer with speed of 3400 and 5000 rpm or by a glass rod. Agitating speed and type could affect particle size and drug dissolution. Dissolution enhancement of APAP might be attributed to decrease of fine particles and increase of particle wettability.

Effect of age on the pharmacokinetics of polymorphic nimodipine in rats after oral administration.

The previous investigation has proved that their existed pharmacokinetic difference between the different crystal forms of the polymorphic drugs after oral administration. However, no systemic investigations have been made on the change of this pharmacokinetic difference, resulted either from the physiological or from the pathological factors. In this paper, we used polymorphic nimodipine (Nim) as a model drug and investigated the effect of age difference (2- and 9-month old) on the pharmacokinetics after oral delivery in rats. As the results shown, for L-form of Nim (L-Nim), the AUC0-24 h in 2-month-old rats was 343.68±47.15 ng·h/mL, which is 23.36% higher than that in 9-month-old rats. For H-form of Nim (H-Nim), the AUC0-24 h in 2-month-old rats was 140.91±19.47 ng·h/mL, which is 54.64% higher than that in 9-month-old rats. The AUC0-24 h ratio between H-Nim and L-Nim was 2.44 in 2-month-old rats and 3.06 in 9-month-old rats. Since age difference could result in unparallelled change of the absorption and bioavailability of the polymorphic drugs, the results in this experiment are of value for further investigation of crystal form selection in clinical trials and rational clinical application of the polymorphic drugs.

Encapsulation of azithromycin into polymeric microspheres by reduced pressure-solvent evaporation method.

Azithromycin loaded microspheres with blends of poly-l-lactide and ploy-D,L-lactide-co-glycolide as matrices were prepared by the atmosphere-solvent evaporation (ASE) and reduced pressure-solvent evaporation (RSE) method. Both the X-ray diffraction spectra and DSC thermographs demonstrated that poly-L-lactide existed in a crystalline form in the ASE microspheres, while an amorphous form was present in the RSE formulations. Besides, solvent removal at atmosphere gave microspheres of porous and rough surfaces, but smooth surfaces appeared in the RSE microspheres. The incorporation efficiency as well as the burst release (cumulative release in the first 24h) in the ASE formulations was 39.94 ± 1.18% and 23.96 ± 2.01% respectively, yet the encapsulation efficiency of the microspheres fabricated under 385 mmHg was high up to 57.19 ± 3.81% and the burst release was 4.12 ± 0.15%. The in vitro drug release studies indicated that the ASE microspheres presented a zero-order profile; while the RSE formulations followed first-order kinetics. Other factors including solidification time, temperature, drug to polymer ratio and pH value of the continuous phase could also influence the physicochemical characteristics and release profiles of microspheres. In conclusion, the overall improvement of microspheres in appearance, encapsulation efficiency and controlled drug release through the RSE method could be easily fulfilled under optimal preparation conditions.

[Preparation of the 5-Fu floating sustained release tablet for gastric retention].

OBJECTIVE: To develop a pH independent floating sustained release tablet for gastric retention using 5-Fluorouracil (5-Fu) as a model drug. METHODS: According to the theory of the Hydro-dynamically Balanced System, the granules for the floating and drug loading layer were prepared separately and pressed together to make two-layer floating tablets for gastric retention. The floating kinetics indexes were measured and the data about drug release studied with media of different pH values. RESULTS: An excellent floating ability was observed in the media of different acidity for the gastric retentive tablet prepared according to the optimum formulation. The in vitro drug release can be modified by the regulation of the formulation ingredients. At the rotating speed of 100 r/min and in 0.1 mol/L HCl, the drug release was found to conform to first-class dynamics rule. CONCLUSION: The two-layer floating tablet made in this experiment,whose floating ability is independent of the gastric acidity variation, is of the possibility to be used for the auxiliary treatment of gastric carcinoma because of its prolonged gastric retention.

Intranasal administration of melatonin starch microspheres.

Using melatonin as model drug, starch microspheres for intranasal administration were prepared by an emulsification-crosslinking technique using a uniform design to optimize preparation conditions. The entrapment ratio of melatonin in the microspheres was 11.0% and particle sizes ranged from 30 to 60 microm. Melatonin was released from the microspheres in a sustained manner in vitro. Nasal clearance of 99mTC labeled starch microspheres was investigated using gamma scintigraphy. It was revealed that >80% of the starch microspheres could be detected in the nasal tissue 2h after administration, compared to 30% for a solution. The pharmacokinetics of melatonin starch microspheres was investigated after intranasal administration. The absorption rate was rapid (T(max) min), and the absolute bioavailability was high, 84.07%. A good correlation was found between in vitro release and in vivo absorption data.