Calcium phosphate: a substitute for aluminum adjuvants?

References

• Relyveld EH, Levaditi J-C, Ravisse P. Adjuvants minéraux. Médecine Mal Infect. 1978;8:494–499.
   Web of Science ®Google Scholar
• De Souza Apostólico J, Lunardelli VAS, Coirada FC, et al. Adjuvants: classification, modus operandi, and licensing. J Immunol Res. 2016;2016:1459394.
   Google Scholar
• Ramon G. Sur l’augmentation anormale de l’antitoxine chez les chevaux producteurs de sérum antidiphtériques. Bull Soc Centr Med Vet. 1925;101:227–234.
   Google Scholar
• Bégué P, Girard M, Bazin H, et al. Les adjuvants vaccinaux: quelle actualité en 2012? Bull Acad Natle Med. 2012;196:1177–1181.
   Google Scholar
• Glenny AT, Pope CG, Waddington H, et al. Immunological notes. XVII–XXIV. J Pathol Bacteriol. 1926;29:31–40.
   Google Scholar
• Tomljenovic L, Shaw CA. Aluminum vaccine adjuvants: are they safe? Curr Med Chem. 2011;18:2630–2637.
   PubMed Web of Science ®Google Scholar
• Gherardi RK, Coquet M, Cherin P, et al. Macrophagic myofasciitis: an emerging entity. The Lancet. 1998;352:347–352.
   PubMed Web of Science ®Google Scholar
• World Health Organization. Macrophagic myofasciitis and aluminum-containing vaccines. Wkly Epidemiol Rec. 1999;74:338–340.
   Google Scholar
• Exley C, Swarbrick L, Gherardi RK, et al. A role for the body burden of aluminium in vaccine-associated macrophagic myofasciitis and chronic fatigue syndrome. Med Hypotheses. 2009;72:135–139.
   PubMed Web of Science ®Google Scholar
• Exley C. Human exposure to aluminium. Environ Sci Process Impacts. 2013;15:1807–1816.
   PubMed Web of Science ®Google Scholar
• Exley C. Why industry propaganda and political interference cannot disguise the inevitable role played by human exposure to aluminum in neurodegenerative diseases, including Alzheimer’s disease. Front Neurol. 2014;5:212.
   PubMed Web of Science ®Google Scholar
• Aprile MA, Wardlaw AC. Aluminium compounds as adjuvants for vaccines and toxoids in man: a review. Can J Public Health. 1966;57:343–360.
   PubMed Web of Science ®Google Scholar
• Exley C. What is the risk of aluminium as a neurotoxin? Expert Rev Neurother. 2014;14:589–591.
   PubMed Web of Science ®Google Scholar
• Relyveld EH. Calcium phosphate gel for adsorbing vaccines. 4016252. 1977.
   Google Scholar
• Relyveld EH, Henocq E, Raynaud M. Etude de la vaccination antidiphterique de sujets allergiques, avec une anatoxine pure adsorbee sur phosphate de calcium. Bull World Health Organ. 1964;30:321.
   PubMedGoogle Scholar
• Coursaget P, Yvonnet B, Relyveld EH, et al. Simultaneous administration of diphtheria-tetanus-pertussis-polio and hepatitis B vaccines in a simplified immunization program: immune response to diphtheria toxoid, tetanus toxoid, pertussis, and hepatitis B surface antigen. Infect Immun. 1986;51:784–787.
   PubMed Web of Science ®Google Scholar
• Gupta RK, Rost BE, Relyveld E, et al. Adjuvant properties of aluminum and calcium compounds. Pharm Biotechnol. 1995;6:229–248.
   PubMedGoogle Scholar
• Moulin A-M. L’Aventure de la vaccination. Paris: Fayard; 1996.
   Google Scholar
• Sesardic D, Rijpkema S, Patel BP. New adjuvants: EU regulatory developments. Expert Rev Vaccines. 2007;6:849–861.
   PubMed Web of Science ®Google Scholar
• Relyveld EH, Raynaud M. Etudes sur le phosphate de calcium comme adjuvant de l’immunite. Int. Symp. Adjuv. Immun., vol. 6, Karger Heidelberg. New York; 1967. p. 77–78.
