Solid lipid nanoparticles (SLNs) are nanocarriers developed as substitute colloidal drug delivery systems parallel to liposomes, lipid emulsions, polymeric nanoparticles, and so forth. Owing to their unique size dependent properties and ability to incorporate drugs, SLNs present an opportunity to build up new therapeutic prototypes for drug delivery and targeting. SLNs hold great potential for attaining the goal of targeted and controlled drug delivery, which currently draws the interest of researchers worldwide. The present review sheds light on different aspects of SLNs including fabrication and characterization techniques, formulation variables, routes of administration, surface modifications, toxicity, and biomedical applications.

Polymers for drug delivery applications have been synthesised via environmentally benign routes and with sustainable feedstocks.

Block co-polymers with a block derived from a sustainable monomer source are used to encapsulate and release the drug indomethacin.

Polymers from natural resources are attracting much attention in various fields including drug delivery as green alternatives to fossil fuel based polymers. In this quest, novel block copolymers based on renewable poly(δ-decalactone) (PDL) were evaluated for their drug delivery capabilities and compared with a fossil fuel based polymer i.e. methoxy-poly(ethylene glycol)-b-poly(ε-caprolactone) (mPEG-b-PCL). Using curcumin as a hydrophobic drug model, micelles of PDL block copolymers with different orientation i.e. AB (mPEG-b-PDL), ABA (PDL-b-PEG-b-PDL), ABC (mPEG-b-PDL-b-poly(pentadecalactone) and (mPEG-b-PCL) were prepared by nanoprecipitation method. The size, drug loading and curcumin stability studies results indicated that mPEG-b-PDL micelles was comparable to its counterpart mPEG-b-PCL micelles towards improved delivery of curcumin. Therefore, mixed micelles using these two copolymers were also evaluated to see any change in size, loading and drug release. Drug release studies proposed that sustained release can be obtained using poly(pentadecalactone) as crystalline core whereas rapid release can be achieved using amorphous PDL core. Further, mPEG-b-PDL micelles were found to be non-haemolytic, up to the concentration of 40 mg/mL. toxicity studies on rats advised low-toxic behaviour of these micelles up to 400 mg/kg dose, as evident by histopathological and biochemical analysis. In summary, it is anticipated that mPEG-b-PDL block copolymer micelles could serve as a renewable alternative for mPEG-b-PCL copolymers in drug delivery applications.

Immense work has been conducted in the field of thermoresponsive polymers specifically of lower critical solution temperature (LCST) type, but upper critical solution temperature (UCST) type polymers remain a significantly unexplored domain. However, in recent years, UCST polymers have attracted increased attention as evidenced by the rise in publications in the same domain, and therefore, this review is an attempt to compile the reported UCST-type polymers. Unlike LCST, UCST polymers are insoluble at low temperature but solubilize in a given solvent as the temperature increases. The synthesis approaches and applications of reported UCST polymers are discussed in this article. Emphasis has been given to the polymers exhibiting UCST behavior in aqueous medium, due to the obvious advantage of their wide applicability. It is quite apparent from this study that the attempts to synthesize novel polymers and copolymers exhibiting UCST has faced an upsurge, but their application part still requires considerable attention. Figure 4. (a) Representative structure of poly(acrylamide-co-acrylonitrile) and (b) turbidity cooling curves of poly(AAmco-AN) with different acrylonitrile content in mole% (numbers in graph). Reproduced with permission from [33],

The ultimate goal of any scientific development is to increase well-being and human health. Novel strategies are required for the achievement of safe and effective therapeutic treatments beyond the conventional ones, and society needs new requirements for new technologies, moving towards clean and green technology development. Green nanotechnology is a branch of green technology that utilizes the concepts of green chemistry and green engineering. It reduces the use of energy and fuel by using less material and renewable inputs wherever possible. Green nanotechnology, in phytoformulations, significantly contributes to environmental sustainability through the production of nanomaterials and nanoproducts, without causing harm to human health or the environment. The rationale behind the utilization of plants in nanoparticle formulations is that they are easily available and possess a broad variability of metabolites, such as vitamins, antioxidants, and nucleotides. For instance, gold (Au) nanoparticles have attracted substantial attention for their controllable size, shape, and surface properties. A variety of copper (Cu) and copper oxide (CuO) nanoparticles have also been synthesized from plant extracts. Titanium dioxide and zinc oxide nanoparticles are also important metal oxide nanomaterials that have been synthesized from a number of plant extracts. International and domestic laws, government and private-party programs, regulations and policies are being carefully reviewed and revised to increase their utility and nurture these nanoscale materials for commercialization. Inspiring debates and government initiatives are required to promote the sustainable use of nanoscale products. In this review, we will discuss the potential of the utilization of plant extracts in the advancement of nanotechnology.

In the present study we developed the novel kind of triazine dendrimers by utilizing differential reactivity of the cyanuric chloride (triazine trichloride) which overcome the limitations associated with the others classes of dendrimers like toxicity, low yield, high synthesis cost etc. Triazine dendrimers were synthesized by divergent method using triazine trichloride as core and diethanolamine as branching unit to avoid the use of protecting group and functional group interconversion up to third generation. These hydroxyl terminated dendrimers were characterized by FTIR, 1HNMR, 13CNMR, ES mass spectroscopy, and by elemental analysis. The yield of pure G3 dendrimers was 63%. This novel dendrimers increases the aqueous solubility of hydrophobic drug Paclitaxel up to 0.562 mg/ml as well as showed control release behavior. Hemolytic and toxicology studies of this dendrimer in mice showed no adverse toxicity to the kidneys and the liver up to 200 mg/kg dose (i.p). Triazine being a hydrophobic compound, the core of this dendrimer is hydrophobic and supposed to easily incorporate the hydrophobic guest while presence of hydroxyl group on periphery increases its water solubility and reduces its toxicity; and thus it is useful in various fields like gene delivery, MRI contrasting agents, vaccines or as solubilization tool.

Aqueous solubility of an active pharmaceutical ingredient (API) is a determining factor that has a direct impact on formulation strategies and overall bioavailability. Fabrication of nanoemulsions of poorly soluble drugs is one of the widely utilized approaches to overcome this problem. However, thermodynamic instability and tedious manufacturing processes of nanoemulsions limit their clinical translation. Therefore, this study was focused on circumventing the abovementioned hurdles by utilizing the polymer as an oil phase, instead of conventional oils. The nanoemulsion was prepared via a facile low-energy nanoprecipitation method using renewable poly(δ-decalactone) (PDL), as an oil phase and Pluronic F-68 as surfactant. The prepared nanoemulsions were characterized in terms of size, drug encapsulation efficiency, stability, and toxicity. Five different hydrophobic drugs were utilized to evaluate the drug delivery capability of the PDL nanoemulsion. The prepared nanoemulsions with sizes less than 200 nm were capable to enhance the aqueous solubility of the drugs by 3 to 10 times compared with the wellestablished Pluronic F-68 micelles. No phase separation or significant changes in size and drug content was observed with PDL nanoemulsions after high-speed centrifugation and 3 months of storage at two different temperatures (20°C and 50°C). PDL nanoemulsions were found to be non-heamolytic up to concentrations of 1 mg/mL, and the cell cytotoxicity studies on MDA-MB-231 and MEF cells suggest a concentration and time-dependent toxicity, where the PDL polymer itself induced no cytotoxicity. The results from this study clearly indicate that the PDL polymer has a tremendous potential to be utilized as an oil phase to prepare stable nanoemulsions via a facile methodology, ultimately favouring clinical translations.