A thermosensitive lipid nanoparticle comprising: (i) at least one phospholipid selected from a phosphatidylcholine, a phosphatidylethanolamine, a phosphatidylglycerol, a phosphatidyl serine, a phosphatidic acid, a phosphatidylinositol, and a sphingolipid; (ii) at least one lysolipid selected from a monoacylphosphatidylcholine, a monoacylphosphatidylglycerol, a monoacylphosphatidylinositol, and a monoacylphosphatidyl-ethanolamine; (iii) at least one phospholipid comprising a hydrophilic polymer wherein the hydrophilic polymer comprises one or more selected from polyethylene glycol, polyvinylpyrolidine, polylactic acid, polyglycolic acid, copolymers of polylactic acid and polyglycolic acid, polyvinyl alcohols, polyvinylpyrrolidone, dextrans, and oligosaccharides; and (iv) at least one structural lipid of formula (I) which has the following general structure: wherein R and R' are long hydrocarbyl hydrophobic chains, Y is a linker element, and PHG is a polar head group described as large according to its van der Waals radius, and which is different from the phospholipid (i); wherein the structural lipid of formula (I) comprises a magnetic resonance imaging (MRI) label comprising the paramagnetic metal lipid gadolinium; wherein (i) phospholipid:(ii) lysolipid:(iii) phospholipid comprising a hydrophilic polymer: (iv) structural lipid of formula (I) are present in the thermosensitive lipid nanoparticle in a molar ratio of (i) 30-90:(ii) 2-15:(iii) 4-10:(iv) 10-50. (i) at least one phospholipid selected from a phosphatidylcholine, a phosphatidylethanolamine, a phosphatidylglycerol, a phosphatidyl serine, a phosphatidic acid, a phosphatidylinositol, and a sphingolipid; (ii) at least one lysolipid selected from a monoacylphosphatidylcholine, a monoacylphosphatidylglycerol, a monoacylphosphatidylinositol, and a monoacylphosphatidyl-ethanolamine; (iii) at least one phospholipid comprising a hydrophilic polymer wherein the hydrophilic polymer comprises one or more selected from polyethylene glycol, polyvinylpyrolidine, polylactic acid, polyglycolic acid, copolymers of polylactic acid and polyglycolic acid, polyvinyl alcohols, polyvinylpyrrolidone, dextrans, and oligosaccharides; and (iv) at least one structural lipid of formula (I) which has the following general structure: wherein R and R' are long hydrocarbyl hydrophobic chains, Y is a linker element, and PHG is a polar head group described as large according to its van der Waals radius, and which is different from the phospholipid (i); wherein the structural lipid of formula (I) comprises a magnetic resonance imaging (MRI) label comprising the paramagnetic metal lipid gadolinium; wherein (i) phospholipid:(ii) lysolipid:(iii) phospholipid comprising a hydrophilic polymer: (iv) structural lipid of formula (I) are present in the thermosensitive lipid nanoparticle in a molar ratio of (i) 30-90:(ii) 2-15:(iii) 4-10:(iv) 10-50. wherein R and R' are long hydrocarbyl hydrophobic chains, Y is a linker element, and PHG is a polar head group described as large according to its van der Waals radius, and which is different from the phospholipid (i); wherein the structural lipid of formula (I) comprises a magnetic resonance imaging (MRI) label comprising the paramagnetic metal lipid gadolinium; wherein (i) phospholipid:(ii) lysolipid:(iii) phospholipid comprising a hydrophilic polymer: (iv) structural lipid of formula (I) are present in the thermosensitive lipid nanoparticle in a molar ratio of (i) 30-90:(ii) 2-15:(iii) 4-10:(iv) 10-50. <EOS>