   Google Scholar
• Lecadet A, Ickovic MR, Thibaudon M. Specific desensitization with allergen extracts absorbed on calcium phosphate (Pasteur Institute). Clinical and biological study apropos of 107 cases. Allerg Immunol (Leipz). 1988;20:153–155.
   Google Scholar
• Relyveld EH. Etudes sur la toxine et l’antitoxine diphtériques et la réaction toxine-antitoxine [ Thèse Paris]. Paris: Editions scientifiques Hermann; 1958.
   Google Scholar
• Raynaud M, Relyveld EH, Turpin A, et al. Preparation of highly purified diphtheric, tetanic & staphylococcic anatoxins absorbed on calcium phosphate (brushite). Ann Inst Pasteur. 1959;96:60–71.
   PubMedGoogle Scholar
• Relyveld E, Bengounia A, Huet M, et al. Antibody response of pregnant women to two different adsorbed tetanus toxoids. Vaccine. 1991;9:369–372.
   PubMed Web of Science ®Google Scholar
• Relyveld EH. Preparation and use of calcium phosphate adsorbed vaccines. Dev Biol Stand. 1986;65:131–136.
   PubMedGoogle Scholar
• Jiang D, Premachandra GS, Johnston C, et al. Structure and adsorption properties of commercial calcium phosphate adjuvant. Vaccine. 2004;23:693–698.
   PubMed Web of Science ®Google Scholar
• Dixon JB, Weed SB. Minerals in soil environments. Madison, WI: Soil Science Society of America (SSSA); 1989.
   Google Scholar
• Bleam WF, Pfeffer PE, Goldberg S, et al. A phosphorus-31 solid-state nuclear magnetic resonance study of phosphate adsorption at the boehmite/aqueous solution interface. Langmuir. 1991;7:1702–1712.
   Web of Science ®Google Scholar
• Seeber SJ, White JL, Hem SL. Predicting the adsorption of proteins by aluminium-containing adjuvants. Vaccine. 1991;9:201–203.
   PubMed Web of Science ®Google Scholar
• Al-Shakhshir R, Regnier F, White JL, et al. Effect of protein adsorption on the surface charge characteristics of aluminium-containing adjuvants. Vaccine. 1994;12:472–474.
   PubMed Web of Science ®Google Scholar
• Singh M, Ugozzoli M, Kazzaz J, et al. A preliminary evaluation of alternative adjuvants to alum using a range of established and new generation vaccine antigens. Vaccine. 2006;24:1680–1686.
   PubMed Web of Science ®Google Scholar
• Lindblad EB. Aluminium compounds for use in vaccines. Immunol Cell Biol. 2004;82:497–505.
   PubMed Web of Science ®Google Scholar
• Aggerbeck H, Heron I. Adjuvanticity of aluminium hydroxide and calcium phosphate in diphtheria-tetanus vaccines—I. Vaccine. 1995;13:1360–1365.
   PubMed Web of Science ®Google Scholar
• Sivananda N, Sundaran B. Studies on adsorption of diphtheria toxoid on aluminium phosphate gel. Indian J Sci Technol. 2010;3:248–249.
   Google Scholar
• Iyer S, HogenEsch H, Hem SL. Effect of the degree of phosphate substitution in aluminum hydroxide adjuvant on the adsorption of phosphorylated proteins. Pharm Dev Technol. 2003;8:81–86.
   PubMed Web of Science ®Google Scholar
• Iyer S, Robinett RSR, HogenEsch H, et al. Mechanism of adsorption of hepatitis B surface antigen by aluminum hydroxide adjuvant. Vaccine. 2004;22:1475–1479.
   PubMed Web of Science ®Google Scholar
• Hayashi M, Aoshi T, Kogai Y, et al. Optimization of physiological properties of hydroxyapatite as a vaccine adjuvant. Vaccine. 2016;34:306–312.
   PubMed Web of Science ®Google Scholar
• Ginebra MP, Driessens FCM, Planell JA. Effect of the particle size on the micro and nanostructural features of a calcium phosphate cement: a kinetic analysis. Biomaterials. 2004;25:3453–3462.
   PubMed Web of Science ®Google Scholar
• Rivera Gil P, Hühn D, Del Mercato LL, et al. Nanopharmacy: inorganic nanoscale devices as vectors and active compounds. Pharmacol Res. 2010;62:115–125.
