A brief review on solid lipid nanoparticles: part and parcel of contemporary drug delivery systems
Drug delivery technology has a wide spectrum, which is continuously being upgraded at a stupendous speed. Different fabricated nanoparticles and drugs possessing low solubility and poor pharmacokinetic profiles are the two major substances extensively delivered to target sites. Among the colloidal carriers, nanolipid dispersions (liposomes, deformable liposomes, virosomes, ethosomes, and solid lipid nanoparticles) are ideal delivery systems with the advantages of biodegradation and nontoxicity. Among them, nano-structured lipid carriers and solid lipid nanoparticles (SLNs) are dominant, which can be modified to exhibit various advantages, compared to liposomes and polymeric nanoparticles. Nano-structured lipid carriers and SLNs are non-biotoxic since they are biodegradable. Besides, they are highly stable. Their (nano-structured lipid carriers and SLNs) morphology, structural characteristics, ingredients used for preparation, techniques for their production, and characterization using various methods are discussed in this review. Also, although nano-structured lipid carriers and SLNs are based on lipids and surfactants, the effect of these two matrixes to build excipients is also discussed together with their pharmacological significance with novel theranostic approaches, stability and storage.
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Principle of lipid nanoparticle formulation
General ingredients
SLNs are comprised of a phospholipid-coated solid hydrophobic core matrix (containing the hydrophobic tails of the phospholipid section) (Fig. 2). Also, SLNs consist mainly of solid lipid(s), emulsifiers together with APIs such as drugs, genes, DNA, plasmid, and proteins. The lipids utilized in the formation of SLNs are surfactant stabilized, and thus solid at both physiological and room temperature. Depending on their structure, lipids are mainly divided into fatty acids, fatty esters, fatty alcohols, triglycerides, and partial glycerides. Ionic and nonionic polymers (Pluronic® such as F-68 and F127), surfactants, and organic salts are used as emulsifiers. However, their physicochemical characteristics also affect the behavior of the corresponding SLNs in both in vivo and in vitro release. The formation of colloidal nanoparticles depends on the interfacial tension and surface tension between two liquids. Thus, the main principle for the formation of solid lipid nanoparticles is the adhesive forces between two liquids. Normally, the interfacial tension between two liquids is less than their surface tension because of the weaker adhesive forces compared to that with gas. Molecules at the interface constitute surface free energy of interfacial tension, while they undergo agitation and form a spherical system to minimize the surface free energy.
From the publication “A brief review on solid lipid nanoparticles: part and parcel of contemporary drug delivery systems” the interesting Table 2 SLN formulations reported by different researchers
| Drug | Lipid | Surfactant/emulsifier | Co-Surfactant | Method for preparation of SLNs |
|---|---|---|---|---|
| Amphotericin B | Compritol® ATO 888, Precirol ATO 5 and stearic acid, | Pluronic® F-68, Pluronic® F-127, | Solvent diffusion method | |
| Compritol® ATO 888 (glycerylbehenate), glycerylpalmitostearate (Precirol® ATO 5), medium chain triglyceride | Tween 20, Pluronic® F-127, Cremophor RH40, polyoxyethylene (40) stearate (Myrj 52) | HPH | DLS, zeta potential, HPLC, TEM, FTIR, DSC, PXRD, 1H NMR | 90–260 |
