The development of amino acid based cancer tracers utilizing the hyperpolarization method of para-hydrogen induced polarization (PHIP) offers inexpensive possibilities in targeting tumors. So far, no amino acid based PHIP-tracer in biocompatible solvents was reported with polarization relevant for in vivo applications. We demonstrate the functionalization of amino acid derivatives and in specific an alanine derivative with which 4% polarization was achieved, representing the highest PHIP polarization of an amino acid derivative to date with potential in vivo applications in the future.¹ Although a high polarization was achieved with the amino acid derivative, a main challenge remains the separation of a necessary, typically homogeneous catalyst to promote polarization utilizing para-hydrogen. Therefore we have developed the first heterogeneous catalyst for PHIP with which significant levels of polarization can be generated in water and improved it.^2,3 It is based on ligand-capped platinum nanoparticles and poses the possibility of a filtration step to separate the catalyst from a hyperpolarized tracer before injection of a clean contrast agent.Amine protected amino acids (glycine, alanine and glutamine) were reacted with hydroxyethyl acrylate (HEA) in a Steglich esterification followed by deprotection of the amine functionalities to yield amino acid esters (aa-HEA). The esters were reacted in the presence of a homogeneous catalyst (1,4-bis-[(phenyl-3-propanesulfonate) phosphine]butane (norbornadiene) rhodium(I)tetrafluoroborate) with 95% para-enriched hydrogen to hyperpolarized hydroxyethyl propionate ester (aa-HEP). Heterogeneous catalysts were synthesized by reducing hexachloroplatinic acid in the presence of glutathione, cysteine or acetylcysteine to yield ligand-capped nanoparticles. The nanoparticles were used to hyperpolarize HEP starting from HEA. ¹H hyperpolarization experiments (for amino acids and nanoparticles) were performed on a Bruker AV600 (B₀=14.1T) by shaking the samples in the earth’s magnetic field followed by a transfer into the high-field magnet and detection. ¹³C experiments were performed on a Bruker Biospec 94/20 (B₀=9.4T). ¹³C polarization is generated in a home-built polarizer⁴ and especially by applying a polarization transfer sequence introduced by Goldman et al.⁵We have investigated the influence of free amine groups of amino acids on the achieved polarization because such amine groups can bind to the catalytic center of the utilized catalyst resulting in partly inactivation and thus reduced polarization. The investigated amino acid derivatives were acetyl-glycine-HEP (no free amine), glycine-HEP (one free amine), alanine-HEP (one free amine), glutamine-HEP (two free amines). We have found that the achieved proton polarization decreases with respect to the free amine moieties with acetyl-HEP yielding the highest polarization and glutamine-HEP the lowest. As free amine-groups of amino acids may contribute to its biological activity (e.g. cell internalization), it is however desirable to use unprotected amino acid derivatives as tracers. In order to demonstrate the feasibility of achieving high levels of polarization with unprotected amino acid derivatives in water we have synthesized a ¹³C-labeled and deuterated alanine derivative. Polarization with a home-built polarizer (Figure 1) yielded 4% polarization in water, which is the highest polarization of unprotected amino acid derivatives utilizing PHIP to date. The amount of polarization allows for pursuing in vivo experiments in the future. To demonstrate the possibility of generating polarization with PHIP heterogeneously and to allow for an easier separation of a catalyst from a molecule of interest, glutathione-capped platinum particles were first utilized to yield 0.3% ¹H polarization. Glutathione in particular contains an amine and a thiol functional group that can bind to the particles surface. In this way the diffusion of hydrogen that adsorbs to the surface is hindered and a pair-wise addition of hydrogen resulting in hyperpolarization is favored. Improving the hyperpolarization up to 0.7% was achieved by optimizing the ligands used for the capping. A smaller ligand that contains an amine and a thiol group is cysteine (Figure 2). More cysteine molecules can cover the platinums surface resulting in an increased hindrance of hydrogen diffusion and thus in more pair-wise addition character. In a similar experiment with above mentioned homogeneous catalyst 1.3% ¹H-polarization was achieved, which is less than a factor of two higher than with the nanoparticles. Therefore, the heterogeneous catalyst poses an excellent alternative for generating ¹H polarization and opens the opportunity for a filtration step to separate hyperpolarized contrast agents from a catalyst.We have demonstrated in vivo relevant polarization of an alanine-derivative achieved with PHIP. Furthermore we have shown the first heterogeneous catalyst for PHIP that yields significant degrees of polarization in water and its improved version. With an optimized automated setup that is compatible with the nanoparticles we expect to achieve high degrees of heteronuclear polarization (e.g. ¹³C) and utilize them for in vivo experiments.