Gorodkiewicz E; Lukaszewski Z

Special Article - Applications of Biosensors

Austin J Biosens & Bioelectron. 2019; 5(1): 1034.

Surface Plasmon Resonance Biosensors

Gorodkiewicz E^1* and Lukaszewski Z²

¹Department of Electrochemistry, University of Bialystok, Poland

²Faculty of Chemical Technology, Poznan University of Technology, Poland

*Corresponding author: Ewa Gorodkiewicz, Department of Electrochemistry, Institute of Chemistry, University of Bialystok, Ciolkowskiego 1K, 15-245 Bialystok, Poland

Received: July 06, 2019; Accepted: August 01, 2019; Published: August 08, 2019

Abstract

A review is made of 86 papers on surface plasmon resonance biosensors, published between 2016 and mid-2019. The reviewed papers are categorized into four groups, depending on the degree of maturity of the reported solution: ranging from simple marker detection to a mature biosensor and analytical procedure. Instrumental solutions and details of biosensor construction are analyzed, including the chips, receptors and linkers used, as well as calibration strategies. Papers concerning the determination of micro RNA and large particles such as vesicles, exosomes and cancer cells are also reviewed. Biosensors with a sandwich structure containing different nanoparticles are considered separately, as are SPR applications for investigating the interactions of biomolecules. An analysis is also made of the markers determined using the biosensors. Concluding, there is shown to be a growing number of SPR applications in the solution of real clinical problems.

Keywords: Surface plasmon resonance; Cancer markers; Biosensors; Receptor immobilization; Antibodies; Nanoparticles

Introduction

Biosensors are the subject of enormous expectations and are gradually gaining in diagnostic importance. These expectations are connected with what is called ‘liquid biopsy’, i.e. diagnosis based on analysis of body fluids such as blood, urine and saliva, and the possibility of early diagnosis of various cancers or other diseases. However, there is still a shortage of biosensors offering near 100% sensitivity and specificity, i.e. respectively 100% of true positive and 0% of false positive results. An illustration of the relationship between true positive and false positive results is provided by ROC curves. An example of such curves obtained with the use of an SPRi biosensor for the determination of podoplanin in blood serum and urine is given in Figure 1. This example is evidence that SPR biosensors can be useful tools in the evaluation of the diagnostic efficiency of new biomarkers.

An ideal biosensor should react exclusively to the target marker despite the presence of numerous similar proteins, glycoproteins, etc. in the analyzed body fluid. Moreover, the biosensor’s dynamic response range should include the concentrations of the marker found in the body fluid both of persons with the disease and of the healthy population. It is also expected that the precision of measurement of the marker concentration will be sufficient to distinguish between samples below and above a ‘cut-off’ value.

A limited number of measuring techniques are used successfully in combination with biosensors, the leader among which is ELISA. Surface Plasmon Resonance (SPR) is still only a promising technique. However, the number of applications of previously developed SPR biosensors in real clinical investigations is growing (Table 1).

Table 1: SPR biosensors applied in clinical investigations.




  
    Disease
    Marker
    Reference
  
  
    Bladder cancer
    Podoplanin
    [1]
  
  
    Thermal injuries
    20S proteasome
    [2] 
  
  
    Bladder cancer
    Cystatin C
    [3] 
  
  
    Thermal injury 
    UCHL1
    [4]
  
  
    Burns
    Laminin 5
    [5]
  
  
    Burns
    Collagen IV
    [5]
  
  
    Burns
    MMP2
    [5]
  
  
    Cryptorchidism
    UCHL1
    [6] 
  
  
    Acute Appendicitis
    20S proteasome
    [7]
  
  
    Acute Appendicitis
    UCHL1
    [8]
  
  
    Cryptorchidism
    20S proteasome
    [9] 
  
  
    Burns
    20S Immunoproteasome
    [10]
  
  
    Appendicitis
    Cathepsin B
    [11]
  
  
    Endometriosis
    Cathepsin G
    [12]
  
  
    Endometriosis
    Cathepsin G
    [13]
  
  
    Endometriosis
    Cathepsin B
    [13]
  
  
    Endometriosis
    Cathepsin D
    [13]
  
  
    Burns
    20S Immunoproteasome
    [67]



Table 1: SPR biosensors applied in clinical investigations.