   PubMed Web of Science ®Google Scholar
• Kato H, Shibano M, Saito T, et al. Relationship between hemolytic activity and adsorption capacity of aluminum hydroxide and calcium phosphate as immunological adjuvants for biologicals. Microbiol Immunol. 1994;38:543–548.
   PubMed Web of Science ®Google Scholar
• Olmedo H, Herrera M, Rojas L, et al. Comparison of the adjuvant activity of aluminum hydroxide and calcium phosphate on the antibody response towards Bothrops asper snake venom. J Immunotoxicol. 2014;11:44–49.
   PubMed Web of Science ®Google Scholar
• Goto N, Kato H, Maeyama J, et al. Local tissue irritating effects and adjuvant activities of calcium phosphate and aluminium hydroxide with different physical properties. Vaccine. 1997;15:1364–1371.
   PubMed Web of Science ®Google Scholar
• Kuroda E, Coban C, Ishii KJ. Particulate adjuvant and innate immunity: past achievements, present findings, and future prospects. Int Rev Immunol. 2013;32:209–220.
   PubMed Web of Science ®Google Scholar
• Zhao L, Seth A, Wibowo N, et al. Nanoparticle vaccines. Vaccine. 2014;32:327–337.
   PubMed Web of Science ®Google Scholar
• Shah RR, O’Hagan DT, Amiji MM, et al. The impact of size on particulate vaccine adjuvants. Nanomed. 2014;9:2671–2681.
   PubMed Web of Science ®Google Scholar
• Ibrahim-Saeed M, Omar AR, Hussein MZ, et al. Systemic antibody response to nano-size calcium phospate biocompatible adjuvant adsorbed HEV-71 killed vaccine. Clin Exp Vaccine Res. 2015;4:88–98.
   PubMed Web of Science ®Google Scholar
• Aggerbeck H, Fenger C, Heron I. Booster vaccination against diphtheria and tetanus in man. Comparison of calcium phosphate and aluminium hydroxide as adjuvants–II. Vaccine. 1995;13:1366–1374.
   PubMed Web of Science ®Google Scholar
• Donat N, Thibaudon M, Peltre G, et al. Desensitization for 4 successive years using calcium phosphate-adsorbed pollen extracts: study of sera with RAST and PRIST immunoimprints. Allerg Immunol (Leipz). 1986;18:24–31.
   Google Scholar
• Martin R, Relyveld EH, Raynaud M, et al. Immunizing strength and tolerance by the human organism of vaccines adsorbed on calcium phosphate. Presse Médicale. 1969;77:341–344.
   PubMed Web of Science ®Google Scholar
• Relyveld EH, Martin R, Raynaud M, et al. Calcium phosphate as adjuvant in vaccinations in man. Ann Inst Pasteur. 1969;116:300–326.
   PubMedGoogle Scholar
• Relyveld EH, Martin R, Raynaud M, et al. Vaccination with calcium phosphate adsorbed antigens. Prog Immunobiol Stand. 1970;4:540–547.
   PubMedGoogle Scholar
• Edelman R. Vaccine adjuvants. Rev Infect Dis. 1980;2:370–383.
   PubMedGoogle Scholar
• Wack A, Baudner BC, Hilbert AK, et al. Combination adjuvants for the induction of potent, long-lasting antibody and T-cell responses to influenza vaccine in mice. Vaccine. 2008;26:552–561.
   PubMed Web of Science ®Google Scholar
• Gupta RK, Relyveld EH, Lindblad EB, et al. Adjuvants a balance between toxicity and adjuvanticity. Vaccine. 1993;11:293–306.
   PubMed Web of Science ®Google Scholar
• Poolman JT. Shortcomings of pertussis vaccines: why we need a third generation vaccine. Expert Rev Vaccines. 2014;13:1159–1162.
   PubMed Web of Science ®Google Scholar
• Petrovsky N. Comparative safety of vaccine adjuvants: a summary of current evidence and future needs. Drug Saf. 2015;38:1059–1074.
   PubMed Web of Science ®Google Scholar
• Mastelic B, Ahmed S, Egan WM, et al. Mode of action of adjuvants: implications for vaccine safety and design. Biologicals. 2010;38:594–601.
   PubMedGoogle Scholar
• Vassilev TL. Aluminium phosphate but not calcium phosphate stimulates the specific IgE response in guinea pigs to tetanus toxoid. Allergy. 1978;33:155–159.