| Baclofen | Stearic acid | Epikuron 200 (92% phosphatidylcholine) | Propionic acid, butyric acid, and sodium taurocholate | Multiple (w/o/w) warm, microemulsion |
| BuspironeHCl | Cetyl alcohol, Spermaceti | Pluronic® F-68, Tween 80 | Emulsification-evaporation followed by ultrasonication | |
| Camptothecin | Soybean lecithin, stearic acid | Pluronic® F-68, Tween 80 | Glycerol, PEG 400, PPG | Hot HPH |
| Carvedilol | Stearic acid | Pluronic® F-68 | Sodium taurocholate and ethanol | Microemulsion |
| Clozapine | Trimyristin, tripalmitin, tristearin, soy phosphatidylcholine | Pluronic® F-68 | Ultrasonication method | |
| Crypto-Tanshinone | Glycerylmonostearate, Compritol 888 ATO | Soy lecithin, Tween 80, sodium dehydrocholate | Ultrasonic and high-pressure homogenization method | |
| Curcumin | Compritol 888 ATO | Soy lecithin, Tween 80 | Microemulsion | |
| Tristearin | Polyoxyethylene (10) stearyl ether (Brij®S10), polyoxyethylene (100) stearyl ether (Brij® S100) | Oil-in-water emulsion technique | PCS, zeta potential | 111–350 |
| Cyclosporine A | Imwitor® 900 | Tagat®S, sodium cholate | HPH, hot HPH | |
| Diazepam | Compritol 888 ATO, Imwitor® 900 | Pluronic® F-68, Tween 80 | Ultrasound techniques modified high-shear homogenization and | |
| Doxorubicin hydrochloride | Glycerylcaprate | Polyethylene glycol 660 hydrox-ystearate (Solutol®HS15) | Ultrasonic homogenization | |
| Fenofibrate | Vitamin E TPGS, Vitamin E 6–100 | Hot HPH | ||
| Hydrocortisone | Precirol® ATO 5, Compritol® 888 ATO, Rylo TM MG 14 Pharma, Dynasan® 114 Dynasan® 118, Tegin® 4100 | Tween 80 | Hot high pressure homogenization | |
| Ibuprofen | Trilaurin, tripalmitin, stearic acid | Pluronic®F127, sodium taurocholate | Solvent-free high-pressure homogenization (HPH) | |
| Idarubicin | Stearic acid | Epikuron 200 (soy phosphatidylcholine 95%) | Taurocholate sodium salt | Microemulsion |
| Emulsifying wax | Polyoxyl 20-stearyl ether (Brij 78), D-alpha-tocopheryl polyethylene glycol succinate (vitamin E TPGS),DSPE-PEG3000 | Sodium taurodeoxycholate (STDC), sodium tetradecylsulfate (STS) | PCS, Zetasizer nano Z | 94.4 (blank), 80–104 (loaded sample) |
| Ketoprofen | Beeswax and carnauba wax | Tween 80, egg lecithin | Microemulsion technique | |
| Lopinavir | Compritol 888 ATO (glycerylbehenate) | Pluronic®F127 | Hot homogenization, ultrasonication | |
| Lovastatin | Triglyceride, and phosphatidylcholine 95% | Pluronic®F68 | Hot homogenization ultrasonication | |
| Methotrexate | Stearic acid, monostearin, tristearin, and Compritol 888 ATO | L-α-Soya lecithin, and Sephadex G-50 | Solvent diffusion method | |
| Nevirapine | Steric acid, Compritol 888 ATO | Dimethyldioctadecyl ammonium bromide (DODAB), Tween 80, Lecithin | 1-Butanol | Microemulsion |
| Nitrendipine | triglyceride and phosphatidylcholine | Pluronic®F68 | Hot homogenization ultrasonication method | |
| Octadecylamine-fluorescein isothiocyanate | Stearic acid | Otcadecylamine, polyethylene glycol monostearate (PEG2000-SA) | Solvent diffusion | |
| Pentoxifylline | Stearic acid, cetyl alcohol, soy lecithin, | Tween 20, Pluronic F®68 | Homogenization followed by the ultrasonication | |
| Praziquantel | Hydrogenated castor oil | Poly vinyl alcohol (PVA) | Hot homogenization and ultrasonication | |
| Puerarin | Monostearin, and soy lecithin | Pluronic F®68 | Solvent injection method | |
| Quercetin | Glycerylmonostearat, soy lecithin | Tween-80 and PEG 400 | Emulsification-solidification | |
| Rifampicin | Stearic acid | PVA | Emulsion-solvent diffusion | |
| Tobramycin | Stearic acid | Epikuron 200 | Sodium taurocholate | Microemulsion |
| Vinpocetine | Glycerylmonostearat, soy lecithin, polyoxyethylene hydrogenated castor oil | Tween 80 | Ultrasonic-solvent emulsification |