This paper reviews the most recent publications on SPR biosensors, appearing between 2016 and early 2019, with a slight extension to include earlier papers by the authors. Earlier work is covered in excellent reviews by Masson [14] and Ferhan et al. [15]. Both Masson and Ferhan et al. conclude that future work should focus more on clinical samples than on improving detection specificity and sensitivity.

Stages of biosensor development

Generally, a mature biosensor and a procedure for the determination of a particular marker are developed in several stages, beginning with the conception of the biosensor, followed by analytical characterization, validation, and determination of the marker in real samples. Therefore, the reviewed papers are categorized into four groups, depending on the degree of maturity of the reported solution. According to Gorodkiewicz and Lukaszewski [16], the following stages of development of a biosensor and a related analytical procedure can be distinguished:

i. The biosensor is used only for the detection of a marker;

ii. The biosensor is characterized in terms of quantitative marker determination (calibration graph, the marker concentration range covered by the biosensor);

iii. The biosensor and related analytical procedure are validated (precision, recovery, interferences, comparison of results with another procedure such as ELISA, examples of natural samples e.g. blood plasma);

iv. The mature biosensor and the analytical procedure are used for investigation of the marker in significant series of clinical samples, including long control series of healthy donors;

The papers pertaining to stages i. and ii. represent incomplete analytical procedures. These papers represent high innovative potential in terms of biosensor construction, which may result in fully developed procedures in the future. The papers pertaining to stages iii. and iv. represent complete analytical procedures. These biosensors and related analytical procedures are ready to be subjected to clinical investigation for subsequent use in diagnosis. Additionally, biosensors in stage iv. are characterized as potential disease markers by series of measurements performed with clinically classified material. Technical solutions for biosensors representing all four stages of development are shown in Tables 2 and 3, for cancer markers and other diseases respectively.

Table 2: Stages of biosensor development and technical solutions for biosensors used for the determination of cancer markers.




  
    Stage 
    Marker
    SPR type
    Fluidic/
      Non fluidic
    Chip
    Linker
      /receptor
    Receptor
      immobilization
    Reference
  
  
    i
    HER2
    SPR
    Micro-fluidic
    Nano-
      whole
      array
    Cysteamine/
      Sandwich/
      2 Antibodies
    Biotin/
      streptavidin
    [17]
  
  
    i
    CEA
    SPR
    Fluidic
    Slide/Cr/Au
    MUA
      /antibody
    EDC/NHS
    [18]
  
  
    i
    Cytokeratin 17
    SPR
    Non fluidic
    Optical fiber/Au
    S2PEG6COOH/ antibody
    EDC/NHS
    [19]
  
  
    i
    E-cadherin
    SPR
    nd
    Au/mica
    MUA/ antibody
    EDC/NHS
    [20]
  
  
    i
    CEA
      EGFR
    SPR
    nd
    Grating/ Au/Al
    nd
    nd
    [21]
  
  
    ii
    Cytokeratin-19
    SPR
    Both
    Prism
    Cysteamine/
      GOCOOOH/
      /antibody
    EDC/NHS
    [22] 
  
  
    ii
    PSA
    SPR
    Fluidic
    Slide/Au/
      MoS2QDs@g-C3N4@CSAuNPs
    PSA targeted
      aptamer
    PSA targeted
      aptamer
    [23]
  
  
    ii
    Cytokeratin 17
    LSPR
    Non-fluidic
    Optical fiber
      Without Au
     
      three protein A
    1.covalent
      2.electrostatic
      3. protein A/antibody affinity
    [24]
  
