Table 3.

Nanomaterials synthesized by microalgae.

Microorganism	Culture Conditions (Synthesis Time)	Nanomaterial	Characteristics (Average Size, Morphology, Modification)	Biosynthetic Pathway	Application	Ref.
Tetraselmis kochinensis	Guillard’s Marine Enrichment medium at 28 °C, 200 rpm, 15 days, light condition. 10 g of washed harvested cells + 1 mM HAuCl4, 200 rpm, 28–29 °C (48 h)	Au NPs	5–35 nm; spherical and triangular shape	Intracellular synthesis; possible reduction via enzymes present in the cell wall and in the cytoplasmic membrane	Various applications including catalysis, electronics and coatings	[63]
Scenedesmus sp. (IMMTCC-25)	Growth in Modified Bold Basal medium, 28 ± 2 °C, 16:8 h light: dark cycle,126 rpm; washed pelleted biomass (harvested in the logarithmic growth phase) + 5 mM AgNO3, 28 °C in the same growth conditions (72 h)	Ag NPs	(living cells) 3–35 nm; spherical shape, highly crystalline cluster; (raw algal extract) (5–10 nm), spherical shape; (boiled algal extract) >50 nm; less stable; colloidal stability >3 months (assessed UV-Vis measures at 420 nm)	Intracellular synthesis not described. Extracellular synthesis (raw algal extracts); reducing and stabilizing agents involved in nucleation points and size control	Good antimicrobial activity against Streptococcus mutans and Escherichia coli (boiled cell extract)	[64]
Desmodesmus sp. (KR 261937)	Growth in BG-11 medium for 15–20 days, 12:12 h light: dark cycle, 28 ± 2 °C, 120 rpm; centrifuged harvested biomass + 5 mM AgNO3, 28 °C in the same growth condition (72 h)	Ag NPs	(whole cells); 10–30 nm; ζ-potential = −20.2 mV; (raw algal extract) 4–8 nm; ζ-potential = −19.9 mV; (boiled algal extract) 3–6 nm; ζ-potential = −14.2 mV	Intracellular synthesis not described Extracellular synthesis: biocomponents (e.g., polysaccharides, proteins, polyphenols and phenolic compounds) possibly involved in control of dimension and stabilization	Antibacterial effect against Salmonella sp. and Listeria monocytogenes; antifungal activity against Candida parapsilosis	[65]
Coscinodiscus concinnus Wm.	One-week growth (cell density 106 cells mL−1) in silicate-enriched seawater media, 18–20 °C, 12:12 h light: dark cycle	Biogenic silica (frustules) modified with murine monoclonal antibody UN1	Green photoluminescence (peaked between 520 and 560 nm) of silanized frustules	Natural silicification process (bio-mineralization)	Using the biogenic silica photo-luminescence for immunosensors development	[72]
Cyclotella sp.	Growth in Harrison’s Artificial Seawater Medium enriched with f/2 nutrients + 0.7 mM Na2SiO3, 22 °C 14:10 h light: dark cycle. The cell suspension was subcultured at 10% v/v every 14 days (336 h)	Biogenic silica (frustules) functionalized with IgG	~200-nm (perimetrical pores) ~100-nm (linear arrays of pores from the center to the rim) at the base of each ~100-nm pore, a thin layer of silica containing four to five nanopores of ~20-nm diameter	Natural silicification process (bio-mineralization)	Label-free photoluminescence-based immunosensor	[73]
Coscinodiscus wailesii	Growth in F/2 seawater medium, 20 °C, continuous photoperiod	Functionalized biogenic silica (frustules)	100–200 μm	Natural silicification process (bio-mineralization)	Electrochemical immunosensor for the detection of C-reactive protein and myelo-peroxidase in buffer and human serum samples	[75]
Cosinodiscus argus and Nitzschia soratensis	Growth in F/2 medium, 20 °C, 12:12 h light: dark cycle. The culture media volume was doubled every week to keep high the diatom reproduction rate About 4000 cells/ml and about 5.5 × 105 cell/ml for C. argus and N. soratensis respectively); (about 1000 h)	Multi-layered package array of biogenic silica (frustules) functionalized with purified primary rabbit IgG	C. argus 80–100 μm uniformly distributed sub-micron elliptical holes (~170–300 nm) and nanopores (~90–100 nm); N. soratensis ~10–15 μm (long axis) and ~5μm (short axis) with nanopores (60–80 nm)	Natural silicification process (bio-mineralization)	Optical immunochip for fluorophore-labeled donkey anti-rabbit IgG detection	[76]