   PubMed Web of Science ®Google Scholar
• Gupta RK, Siber GR. Comparison of adjuvant activities of aluminium phosphate, calcium phosphate and stearyl tyrosine for tetanus toxoid. Biol J Int Assoc Biol Stand. 1994;22:53–63.
   Google Scholar
• Gateff C, Relyveld EH, Le Gonidec G, et al. Study of a new pentavalent vaccine combination. Ann Microbiol (Paris). 1973;124:387–409.
   PubMed Web of Science ®Google Scholar
• Petrovsky N, Aguilar JC. Vaccine adjuvants: current state and future trends. Immunol Cell Biol. 2004;82:488–496.
   PubMed Web of Science ®Google Scholar
• Organisation Mondiale de la Santé. Adjuvants de l’immunité. Sér Rapp Tech. 1976;595:43.
   Google Scholar
• Relyveld EH, Lavergne M, De Rudder J. Titers of immunoglobulins (IgG, IgA, IgM, and IgE) after antigenic stimulation in European and African subjects. Dev Biol Stand. 1974;27:79–90.
   PubMedGoogle Scholar
• Ickovic MR, Relyveld EH, Hénocq E, et al. Calcium-phosphate-adjuvanted allergens: total and specific IgE levels before and after immunotherapy with house dust and Dermatophagoides pteronyssinus extracts. Ann Immunol. 1983;134D:385–398.
   Google Scholar
• Parish WE. Homologous serum passive cutaneous anaphylaxis in Guinea pigs mediated by two γ1 or γ1-type heat-stable globulins and a non-γ1 heat-labile reagin. J Immunol. 1970;105:1296–1298.
   PubMed Web of Science ®Google Scholar
• Relyveld EH. Immunoglobulins and reaginic activity. Rev Fr Allergol. 1969;9:219–232.
   PubMedGoogle Scholar
• Hubscher T. Immune and biochemical mechanisms in the allergic disease of the upper respiratory tract; role of antibodies, target cells, mediators and eosinophils. Ann Allergy. 1977;38:83–90.
   PubMedGoogle Scholar
• Kishimoto T, Ishizaka K. Regulation of antibody response in vitro. VII. Enhancing soluble factors for IgG and IgE antibody response. J Immunol Baltim Md 1950. 1973;111:1194–1205.
   Google Scholar
• Nagel J, Svec D, Waters T, et al. IgE synthesis in man. I. Development of specific IgE antibodies after immunization with tetanus-diphtheria (Td) toxoids. J Immunol Baltim Md 1950. 1977;118:334–341.
   Google Scholar
• Mitani S, Yamamoto A, Ikegami H, et al. Immunoglobulin E-suppressing and immunoglobulin G-enhancing tetanus toxoid prepared by conjugation with pullulan. Infect Immun. 1982;36:971–976.
   PubMed Web of Science ®Google Scholar
• Cogné M, Ballet JJ, Schmitt C, et al. Total and IgE antibody levels following booster immunization with aluminum absorbed and nonabsorbed tetanus toxoid in humans. Ann Allergy. 1985;54:148–151.
   PubMedGoogle Scholar
• Balouet G, Levaditi JC, Relyveld E. Le granulome immunogène: histopathologie expérimentale des lésions liées à des injections vaccinantes associées à divers adjuvants de l’immunité. Bull Inst Pasteur. 1975;73:383–409.
   Google Scholar
• Balouet G, Baret M, Relyveld E, et al. Role of antigens and adjuvant substances in the histological response in experimental granulomas (immunogenic granuloma). Ann Anat Pathol (Paris). 1977;22:159–170.
   PubMedGoogle Scholar
• Levaditi JC, Relyveld E. Local tolerance of vaccines adsorbed on immuno-stimulating substances. Sem Hôp Ther. 1975;51:117–118.
   PubMedGoogle Scholar
• Dorozhkin SV, Epple M. Biological and medical significance of calcium phosphates. Angew Chem Int Ed. 2002;41:3130–3146.
   PubMed Web of Science ®Google Scholar
• Jarcho M. Calcium phosphate ceramics as hard tissue prosthetics. Clin Orthop. 1981;157:259–278.
   PubMed Web of Science ®Google Scholar
• Alberts B, Johnson A, Lewis J, et al. Molecular biology of the cell. 4th ed. New York: Garland Science; 2002.