  
    iii
    PSA
    SPRi
    Fluidic
    Slide/Au/
       
    Allyl mercaptan
    PSA imprinted
      polymer
    [25]
  
  
    iv
    Rac1, Rac1b
    SPR
    Fluidic
    CM5 chip
    Dextran-COOH/
      Antibody
    EDC/NHS
    [26]
  
  
    iv
    5LOX
    SPR
    Fluidic
    CM5 chip
    Dextran-COOH/
      Antibody
    EDC/NHS 
    [27] 
  
  
    iv
    CDK4
    SPR
    Fluidic
    CM5 chip
    Dextran-COOH/
      Antibody
    EDC/NHS 
    [28] 
  
  
    iv
    Laminin-5
    SPRi
    Non fluidic
    Slide /Au/
      Array
    Cysteamine/
      Antibody
    EDC/NHS 
    [29]
  
  
    iv
    Collagen IV
    SPRi
    Non fluidic
    Slide /Au/
      Array
    Cysteamine/
      Antibody
    EDC/NHS 
    [30]
  
  
    iv
    MMP1
    SPRi
    Non fluidic
    Slide/Au/
      Array
    Cysteamine/
      Antibody
    EDC/NHS 
    [31]
  
  
    iv
    20S immune-proteasome
    SPRi
    Non fluidic
    Slide /Au/
      Array
    1-octadecano-thiol / Inhibitor ONX 0914
    Hydrophobic
      interaction
    [32]
  
  
    iv
    MMP2
    SPRi
    Non fluidic
    Slide /Au/
      Array
    1-octadecano-thiol / Inhibitor ARP 101 
    Hydrophobic
      interaction
    [33] 
  
  
    iv
    Cathepsin L
    SPRi
    Non fluidic
    Slide /Au/
      Array
    1-octadecano-thiol / Inhibitor RKLLW-NH2 
    Hydrophobic
      interaction
    [34]
  
  
    EDC/NHS: Covalent Amid Bond Formed    Due to EDC/NHS Protocol; MoS2QDs@g-C3N4@CSAuNPs; g-C3N4: Graphitic Carbon    Nitride; MoS2 QDs: Nanosheets And Mos2 Quantum Dots, followed by decoration    with chitosan-stabilized Au nanoparticles; ND: No Data



Table 2: Stages of biosensor development and technical solutions for biosensors used for the determination of cancer markers.

Table 3: Stages of biosensor development and technical solutions for biosensors used for the determination of various markers, excluding cancer markers.




  
    Stage 
    Marker
    SPR type
    Fluidic/
      Non fluidic
    Chip
    Linker
      /receptor
    Receptor
      immobilization
    Reference
  
  
    i
    BSA
    SPR
    Both
    Prism/Au
    Cysteamine/
      GOCOOOH/
      /antibody
    EDC/NHS 
    [35] 
  
  
    i
    BSA
    SPR
    Non fluidic
    Sidle/Au 
    mercapto
      propane
      sulfonate/
      modified GO
    EDC/NHS
    [36]
  
  
    i
    Cytochrom C
    SPRi
    Fluidic
    Easy2Spot
    antibody
    Sensor pre-activated G-type Senseye
    [37]
  
  
    i
    ampicilin
    EC-SPR
    Fluidic
    Slide/Cr/Au
    thiolated aptamer 
    Aptamer/
      /ampicilin
    [38]
  
  
    ii
    Pf glutamate
      dehydro-genase
    SPR
    Fluidic
    Au
    thiolated aptamer 
    Thiolated aptamer 
    [39]
  
  
    ii
    Transferrin
    SPR
    Fluidic
    Slide/Au
    4-Mercapto phenylboronic
    4-Mercapto phenylboronic
    [40]
  
  
    ii
    Folic acid
    SPR
    Fluidic
    Prism/Ti/
      Au/graphene
    FAP
    Hydrophobic
      Interaction
    [41]
  
  
    iii
    CBP
    SPR
    Fluidic
    CM5 chip
    Dextran-COOH/
      Antibody
    EDC/NHS
    [42]
  
  
    iii
    Troponin T
    SPR
    Fluidic
    Slide/Au
    Polydopamine/
      Epitop/
       
