-Liposomes are lipid based vesicular systems that offer novel platform for versatile drug delivery to target cell. Liposomes were first reported by Bangham and his co-workers in 1964 (1). Since then, liposomes have undergone extensive research with the prime aim to optimize encapsulation, stability, circulation time and target specific drug delivery. Manipulation of a liposome's lipid bilayer and surface decoration with selective ligands has transformed conventional liposomes into adaptable and multifunctional liposomes. Development of liposomes with target specificity provide the prospect of safe and effective therapy for challenging clinical applications. Bioresponsive liposomes offer the opportunity to release payload in response to tissue specific microenvironment. Incorporation of novel natural and synthetic materials has extended their application from stable formulations to controlled release targeted drug delivery systems. Integration and optimization of multiple features into one system revolutionized research in the field of cancer, gene therapy, immunotherapy and infectious diseases. After 50 years since the first publication, this review is aimed to highlight next generation of liposomes, their preparation methods and progress in clinical applications.

Thermoresponsive drug delivery systems are designed for the controlled and targeted release of therapeutic payload. These systems exploit hyperthermic temperatures (>39°C), which may be applied by some external means or due to an encountered symptom in inflammatory diseases such as cancer and arthritis. The objective of this paper was to provide some solid evidence in support of the hypothesis that solid lipid nanoparticles (SLNs) can be used for thermoresponsive targeting by undergoing solid–liquid phase transition at their melting point (MP). Thermoresponsive lipid mixtures were prepared by mixing solid and liquid natural fatty acids, and their MP was measured by differential scanning calorimetry (DSC). SLNs (MP 39°C) containing 5-fluorouracil (5-FU) were synthesized by hot melt encapsulation method, and were found to have spherical shape (transmission electron microscopy studies), desirable size (<200 nm), and enhanced physicochemical stability (Fourier transform infrared spectroscopy analysis). We observed a sustained release pattern (22%–34%) at 37°C (5 hours). On the other hand, >90% drug was released at 39°C after 5 hours, suggesting that the SLNs show thermoresponsive drug release, thus confirming our hypothesis. Drug release from SLNs at 39°C was similar to oleic acid and linoleic acid nanoemulsions used in this study, which further confirmed that thermoresponsive drug release is due to solid–liquid phase transition. Next, a differential pulse voltammetry-based electrochemical chemical detection method was developed for quick and real-time analysis of 5-FU release, which also confirmed thermoresponsive drug release behavior of SLNs. Blank SLNs were found to be biocompatible with human gingival fibroblast cells, although 5-FU-loaded SLNs showed some cytotoxicity after 24 hours. 5-FU-loaded SLNs showed thermoresponsive cytotoxicity to breast cancer cells (MDA-MB-231) as cytotoxicity was higher at 39°C (cell viability 72%–78%) compared to 37°C (cell viability >90%) within 1 hour. In conclusion, this study presents SLNs as a safe, simple, and effective platform for thermoresponsive targeting.

Nanocarriers have provided the versatile platform for the delivery of various therapeutic and diagnostic agents. Liposome, niosomes, polymeric and solid lipid nanoparticles are the most promising nanocarriers that have been entered in the clinical trials and become commercially available. However, each system has been associated with some problems that can be minimized by using the combinatorial approach of hybrid nanocarriers. These hybrid systems combine the benefits of different structural components to synergize the outcome of the therapy. In this chapter, the different types of hybrid nanocarriers have been described with particular emphasis on the brief rationale for the development of these hybrid nanocarriers along with different fabrication approaches with greater emphasize on the lipid polymer hybrid nanoparticles. A brief description factors governing the optimized response characteristics and their potential application of these hybrid nanoparticles are also presented.

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Background Most of the traditional nanocarriers of cancer therapeutic moieties present dose-related toxicities due to the uptake of chemotherapeutic agents in normal body cells. The severe life-threatening effects of systemic chemotherapy are well documented. Doxorubicin, DOX is the most effective antineoplastic agent but with the least specific action that is responsible for severe cardiotoxicity and myelosuppression that necessitates careful monitoring while administering. Stimuli-sensitive/intelligent drug delivery systems, specifically those utilizing temperature as an external stimulus to activate the release of encapsulated drugs, have become a subject of recent research. Thus, it would be ideal to have a nanocarrier comprising safe excipients and controllable drug release capacity to deliver the drug at a particular site to minimize unwanted and toxic effects of chemotherapeutics. We have developed a simple temperature-responsive nanocarrier based on eutectic mixture of fatty acids. This study aimed to develop, physicochemically characterize and investigate the biological safety of eutectic mixture of fatty acids as a novel construct for temperature-responsive drug release potential. Methods We have developed phase change material, PCM, based on a series of eutectic mixtures of fatty acids due to their unique and attractive physicochemical characteristics such as safety, stability, cost-effectiveness, and ease of availability. The reversible solid-liquid phase transition of PCM is responsible to hold firm or actively release the encapsulated drug. The eutectic mixtures of fatty acids (stearic acid and myristic acid) along with liquid lipid (oleic acid) were prepared to exhibit a tunable thermoresponsive platform. Doxorubicin-loaded lipid nanocarriers were successfully developed with combined hot melt encapsulation (HME) and sonication method and characterized to achieve enhanced permeability and retention (EPR) effect-based solid tumor targeting in response to exogenous temperature stimulus. The cytotoxicity against melanoma cell lines and in vivo safety studies in albino rats was also carried out. Results Doxorubicin-loaded lipid nanocarriers have a narrow size distribution (94.59–219.3 nm), and a PDI (0.160–0.479) as demonstrated by photon correlation microscopy and excellent colloidal stability (Z.P value: −22.7 to −32.0) was developed. Transmission electron microscopy revealed their spherical morphology and characteristics of a monodispersed system. A biphasic drug release pattern with a triggered drug release at 41°C and 43°C and a sustained drug release was observed at 37°C. The thermoresponsive cytotoxic potential was demonstrated in B16F10 cancer cell lines. Hemolysis assay and acute toxicity studies with drug-free and doxorubicin lipid nanocarrier formulations provided evidence for their non-toxic nature. Conclusion We have successfully developed a temperature-responsive tunable platform with e...

Applications of nanotechnology and material sciences emerge in the development of various novel drug delivery systems that have been proven as promising clinically. Among these, liposomes, noisome, polymeric carriers and lipid-based delivery system were extensively explored and enter into clinical trials and clinical applications. However, each system has its own pros and cons in term of different physicochemical, pharmacokinetics and therapeutics aspects. Lipid-polymer hybrid carriers merge the potential benefit of these structural components and can be prepared by different approaches to improve the therapeutic outcomes. In this chapter, we provide the useful insight about the lipid-polymer hybrid nanoparticles (LPHNPs) that can be prepared by using the different structural components including the synthetic and natural polymers and lipids. Among these, we also explain the various methods to prepare the LPHNPs with various desired characteristics. Finally, the various therapeutic and clinical applications have been presented briefly.

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