Pseudostaurosira trainorii	Growth in F/2 medium + silica 7 mg mL−1, under aeration 12:12 h light: dark cycle	Biogenic silica (frustules) integrated with Au NPs functionalized with 5,5′-dithiobis (2-nitrobenzoic acid) + anti-interleukin-8 antibodies	4–5 μm; 98% silica Perpendicular oriented rows of 4–5 pores (100–200 nm) decreasing in size towards the central axis; neighboring rows separated by ~450 nm; neighboring pores in a row separated by ~100 nm	Natural silicification process (bio-mineralization)	Surface-enhanced Raman scattering immunosensor for the detection of interleukin 8 in blood plasma	[77]
Pinnularia sp. (UTEX #B679)	Growth in Harrison’s artificial seawater medium + 0.5 mM Na2SiO3, 22 °C, 14:10 h light: dark cycle for 21 days. (336 h)	Biogenic silica (frustules) functionalized with anti- 2,4,6-TNT single chain variable fragment derived from the monoclonal antibody 2G5B5	Ellipsoidal shape with major axe ~20 μm minor axe ~6 μm; pores in rectangular array (~200 nm diameter) spaced 300–400 nm apart. 4–5 nanopores (~50 nm diameter) at the base of each pore	Natural silicification process (bio-mineralization)	Label-free photo-luminescence quenching -based sensor for 2,4,6-trinitro-toluene detection	[77]
Aulacoseria sp.	N/A	Biogenic silica (frustules) coated with gold (multiple layers of Au particles)	5–10 μm cylindrical-shaped frustules	Natural silicification process (bio-mineralization)	Functional support for surface-enhanced Raman scattering sensor	[78]
Melosira preicelanica	N/A	biogenic silica (frustules) tailored with Au NPs	~20 nm cylindrical-shaped frustules	Natural silicification process (bio-mineralization)	Detection of bovine serum albumin and mineral oil by surface-enhanced Raman spectroscopy	[79]
Coscinodiscus concinnus	Same conditions reported in [70]	Biogenic silica (frustules) loaded with streptomycin	Homogeneous size distribution with a radius of 220 ± 15 µm	Natural silicification process (biomineralization	Drug delivery	[80]
Thalassiosira weissflogii CCAP strain 1085/10	Growth in silicate-enriched seawater media, 18–20 °C, 12:12 h light: dark cycle, final cell density 106 cells mL−1 (168 h)	Biogenic silica (frustules)	Mainly composed of separated valves, porosity and hierarchically ordered nanostructure; luminescent and nanostructured silica shells, combining the dye photoluminescence with the photonic silica nanostructure	Natural silicification process (bio-mineralization)	Loading and delivery of fluoro-quinolone ciprofloxacin	[81]
Fossil diatoms	N/A	Biogenic silica (frustules) integrated with 50–60 nm gold nanoparticles	~400 μm (width of the diatomite channels porous); disk-shaped; extremely high confinement of the analyte and increase the concentration of target molecules at the sensor surface; photonic crystals (substrate for surface-enhanced Raman scattering) with 50–60 nm Au NPs	N/A	On-chip chromatography-surface-enhanced Raman scattering -based microfluidic label-free device for cocaine detection in biological samples	[84]
Fossil diatoms	N/A	Biogenic silica (frustules) integrated with 50–60 nm Au nanoparticles	10 to 30 μm; dish-shaped with two-dimensional periodic pores; thickness of the diatomite layer on the glass ~20 μm, (one-third of that of a commercial Thin Layer Chromatography, chip) photonic crystals (substrate for surface-enhanced Raman scattering	N/A	On-chip chromatography-surface-enhanced Raman scattering -based microfluidic label-free device for histamine in salmon and tuna	[85]
Amphora-46	Growth in F/2 medium made with filter sterile brackish water (salinity 3%, pH 8.2), 30 °C, 16:8 h light: dark cycle, 130 rpm; Aqueous cell extract + 2 mM AgNO3, 35–40 °C (30 h)	polycrystalline Ag NPs	20–25 nm	Extracellular synthesis; photosynthetic pigment fucoxanthin acts as a reducing agent	Antimicrobial activity against Escherichia coli, Bacillus stearothermophilus, and Streptococcus mutans	[86]
Emiliania huxleyi strain CCMP371	Growth in Artificial seawater (ASW) + f/2 nutrients (without added Si), 20 °C, 12:12 h light: dark cycle, 130 rpm. Cells were harvested at late exponential phase	Aptamer-modified coccolith electrodeposited on the screen-printed Au electrode	N/A	Natural calcification process (coccolitho-genesis)	Aptamer-based sandwich-type electrochemical biosensor for Vaspin (type 2 diabetes biomarker)	[88]