    Polimer
      Imprinted epitop
    [43] 
  
  
    iii
    IgG
    LSPR
    Fluidic
    photonic crystal    fiber/Au 
       
    Dithiothreitol/ antibody 
    EDC/NHS 
    [44]
  
  
    iii
    P. fijiensis 
    SPR
    Fluidic
    Prism/Cr/
      Au
    MHDA/antibody
    EDC/NHS 
    [45]
  
  
    iv
    Avian Influenza A H7N9 Virus
    IM-SPR
    Non fluidic
    Ag/Au
    MUA/antibody
    EDC/NHS
    [46]
  
  
    iv
    YKL40
    SPR
    Fluidic
    CM5 chip
    Dextran-COOH/
      Antibody
    EDC/NHS 
    [47] 
  
  
    Iv
    Mortalin & a-Synuclein 
    SPR
    Fluidic
    CM5 chip
    Dextran-COOH/
      Antibody
    EDC/NHS 
    [48] 
  
  
    Iv
    Fibronectin 
    SPRi
    Non fluidic
    Slide/Au
    Cysteamine/
      Antibody
    EDC/NHS 
    [49]
  
  
    EDC/NHS: Covalent Amid Bond Formed    Due to EDC/NHS Protocol; IM-SPR: Intensity-Modulated SPR; MHDA: 16-Mercaptohexadecanoic    Acid; P. fijiensis: Fungus Pseudocercospora Fijiensis



Table 3: Stages of biosensor development and technical solutions for biosensors used for the determination of various markers, excluding cancer markers.

The number of fully developed biosensors (stages iii and iv) in Tables 1 and 2 outnumber those with incomplete analytical procedures (stages i and ii). This is a positive observation and a good prognostic factor for future SPR biosensors. This is a tendency corresponding to that recommended in the reviews by Masson and Ferhan et al. [14,15], and gives an indication of the future growing significance of SPR.

In the reviewed papers, classical SPR or SPR Imaging apparatus was used in the majority of cases. SPRi was frequently associated with non-fluidic measurement techniques. Occasionally, Localized SPR (LSPR) or Intensity-Modulated SPR (IM-SPR) were used. Instrumental differences between these versions of SPR are excellently reviewed in a paper by Wang et al. [50].

Fluidic vs. non-fluidic measurements

Approximately the same number of reviewed papers reported the use of fluidic and non-fluidic measurement technique. There is a significant difference in the arrangement of a fluidic or non-fluidic measurement: a fluidic measurement is usually performed with in situ creation of a biosensor, while in the non-fluidic case the biosensor is prepared ex situ. In the fluidic version measurement is performed with the biosensor in contact with solution. This is the major difference from the non-fluidic case. In the in situ version a biosensor is created during the measurement by sequential introduction of a linker, a receptor and a solution containing the determined marker. Finally, the chip sensor is cleaned to prepare it for the next measurement. Subsequent measurements can be performed rapidly, as in flowinjection analysis. A single biosensor usually contains several channels, processed simultaneously for multi-sample measurement or for processing the same solution to gain better precision. The volume of processed solution also constitutes a difference between fluidic and microfluidic techniques: in the microfluidic case there is a tendency towards the miniaturization of the measuring process. Microfluidic measurement also uses an array of measuring points [17]. An example of such a solution is shown in Figure 2.

Non-fluidic measurement is usually performed in a stationary arrangement, with an array of separated measuring points. An example of non-fluidic measurement is shown in Figure 3. An array of measuring points is used for a single sample measurement to improve the precision of the result. Multi-sample measurement is also performed, as shown in Figures 3 and 4, as well as regeneration of the chip after measurement.

Non-fluidic ex situ SPR measurement is performed following gentle removal of solution from the biosensor surface, which is the major difference compared with fluidic measurements. No information has yet been published concerning the comparison of fluidic and non-fluidic versions of SPR measurements.