   Google Scholar
• Wang S, McDonnell EH, Sedor FA, et al. pH effects on measurements of ionized calcium and ionized magnesium in blood. Arch Pathol Lab Med. 2002;126:947–950.
   PubMed Web of Science ®Google Scholar
• Gherardi RK, Eidi H, Crépeaux G, et al. Biopersistence and brain translocation of aluminum adjuvants of vaccines. Front Neurol. 2015;6:4.
   PubMed Web of Science ®Google Scholar
• Ahmed KK, Geary SM, Salem AK. Applying biodegradable particles to enhance cancer vaccine efficacy. Immunol Res. 2014;59:220–228.
   PubMed Web of Science ®Google Scholar
• Relyveld EH, Bizzini B, Gupta RK. Rational approaches to reduce adverse reactions in man to vaccines containing tetanus and diphtheria toxoids. Vaccine. 1998;16:1016–1023.
   PubMed Web of Science ®Google Scholar
• Goto N, Kato H, Maeyama J, et al. Studies on the toxicities of aluminium hydroxide and calcium phosphate as immunological adjuvants for vaccines. Vaccine. 1993;11:914–918.
   PubMed Web of Science ®Google Scholar
• Wang S, Liu X, Fisher K, et al. Enhanced type I immune response to a hepatitis B DNA vaccine by formulation with calcium- or aluminum phosphate. Vaccine. 2000;18:1227–1235.
   PubMed Web of Science ®Google Scholar
• Léry L. Haemolytic activity of calcium phosphate adjuvant. Vaccine. 1994;12:475.
   PubMed Web of Science ®Google Scholar
• He Q, Mitchell AR, Johnson SL, et al. Calcium phosphate nanoparticle adjuvant. Clin Diagn Lab Immunol. 2000;7:899–903.
   PubMedGoogle Scholar
• Koppad S, Raj GD, Gopinath VP, et al. Calcium phosphate coupled Newcastle disease vaccine elicits humoral and cell mediated immune responses in chickens. Res Vet Sci. 2011;91:384–390.
   PubMed Web of Science ®Google Scholar
• He Q, Mitchell A, Morcol T, et al. Calcium phosphate nanoparticles induce mucosal immunity and protection against herpes simplex virus type 2. Clin Diagn Lab Immunol. 2002;9:1021–1024.
   PubMedGoogle Scholar
• Neumann S, Kovtun A, Dietzel ID, et al. The use of size-defined DNA-functionalized calcium phosphate nanoparticles to minimise intracellular calcium disturbance during transfection. Biomaterials. 2009;30:6794–6802.
   PubMed Web of Science ®Google Scholar
• Behera T, Swain P. Antigen adsorbed calcium phosphate nanoparticles stimulate both innate and adaptive immune response in fish, Labeo rohita H. Cell Immunol. 2011;271:350–359.
   PubMed Web of Science ®Google Scholar
• Viswanathan K, Gopinath VP, Raj GD. Formulation of Newcastle disease virus coupled calcium phosphate nanoparticles: an effective strategy for oculonasal delivery to chicken. Colloids Surf B Biointerfaces. 2014;116:9–16.
   PubMed Web of Science ®Google Scholar
• Gupta RK. Aluminum compounds as vaccine adjuvants. Adv Drug Deliv Rev. 1998;32:155–172.
   PubMed Web of Science ®Google Scholar
• Aimanianda V, Haensler J, Lacroix-Desmazes S, et al. Novel cellular and molecular mechanisms of induction of immune responses by aluminum adjuvants. Trends Pharmacol Sci. 2009;30:287–295.
   PubMed Web of Science ®Google Scholar
• Marrack P, McKee AS, Munks MW. Towards an understanding of the adjuvant action of aluminium. Nat Rev Immunol. 2009;9:287–293.
   PubMed Web of Science ®Google Scholar
• Wang X, Li X, Ito A, et al. Rod-shaped and substituted hydroxyapatite nanoparticles stimulating type 1 and 2 cytokine secretion. Colloids Surf B Biointerfaces. 2016;139:10–16.
   PubMed Web of Science ®Google Scholar
• Wang X, Li X, Ito A, et al. Rod-shaped and fluorine-substituted hydroxyapatite free of molecular immunopotentiators stimulates anti-cancer immunity in vivo. Chem Commun Camb Engl. 2016;52:7078–7081.