Receptors

A crucial part of a biosensor is the receptor. The receptor must ensure that only the target marker is captured from the analyzed sample, as well as ensuring suitable effectiveness in terms of the strength of analytical signal sufficient for the determination of a marker in real samples. In the reviewed papers, appropriate antibodies were most frequently used as receptors. The antibody was attached to the gold chip surface via a linker. Most frequently, cysteamine (2-aminoethanethiol) was used as the linker. Cysteamine is fixed onto the gold surface by the thiol group, while the amine group is used for attachment of the antibody. An example of such receptor immobilization is shown in Figure 4 left.

An EDC/NHS protocol is applied for this purpose, with amide bond formation between the antibody’s carboxyl group and the linker’s amine group. Alternatively, MUA (11-mercaptoundecanoic acid) may be used in conjunction with the EDC/NHS protocol [18]. The amine group of the antibody is used for the junction. Similarly, HS-OEG-COOH [51,52], S2PEG6COOH [19] (where OEG and PEG denote oxyethylene subunits) and mercapto propane sulfonate [36] have been used. In numerous papers, the commercially available CM5 chip with carboxylated dextran as the linker was employed. Another commercially available chip (Easy2Spot) is supplied in a form ready for antibody bonding [37].

Several solutions other than antibodies have been used as receptors. A marker’s inhibitor can be used as the receptor, as in the cases of the inhibitor ONX 0914 [32] and the inhibitor ARP 101 [33]; in both cases 1-octadecano-thiol was used as the linker, and the inhibitor was attached to the linker via hydrophobic interactions. An example of this type of receptor immobilization is shown in Figure 5 right.

Tionylated aptamer targeting analyte is also used as a receptor [23,38,39]. In such a case no linker is used. A receptor-imprinted polymer may also be used as the receptor [25,43].

A glass slide covered with gold is a typical chip base (Figure 4). Alternatively, a gold-covered glass prism is used. Usually, a chromium—or alternatively, titanium—under-layer is employed. Only a few papers report other solutions, such as a gold-covered glass fiber [19], also with additional graphene layer [53], a gold nanohole array [17,54], or a gold nanoslit substrate [51] or a prism covered with gold and graphene [55]. Frequently, a gold chip surface is covered by a polymer with holes, creating an array of free gold measuring points (Figures 3 and 4). A thick inert polycarbonate protective layer is also proposed [56].

Enhancement of the SPR signal

As demonstrated by Brolo’s research group in Canada, periodic areas of nanoholes in a sandwich configuration may be used to enhance the SPR signal [17]. The first antibody captures the marker, while the marker captures the second antibody. The introduction of different nanoparticles in the sandwich can lead to much greater enhancement of the SPR signal. Table 4 summarizes the cases in which nanoparticles were applied. In the simplest solution, the first antibody attached by the EDC/NHS protocol captures the marker, which captures an aggregate consisting of a gold nanoparticle covered by a second antibody attached to the antibody surface by the same EDC/NHS protocol [52]. A similar solution is reported [57] in which the EDC/NHS protocol is used for the first antibody attachment, and a biotinylated antibody attached to streptavidin-decorated gold nanoparticles serves as the second. The preconcentration of the marker with magnetic microparticles covered by the antibody has been reported [58]. Finally, the signal is created indirectly by a selected aptamer released from the magnetic microparticles–antibody– marker–aptamer structure. A quantum dot having CdSe/ZnS core/ shell structure has also been used for SPR signal enhancement in a sandwich configuration [59], as have polydopamine-wrapped magnetic multi-walled carbon nanotubes [60]. Two very efficient signal enhancement procedures have been used for the determination of microRNA-141 [61,62]. Gold nanoparticle-decorated molybdenum sulfide containing thiol-modified DNA oligonucleotide probes, having a sequence complementary to the target miRNA-141, was attached to the Au film containing the segment sequence of the target miRNA-141 by means of the miRNA-141 [61]. Similarly, a graphene oxide–gold nanoparticle hybrid with attached thiol-modified DNA oligonucleotide probe was used [62].

Table 4: Stages of biosensor development and technical solutions for biosensors with the use of nanoparticles.




  
    Stage
    Marker
    SPR type
    Fluidic/
      Non fluidic
    Chip/NP
    Sandwich/
      /other
    receptors
      immobilization (chip/NP)
    Reference
  
  
    ii
    miRNA141
    SPR
    Non fluidic
    Au/DNA
      AuNPMoS2 
    sandwich
    Thionylated DNA/DNA linked
      AuNPMoS2 
    [61]
  
  
    ii
    miRNA141
    SPR
    Non fluidic
    Au/DNA
      GO–AuNP 
    sandwich
    Thionylated DNA/DNA linked
      GO-AuNP
    [62]
  
  
    ii
    Folic acid
    SPRi
    Non fluidic
    Array/Cr/Au/ FA-AuNP
    Sandwich
    HS-(CH2)11- EG3-NTA/polyhistidine
    [41]
  
  
    ii
    Troponin I
    SPR
    fluidic
    Slide/Au/
      /HGNP/ MMWCNTs-PDA
    Sandwich/
      / MMWCNTs-PDA
    Polydopamine/
      Polydopamine 
    [60]
  
  
    ii
    PSA
    SPR
    fluidic
    AuNP/CS/
      /C3N4/
      /MoS2QD
    Multi-component
      structure
    nanosheet/
      /aptamer
    [23]
  
  
    ii
    Rabbit IgG
    SPR
    nd
    Slide/Au/
      /HGNP
       
    sandwich
    1,6-hexanedithiol/ /PDA-Ag@Fe3O4/rGO
    [63]
  
  
    ii
    Prion Sc protein
    SPR
    Fluidic
    Slide/Au/
      / Fe3C@C
    sandwich
    ?/ Fe3C@C-aptamer
    [64] 
  
  
    ii
    miRNA200
    SPR
    nd
    Prism/Au/ AuNP-surrogate DNA
    Sandwich-competition
    MUA/ surrogate DNA/
    [65]
  
  
    iii
    CEA
    SPR
    fluidic
    Slide/Ti/Au
      /AuNP
    Sandwich
    HS-OEG-COOH/ HS-OEG-COOH/ EDC/NHS
    [52]
  
  
    iii
    HER 2
    SPR
    Micro-
      fluidic
    Prism/Au/
      SAv-GNPs 
    Sandwich
    MUA/ EDC/NHS/
      biotinylated antibody
    [57] 
  
  
    iii
    IgG
    LSPR
    Fluidic
    photonic crystal fiber/Au/AuNP 
    other
    Dithiothreitol/EDC/NHS/antibody 
    [44]
  
  
    iii
    IgG
    LSPR
    Fluidic
    photonic crystal fiber/Au/AuNP/protein A 
    other
    Dithiothreitol/EDC/NHS/protein A/antibody
    [44]
  
  
    iii
    cTnI
    SPR
    Fluidic
    Slide Au/
      PDA/AuNP/
      /antibody1
    Sandwich/
      /MMP/PDA/
      /antibody1
    PDA
    [66]
  
  
    iii
    cTnI
    SPR
    Fluidic
    Sandwich/
      /MMP/PDA/
      /antibody1
    Sandwich//MMP/PDA/
      /antibody1/ MWCNTs-PDA-AgNPs/antibody2
    PDA
    [66]
  
  
    iv
    Cytochrom C
    SPR
    fluidic
    Slide/Au
      /AuNR 
    Sandwich/
      /MMP
    Straptavidin/
      /biotinylated aptamer/
      /antibody/MMP
    [58]
  
  
    iv
    AFP,
      CEA CYFRA 21-1
       
    SPR
    Micro-
      fluidic
    Prism/Au
    Sandwich/
      /QD
    Hexanedithiol/
      /antibody/ DTBE 
       