   PubMed Web of Science ®Google Scholar
• Sokolova V, Knuschke T, Buer J, et al. Quantitative determination of the composition of multi-shell calcium phosphate-oligonucleotide nanoparticles and their application for the activation of dendritic cells. Acta Biomater. 2011;7:4029–4036.
   PubMed Web of Science ®Google Scholar
• Knuschke T, Epple M, Westendorf AM. The type of adjuvant strongly influences the T-cell response during nanoparticle-based immunization. Hum Vaccines Immunother. 2014;10:164–169.
   PubMed Web of Science ®Google Scholar
• Zhou W, Moguche AO, Chiu D, et al. Just-in-time vaccines: biomineralized calcium phosphate core-immunogen shell nanoparticles induce long-lasting CD8(+) T cell responses in mice. Nanomed Nanotechnol Biol Med. 2014;10:571–578.
   PubMed Web of Science ®Google Scholar
• Jones S, Asokanathan C, Kmiec D, et al. Protein coated microcrystals formulated with model antigens and modified with calcium phosphate exhibit enhanced phagocytosis and immunogenicity. Vaccine. 2014;32:4234–4242.
   PubMed Web of Science ®Google Scholar
• Jilek S, Merkle HP, Walter E. DNA-loaded biodegradable microparticles as vaccine delivery systems and their interaction with dendritic cells. Adv Drug Deliv Rev. 2005;57:377–390.
   PubMed Web of Science ®Google Scholar
• Issa AM, Salim MS, Zidan H, et al. Evaluation of the effects of aluminum phosphate and calcium phosphate nanoparticles as adjuvants in vaccinated mice. Int J Chem Eng Appl. 2014;5:367–373.
   Google Scholar
• Muddana HS, Morgan TT, Adair JH, et al. Photophysics of Cy3-encapsulated calcium phosphate nanoparticles. Nano Lett. 2009;9:1559–1566.
   PubMed Web of Science ®Google Scholar
• Oberdörster E. Manufactured nanomaterials (fullerenes, C60) induce oxidative stress in the brain of juvenile largemouth bass. Environ Health Perspect. 2004;112:1058–1062.
   PubMed Web of Science ®Google Scholar
• Tamuly S, Saxena MK. Preparation of calcium phosphate nanoparticles and evaluation of their effects on muscle cells of rat. Curr Sci. 2012;102:610–612.
   Web of Science ®Google Scholar
• Relyveld EH, Raynaud M, Martin R, et al. Tolerance in humans of pertussis vaccines adsorbed onto calcium phosphate. Symp Ser Immunobiol Stand. 1970;13:171–179.
   Google Scholar
• Sureau P, Fabre PS, N’Garo SB, et al. Vaccination simultanée de nourrissons en milieu tropical contre le tétanos et la poliomyélite. Bull World Health Organ. 1977;55:739.
   PubMed Web of Science ®Google Scholar
• McLachlan DR, Lukiw WJ, Kruck TP. New evidence for an active role of aluminum in Alzheimer’s disease. Can J Neurol Sci J Can Sci Neurol. 1989;16:490–497.
   PubMed Web of Science ®Google Scholar
• Relyveld E, Chermann JC. Humoral response in rabbits immunized with calcium phosphate adjuvanted HIV-1 gp160 antigen. Biomed Pharmacother Bioméd Pharmacothér. 1994;48:79–83.
   PubMed Web of Science ®Google Scholar
• Relyveld E, Bizzini B. Production in rabbits of high levels of anti-HIV-1 gp160 antibodies. Cell Mol Biol Noisy–Gd Fr. 1995;41:389–393.
   PubMed Web of Science ®Google Scholar
• Li X, Wang X, Sogo Y, et al. Mesoporous silica-calcium phosphate-tuberculin purified protein derivative composites as an effective adjuvant for cancer immunotherapy. Adv Healthc Mater. 2013;2:863–871.
   PubMed Web of Science ®Google Scholar
• Wang X, Li X, Onuma K, et al. Zn- and Mg- containing tricalcium phosphates-based adjuvants for cancer immunotherapy. Sci Rep. 2013;3:2203.
   PubMed Web of Science ®Google Scholar