    [59]
  
  
    SAv-GNPs:    Streptavidin Decorated Gold Nanoparticles; FA-AuNP: AuNP Functionalized with Polyhistidine Tagged Folic Acid Binding Protein; AuNR: Au Nanorods;    MMP: Micro Magnetic Particles; QD: Quantum Dot (CdSe/ZnS core/shell structure); DTBE - 2,2': Dithiobis[1-(2-Bromo-2-Methylpropionyloxy)]Ethane;    AFP: a-Fetoprotein;    MMWCNTs-PDA: Polydopamine-Wrapped    Magnetic Multi-Walled Carbon Nanotubes; HGNP: Hollow Gold Nanoparticles; MoS2QDs@g-C3N4@CS-AuNPs: Graphitic Carbon Nitride (g-C3N4) Nanosheets and MoS2    QDs: MoS2 Quantum Dots
      Followed by    decoration with chitosan-stabilized Au nanoparticles
      PDA-Ag@Fe3O4/rGO:    Polydopamine-Ag@Fe3O4/reduced Graphene Oxide; DNAAuNPMoS2:    DNA-Linked AuNPs-MoS2 Hybrids; GO–AuNP: Graphen Oxide – Au Nanopaticles Hybrid; Nd:    No data



Table 4: Stages of biosensor development and technical solutions for biosensors with the use of nanoparticles.

Calibration strategy

In our opinion, the most significant information concerning the calibration strategy is whether the range of measurable concentration covers the range of concentrations of the marker in cancer samples and a representative level for the healthy population. In some cases, the reported dynamic response range covers several orders of magnitude (e.g. [52]). However, linearity of the analytical response is obtained when the analytical signal is plotted against log marker concentration. In other cases, linearity of the analytical signal against the marker concentration is reported, but in a significantly narrower concentration range. Generally, all calibration graphs represent the Langmuirian curve type, in which the initial sections may approximately follow the strain lines, while the whole curve may be approximately linear when the analytical signal is plotted against log marker concentration (Figure 5). Almost all of the reviewed papers containing calibration data report calibration on the basis of a linear calibration graph. Only two papers refer to semi-log calibration [22,42]. This appears to be a reasonable choice, because determination of the logarithm of the marker concentration does not satisfy expectations for clinical results.

Molecular markers

In the reviewed papers, the targets of the developed—or merely applied—biosensors are various types of cancer, as well as other diseases. These targets are listed in Table 5. Lung, bladder and breast cancers are most frequently represented. Single papers have been devoted to colorectal, prostate, and head and neck squamous cell cancers, as well as acute leukaemia. Among non-cancer applications, thermal injuries have been most frequently investigated, as well as acute myocardial infarction and acute appendicitis. Papers devoted to apoptosis, asthma, megaloblastic anemia, Parkinson’s disease, hypertension, primary renal disease and diabetes have also been published. Some biosensors have found applications with several diseases; for example, 20 S proteasome and UCHL1. In the majority of cases, the biosensors were used for the determination of markers in the blood serum or plasma, although in several cases urine was the target body fluid.

Disease	Marker	Reference
Bladder cancer	Podoplanin	[1]
Thermal injuries	20S proteasome	[2]
Bladder cancer	Cystatin C	[3]
Thermal injury	UCHL1	[4]
Burns	Laminin 5	[5]
Burns	Collagen IV	[5]
Burns	MMP2	[5]
Cryptorchidism	UCHL1	[6]
Acute Appendicitis	20S proteasome	[7]
Acute Appendicitis	UCHL1	[8]
Cryptorchidism	20S proteasome	[9]
Burns	20S Immunoproteasome	[10]
Appendicitis	Cathepsin B	[11]
Endometriosis	Cathepsin G	[12]
Endometriosis	Cathepsin G	[13]
Endometriosis	Cathepsin B	[13]
Endometriosis	Cathepsin D	[13]
Burns	20S Immunoproteasome	[67]

Marker	Abbrev.	Cancer /or other disease	Body fluid	Reference
Arachidonate 5- lipoxygenase	5LOX/ ALOX5	Breast cancer	Blood plasma	[27]
Carcinoembryonic antigen	CEA	Colorectal cancer	Blood serum	[18]
Calcium Binding Protein	CBP	Acute myocardial infarction	Blood serum	[42]
Cathepsin B	Cath B	Appendicites	Blood plasma	[11]
Chitinase-3-like protein 1	CHI3L1/ YKL-40	Asthma	Blood serum	[47]
Collage IV		Breast cancer/ burns	Blood serum	[30]
Cyclin-dependent kinase 4	CDK4	Lung, head and neck cancers	Blood serum	[28]
Cystatin C		Bladder cancer	Blood serum, urine	[3]
Cytochrom C		Apoptosis	No information	[37]
Cytokeratin 17	CK 17	Lung cancer	No information	[19]
Cytokeratin 19	CK19	Lung cancer	Blood plasma	[35]
Epidermal receptor protein-2 antigen	HER	Breast cancer	No information	[17]
Fibronectin		Burns	Blood plasma	[49]
Folic acid	FA	Megaloblastic anemia	Blood	[41]
20S-immunoproteasom	20Si	Acute leukemia	Blood plasma	[32]
20S Immunoporoteasom	20Si	Burns	Blood plasma	[67]
Laminin 5		Bladder cancer/burns	Blood plasma	[5,29]
Matrix metalloproteinase-1	MMP1	Bladder cancer/ acute appendicitis	Blood serum	[31]
Matrix metalloproteinase-2	MMP2	Burns	Blood plasma	[5,33]
Mortalin/mitochondrial 70kDa heat shock protein,	mtHsp70	Parkinson’s Disease	Blood serum	[48]
Podoplanin		Bladder cancer	Blood serum, urine	[1]
20S-proteasom	20Sc	Burns, acute appendicitis, Cryptorchidism	Blood plasma	[7]
Prostate specific antigen	PSA	Prostate cancer	Blood serum	[25]
Ras-related C3 botulinum toxin substrate 1	Rac1	Non Small Cell Lung Cancer	Blood serum	[26]
Ras-related C3 botulinum toxin substrate 1b	Rac1b	Non Small Cell Lung Cancer	Blood serum	[26]
Transferrin	Trf	Hypertension, primary renal disease, diabetes.	Artificial urine	[40]
Troponin T	TnT	Acute myocardial infarction	Blood serum	[16]
Ubiquitin carboxyl-terminal hydrolase L1	UCHL1	Burns, Cryptorchidism, Acute Appendicitis	Blood serum	[10] [4] [8]

Interaction of	with	Reference
CA 125	aptamers	[75]
recombinant Smurf2 protein	CNKSR2 protein	[76]
galectin-3	pectin	[77]
galectin-8	ALCAM	[78]
caffeoylquinic acids	PD-1	[79]
PSA	lectins	[80]
NTV1	VEGFR2 D3	[81]
GP2	VHH	[82]
Tau protein	aptamers	[83]
HIV-1 gp120	antibody fragments (ScFab or ScFv)	[86]
Angiotensin converting enzyme	potential inhibitors	[84]
Porcine mucin	tannins	[85]
CA 125: Cancer Antigen 125; ALCAM: Activated Leukocyte Cell Adhesion Molecule: PD-1: Programmed Cell Death Protein 1; NTV1: Nanobody-Targeting VEGFR; GP2: Zymogen-Granule Membrane Glycoprotein 2; VHH: Camelid Recombinant Single Domain Antibodies

Surface Plasmon Resonance Biosensors

Abstract

Introduction

Stages of biosensor development

Fluidic vs. non-fluidic measurements

Receptors

Enhancement of the SPR signal

Calibration strategy

Molecular markers

Other circulating markers

Molecular interactions

Conclusion

Acknowledgement

References